In: Civil Engineering
The 45∘ strain rosette is mounted on the surface of a shell. The
following readings are obtained for each gage: ϵa=−200(10−6),
ϵb=300(10−6), and ϵc=250(10−6)
Determine the in-plane principal strains
Ans) Gicen,
a
= -200 x 10^(-6)
b
= 300 x 10^(-6)
c
= 250 x 10^(-6)
Since, the rosette is arranged at 45 degree,
x
=
a
y =
c
xy
= 2
b
- (
a
+
c)
Putting given values,
x
=
a = -200 x 10^(-6)
y =
c = 250 x 10^(-6)
xy
= 2
b
- (
a
+
c) = 2(300) x 10^(-6) - ((-200 + 250) x 10^(-6)) = 550 x
10^(-6)
Now,
tan 2
=
xy
/ (
x
-
y)
=> tan 2
= 550 / (-200 - 250) = -1.222
=> 2
= arctan(-1.222) = -50.70 degree
=>
= -25.35 degree
Hence,
' = 90 +
= 90 - 25.35 = 64.65 degree
Also,
= [(
x
+
y) / 2] + [(
x
-
y) /2] Cos 2
+ (
xy/2)Sin
2
Putting values,
=>
= [(-200 + 250) / 2 + [(-200 - 250)/2] Cos(-50.70) +
(550/2)Sin(-50.70)] x 10^(-6)
=>
= (25 + 142.51 - 212.80) x 10^(-6)
=>
= -45.29 x 10^(-6)
Now,
' =
x +
y -
=>
' = (-200 + 250 - (-45.29)) x 10^(-6)
=>
' = 95.29 x 10^(-6)