buletin_stiintific_nr1_2008.pdf

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BULETINUL TIINIFIC

AL

UNIVERSITII TEHNICEDE CONSTRUCII

BUCURETI

NR.1/2008


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CUPRINS

STUDII

Modelarea activitilor experimentale pentru caracterizarea termomecanic a aliajelor cubaza titan (II). Rezultate obinute la ncercri pe epruvete din aliajul Ti-5Al-2,5Sn ..................... 3Indira Andreescu

Alegerea personalizat a materialului la proiectarea construciilor metalice ................................. 8Mariana Petrescu

Performantele n regim dinamic de lucru a utilajelor de spat i transportat pentruconstrucii drumuri (I) .............................................................................................................................. 14Srbu Laureniu

Performantele n regim dinamic de lucru a utilajelor de spat i transportat pentruconstrucii drumuri (II) ............................................................................................................................ 25Srbu Laureniu

Caracterizarea termomecanic a aliajelor cu baza titan. Date experimentale obinute lancercri pe epruvete din aliajul Ti-8Al-V-Mo ..................................................................................... 36

Indira Andreescu

Aspecte privind stabilitatea dimensional a rezistenei mecanice ale betonului cu adaos dedeeuri de sticlE....................................................................................................................................... 40Maria Gheorghe, Lidia Radu, Nastasia Saca

Influena forei reactive la eava de refulare asupra reaciunilor din cuplele cinematice ............. 54Nicolae tefan Trache

Modelarea desfurrii unui proces tehnologic de montaj prin utilizarea reelelor Petri i a

teoriei ateptrii.......................................................................................................................................... 62tefan Rusu, Marian Unguroiu

Analiza stabilitii unor stlpi cu seciune variabil n trepte ............................................................ 80Valeriu Bnu, Mircea Eugen Teodorescu

Construcii rezideniale cu structura metalic..................................................................................... 92Monica Gheorghiu

Principiile de baza ale redactarii tehnicecompetente ............................................................. 102Zoia Manolescu


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Buletinul tiinific nr.1 2008 3

Modelarea activitilorexperimentale pentru caracterizareatermomecanic a aliajelor cu baza

titan (II). Rezultate obinute lancercri pe epruvete din aliajulTi-5Al-2,5Sn.

Experimental activities modeling forthe thermo-mechanicalcharacterization of the titanium

alloys (II). Data obtained for theTi-5Al-2,5Sn alloy sample testing.

Indira Andreescu, prof.univ.dr.ing. Facultatea de Utilaj Tehnologic, Universitatea Tehnica de Constructii BucurestiProfessor Dr., Faculty of Machine Tools, Technical University of Civil Engineering Buchareste-mail: [email protected]

O util adiionare la examinarea comparativ aaliajului Ti-6Al-4V a constituit-o activitateainvestigational a aliajului Ti-5Al-2,5Sn.

Asupra acestuia s-au comunicat n ultimii ani(2002-2005), la mai multe prestigioasemanifestri tiinifice din omeniu, datesugernd atenia special acordat materialuluirespectiv de firme germane i franceze derenume, constructoare de aeronave.

In baza acestor consideraii, s-au efectuatncercri termomecanice detaliate.

S-au ncercat, astfel, apruvete din aliajul Ti-5Al-2,5Sn la ntindere, n mai multe paliere termice,

ntre 1000

C i 5000

C, cu meninerea epruvetelorn palier un timp diferit. Rezultatelecorespunztoare obinute la asemenea ncercri lacare timpul de meninere n palier a fost de 100ore sunt grafiate i tabelate n Fig.1.

A useful addition for the Ti-6Al-4V alloycomparative examination was represented bythe investigational activity over the Ti-5Al-

2,5Sn alloy.There were several dissertationsat prestigious reunions in the field in the lastfew years (2002-2005) about this alloy, thedata suggesting the special attention given tothat matter by French and German wellknown aircraft building companies.

Under these considerations detailed thermo-mechanical tests were made.

Ti-5Al-2,5Sn alloy samples were tested intensile action at different thermal levels

between 1000

C and 5000

C, maintaining thesamples on the level for a different time.The corresponding results obtained at suchtests for which the maintaining time on alevel was of 100 hours are plotted in Fig.1.

Fig. 1 Variaia cu temperatura a rezistenei la ntindere, ultime i de curgere, a epruvetelor din aliaj Ti-5Al-2,5Sn.The ultimate and yield tensile strength variation with temperature of the Ti-5Al-2,5 Sn alloy samples.

Percentage of Rctrand Rutrat 200C (left). Time of maintaining on each thermal level 100 h (right)


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4 Buletinul tiinific nr.1 2008

Curbele variaiei rezistenelor Rutr i Rctr pediverse trepte de nclzire prezint o alurinversativ: pn la 250OC curba Rctr sesitueaz deasupra curbei Rutr, pentru ca mai

departe, pe intervalul termic examinat, de la350OC la 500OC, cele dou curbe s-iinverseze poziionarea.

S-a evideniat o pant mai pronunat a curbeiRctri aproape o linearitate a acesteia, fa decurba conjugat, Rutr ,care are o descretere npant mai puin pronunat, mai ales de la150OC pn la 400OC.

In fig.2 sunt grafiate datele privitoare la

efectele nclzirii epruvetelor din aliajul Ti-5Al-2,5Sn, simultan cu solicitarea lacompresiune, n fiecare palier termic timp de100 de ore.

The Rutrand Rctrstrength variation curves fordifferent heating levels have a reverse rate:up to 2500C the Rctrcurve is placed above Rutrcurve but further away for the 3500C to

5000C thermal interval the two curves reversetheir positioning.

A stronger slope and almost a linearity forRctr curve is pointed out in comparison withthe Rutr conjugated curve, which has a lessstrong decreasing slope, especially between1500C and 4000C.

In Fig.2 data are plotted concerning theheating effects for the Ti-5Al-2,5Sn alloy

samples, simultaneously with thecompressive action for each thermal levelduring 100 h.

Fig.2 - Curba variaiei cu temperatura a rezistenei de curgere la compresiune a epruvetelor din aliaj Ti-5Al-2,5Sn.The yield compression strength variation with temperature of the Ti-5Al-2,5Sn alloy samples.

Percentage of Rcc at 200C (right). Time of maintaining on each thermal level 100 h. (left)

Alura curbei variatiei cu temperatura arezistenei de curgere la compresiune, Rcc, ncondiii de nclzire n mai multe paliere, de la1000C la 5000C, prezint o scdere abruptpn ctre T = 2000C, urmat de o coborre npant mult mai mic pn spre T = 3500C. Inaceste ultime dou paliere termice Rcc a sczutrespectiv la 69% i 57% din valoarea sa larece.

The yield compression strength variationwith temperature Rcc shape between 100

0Cand 5000C on several levels heatingconditions shows a sudden decrease up to T =2000C, followed by a lower slope descent upto T = 3500C. In these two last thermal levelsRcc decreased from its in cold value to 69%and 57% respectively.


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n aceeai schem de analiz au fostinterpretate rezultatele de la ncercrilemecanice de forfecare la cald ale epruvetelordin aliajul TI-5Al-2,5Sn, oglindite de graficul

din fig.3.

In the same analysis set-up the heat shearmechanical tests results were explained forthe Ti-5Al-2,Sn alloy samples showed infig.3.

Fig. 3 - Curba Ruf= f(T) a variaiei, sub solicitare termic ( nclzireprogresiv) a rezistenei ultime la forfecare a epruvetelor din aliajul Ti-5Al-2,5Sn

The ultimate shear stress variation with temperature of the Ti-5Al-2,5Sn alloy samples.Percentage of Rufat 20

0C (left); Time of maintaining on each level: 100 h (right)

Sinteza grafic-tabelar din fig.3 arat ocoborre abrupt important a curbei

caracteristice Ruf, ntre 1000C si ~3000C.Aceasta semnific o reducere a rezistenei dela 49 daN/mm2 la 34 daN/mm2, adic omicorare cu 32,5%fa de ct msura Ruf latemperatura ambiant. Mai departe scderealui Ruf este tot mai lin, nct la 500

0Cepruvetele probeaz o rezisten rmas Rufvalornd nc 61% din Rufla T ambiant.

Ultimul test din setul de determinri la caldale rezistenei mecanice a epruvetelor din

aliajul Ti-5Al-2,5Sn l-a constituit rezistena lapresiunea de contact, Rpc, de curgere i ultim.Curbele reprezentnd variaia cu temperatura aacestei caracteristici, pentru mai multe treptesemnificative de nclzire, sunt trasate n fig.4.

De observat linearitatea n pant abrupt a luiRcpe la nclziri de pn la cca.200

0C i ntr-opant mai mic a lui Rupc pn la cca.250

0C.

The graphic-table in Fig.3 shows animportant sudden descent of the characteristic

curve Ruf between 1000C and ~3000C. Thismeans a decrease of the strength from 49daN/mm2 to 34 daN/mm2, in other words adecreasing by 32,5% in comparison to the Rufvalue at 200C. Further on the decrease of Rufis slower, so that at 5000C the samples have aRuf strength still evaluated at 61% of Ruf at200C.

The last test from the heat determinationsof the Ti-5Al-2,5Sn alloy samples

mechanical strength was represented by theyield and ultimate bearing stress Rpc. Thecurves showing the temperature variation ofthis characteristic for several significantlevels are plotted in Fig.4.

The linearity in abrupt slope of Rcpc must benoted for heating up to 2000C and in asmaller slope for Rupe up to 250

0C.


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Fig.4. Variaia cu temperatura a rezistenei la presiunea de contact ultime i decurgere, a epruvetelor din aliaj Ti-5Al-2,5Sn

The ultimate and yield bearing stress variation with temperature of the Ti-5Al-2,5Sn alloy samplesPercentage of Rupc and Rcpc at 20

0C (left). Time of maintaining on each level 100 h (right)

Concluzii

Aliajul Ti-5Al-2,5Sn este bine apreciat nindustria constructoare de avioane pentrucomportamentul su n timpul solicitrilortermomecanice n comparaie cu aliajul Ti-6Al-4V . Rezistenele ultim i de curgere auvalori mai mici n timpul nclzirii.

Conclusions

The Ti-5Al-2,5Sn alloy is well appreciated inaircraft manufacturing for its behavior duringimportant thermo-mechanical actions. Incomparison to Ti-6Al-4V its ultimate andyield strength have smaller values duringheating.

