- #1

Confusedbiomedeng

## Homework Statement

consider the rectangular bar undeformed a=b=2cm and c=20cm . The elastic modulus of the bar material is E=100 Gpa and its poissons ratio is u=0.3. The bar is subjected to biaxial forces in the x and y directions such that Fx=Fy=0.4x10

^{6}N and that Fx is tensile while Fy is compressive . Assuming that the bar material is linear elastic

Determine:

i)the average normal stresses σx,σy and σz developed in the bar

ii)the average normal strains ∈x,∈y and ∈z

iii)dimension c' of the bar in the x-direction after deformation

## Homework Equations

σx=fx/(ab) σy=Fy/(cb) σz=no force no stress

∈x=1/E(σx-u(σy+oz))

∈y=1/E(σy-u(σx+σz))

∈z=1/E(σz-u(σx+σy))

∈=ΔL/L

## The Attempt at a Solution

σx=0.4x10

^{6}/0.02x0.02=1x10

^{9}

σy=0.4x10

^{6}/0.2x0.02=1x10

^{8}

σz=no force no stress

using above equation

∈x=9.7

∈y= -2

∈z= -3.3

new c dimension

.-3.3=ΔL/0.2

-0.66

0.2+-0.66= -0.46

however you can't have negative length??

can anyone show me where I am going wrong?