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7/25/2019 Barra Cilindrica
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TEMA:ESFUERZOS COMBINADOS Y MEDICIN DE ESUERZOS
BARRA CILNDRICA BAJO ESFUERZOS DE FLEXIN, TORSIN Y FUERZA
CORTANTE.
OBJETIVO:
Comparar los s!"r#os $%r&'os 'o( los o)$(&*os "$&la(*o la l+ * oo- *l s$a*o
pla(o * s!"r#os.
MARCO TERICO:
Mtodo para determinar la combinacin de esfer!os"
#" S *&)"a l lm($o s$r"'$"ral o * m/0"&(a a a(alar 'o( las !"r#as 1$r(as.$" S sl''&o(a la s''&%( $ra(s2rsal &($r(a *o(* s 2a a ralar l a(/l&s&s *
s!"r#os.%" S ")&'a( las !"r#as + mom($os &($r(os ( la s''&%( 'o( rsp'$o a los s
pr&('&pals, &(*&'a(*o l 'orrspo(*&($ 2alor, *&r''&%( + s($&*o * los m&smos.&" S sl''&o(a l p"($o * la s''&%(, *o(* s *sa o)$(r l s$a*o * s!"r#os.'" S 'al'"la( los s!"r#os &(*&2&*"als 0" pro*"'( 'a*a "(a * las !"r#as +
mom($os &($r(os ( l p"($o sl''&o(a*o para lo '"al s "$&la( las !%rm"las
s$"*&a*as a($r&orm($.
=P
A;=
My
I ; =
T
J ; =
VQ
Ib '"al0"&r o$ra 0" prm&$a *$rm&(ar los s!"r#os (ormals o 'or$a($s ( "(
lm($o s$r"'$"ral.(" Cal'"la*os los s!"r#os &(*&2&*"als s s"ma( o rs$a( los s!"r#os (ormals 3 0"
$(4a( la m&sma *&r''&%(, $am)&5( s p"*( s"mar o rs$ar ($r s6, *p(*&(*o *l
s($&*, los s!"r#os 'or$a($s 7 0" $(4a( la m&sma *&r''&%( 8los m&smos s")6(*&'s9.)" S 'om)&(a los s!"r#os $o$als o)$(&*os a $ra25s *l s$a*o * s!"r#o.
ME*ICI+ *E E,-.ER/O,
Co( la a+"*a * la ros$a * *!orma'&%(.
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E( l a(/l&s&s s s"po( 0"
a
, b
, c
a , b ,c} So( 2alors 'o(o'&*os, o)$(&*os a $ra25s * "(a sol"'&%(
E( 'am)&o los 2alors
x , y , xy } S s"po(( 0" so( 2alors *s'o(o'&*os 0" a'$"ar6a( 'omo &('%4(&$as *l
s&s$ma. S !orma( : '"a'&o(s 'o( : &('%4(&$as.
Sistemas de ecuaciones:
x 1=a=x+y2 +(
xy2 )
cos (2 a )+xy
2 sen (2 a )
x 1=b=x+y2
+( xy2 ) cos (2 b )+xy
2sen (2 b )
x 1=c=x+y
2+(xy2 ) cos (2c )+
xy
2 sen (2 c )
Rs"l$o l s&s$ma s o)$&(( los 2alors * x , y , xy 'o( lo 0" s p"* apl&'ar laLey
de Hooke del estado plano de esfuerzos, para *$rm&(ar los s!"r#os pr/'$&'os x , y , xy ;
x= E
12+(x+ y)
y= E
12+(y+ x)
xy=G (xy )
Do(*;
G= E
2(1+)
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E0.I1O:
Cal&)ra*or p& * r+, !l1%m$ro. = mm.
Lo(4&$"* L>. =@ mm.