Modelage des activits exprimentales afin de characterizer les aliages base de titan du point de vuethermomcanique(II). Donnes obtenues suite aux essais sur les prouvettes-tmoin en alliage Ti-5Al-2,5Sn

Resum

On prsente des rsultats suite aux mesures de la rsistance de rupture et de la limite dcoulement en fonction detemprature aux sollicitations axiales, aux sollicitations de cisaillement, et aux pressions de contact, effectues sur desprouvettes-tmoin en alliage Ti-5Al-2,5Sn.


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Bibliografie

[1] I. ANDREESCU, T.A. MUTIU, Concepte i evaluri privind metodologia caracterizrii aliajelor Al-Ti(Conceptsand assessments regarding Al-Ti alloy characterization methodologies), research project, EI/2002, Activity report,Contract INCAS/ Societatea Academic Romn (SAR) - MEC/ASR

[2] COOMBE, T.W. et HURLEY, J.H.R., Quelques utilisations et perspectives davenir du titane dans les cellulesdavions, The Aeronautical Journal, novembre, 1971.

[3] DEMCHENKOV, G.G.,Production of PM Titanium Alloy Blises for the Aerospace Industry, Ti-2003 10th WorldConference on Titanium, Hamburg Germany, 2003.

[4] K. FARMANESH, A. NAJAFI-ZADEH,A.Thermomecanical Behavior of Ti-6Al-4V Alloy, 10th WorldConference on Titanium, Hamburg Germany, 2003.

[5] GIRAUD,R.,Alliages base de titane en construction arospatiale. LAronautique et lAstronautique,No.42 1973.

[6] [5] GIRAUD,R.,Alliages base de titane.Traitements thermiques. Vieillissement. Soudabilit. LAronautique etlAstronautique, No.42 1973.

[7] MOTYKA,M., KUBIAK, K.,SIENIAWSKI, J., FILIP, R. Effect of Heat Treatment on Superplasticity of Forged Ti-6Al-4V Alloy, Ti-2003 10th World Conference on Titanium, Hamburg Germany, 2003.

[8] MULLER, W., BUBEK, E., GEROLD, V. Procedings of the Third International Al-Li Conference, Oxford 1985,Institut of Metals, vol.III, London, p.435.

[9] PEEL, C..J. The development of Al-Li alloys: An overview-Materials and structure, Department of RoyalAerospace, Famborough Hants UKGU 14-6TD, 1990.

[10] STERE, M., ANDREESCU I., Studii i cercetri pentru noi tipuri de aliaje rezistente uoare Al-Li si Al-Li-Ti

(Studies and Research for new types of light bearing stress alloys), Research report, INCAS/ASR SAR ,Bucharest, 2003.

[11] VASILESCU, M., DOBRESCU, M., VASILESCU I., The Influence of Heat Treatments on Mechanical Propertiesof Titanium Alloys Previous Treated by Shot-Peening Ti-2003 10th World Conference on Titanium, Hamburg Germany, 2003.

[12] *** Catalog preliminar pentru avionul IAR-S (Preliminary catalogue for aircraft IAR-S), Institutul Naional pentruCreaie Stiinifici Tehnic, 1983.

[13] *** MIL-HDBK-5 (Military Handbook), Metallic Materials and Elements for Flight Vehicle Structures, U.S.Government Printing Office, Washington, D.C., 1988.


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Alegerea personalizat a materialului laproiectarea construciilor metalice

The Personalized Choice of Materials inMetallic Structure Design

Mariana Petrescu, Conf. dr. ing., Facultatea de Utilaj tehnologic, Universitatea Tehnic de Construcii Bucureti,

Faculty of Machine Tools, Technical University of Civil Engineering Bucharest

The study has a documentary profile with applications on a wide range of steel utilization. Modern concepts in metallicstructure design, the evolution of the stress state of the cracking edge, as well as the factors that influence the materialsresponse in the limit state, during the cracking process, are, in turn, presented.

1. INTRODUCEREi atunci cnd sunt luate toate msurile pentrurealizarea unei construcii metalice n condiiide proiectare i execuie controlate riguros,exist posibilitatea ca dup montajul general,nainte de intrarea structurii metalice nexploatare, n zonele cele mai solicitate aleelementelor metalice fabricate s fie prezentedefecte, care la solocitri variabile s generezefisurile. Nu trebuie neglijate nici defecteleinterne, goluri sau incluziuni aprute laelaborare sau n fabricaie. Acestor defecte li seadaug i cele care pot aprea n exploataredatorit incidenei unor factori mecanici sau demediu.Toi aceti factori influeneaz tenacitatea larupere a materialului

2. CONCEPTE PRIVIND PROIECTAREASTRUCTURILOR

2.1. SOLICITRILE I CALCULUL DEREZISTENPentru a efectua un calcul ale crui rezultate

s fie acceptate cu ncredere este necesarcompararea solicitrii elementului proiectat cu

rezistena pe care o confer materialul i formaalese, precum i prelucrrile la care este supuspn la forma final stabilite de proiectant.

2.2. ALEGEREA MATERIALULUIOdat tensiunile determinate, sunt necesare

informaii ct mai ample privind proprietilematerialelor. n present au fost elaborateprograme de optimizare a alegerii materialuluimetalic bazate pe conceptele mecanicii ruperii.

1. INTRODUCTION

Even when all measures are taken fordeveloping a metal structure in thoroughlycontrolled design and execution conditions,there is the possibility that (after the generalassembly and before the proper exploitation ofthe metallic structure, in the most stressed areasof the metallic elements) faults may occur. Atvarious stresses, such faults could causefractures. Nor the internal faults, i.e. the cavitiesor the air pockets generated during thefabrication or the elaboration process, are to beneglected. Due to the action of mechanical orenvironmental factors, to these faults those thatmay occur in exploitation can frequently add.All these factors influence the material tenacityon fracture.

2. CONCEPTS REGARDING STRUCTUREDESIGN

2.1. STRAIN AND STRENGTHCALCULATION

To perform a calculation with reliableresults, it is necessary to make a comparisonbetween the stress of the designed element andthe strength that the material displays, the

chosen form, as well as the processing stagesthe material is subjected to until it reaches thefinal form desired by the designer.

2.2. THE CHOICE IN MATERIALOnce the tensions defined, complete

information on the properties of the material isrequired. Presently, optimization programs inmaterial choice have been developed, based onthe mechanics of fracture concept.


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Pentru calculele de propagare a fisurii, elementalesenial este factorul de intensitate a tensiunii K.Chiari n cazul unei solicitri compuse modul defisurare predominant este modul I de deschidere afisurii. Determinarea valorii factorului KI pentrucomponentele care conin fisuri se pot folosiexpresiile din literatura de specialitate, fie cutndsoluii analitice, numerice (prin metodaelementului finit) sau experimentale. Iniiereafisurii este determinat de amplitudinea sauvariaia tensiunii, n timp ce propagarea seproduce datorit tensiunilor maxime Studiul carese realizeaz la proiectare este de a gsi asociereacea mai convenabil ntre solicitare i durata devia a elementului sau sistemului. Aceastapresupune cunoatrea durabilitii materialului nfuncie de tensiuni sau deformaii specifice.n cazul n care durata de via obinut princalcul nu este satisfctoare, inginerul proiectantare posibilitatea de a interveni acionnd asupra atrei factori:

Solicitarea, n sensul reducerii ei;Materialul, n sensul schimbrii saumbuntirii materialului ales;

Modificarea formei constructive.Tendina actual este de a analiza n faza deproiectare toate modurile posibile de rupere i de antocmi pe aceast baz un program de controlal ruperii aferent elementului proiectat. Subaceast denumire n literatura de specialitatentlnim un ansamblu de activiti care cuprinde

I identificarea factorilor care potcontribui la rupere i definireacondiiilor de serviciu;

II stabilirea contribuiei fiecrui factor laposibila rupere;

III alegerea criteriului de proiectare nmsur s reduc la minim probabilitateaapariiei fiecrui mod de rupere;

IV recomandarea datelor de proiectare ca:alegerea materialului, valoriletensiunilor admisibile, msuri defabricaie i control pentru realizareasiguranei i fiabilitii scontate.

For crack propagation calculations, the essentialelement is the intensity factor of stress:K. Evenin the situation of a composed stress, thedominant cracking module is the I one. For the

determination of the value of the KI factor forthe elements that contain cracks, either theexpressions from the specialist literature can beused or the search for analytical numerical orexperimental solutions, (through the method ofthe finite product). The crack initiations aredetermined by the strain amplitude or variation,while propagation occurs due to maximalstrains.The study developed during the design periodaims at finding the most convenient association

between the strain and the "life" of the elementor that of the system. This implies an accurateknowledge of the material durability in relationwith strains or specific deformations.In case the "life time " of the material obtainedthrough calculations is not satisfactory, thedesign engineer has the possibility to interveneon the following factors: Strain, by reducing it; Material, by changing or improving it; Construction form, by modifying it.

During the design stage, the present trend is toanalyze all possible cracking ways and, on thisbasis, to generate a cracking control programrelated to the designed element. In the literature,under this name, one can find an assembly ofactivities that contains:

I identifications of factors that cancontribute to fractures and defining theservice conditions.

II determination of the contribution ofeach factor on the possible fracture.

III choice of the design criterion so that theoccurrence of each fracture type couldbe reduced to a minimum.

IV design data recommendation such as:the material selection, the toleratedstrain values, production measures andcontrol in order to achieve the desiredsafety and indurance level.


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2.3. ALEGEREA CRITERIULUI DEPROIECTARELa alegerea criteriului de proiectare trebuieluate n consideraie interaciunile dintre factorii

care controleaz diferite moduri de rupereprecum sunt:

- tensiunile de ntindere care au influenmajor asupra duratei de via. Astfel vitezade cretere a fisurilor scade semnificativ atuncicnd amplitudinea tensiunii de ntindere sereduce;

- dimensiunile de defect au influen asupraduratei de via. Astfel viteza de cretere afisurilor de oboseal este foarte mic ladimensiuni de defect mici;

- tenacitatea materialului, atunci cndsolicitarea materialului se face n domeniul decomportare elastic sau elasto-plastic,infleneaz mrimea defectului critic. Valorilemari ale tenacitii specifice domeniului decomportare plastic a materialului, contribuiesemnificativ la mrimea durabilitii.

