Stress strain

[mike0123m]

This is probably really simple but I'm just not seeing it. What error is made if you measure strain at a point ex and estimate the stress as Eex where E is young's modulus?

 

[civilperson]

None, if the measurement is unitless, (inch/inch or %).

 

[hokie66]

That's correct, as long as you are in the elastic range and the material has a straight line up to yield.

 

[prost]

Depends on the strain field where you put the gage--is the strain in a uniaxial strain field (say the gage section of a dogbone coupon), so that the x-direction is the only direction with non-zero stress? If so, you can use E*ex=sigma-x to estimate normal stress in the x-direction. Otherwise, it's more complicated than that.