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MĂSURAREA FORŢELOR PRIN
METODA TENSOMETRIEIELECTRICE REZISTIVE
Prof.univ.dr.ing. Kov!" Io"if
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PRINCIPIUL TENSOMETRIEI ELECTRICE REZISTIVE
M#"urr$ %#ri%i&or n$$&$!'ri!$ (%$!ni!$)!u"'i!$) *idru&i!$) +n$u%'i!$) $'!., "$ +o'$ r$&i-!u %r$ +r$!i-i$ !u u'oru& unor %$'od$ d$ %#"urr$
+$ !&$ $&$!'ri!#.Un din !$"'$ %$'od$ (!$ %i r#"+/ndi'# 0n
+r!'i!#, o r$+r$-in'# %$'od '$n"o%$'ri$i $&$!'ri!$r$-i"'iv$) !r$ "$ 1-$-# +$ fo&o"ir$ unor 'rdu!'or$'$n"o%$'ri!$ r$-i"'iv$) nu%i'$ 2i 'i%1r$ '$n"o%$'ri!$.A!$"'$ u +ro+ri$''$ d$ 32i "!*i%1 r$-i"'$n4o*%i!# d!# "un' "u+u"$ unor d$for%4ii (0n'ind$r$)!o%+r$"iun$,.
5n figur 6 "un' +r$-$n''$ dif$ri'$ for%$ d$'i%1r$ '$n"o%$'ri!$.5n figur 7 $"'$ d' un $8$%+&u "i%+&u d$
"o&i!i'r$ un$i 1r$ 0n!"'r'$ d$ !#'r$ for4 F 0n"$!4iun$ S3S. D!# for4 r$+r$-in'# un v$!'or &$'or!r$ 02i "!*i%1# 0n 'i%+ %#ri%$) dir$!4i 2i "$n"u&du+# o &$gi''$ n$!uno"!u'#) 'un!i n$!$"i'#0nr$gi"'rr$ v&ori&or for4$i 2i +oi "'udiu& digr%$i
0nr$gi"'r'$. Li+ind 'i%1r$&$ '$n"o%$'ri!$ T6 2i T7 +$ 1r# 0n "$!4iun$ S3S 2i f#!/nd &$g#'ur &or $&$!'ri!#0n'r3o +un'$ !onfor% figurii 9) !u u'oru& unui +r'0nr$gi"'r'or "$ 0nr$gi"'r$-# un "$%n& !r$ $"'$ +ro+or4ion& !u v&or$ for4$i F.
A"'f$& "$ +o' %#"ur 2i 0nr$gi"'r +rin'r3un "$%n&$&$!'ri! %o%$n'$ 0n!ovoi'or$) +r$"iuni) %o%$n'$ d$'or"iun$) $'!.
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Din%o%$'ru '$n"o%$'ri!
Mon'r$ 'rdu!'or$&or '$n"o%$'ri!$ r$-i"'iv$
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Din%o%$'ru& '$n"o%$'ri! r$&i-'
S!*$% 1&o! in"'&4i$i $&$!'ri!$ d$ %#"urr$
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In"'&4i$ $&$!'ri!# d$ %#"urr$ !u o"!i&ogrf
In"'&4i$ $&$!'ri!# d$ %#"urr$ !u !&!u&'or
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ETALONAREA
E'&onr$ "i"'$%u&ui d$ %#"urr$ +$n'ru F8
E'&onr$ !u di"+o-i'iv +$n'ru F8
E'&onr$ !u di"+o-i'iv +$n'ru F<
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Tr$+'$ d$ for4# & $'&onr$
Cur1$ d$ $'&onr$ +$n'ru for4 F8
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FILTRARE
Fi&'ru 'i+ T ='r$!$ o"> & in"'&4i$i d$ %#"urr$
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5NRE;ISTRAREA FORŢELOR
Digr%$ 0nr$gi"'r'$ d$ for4$ Digr%$ !u 'r$+'$ d$ for4#
Digr%$ 0nr$gi"'r'$ !u v&ori $'&on'$Digr%$ !u 'i%+u& d$ 0nr$gi"'rr$ %r!'