3. COMPORTAREA MATERIALELOR LANTINDERE

Metoda de ncercare cu cea mai larg utilizareeste ncercarea la traciune i caracterizeazproprietile mecanice ale metalelor. Rspunsulacestora la solicitare este diferit n termini detensiune i deformaie specifici anume:

2.3. CHOICE OF THE DESIGNCRITERIONOn choosing the design criterion, theinteractions among the factors that control

different types of fractures need to be taken intoconsideration; these are:

- elongation strains that have a majorinfluence on the "life" of the material. So, thepropagation speed of the cracks is significantlydecreasing when the amplitude of the elongationstrain is reduced;

- the fault dimension also influences the"life" of the material. So, the growing speed infatigue crack is very low with reduced faultdimensions;

- the material tenacity - when the materialstrain is applied in the elastic or the elasto-plastic behaviour domain - influences the size ofthe critical fault. The big tenacity values,specific to the plastic behaviour domain,significantly contributes to the increase of thematerial durability.

3. MATERIALS BEHAVIOUR ATTENSILE STRESS

The most widely spread testing method is thetensile test and it characterizes the mechanicalproperties of metals. Their response to strain isdifferent in terms of strain and specificdeformation as in:

0A

F= , respectiv,

0

0

l

ll= (3.1)

unde: - tensiunea convenional;F - fora aplicat;

0A - aria iniial; - deformaia specific convenioanal;

0l - distana iniial ntre repere;

l - distana ntre repere la foraF.

De asemenea se folosesc i definiiile:

where: - conventional strain;F - applied force;

0A - initial area;

- conventional specific deformation;

0l - the initial distance between points;

l - the distance between points under forceF.The following definitions are also used:

A

F=* , respectiv (respectively)

0

lnl

l= (3.2)


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unde:* - tensiunea real;

A - aria seciunii transversale laF; - deformaia specific real.

Necesitatea utilizrii tensiunii i deformaieispecifice reale rezult din:

- exprimarea mai fidel a creterii capacitiide ncrcare pe msura solicitrii materialului;

- exprimarea creterii de lungime subaciunea solicitrii printr-o mrime care s nudepind de faptul c deformaia s-a produs ntr-un pas sau mai muli pai;

- satisfacerea ipotezei volumului constant ncazul deformaiei plastice 0=++ zyx spre

deosebire de relaia 1)1)(1)(1( =+++ zyx n cazul deformaiei specifice convenionale

where:* - real strain;

- the transversal section area underF; - the real specific deformation.

The necessity of the use of strain and the realspecific deformation results from:

- a more realistic representation of the increasein loading capacity, as the material is strained;

- the representation of length growth understrain action through a value that is not dependableon the fact that the deformation was induced in oneor several steps;

- the attainment of the constant volumehypothesis in the case of plastic deformation

0=++ zyx as different from the relation1)1)(1)(1( =+++ zyx in the case of

conventional specific deformation.

=++==

...lnln1

2

0

1

1 l

l

l

ln

ii (3.3)

Legtura ntre caracteristicile la traciune realei cele convenionale este dat de relaiile:

The relation between the real tractioncharacteristics and the conventional ones isgiven by:

)1(* += (3.4))1ln( += (3.5)

Rspunsul metalelor la solicitarea de ntinderepoate corespunde uneia dintre tipurile de curbe:

Tipul I comportare elastic exprimat prinlegea lui Hooke specific strii liniare desolicitare:

The metals response under tensile strains maycorrespond to one of the curve types:

Type I elastic behaviour expressedthrough the Hooke Law specific to the linearstress state

E= sau (or) =E* (3.6)E - modulul de elasticitate longitudinalValoarea lui E depinde de natura legturilorinteratomice.

Tipul II comportare elastic omogen

plastic exprimat empiric prin starea liniar desolicitare printr-o relaie de form parabolic

E - the longitudinal elasticity module.TheEvalue depends on inter-atomic relations.

Type II elastic behaviour uniformlyplastic, empirically expressed through the linear

stress state through a parabolic relation:nC=* (3.7)

n care:n - este coeficient de ecruisare;C - constanta de material definit ca

tensiune real corespunztoare uneideformaii specifice reale de valoareunitar.

where:n - the cold-hardening coefficient;C - the material constant defined as the real

strain, corresponding to a real specificdeformation of unitary value.


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Dup unii autori, oelurile pentru construciimetalice de rezisten joas pot prezenta doustadii n procesul de ecruisare prin deformareplastic, astfel nct ecuaia devine:

According to other opinions, the steel used forlow resistance metallic constructions couldexhibit two stages in the cold-hardening processthrough plastic deformation, so that the equation

becomes:

11* logloglog Cn += pentru c (3.8.a)

22* logloglog Cn += pentru c> (3.8.b)

unde:

c reprezint deformaia criric la care auloc tranziia procesului de ecruisare de lastadiul 1 (rel. 3.8.a) la stadiul 2 (rel. 3.8.b).Departajarea n ceea ce privete comportareaunui oel dup o relaie de tip (3.7) sau (3.8) sepropune a se efectua n funcie de compoziiachimici microstructura oelului.

Tipul III comportare plastic eterogenplastic n care zona de deformare plasticeterogen corespunde unor valori %3...1 ,dup care comportarea materialului este de tipomogen (tipul II).

4. STUDIU DE CAZ4.1. STUDIUL EVOLUIEI RUPERII LAMATERIALE DUCTILE

Pentru studiul fenomenului de rupere s-au fcutncercri de traciune pentru dou oeluri, alecror caracteristici sunt date (n tabelul 1).

where:

c represents the critical deformation onwhich the transition in the cold-hardeningprocess takes place from stage 1 (3.8.a.) tostage 2 (3.8.b).The difference in the matter of steel behaviourafter a type (3.7) or (3.8) relation comes fromthe chemical composition and the steelmicrostructure.Type III plastic behaviour, heterogeneouslyplastic, in which the heterogeneous plasticdeformation area coresponds to some values

%3...1 after the behaviour of the materialbecomes uniformly plastic of Type II.

4. EXPERIMENTAL STUDY4.1. STUDY OF FRACTURE EVOLUTIONIN DUCTILE MATERIALS

For the study of fracture phenomenon sometraction essays where made for two steel typeswith the characteristics written in table 1.

TABELUL 1Nr.crt.

Materialul % C % Mn % P % SRm

[MPa]Rp0,2[MPa]

KV[J]

KIc[MPa/mm3/2]

1. OL 44.4EN 10027-2

0,22 1,16 0,045 0,045 430 280 27 2025

2.OL 52.4

EN100027-20,2 1,65 0,045 0,045 510 350 27 2120

Rezultatele ncercrilor sunt prezentate ntabelul 2.

The results of the essays are presented inTable 2.


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TABELUL 2

MsurtoriF[N]

d0[mm] 4

20

0d

S

=

[mm2]

du[mm] 4

2f

u

dS

[mm

2

]

1000

0

=S

SSZ u

[%]

[MPa]

* [MPa]

1 1200 6 28,26 5 19,625 31 42 612 3000 6 28,26 4,6 16,48 43 106 182,53 3500 6 28,26 4,2 13,85 52 124 2534 4000 6 28,26 3,9 11,85 59 141,5 353

Materialul

1

5 4500 6 28,26 3,8 11,33 61 159,5 379

1 2500 6 28,26 5,2 21,19 26 88 188

2 5000 6 28,26 5,0 19,62 31 180 255

Materialul2

3 5400 6 28,26 4,8 18,05 37 191 299

5. CONCLUZII

Din examinarea rezultatelor experimentaleobinute se constat urmtoarele:

materialul 2 are o comportare elastic de

tip I ( 2,0*

pR


14/108


Performantele in regim dinamic delucru a utilajelor de sapat si transportatpentru constructii drumuri (I)

Performance of digging and transportingmachines in a dynamic working regimefor road-construction (I)

Sarbu Lurentiu, prof.univ.dr.ing. Facultatea de Utilaj Tehnologic, Universitatea Tehnica de Constructii BucurestiSarbu Lurentiu, Professor Dr., Faculty of Machine Tools, Technical University of Civil Engineering Buchareste-mail: [email protected]

1. IntroducereArticolul ii propune analiza modelului dinamicalctuit din: motor diesel - transmisiehidromecanic THM - sol pentru utilajele despat i transportat la funcionarea lor peelementele componente ale ciclului tehnologic

de lucru n regim real.

2. Calitile de traciune ale utilajului de spati transportat

n cazul unui utilaj pentru construcii , care serealizeaz prin folosirea unui autoasiu (tractor)existent este necesar studiul performanelorautoasiului i al capacitii sale portante pentruechipament (buldozer, buldozer cu scarificator,screper, sau ncrctor etc.) .

Astfel, trebuiesc cunoscui parametrii principaliai autoasiului: greutatea proprie, capacitatea dencrcare, viteza maxim de drum n prizdirect, valoarea pantei maxime pe care o poateinvinge n priz direct i n treapta I de viteze,caracteristicile motorului cu care este echipat,tipul transmisiei (mecanic sau hidromecanic,etc.) i repartiia greutii pe puni [3].De exemplu, n calculul de traciune alautoscreperului, se folosesc urmtoarele ipotezede calcul [3] :

-se neglijeaz forele de rezisten la rulare Friimomentele de inerie ale roilor Mrj ;- = Rs/Rt reprezint raportul dintre rezistena laspare Rs i reaciunea solului Rt asupraorganului de lucru . Coeficientul este funciede tipul echipamentului care afecteazcaracteristica de traciune .-calculul reaciunilor dinamice se face pentru opatinare maxim de 20% , respectiv considerndvaloarea maxim pe care o poate lua fora detraciune calculat din condiia de aderen :

1. IntroductionThis article is aimed at analyzing the dynamicpattern including: the diesel engine hydromechanics transmission (THM) earth, forearth removing and conveyor units whenoperating in real life, on the components of the

dynamic technological cycle.

2. Traction features of the earth removal andtransport equipments

For public works equipment using the existingcar frame it is necessary to study the features ofits frame and the supporting power of theequipment (bulldozers, scarifiers, scrapers,loading units, etc).

Thus the main parameters of the car frame haveto be known: its weight, loading capacity,maximum direct speed, the value of themaximum slope conquered both in direct speedand in the first velocity stage, the enginecharacteristics, the type of transmission(mechanics or hydromechanics, etc), as well asthe weight distribution on axles [3].For instance, we use the following calculationhypotheses to determine the traction value for thecar scraper [3]:

-road resistance forces Fri and the inertiamovement of wheels Mri are left aside;-p= Rs/Rt represents the ratio between the soilresistance (Rs) and ground reaction (Rt) onto theworking equipment. The coefficient depends onthe equipment type, and it influences the drivespecificity;-the dynamic reaction calculation is made for amaximum slide of 20%, taking into account themaximum value of the driving force computedaccording to the adherence condition:


15/108


maxt ir ir F X W F + (2.1)care este condiia de deplasare n regimstabilizat pe teren cu nclinare longitudinal .