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1osicin #
1osicin $
1RE5.+TA, 1ARA E4 I+-ORME:
#" *ib6ar tericamente el estado de esfer!os en el centro de 7ra8edad de la roseta de
deformaciones"
Fy=0V4=0
V=4 [ kg ]
Y
Mz T
V
Z
X
*eformacin 9n7lo
a > 1 =@ > 1 =@ a G
b H 1 =@ H @ 1 =@ b >G
c @ 1 =@ @ 1 =@ c =>G
*eformacin 9n7lo
a a =G
b K 1 =@ K 1 =@ b @G
c 1 =@ 1 =@ c :G
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Mx=0T4(241)=0T=964 [ kg!! ]
M"=0M"4(106)=0M"=424 [ kg!! ]
A=# $2=#(82 )=201,06!!2
I=# %
4
64=
#(16)4
64=3216,99!!4
J=# %
4
32 =
#(16)4
32 =6433,98!!4
En ;#:
-er!a A
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En ;$:
-er!a A
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$" Medir en forma pr=ctica el estado de esfer!os en el centro de 7ra8edad de la roseta
de deformaciones"
1ara la posicin #
42106=x+y
2+( xy2 ) cos (20 & )+
xy
2sen (2 0& )
42106=x+y2
+( xy2 )84106=x+y+xy
84106=2x
x=42106
59106=42106+y
2+(4210
6y2 ) cos (2240)+ xy2 sin(2240)
118106=42106+y+(42106y ) (0.5 )+xy (0.866025 )
118106=21106+1.5y+xy (0.866025)
97106=1.5 y+xy (0.866025)
60106=42106+y
2+(4210
6y2 ) cos (2120)+ xy2 sin(2120)
120106=42106+y+(42106y ) (0.5)xy (0.866025)
120106=21106+1.5yxy (0.866025)
99106=1.5yxy (0.866025)
y=14.666106
xy=137 4093106
x=210109
10.302(42106+0.314.66106 )=8676969.23(
!2=88.45
kg
c !2
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y=210109
10.302(14.66106+(0.3)42106 )=6290869.23 (
!2=6 4.125
kg
c !2
xy=
210109
2 (1+0.3)(137.4093106 )=11098443.5(
!2=113.1335
kg
c !2
1ara la posicin $:
0=x+y
2+(xy2 ) cos (2180& )+
xy
2sen (2 180& )
0=x+y
2+(xy2 )
0=x+y+xy
0=2x
x=0
57106=0+y2
+(0y2 )cos (2 60 )+xy
2sen (2 60& )
114106=y+(y) (0.5 )+xy (0.866025)
114106=1.5y+xy (0.866025)
114106=1.5y+xy(0.866025)
58106=0+y2
+( 0y2 ) cos (2300)+xy
2 sen (2300& )
116106=y+ (y ) (0.5 )xy (0.866025 )
116106=1.5yxy (0.866025)
y=0.6667106
xy=132.7905106
x=210109
10.302(0+0.30.6667106 )=46156.1538 (
!2=0.4704
kg
c!2
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y=210109
10.302(0.6667106+(0.3)0 )=153853.846 (
!2=1.559
kg
c !2
xy=
210109
2 (1+0.3)(132.7905106 )=10725386 .5(
!2=109.330
kg
c!2
%" *eterminar el error porcental entre los esfer!os tericos > pr=cticos"
1nto Esfer!oValor E= (")$%
&" Conclsiones"
La apr'&a'&%( o)$(&*a por los s$r&(4 4a4s s m"+ p0"a, * = @por lo 0" s
p"* 'o('l"&r 0" so( *&spos&$&2os ( los '"als po*rmos o)$(r "( mar4( * rror
a'p$a)l. T%r&'am($ ( los p"($os > + prs($aro( s!"r#os !l'$ors + s!"r#os
'or$a($s m&($ras 0" ( los p"($os = + : solo s prs('&aro( s!"r#os 'or$a($s
por $ors&%( + por la ra''&%( . Los /(4"los a, ), + ' m*&*os ( los s$r&(4 4a4s 'am)&a( ("m5r&'am($ * a
a'"r*o a la pos&'&%( ( la '"al s 'olo0" la )arra *)&*o a 0" s los m&* 'o(
rsp'$o al a1&al ( s($&*o a($& H ?orar&o, s&( m)ar4o s" 'ompro)% 0" s p"*(
"sar los m&smos /(4"los m*&*os ( "(a pos&'&%( para l rs$o * pos&'&o(s. S o)sr2a 0" los $oma*os ( los s$r&(4 4a4s *l la)ora$or&o, (o so( *l $o*o 1a'$os,
*)&*o a 0" ( los '/l'"los (o s prs($aro( s!"r#os a1&als + !l'$ors ( l Y,
m&($ras 0" ( las m*&'&o(s s r4&s$raro( 2alors m"+ )aos 1&s$($s ( *&'?o . Los ma+ors rrors por'($"als s o)$"2&ro( ( l '/l'"lo * los s!"r#os !l'$ors
( las pos&'&o(s > + .
A+EO,:
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Grfica 1 Dispositivo electrnico para medicin de deformaciones en los strain gages
Grfica ! "arra de #cero $structural con la implementacin de la roseta de deformaciones
OB,ERVACIO+E,:
Tra)aar ( "(&*a*s 4, 'm, 4P'm>.