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Digr%# 0nr$gi"'r'# +$n'ru for4 d$ '#i$r$
Digr%# d$ for4# !u !roiu& d$ $'&onr$
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DETERMINAREA VALORILOR CARACTERISTICE
Determinarea experimentală a forţelor de tăiere x
For4$&$ d$ '#i$r$ F8 !4ion$-# 'ng$n4i& & 'ri$!'ori din'$&ui d$ +$ !u+ $8!v'oru&ui) r$ vri4i$
&$'or$) i nu%i v&ori +o-i'iv$ !$$ !$ 0n"$%n# !# "$ o+un$ d$+&"#rii din'$&ui 0n %"iv 2i r$ v&ori&$ 1"o&u'$!$&$ %i %ri din'r$ !o%+on$n'$&$ for4$i r$-u&'n'$ !$ !4ion$-# +$ un din'$ f&' 0n'r3o +o-i4i$ r$&'iv# or$!r$ f4#d$ %"ivu& d$ ro!#.
5n 'i%+u& 0n!$r!#ri&or in"'&4i d$ %#"urr$ 0nr$gi"'r$-# 0n 'i%+ vri4i !$"'$i for4$) "i%u&'n !u!$&$&&'$ dou# !o%+on$n'$.
5n figur ? "$ +r$-in'# o digr%# d$ +rin!i+iu vri4i$i 0n 'i%+ for4$i d$ '#i$r$ F8. P$ !$"'#digr%# "un' %r!'$@ v&or$ %8i%# F8 %8) !or$"+un-#'or$ 0n#&4i%ii %8i%$ *%8) 0n %%) v/rfu&ui d$ for4#)
v&or$ %$di$ F8 %v v/rfuri&or) !or$"+un-#'or$ 0n#&4i%ii *%v) 0n %%) 2i v&or$ %$di$ $f$!'iv# F8%)!or$"+un-#'or$ 0n#&4i%ii %$dii *%) 0n %%. P$ 8 1"!i"$&or $"'$ %r!' 'i%+u& '6) 0n ") d$ 0n!$+$r$ '#i$rii)!or$"+un-#'or &ungi%ii d$ digr%# &6) 0n %%) 2i 'i%+u& '7) 0n ") d$ d$'$r%inr$ '#i$rii) !or$"+un-#'or &ungi%ii d$digr%# &7) 0n %%) ir Ω8) 0n %%7) r$+r$-in'# ri "u+rf$4$i din'r$ !ur1 d$ vri4i$ &ui F8 2i 8 'i%+u&ui 0nin'$rv&u& '6...'7.
Fig. ?. Digr% d$ vri4i$ for4$i F8
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V&ori&$ for4$&or %8i%$ 2i %$dii "$ d$'$r%in# din d'$&$ !on4inu'$ 0n digr% 0nr$gi"'r'#)du+# !u% ur%$-#@
For4 %8i%# d$ '#i$r$@) N (6,
und$ "8 r$+r$-in'# !o$fi!i$n'u& d$ "!r# 0nr$gi"'r#rii) 0n NB%%) +$ !n&u& for4$i F8) !$ r$-u&'# din$'&onr$ in"'&4i$i d$ %#"urr$30nr$gi"'rr$.
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5n +r!'i!#) & +r$&u!rr$ digr%$&or 0nr$gi"'r'$ "3 u'i&i-' un "of'r$ d$!v' +r$&u!r#ri&or "''i"'i!$)!r$ "3u $f$!'u' !u u'oru& unui !&!u&'or $&$!'roni! PC.
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Determinarea experimentală a forţelor de pătr!ndere "
For4$&$ d$ +#'rund$r$ F< !4ion$-# du+# nor%& & 'ri$!'ori din'$&ui d$ +$ !u+ $8!v'oru&ui)r$ vri4i$ &$'or$) +o'$ &u v&ori +o-i'iv$ ("$ o+un$ +#'rund$rii din'$&ui 0n %"iv, 2i v&ori n$g'iv$ (u'#
+#'rund$r$ din'$&ui 0n %"iv d'ori'# +#"#rii 2!*i$i +$ "u+rf4 d$ d$gr$ din'$&ui,.5n figur "$ +r$-in'# o digr%# d$ +rin!i+iu vri4i$i 0n 'i%+ for4$i d$ +#'rund$r$ F
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)N (,
P$n'ru $8+&i!i'r$ %i f!i for4$&or d$ +#'rund$r$ F
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Fig. H. Digr% d$ vri4i$ for4$i F-
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