Pentru deplasarea la sfrit de spare :t m ir F Z F (2.2)

care este condiia pentru regimul de transport alutilajului .Se utilizeaz relaiile :

max mX Z= n care :

Xmax - fora de aderen maxim;Zm - reaciunea dinamic normal a roilormotoare ;

Wir rezistena total la spare a

solului ; coeficientul rezistenei drumului ladeplasarea utilajului , Fir= Ga ;Ga greutatea total a utilajului de spat itransportat ;Ft fora de traciune la roile motoareFir Ff rezistena global la rulare .Posibilitatea de deplasare a utilajului cu cupaplin pe terenuri moi sau accidentate depinde deraportul dintre coeficientul de aderen () icoeficientul rezistenei totale a drumului ,

notat cu CT :/ /TC D D = = (2.3)

unde :CT factorul capacitii de trecere ;D factorul dinamic n priz direct ( sau pentruo anumit treapt din cutia de viteze ) ;D factorul dinamic la limita de aderen , carelimiteaz caracteristica dinamic de traciune D= f(v) n funcie de ncrcarea mainii .

daca:

CT/ deplasarea utilajului este posibil ;CT/ - deplasarea utilajului nu este posibilPentru tractorul industrial, care lucreaz cu

anumite echipamente (buldozer , buldozer cuscarificator, screper sau ncrctor, etc.) nu seiau n considerare forele de inerie ale maseloraflate n micare de translaie

3. Indicii de performan n regim dinamic amainilor de spat i transportat[1].

n exploatarea mainilor de spat i transportat,

comportarea dinamic a utilajului se bazeaz pe

maxt ir ir F X W F + (2.1)which is the movement condition in stableoperation, on a longitudinal slope.

For the movement at the end of the diggingprocess:

t m ir F Z F (2.2)representing the condition for the equipmenttransport regime.

We use:

max mX Z= where:

Xmax maximum adherence forceZm normal dynamic reaction of the drivers;

Wir total soil resistance road resistance coefficient during equipmentmovement, Fir = GaGa total weight of the digging and transportequipmentFt traction force at drivers levelFir Fj global resistance against rolling

The possibility of moving the equipment with fullbuckets on soft or bumpy ground depends on theratio of the adherence coefficient () and the totalresistance coefficient of the road , noted as CT:

/ /TC D D = = (2.3)where:CT travel capacity factorD dynamic factor in direct speed (or for acertain gear box step):D dynamic factor at the adherence limit,restricting the dynamic thrust characteristicD=f(v) depending on the car load;

if:CT/ equipment movement is possible

CT/ equipment movement is not possibleFor the car frame (industrial tractors)

working with certain equipment (bulldozer,scarifiers, scraper, dumper, etc) the mass inertiaforces during the translation movement are nottaken into account.

3. Performance parameters of digging andtransport machines in a dynamic regime [1]

During the operation of digging and transport

machines, the dynamic behavior of the machine


16/108


fundamentarea criteriilor i indicilor deperformant n regim real de funcionare pe ciclultehnologic de lucru.Bilanul energetic al mainii se analizeaz pentru

(fig.1):-tractor + echipament care lucreaz n regimstaionar cu THM sau TM pentru ncrcare cup;-tractor + echipament n regim dinamic cu THMsau TM i mecanism hidraulic de incrcare(basculare).Patinarea este dat n funcie de timpul dencrcare:-pentru 20% timp de ncarcare cup, patinareaeste cuprins ntre 12-60% ;-pentru 20-30 % timp de ncrcare, patinarea

atinge 60%.Pentru regimul tehnologic pe faze patinarea se ia10-30%. Caracteristica de functionare amotorului n regim dinamic, corespunde pentruputerile consumate de tractor + echipament: lapatinare Pp = f( Fcr), la nvingerea rezisteneiglobale Pf= ( Fcr, Vt) i mecanismul hidraulicde ncrcare Pmh= f ( Pe).

Caracteristica de funcionare a motorului nregim staionar se ia pentru o patinare de 10-30%, un coeficient de aderen maxim de 0,8-1,1 i un coeficient de aderen pentru lucrul nagregat tractor + echipament de 0,5-0,7.

is based on the real-time assessment of criteriaand performance parameters of the technologicalworking cycle.The energetic balance of the machine is analyzed

for (fig.1):-tractor + stationary equipment with THM or TMfor bucket loading;-tractor + dynamic equipment with THM or TM,and a hydraulic loading mechanism (dumping)The slide value is given function of the loadingtime:- for 20% bucket loading time, the resulting slideis between 12-60%;-for 20-30 % bucket loading time, the slidereaches 60%;For the phase routine the slide takes values

between 10-30%. The engine operation featuresin a dynamic regime, for the effort of the tractor+ equipment system is as follows:- during the slide Pp = f( Fcr) when overcomingglobal resistance Pf= ( Fcr, Vt) and the hydraulicloading equipment Pmh= f ( Pe).

The engine operation characteristic in a stationaryregime is taken for a slide between 10-30%, amaximum adherence coefficient between 0,8-1,1and an adherence coefficient for functioning inthe tractor +equipment aggregate of 0,5-0,7.

Fig. 1.Caracteristica potential de lucru ( Pcr) i bilanul energetic al tractorului etalon (P = 60 kW) dup[ 2] :a)- pentru ncrcare staionar; b)- pentru regim dinamic; I, II- tractor cu THM i TM; Pmh - puterea la mecanismul

hidraulic; PHT, PM- puterea la HT (hidrotransformator) i puterea mecanic.

The potential working characteristic (Pcr) and the energetic balance of the standard tractor (P = 60 kW) after [ 2] a)for stationary loading; for a dynamic regime; I, II- tractor with THM and TM; Phm - hydraulic mechanism power;

PHT, PM- HT (hydro- transformer) power and mechanical powerAlte notaii : Pm putere motor (la pomp) ; Pcr

puterea critic; Pp puterea la patinare; p-

coeficientul de patinare; Pf- puterea rezistenei

global la naintare; Ff rezistena global.


17/108


La ncrctoarele frontale, analizate n [1],fundamentarea criteriilor i indicilor deperforman n regim real de funcionare are labaz evaluarea i analiza evoluiei valorilor

parametrilor statistici ai unei mrimi fizice, care"cuprinde" influenele datorate tuturorperturbaiilor interne i externe ale sistemuluiconsiderat, bazate att pe traciunea utilajului nprocesul de spare dar i pe manipulareaechipamentului de ncrcare n procesultehnologic.innd cont de structura constructiv ifuncional a ncrctoarelor frontale, precum ide condiiile de lucru specifice acestui tip deutilaj, n lucrarea [1] a fost adoptat ca parametruce trebuie "monitorizat", puterea necesarsistemului de acionare a mainii.Aciunea are ca rezultat producerea efectelordinamice diferite ca intensitate, de la o faz delucru la alta. Aceste efecte dinamice se potevalua cu ajutorul indicilor de performan nregim dinamic real de lucru al utilajulului:

- indicele mediu de utilizare static a puterii,i1 - definit ca raportul dintre componena statica puterii medii necesar pe o faz de lucru iputerea maxim instalat a utilajului;

-indicele mediu de utilizare dinamic aputerii, i2- definit ca raportul dintre componenadinamic a puterii medii necesar pe o faz de

lucru i puterea maxim instalat a utilajului ;Other notations: Pm-engine power (at pumplevel); Pcr- critical power; Pp- sliding power; p -

sliding coefficient; Pf power of global resistanceto movement; Ff global resistance.In the case of frontal loaders, analyzed in [1], theappraisal of criteria and performance parameters

in a real time operation regime is based on theassessment and analysis of the development ofstatistical parameters values for a physical unit,which covers the effects caused by all internaland external perturbations of the consideredsystem, based both on the traction of the machineduring the digging process, and on the loadingequipment handling during the technologicalprocess.Taking into account the functional andconstructive structure of the frontal loaders, aswell as the working conditions specific for thistype of machine, paper [1] chose the powerrequired for operating the machine drive, as aparameter to be monitored.The action has as a result the production of dynamiceffects with a different intensity level for each phase.These dynamic effects can be assessed with the helpof performance parameters in the real time workingregime of the machine [1] .

-the average parameter of static usage ofpower i1 - defined as a ratio between the staticcomponent of the average power needed during aworking phase and the maximum installed powerof the machine;

-the average parameter of dynamic usage ofpoweri2- defined as a ratio between the dynamiccomponent of the average power needed duringa working phase and the maximum installedpower of the machine;

Fig. 2. Necesarul de putere pentru un ciclu standard de lucru la un ncrcator frontal rapid( tip MMT 45 - Promex S.A.) dup [ 1 ].

The necessary power for a standard working cycle of a fast-frontal-loader(MMT 45 type - Promex S.A.) after[ 1]

- indicele mediu real de utilizare a puterii,

i3 - definit ca raportul dintre valoarea total a

puterii medii necesar pe o faz de lucru i

puterea maxim instalat a utilajului;

0

5

10

15

20

25

30

0.0 3.5 6.6 9.7 12.7 15.7 18.8 22.0 27.8 31.7 34.5 38.5

Timp, [s ]

P

utere,

[kW]

putere totala instantanee

putere totala medie


18/108


-indicele mediu de multiplicare dinamic aputerii, i4 - definit ca raportul dintre valoareatotal a puterii medii i componenta static aacesteia, necesare pe o faz de lucru.

Valoarea indicilor de performan aincarcatoarelor frontale rapide se analizeazpentru fiecare faz a procesului tehnologic delucru ( fig.3).

4.Dinamica funcionarii utilajului de spat itransportat n funcie de regimul tehnologicde lucruefectuat

Pentru stabilirea modelului matematic de lucru

al tractorului industrial ( cu THM ) cuechipamente de construcii drumuri, n [2] sepornete considernd regimul dinamic detraciune al tractorului n agregat cuechipamentul buldozer scarificator .

Se consider funcionarea acestuia pe elementeleciclului tehnologic de exploatare . Pentru anvinge rezistena totala la naintare , fora detraciune pe elementele ciclului este asigurat cuajutorul rapoartelor de transmitere . n [2] sefolosete noiunea de factor de transmitere ( iM )pentru treptele de viteze deoarece la proiectareaunui utilaj nou nu se tie nc raza roii motoare( iM = it / rR ), cu ajutorul cruia se obine forade tractiune necesar pentru spare transport amaterialului i se determin potenialul energeticpe ciclul tehnologic de lucru .

Potenialul energetic specific mediu pe treptelede lucru este o funcie care ine seama de:factorii de transmitere ai tractorului, de aderenmaxim la roat pe treptele de viteze folosite. El

este apreciat cu ajutorul schemei dinamica delucru a transmisiei, i respectiv, de distana despare [2] .

Potenialul energetic specific mediu este egal cusuma potenialelor energetice pe treptele deviteze care depind de distribuia aderenei i adistanei de spare n funcie de tipul de agregareal tractorului cu echipamentul.

-the average real usage parameter of power i3 -defined as a ratio between the final value of theaverage power needed for a working phase andthe maximum installed power of the machine;

-the average dynamic multiplication powerparameter i4 - defined as a ratio between the finalvalue of the average power and its staticcomponent, necessary in one working phase.

The value of the performance parameters of thefast-frontal-loaders is analyzed for each phase ofthe technological working process (fig.3).

4. Dynamics of the digging and transportingequipment operation according to thetechnological working regime

To set the mathematical working pattern for theindustrial tractor (with THM) using road buildingequipment, paper [2] uses the dynamic regime ofthe tractor in an aggregate with a bulldozer scarifier equipment.

Take its operation on the components of thetechnological cycle being used. To overcome thetotal resistance to advance, the traction force oncycle components is reached with the help oftransmission ratios. In paper [2] the transmissionfactor (iM) is used for speed stages, because whendesigning a new machine the driver radius (iM = it/ rR) is not known yet; this is used to reach thetraction force required for the digging andtransport of the building material, and to set thepower potential of the technological workingcycle.

The specific average power potential on workingstages is a function of the tractor transmissionfactors, of the maximum wheel adherence for

each speed stage, and of the digging distance,respectively.

The specific average power potential equals thesum of the power potential levels for the speedstages depending on the adherence distributionand on the digging distance, depending on tractor equipment aggregate type.


19/108


( )

( )( )

( )

( ) ( ) ( )

( ) ( ) ( )

1

max

1

max

max

1

1 2 1

max max max

1 max max max

max max max

, , , , , , , , ,

, ,

, ,

, ,

pv

pi

pv

pi

pv

n pi

spn MI MII M Mn M p n

S

spn n R p R p R pR S

S

spn M R p R p R pR S

SR V

spI MI R p p R pS

P i i i i i S y y

P iM S F F S d dS

P i S F F S d dS

P i S F R F S d dS

=

+

+

+

L L

L

(4.1)

Limitele de integrare ale funciei de aderensunt mprite de la Rmaxi ( pe trepteleinferioare cu patinare) la RmaxV (corespunztoare vitezei de transport) .

Limitele de integrare ale functiei reprezentate dedistana de spare , variaz ntre cea parcurs (funcie de factorul de transmitere iM ) cupatinare i cea parcurs cu viteza tehnologic detransport corespunztoare funcionrii TH1 , 2 , . , n-1 intervalele de lucru alefunciei de aderen corespunztoare rapoartelorde transmitere ( de la 1 la n) pentru transport pe

ciclul tehnologic.

F(Rmax) , F(Sp) distribuiile probabilistice alefunciei de aderen i respectiv a distanei despare.

Se consider c tehnologia de lucru a utilajuluise execut cu Rmax i STp = const . Atunciacceleraia jTP i viteza Tp caracterizeazprocesul de lucru al utilajului.

Acceleraia i viteza medie THj

i TH

lafuncionarea THM ( pentru. spare transport )sunt exprimate n funcie de: puterea mainii ,viteza de transport i legile de distribuie aleaderenei pe distana de spare. Acestea suntexprimate prin relaii de forma [2] :

The integration limits of the adherence functionare divided from Rmaxi (on lower speed stages atsliding operation) to Rmaxi (corresponding to thetechnological transport speed).

The integration limits of the function representedby the digging distance vary between the slidingadvance (depending on the transmitting factor iM)and the advance with a transport technologicalspeed corresponding to TH operation.1 , 2 , . , n-1 working intervals of theadhesion function corresponding to thetransmission ratios (from 1 to n) for transport on

the technological cycle

F(Rmax) , F(Sp) - likely distributions of theadherence function and digging distance,respectively

The application of the working technology isachieved with Rmax and STp = constant. Then, thetransmission acceleration jTP and speed Tp arecharacteristic for the working process.

The mean acceleration and speed THj

and TH

for THM operation (for digging - transport)depend on: car power, transport speed andadherence distribution laws over the diggingdistance. These are expressed as follows [2]:


20/108


( ) ( )

( ) ( )

( ) ( )

1

max

1

, , ,0

, , ,

, , ,

, ,

, ,

, ,

p n

p n

R

p I

n

I

cr S T R TH R TH R TH

II

THTH cr S T R TH R TH R TH

I TH

cr S T R TH R TH R TH

N f d

Sj N f d

N f d

+

= + + +

L

L(4.2)

( ) ( ) ( ) ( )( )

( ) ( )( )

, , , , , , , ,0 0

, , ,0

n n

I II

TH TH T R TH R TH R TH TH T R TH R TH R TH

II

THI R TH R TH R TH

V f d V f d

V f d

= + +

+L

(4.3)

unde:I , II , .. , n-1 reprezint intervalele delucru a TH n funcie de aderenRpe treptele deviteze pentru spare transport .

Dac aderena critic cr este considerat i eavariabil n procesul de lucru datorit modificriincrcrilor dinamice pe punti, se poate exprimaacceleraia i viteza medie pe treptele de vitezeinnd seama de timpii de funcionare ai TH pe

treptele respective (funcie de turaie) :

where: I, II, ., n-1 represent the workingintervals of TH depending on the adherencefunction R over speed stages for digging andtransport using THM.If the critical adherence cris also considered as avariable in the working process, due the changesof the dynamic loads on bridges, the averageacceleration and speed of the hydro-mechanicaltransmission can be rendered over the working

stages, taking into account the working periods ofTH on the corresponding stages (depending onthe rotation speed );

( ) ( ) ( ) ( )

( ) ( )

, ,

,1

,

, 1

, , , , , 1 ,

0, ,

, , ,

,

TH TI TH TII

TH TI n n

TH Tn

TH Tn

T Tcr TH TH TH n cr TH TH cr TH TH TH n cr TH TH

TH THT

TH T TH T

THT

cr TH TH TH TI cr TH TH

THT

TH TI

TH

TH

t V t t V t dt dt

T Tj

t V tdt

T

S

+ +

=

(4.4)

( ) ( )

( )

, ,

, 1

,

, 1

, , , 1 ,

0 , ,

, ,

,

TH TI TH TII

n

TH TI n n

TH Tn

TH Tn

T TTH T cr TH TH TH n cr TH TH

TH TH TH TTH T TH T

TTH TI cr TH TH

THT TH TI

V t V t dt dt

T T

V tdt

T

= + +

+

L (4.5)


21/108


unde:TTH,TI , TTH,TII , .. , TTH,Tn timpii de lucrucorespunztori treptelor de viteze a THM pentrutransportul materialului .

Diapazonul de exploatare al mainii se face laRmax i STp ( adic distana de transport apmntului ).

Potenialul energetic specific mediu pe trepteleinferioare de lucru la spare (cu raportul iMP) estefuncie de aderena roilor pe aceste intervale despare, la funcionarea utilajului pe caracteristicade lucru a motorului [2] .

where:TTH,TI, TTH,TII,.TTH,Tn working periodscorresponding to speed stages of hydro-mechanical transmission operation for the

transport of the building material.

The machine operation range is calculated forRmax and STp (that is, the distance to whichbulldozers are taking the soil load).

The specific mean power potential on lowerspeed stages during digging (using the iMP ratio)depends on the wheel adherence over theseintervals, and on the digging distance accordingto specific engine working characteristics [2].

( )

( ) ( ) ( )

( )

max

1

max max max

max

max

max

1

, 1 1 2 1

,

,

, , , , , , , , , , , , , , ,

, , , , , ,

, , , ,

n p

THV

R THI

R THV

n THI

sp nc MPI MPII MP MTI MTII R T I II n n

S

SP Pn MPn MTI MTII MTn R TH R TH R TH S

S

SP PI MPI MTII MTn R TH S

P i i i i i S

P i i i i S F F S d dS

P i i i S

=

+

+

L L L

L L

( ) ( )max maxR TH R TH

F F S d dS

(4.6)

unde: iMP, iMT sunt factorii de transmitere pe

treptele inferioare de spare, respective pe celesuperioare de transport a materialului.F(Rmax ) , F( STH ) distribuiile probabilistice aleaderenei roilor i distanei de spare apmantului la funcionarea THM a tractorului nagregat cu buldozer scarificator sau screper .

Ecuaiile ( 4.1 4.6 ) reprezint modelulmatematic al funcionrii tractorului cu THM nagregat cu echipamente de spat i transportatpentru un ciclu tehnologic de lucru .

Pe componentele ciclului tehnologic utilajul poatefunciona n regim staionar sau n regim dinamic .

Potenialul energetic specific mediu corelatpe ciclul de lucru este egal cu suma potenialelorspecifice medii realizate n cazul agregriitractorului (cu buldozer, buldozer - scarificatorsau screper), dat de relaia :

3

0,1

sp sp ii

P P

== (4.7)

where: iMP, iMT the transmission factors of

lower digging stages, and upper materialtransport stages respectively. F(Rmax), F(STH) are the likely distribution values of wheeladherence and ground digging distance forTHM tractor operation with scarified orscraper.

The equations (4.1-4.6) represent themathematical pattern of a THM tractor,operating together with digging and transportequipment for a technological working cycle.

On the technological cycle components, theequipment may run steadily or dynamically.

The specific mean power potential correlatedon the working cycle is equal to the sum of thespecific mean potentials for the tractoraggregation (with bulldozer, scarifier orscraper) given in the equation:

3

0,1

sp sp ii

P P

== (4.7)


22/108


unde: i este funcia de corelaie , corespunztoareagregrii tractorului n procesul de spareGreutate medie a pmntului spat raportat laputere [2] :

/Trp a spg G G P =

(4.8)

- -unde : GTr , Ga este media matematic a greutiipmntului transportat pe ciclul tehnologic ,respectiv greutatea agregatului tractor echipament ( care este determinata de masaaparenta corespunzatoare regimului dinamic alutilajului ).Media factorului de greutate al pmantului spat ,

va depinde la rndul ei de aderen , distana despare prin funciile de distribuie la categoriarespectiv de utilaje :

( ) ( )max

max max max

max

R pv

R pi

S

p p R p R R pS

g g F F S d d dS

= (4.9)

unde: funciile F(Rmax ) i F( Sp) respectdistribuia Waibull specific proceselor de lucru lautilajele de spat i transportat , determinatexperimental n [2] .

5. Comentarii

1.THM la utilajele de spat i transportat lucreazpe toate treptele de viteze ale transmisiei. Pentrubuldozer cu scarificator, iTH ia valori apropiate [2]ntre 0.76 0.79.2. Utilajele de spat i transportat execut spareapmntului cu patinarea roilor motoare. Pentrucalculul forei de traciune n funcie de aderense ia n considerare patinarea roilor n regim de20, 30, 70 sau 100% .3. Fora de rezisten global la rulare Ff i fora

critic dezvoltat la spare Fcr pentru transmisiilehidromecanice sunt funcie de viteza de transport VT .Fora de rezisten global la rulare n regim detransport depinde de :

Ff= Ff[VT(T)] = Ff(VT) (5.1)

4. Aciunea forelor de rezistent n procesul dencrcare a cupei este un proces aleator. Aceastafaz de lucru ( la fel ca i la screper), este cea maisolicitant din punct de vedere dinamic pentrusistemul de acionare a mainii (fig.3).

where: i is the correlation functioncorresponding to the tractor aggregation duringthe digging process.The ration of the medium dug soil weight and

the power [2]:

/Trp a spg G G P =

(4.8)

where: GTr, Ga the mathematical average ofthe soil weight transported on the technologicalcycle, and the tractor-equipment weight,respectively (determined by the apparent masscorresponding to the dynamic regime of theequipment).The average weight factor of the sunken soil

also depends on the adherence and diggingdistance, by means of the distribution functionsof the respective equipment category:

( ) ( )max

max max max

max

R pv

R pi

S

p p R p R R pS

g F F S d d dS

= (4.9

where: functions F(Rmax) and F(Sp) keep theWaibull distribution of the working process ofthe digging and transport equipment,experimentally determined in [2].

5. Comments

1. For the digging and transport machinesequipped with THM, working on all operatingstages (scarified) iTH has close values between0.76 0.74 according to [2].2. The digging and transport units sink the soilby driver sliding. To estimate the drive forcedepending on the adherence, the wheel slidingin a 20, 30, 70 or 400% regime is in use.3. The digging global resistance force fortractors (Ff) and the critical sinking force (Fcr)

for hydromechanics transmission depend on thetransport speed VT.Ff= Ff[VT(T)] = Ff(VT) (5.1)

4. The action of resistance forces in the bucketloading process is a random process. Thisworking phase (as in the case of scrapers) is thetoughest from a dynamic point of view for thecontrol drive system of the machine (fig.3).


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Fig.3. Diagrama indicatorilor de calitate pe regimul de lucru real bazat pe evaluarea i analiza statistic a valorilorparametrilor consumului de putere pentru incrctorul frontal (la nisip i pamnt) ; pe fiecare regim tranzitoriu de lucru real :

deplasare cu cupa goal, ncrcare cupi retragere cu cupa plin [1].

Diagram of the quality indices on the real working state based on the assessment and analysis of thepower consumption for the frontal loader (for sand and soil) ; on each transient working

state : movement with the empty bucket, loaded bucket and retreat with a full bucket [1].

5.Unele rezultate obinute din studiile efectuate n[2], asupra performanelor de lucru a utilajelor despat i transportat , care folosesc motoare Dieseli THM cu diferite caracteristici [i variaiaparametrilor (Psp , gp , Cs) = f(iM) ] sunt prezentaten figura 4.

Coeficientul solicitarii transmisiei hidrtomecaniceTHM comparativ cu cea mecanica TM este dat de

relaia (5.2). Variaia sa fiind prezentat n fig.4[2]:mecanica TM este dat de relaia (5.2). Variaiasa fiind prezentat n fig.4,c [2]:

100 1 spTMsspTHM

PC

P

=

(5.2)

5. Some of the results of the studies made in [2]about the operating performances of the diggingand transport units using Diesel engines andTHM with different characteristics [and theparameters variation (Psp , gp , Cs) = f(iM) ] areshown in fig. 4

The coefficient of the THM hydromechanicstransmission stress compared to the mechanic

TM is given by the relation (5.2). Its variation isshown in Fig.4,c [2]:

100 1 spTMsspTHM

PC

P

=

(5.2)


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Fig 4. Variaia parametrilor Psp,gp,Cs n funcie de iM : a) un singur raport de transmisie ; b) mai multe rapoarte detransmisie ; c) numai unul (curba 1) , dou rapoarte (curba 2,I TM ; curba 2,II THM)[2] Psp puterea specificmedie la TM; Psp,t puterea specific medie la THM; gp factorul de greutate medie al pmantului spat ; Cs coeficientul de solicitare a transmisiei TM-THM.

Variation of parameters Psp,gp,Cs depending on iM: a single transmission ratio; b) several transmission ratios; c) only oneratio (curve 1), two ratios (curve 2, I TM/3, curve 2, II THM); Psp mean specific power for TM; Psp,t mean specific

power for THM; gp mean weight factor of sunk soil; Cs coefficient of transmission stress TM-THM

Les performances en rgime dynamique de travail des utillages ncessaires au piochage et au transport pour laconstruction des chemins (I)

RsumL article propose lanalyse du modle dynamique de moteur diesel-transmission hydrodynamique (THM)-sol, pour desoutillages de piochage et de transport (UST).Lanalyse du fonctionnement des machines est fonde sur les elements du cycle technologique de travail en rgime rel.On port du potentiel et du bilan nergetique du tracteur en agrgat avec des quipments diffrents.On dtermine ensuite la consolidation des critrions de performance en rgime rel de fonctionnement.

Bibliografie:

[1]. DEBELEAC,C. - O metod nou de analiz a performanei n regim dinamic a ncrctoarelor frontale,SINUC 2006, Universitatea Tehnic de Construcii Bucureti, Facultatea Utilaj Tehnologic, dec.2006.

[2]. GHINZBURG, IU,V. s.a.- Promisiennie Tractor, Moscova, Masinostroenie, 1986.

[3]. SARBU, L. Maini de traciune i transport pentru construcii, Vol. 1+2, Editura Ion Creanga,Bucureti, 2002.

[4]. *** - CASE Construction Equipment, Professional Partner, Printed, in Italy, 2006.

[5]. *** - Komatsu Krauler Dozer D 65 Ex-15/D65 Px-15, 16p.

[6]. *** - D3G, D4G, D5G, Trak-Type Tractors, Gros power 57,65,74 kw, Caterpillar, 2003.

[7]. *** - 950H wheel loader caterpillar, C7 Diesel Engine with ACERT Technology, Bucket capacities1,7 to, 4,6 cm, Caterpillar, 2006.

[8]. *** - Wheel loader WA 700-3 Komatsu, Flywheel Horse-power 478 kw (641 CP), Bucketcapacities 8,7 to, 9,4 mc, Komatsu Europe International, Printed in Belgium, 2001.


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Performanele n regim dinamic delucru a utilajelor de spat i transportatpentru construcii drumuri (II)

Performance of digging and transportingmachines in a dynamic working regimefor road - construction (II)

Sarbu Lurentiu, prof.univ.dr.ing. Facultatea de Utilaj Tehnologic, Universitatea Tehnic de Construcii BucuretiProfessor Dr., Faculty of Machine Tools, Technical University of Civil Engineering Bucharest, e-mail:[email protected]

1.Introducere

Una din problemele fundamentale ale calcululuide traciune la utilajele de spat i transportat estedeterminarea puterii motorului, stabilirea

caracteristicilor sale exterioare, i a rapoartelor detransmitere ale transmisiei, care asigur mainiicalitile de traciune necesare.

Se analizeaz modelul dinamic alctuit din:motor termic- transmisie hidromecanic THM -sol pentru utilajele de spat i transportat lafuncionarea lor pe elementele componente aleciclului tehnologic de lucru n regim real.

2. Tractiunea screperului cu transmisie

hidromecanic (THM)

Pentru tractorul industrial, care lucreaz cuanumite echipamente (buldozer, buldozer cuscarificator, screper sau ncrctor, etc.) nu seiau n considerare forele de inerie ale maseloraflate n micare de translaie .

Calitile de traciune i de vitez ale tractoruluicuplat cu screperul sunt determinate de [4]:

-caracteristica de regulator a motorului,Fm

* ;-caracteristica exterioar a convertizorului

hidraulic ( CH) ;-raportul de transmitere al prii mecanice

a transmisiei hidromecanice ;-caracteristica forelor motoare .

Pentru calculul de traciune al utilajului sefolosete metoda grafo analitic indicat n [4].

1. Introduction

One of the basic problems of traction calculationis to set the engine power and establish itsexternal characteristics, as well as the rates of

transmission convection that give the car therequired drive features.

This article is aimed at to analyzing the dynamicpattern of the diesel engine- hydromechanicstransmission (THM) soil, for the soil-diggingand transport machines operating on thecomponents of the dynamic technological cyclein a real life regime.

2. Scraper Traction Power with

Hydromechanics Transmission (THM)

For the car frame (industrial tractors) workingwith certain equipment (bulldozer, scarifiers,scrapers, dumpers, etc) the inertia forces of themasses in translation movement are not taken intoaccount.

The drive and speed characteristics of the tractorconnected with the scraper are determined by [4]:

-engine regulating characteristic, Fm*;-external characteristic of the

hydraulic converter (CH)-transmission ratio of the mechanicalpart of hydromechanics transmission

- driving force characteristic

To calculate the equipment traction the graph-analytical method in [4] is used.


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Fig 1. Metoda grafic pentru calculul raportului de transmitere pe treapta I de vitezea screperului cu THM [4]

Graphic method to calculate the transmission ratio on the first speed stage of the scraper with THM [4]

Parametrul principal iniial este caracteristica deieire a cuplului motor convertizor ( cadranul II ,fig. 1) , unde n loc de t se introduce t c , ncare :c randamentul maxim al convertizorului ;t randamentul prii mecanice din THM .

Particularitile calculului de traciune (la asiul cuTHM indicat n [4]), const n determinarearaportului de transmitere al prii mecanice dinTHM pe prima treapt de lucru.

n cadranul II se reprezint caracteristica de ieirea grupului M C n funcie de momentul obinutla roata turbinei Mmt ; Mmp momentul motor lapompa TH ;

Pmp este puterea la pompa TH .

n cadranul I se traseaz curba coeficientului depatinare a roilor motoare . Se determin 001= Fr fora de rezisten la rulare . Pe vertical setraseaz valoarea coeficientului de patinare aroilor motoare p = 100% , care trebuie scorespund lui c , Mmsup , Mminf - sunt valorilemomentului motor superior i inferior pecaracteristica de funcionare comun a motoruluicu THM , ( fig. 1 , cadranul II ) .

The main initial parameter is the outputcharacteristic of the engine-converter (quadrantII V, Fig.) where t c take the place of t,where:c converter maximum outputt mechanical part output from THM

Traction computation features (for the car framewith THM shown in [4]), consists indetermining the ratio of transmitting themechanical part from THM on the first workingstage.

Quadrant II shows the output characteristic forthe M-C group depending on the momentobtained at the turbine wheel Mmt; Mmp =driving moment at pump TH

Pmp = power at pump THIn quadrant I the curve of the drivers slidingcoefficient is drawn. The run resistance force001 = Fr is calculated. The value of the driverssliding coefficient is vertically drawn, p =100%, notably corresponding to c; Mmsup, Mminf- are the upper and lower values of the drivingmoment on the common working characteristicof the engine with THM (Fig. 1, quadrant II).


27/108


Din a1 se duce orizontala care intersecteaz p n a2,se coboar apoi pe vertical i se obine Ft ,adic fora de traciune determinat din condiia deaderen . Valoarea forei nominale de traciune

Ftn = ( 0.7 0.73 ) Ftcorespunde unei patinri p =20% . Se stabilesc n cadranul II , valorile : Pmmax puterea caracteristicii motor convertizor irandamentul cmax , prin punctele a4i a5 .

Calculul raportului general de transmitere a priimecanice a THM , i1 , se face punnd condiia capentru Ftn , regimul de lucru al roilor motoare scoincid cu regimul de lucru M C.

n acest scop , prin a3 se duce o verticali prin a4o orizontal care se ntlnesc n a. Pentru a obinecoincidena regimurilor de lucru, trebuie cadreapta FR s treac prin O1 i a. Deci, raportulgeneral de transmitere al prii mecanice va fi:a) Ft< Ftn , i1= [(Ftn + Fr) r] / ( Mmt t )b) Ft> Ftn , i1= [(Ft + Fr) r] / ( Mmax t ),

(2.1)unde: Mmt este momentul motor la arboreleturbinei corespunztor puterii maxime pecaracteristica M C .

Mmax - este momentul maxim al motorului.

3. Performana n regim dinamic a mainilor despat i transportat n funcie de ciclultehnologic efectuat[1,2].

Pentru regimul tehnologic pe faze patinarea se ia10-30%. Caracteristica de funcionare a motoruluin regim dinamic, corespunde pentru puterileconsumate de tractor + echipament: la patinare Pp= f (Fcr), la nvingerea rezistenei globale Pf =(Fcr,Vt) i pentru mecanismul hidraulic dencrcare Pmh = f ( Pe).Caracteristica de funcionare a motorului n regim

staionar se ia pentru o patinare de 10-30%, uncoeficient maxim de aderen de 0,8-1,1 i uncoeficient de aderen pentru lucrul n agregattractor + echipament de 0,5-0,7.La ncrctoarele frontale, fundamentareacriteriilori indicilor de performan n regim realde funcionare are la baz evaluarea i analizaevoluiei valorilor parametrilor statistici pentruputerea necesar sistemului de acionare almainii, care cuprinde influenele datorate tuturorperturbaiilor interne i externe ale sistemuluiconsiderat, bazate att pe traciunea utilajului n

procesul de spare dari pe manipularea

From a1 the horizontal which crosses p in a2 isdrawn; it descends on the vertical axis and weget Ft, i.e. the traction force stated from theadherence condition. The nominal traction force

value Ftn = (0.7-0.73) Ft corresponds to asliding movement of p = 20%. In quadrant II thefollowing values are set: Pmmax the power ofengine-converter characteristic, along withoutput cmax, through points a4 and a5.

The general transmission computation ratio for themechanical part of THM, i1 is done provided thatfor Ftn , the M-C working regime stays the same.

For this, a vertical axis is drawn through a3 and ahorizontal through a4 that meet in a. To gain acoincidence of the working regimes, the straightline FRmust pass through O1 and a. So, the generaltransmission ratio of the mechanical part is:a) Ft< Ftn , i1= [(Ftn + Fr) r] / ( Mmt t )b) Ft> Ftn , i1= [(Ft + Fr) r] / ( Mmax t ),

(2.1)where: Mmt is the driving moment at the levelof the turbine shaft corresponding to amaximum power with M-C characteristic.

Mmax - engine maximum moment

3. Performance of digging and transportingmachines in a dynamic regime according tothe technological working cycle [1,2].

For the technological regime on phases thesliding takes values between 10-30%. Theworking characteristics of the engine in a realtime regime correspond for the consumed powervalues of the tractor + equipment aggregate:-in sliding mode Pp = f (Fcr), exceeding globalresistance Pf = (Fcr,Vt) and for the hydraulicloading equipment Pmh = f ( Pe).The operational characteristic of the engine inreal time regime is taken for a slide between 10-30%, an adherence coefficient of maximumvalue between 0,8-1,1 and an adherencecoefficient for functioning in the tractor +equipment unit of 0,5-0,7.At frontal loaders, the appraisal of criteria andperformance parameters in real time operationalregime is based on the assessment and analysisof the statistic parameters values, which includesthe influences caused by all internal and external

perturbations


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echipamentului de ncrcare n procesultehnologic. Aciunea forelor de rezisten nprocesul de ncrcare a cupei este un procesaleator. Aceast faz de lucru (la fel ca i la

screper), este cea mai solicitant din punct devedere dinamic pentru sistemul de actionare amainii.Aciunea are ca rezultat producerea efectelordinamice diferite ca intensitate, de la o faz delucru la alta. Aceste efecte dinamice se pot evaluacu ajutorul indicilor de performan n regimdinamic real de lucru al utilajulului [1]:- indicele mediu de utilizare static a puterii, i1 ;- indicele mediu de utilizare dinamic a puterii,i2 ;- indicele mediu real de utilizare a puterii, i3;- indicele mediu de multiplicare dinamic aputerii, i4 .Valoarea indicilor de performan aincrctoarelor frontale rapide se analizeazpentru fiecare faz a procesului tehnologic delucru (v. graficul din fig.3, Partea I).Pentru stabilirea modelului matematic de lucru altractorului industrial (cu THM) cu echipamente deconstrucii drumuri , n lucrarea [2] se porneteconsidernd regimul dinamic de traciune altractorului n agregat cu echipamentul buldozer scarificator .

Se consider funcionarea acestuia pe elementeleciclului tehnologic de exploatare. Pentru a nvingerezistena total la naintare, fora de traciune peelementele ciclului este asigurat cu ajutorulrapoartelor de transmitere. n [2] se folosetenoiunea de factor de transmitere iM pentrutreptele de viteze, deoarece la proiectarea unuiutilaj nou nu se tie nc raza roii motoare ( iM = it/ rR), cu ajutorul cruia se obine fora de traciunenecesar pentru spare transport a materialului ise determin potenialul energetic pe ciclul

tehnologic de lucru .

Potenialul energetic specific mediu pe treptele delucru este o funcie care ine seama de: factorii detransmitere ai tractorului, de aderena maxim laroat pe treptele de viteze folosite. El esteapreciat cu ajutorul schemei de lucru a transmisieiindicat in figura 2: a) TM i b) THM], i distanade spare [2].Potenialul energetic specific mediu este egal cusuma potenialelor energetice pe treptele de viteze

care depind de distribuia aderenei

of the considered system, based on the machinetraction during the digging process and on thehandling of the loading equipment during thetechnological process. This work phase (the

same as for scrapers) is the toughest, from adynamic point of view, for the control drivesystem of the machine.The action has as a result the production ofdynamic effects with different intensity fromone phase to another. These dynamic effects canbe assessed with help of performanceparameters in the real time working regime ofthe machine [1] .-the average parameter of static usage of poweri1;-the mean parameter of dynamic usage of poweri2;-the mean real usage parameter of power i3;-the average dynamic multiplication powerparameter i4The value of performance parameters of fast-frontal-loaders is analyzed for each phase of thetechnological working process (fig.3, Part I).To set the mathematical working pattern for theindustrial tractor (with THM) with road-building equipment, in paper [2] the dynamicregime of the tractor with bulldozer scarifier istaken into account.

Its operation is set on the components of thetechnological cycle in use. To overcome thetotal road resistance the traction force on thecycle components is ensured with the help oftransmission ratios. Paper [2] uses the term oftransmission factor (iM) for speed stages,because when designing a new machine tool thedriver radius is not known yet (iM = it/tR); this isused to set the traction force necessary fordigging and transport, and to determine thepower potential on the technological cycle.

The specific average power potential onworking stages is a function of the tractortransmitting factors, of the wheel maximumadherence on the used speed stages: see Fig 2:a) TM and b) THM, and the digging distance,respectively [2].

The specific average power potential is equalwith the sum of the power potentials on thespeed stages depending on the adherence


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i a distanei de spare n funcie de tipul deagregare al tractorului cu echipamentul (relatia 4.1,partea I)Limitele de integrare ale funciei de aderen sunt

mprite de la Rmaxi ( pe treptele de vitezeinferioare cu patinare ) la RmaxV ( corespunztoarevitezei de transport) .n cazul screperului sau buldozerului cu scarificator,ciclul de lucru const n sparea pmntului (sauscarificare) urmat de transportul acestuia i apoideplasarea n gol pentru reluarea cicluluitehnologic. THM poate funciona pe toate treptelede transmitere. Raportul de transmitere iTH al priihidraulice a transmisiei se schimb n procesul despare transport n funcie de caracteristica de

lucru a TH

Acceleraia i viteza medie THj

i TH

la

funcionarea THM ( pentru. spare transport ) suntexprimate n funcie de: puterea mainii , viteza detransport i legile de distribuie ale aderenei pedistana de spare (v. relatiile 4.2-4.3, ParteaI).Calitile de traciune vitez ale tractorului (cuTHM) cu echipamente de spat i transportat ,specifice analizei regimurilor dinamice de lucru ,sunt determinate de caracteristicile medii de

funcionare ale ansamblului motor transmisie ,exprimate n funcie de aderena roilori legea dedistribuie a acesteia ; ele fiind indicate n [2] subforma :-Momentul motor mediu dezvoltat din condiia deaderen a utilajului( pct.1)

( ) ( )max

0

R

m m R R RM f d

= (3.1)

-Puterea medie dezvoltat la turbina TH dincondiia de aderen a utilajului :

( ) ( )max

0

R

T T R R RN N f d

= (3.2)

-Turaia medie la arbore a turbinei TH din condiiade aderen a utilajului :

( ) ( )max

0

R

T T R R Rn n f d

= (3.3)

-Raportul de transmitere mediu al TH din condiiade aderen a utilajului (pct.1) :

distribution and digging distance, according tothe type of equipment connected to the tractor(4.1, part I).The integration limits of the adherence function

are from Rmaxi (on lower speed stages forsliding operation) to RmaxV (corresponding tothe technological transport speed).For scrapers and scarifiers, the working cyclemeans the earth digging (or scarifying), itstransportation and idle movement to restart thetechnological cycle. THM may work on alldrive stages. The transmission ratio iTH of thehydraulic part is changed during the digging-transport process according to the workingcharacteristic of TH.

The mean acceleration and speed, THj

and

TH

at THM operation (for digging-transport)

depend on: car power, transport speed anddistribution laws of the adherence functionalong the digging distance. (These are done 4.2-4.3, Part I [2]).The traction-speed tractor features (with THM)with digging and transport units specific forthe analysis of working dynamic regimes, are

determined by the mean operatingcharacteristics of the engine-transmissionassembly, depending on the wheel adherence aswell as on its distribution law; they are shown in[2] as follows:-The necessary mean motor moment expandedfrom the implement adherence condition (pt. 1):

( ) ( )max

0

R

m m R R RM f d

= (3.1)

-The mean power expanded at the TH turbine

derived from the adherence condition:

( ) ( )max

0

R

T T R R RN N f d

= (3.2)

-Mean rotation speed of TH turbine shaftderived from the adherence condition:

( ) ( )max

0

R

T T R R Rn n f d

= (3.3)

-Mean transmission ratio of TH hydraulic partderived from the adherence condition (point 1):


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( ) ( )max

0

R

TH TH R R Ri i f d

= (3.4)

-Viteza de deplasare medie a tractorului cu TH din

condiia de aderen (reg. tehnologic) :

( ) ( )max

0

R

d d R R RV V f d

= (3.5)

-Puterea critic medie de traciune din ecuaiabilanului de traciune la funcionarea n regimdinamic ( regim tehnologic de spare):

( ) ( )max

0

R

cr cr R R RN N f d

= (3.6)

4. Modelul dinamic al transmisiei

Schemele dinamice ale transmisiilor pentruautoasiuri echipate cu TM sau THM suntprezentate n figura 2 [2,3]

Ecuaia diferenial a funcionrii tractoruluicu TM redus la arborele motorului este o funciede vitez unghiular a motorului M .

Aceasta are expresia : .MM(M) Ms(t) = ( JM + Jd1 + Jd2 ) M , (4.1)

Unde : MM , Ms este momentul motoruluirespectiv momentul static redus

.M , M viteza unghiular a motorului irespectiv acceleraiaJM momentul de inerie al maselor motorului nmicare de rotaieJd1 momentul de inerie al agregatului ( tractor +echipament), n regim de patinare, redus laarborele motorului

( ) ( )max

0

R

TH TH R R Ri i f d

= (3.4)

-TH-tractor average moving speed from

adherence condition (technological regime):

( ) ( )max

0

R

d d R R RV V f d

= (3.5)

-Men critical traction power from tractionbalance equation when operating in a dynamictransient regime (technological digging regime):

( ) ( )max

0

R

cr cr R R RN N f d

= (3.6)

4 Dynamic Transmission Pattern

The dynamic transmission forms for car frameswith TM or THM are shown in Fig. 2 [2, 3].

The differential equation of TM-tractoroperation, reduced to the engine shaft is afunction of the M angular engine speed.

This is as follows:MM(M) Ms(t) = ( JM + Jd1 + Jd2 ) M , (4.1)

Where: Mm, Ms are the engine momentand reduced static moment, respectively .M , M angular engine speed andacceleration, respectivelyJM inertia moment of engine masses inrotationJd1 aggregate inertia moment (tractor +equipment) in a sliding regime, reduced toengine shaft

Fig 2. Schema dinamic de lucru a transmisiei tractorului : a) mecanic , b) hidromecanic [2] : C cuplajul cufriciune ;CHT cuplajul hidrotransformatorului ; MM momentul motorului diesel ; MS momentul static dat derezistenele la rulare, respectiv rezistena critic la spare (Ff+ Fcr).

Dynamic work diagram of tractor transmission a) mechanical; b) hydro mechanical [2]: C friction clutch;CHT hydraulic transformer clutch; Mm Diesel engine moment; Ms static moment of run resistance,

and of digging critical resistance (Ff+ F

er) respectively.


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Ecuaiile difereniale pentru funcionareatractorului cu THM , sunt exprimate n funcie deviteza unghiular a motorului M , respectiv cea aturbinei TH , T . Ele definesc procesul de lucru

al utilajului cu astfel de transmisii :MM(H) MH = JHM (4.2)MT ( Fcr+ Ff) 1/ ( iMt ) = ( JT + Jd1 + Jd2 ) .T (4.3)Unde: MM momentul de rsucire al motorului ;M viteza unghiular nominal a motorului ;MH , MT momentul de torsiune la arborelepompei , respectiv la turbina TH ;JH , JT momentul de inerie al maselor la arborelepompei , respectiv la arborele turbinei TH ;

H , T viteza unghiular la pomp , respectiv laturbina TH ;Jd1 - momentul de inerie al agregatului , n regimde patinare redus la arborele turbinei ;Jd2 momentul de inerie al masei pmntuluispat i transportat n regim de patinare alutilajului , redus la arborele turbinei ;iM factorul de transmitere (iM = iT / rR) ;t randamentul transmisiei ;Ff , Fcr fora de rezisten global la rulare ,respective fora critic dezvoltat la spare de

organul de lucru .Utilizarea ambreiajului mecanic montat in schemadin fig. 2,b, la THM, are drept scop schimbareatreptelor n cutia de viteze fr ocuri. Pentrucalculul procesului de ambreiere al THM sefolosete schema din fig. 2,b [3].

5. Observaii asupra modelelor prezentate

1.THM la utilajele de spat i transportat lucreazpe toate treptele de viteze. Pentru buldozer cu

scarificator, iTH ia valori apropiate [2] ntre 0.76 0.79.2. La schimbarea treptelor de viteze pentrueliminarea ocurilor n transmisie se monteaz nschema cinematic un ambreiaj mecanic dup TH,care decupleaza motorul de restul transmisiei .

Caracteristica de patinare a ambreiajuluimecanic la schimbarea vitezelor este dat subdiferite forme[2]:

. . . = [vT , T] = (T) ; = [T , T] (5.1.)

The differential equations for a THM-tractoroperation depend on the M angular enginespeed and TH turbine t respectively. Theyshow the operating process of the implement

with such transmission:MM(H) MH = JHM (4.2)MT ( Fcr+ Ff) 1/ ( iMt) = (JT + Jd1 + Jd2) .T (4.3)Where: MM engine twisting momentM engine nominal angular speed;MH. MT torsion moment at pump shaft andTH turbine, respectively;JH, JT mass inertia moment at pump shaft andTH turbine shaft, respectively;

H, T angular speed at pump and TH turbine,respectively;Jd1 aggregate inertia moment, in reducedsliding at turbine shaft;Jd2 mass inertia moment of the soil dug andtransported in a machine sliding regime,reduced at the level of the turbine shaft:iM transmission factor (iM = iT/rR);t transmission outputFf, Fcr = global resistance force at running andcritical force expanded at digging, respectively.

The use of the mechanical clutch (see diagramin fig 2,b) for THM is meant to assist the gearstage change. To calculate the THM clutchprocess the dynamic scheme in Fig 2,.b [3] isused.

5. Observation about the present patterns.

1. For the digging and transport implementsequipped with THM, working on all operating

stages (scarifier) iTH has close values between0.76 0.74 according to [2].2. When changing the speed stages to avoid thetransmission shocks a mechanic clutch ismounted in the kinematical diagram after theTM, which releases the engine from the drive.

The sliding characteristic of themechanical clutch at speed change is doneunder different forms [2]:

. . . = [vT,T] = (T) ; = [T, T] (5.1.)


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3. Fora de rezisten global la rulare Ff i foracritic dezvoltat la spare Fcr pentru transmisiilehidromecanice sunt funcie de viteza de transportVT .

Fora de rezisten global la rulare n regim detransport depinde de :

Ff= Ff[VT(T)] = Ff(VT) (5.2)4. Pentru tractoarele cu THM care lucreaz nagregat cu echipamente de spat i transportat,ecuaiile integro diferenial ale transmisiei(THM) au urmtoarea forma [2]

. . . . .1[H , T , H , T ,(T , T),Ff(T , T),JH(T , T)] = 0

. . . . .

1[H , T , H , T ,(T , T),Ff(T , T),JH(T , T)] = 0

(5.3)Relaiile (4.3.) reprezint un sistem deecuaii neliniare care se rezolv prin metodelecunoscute. La rezolvarea sistemului de ecuaiipasul timpilor de integrare se ia t = 0.01s .

Intervalele de variaie pentru patinarea aambreiajului mecanic i a rezistenei la rulare sepot lua ntre 0.005 0.01s .

5. Unele rezultate obinute asupra performanelorde lucru a utilajelor de spat i transportat, care

folosesc motoare Diesel i TM sau THM (cudiferite caracteristici), i variaia parametrilor (Psp,gp , Ca) = f(iM) sunt prezentate n figurile 3 si 4.

Fig 3. Variaia parametrilor Psp,gp funcie de iM ,Rmax = 0.95 i coeficientul de adaptabilitate al

motorului Ca la tractor cu TM : curba(1) Ca = 1.17;curba(2)-Ca= 1.3 ; curba(3) Ca = 1.5 [2].

Variation of parameters Psp, g, dependent on iM, Rmax= 0.95,and coefficient of adjusting Ca engine to a tractor withTM curve (1) Ca = 1.17; curve (2) Ca = 1.3, curve (3)

Ca = 1.5 [2]

3. The running global resistance force fortractors (Ff) and the critical digging force (Fcr)for hydromechanics transmissions depend on

the transport speed VT.The running global resistance force in atransport regime depends on:

Ff= Ff[VT

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