What is Poisson's ratio and how does it relate to stress and strain?

[joemte]

Homework Statement

A tensile test is performed on a 10mm thick sample of nylon with a width of 20mm. The sample was tested to fracture and had a total length of 94mm (original 90mm) at 33kN. Calculate the stress at the point of failure.

Relevant Equations

none.

I'm working through the equations and I have a lot of information missing. I have calculated the longitudinal strain to be 0.4mm (4/90)

is the lateral strain directly proportional to the longitudinal strain? As I need to work out poisson's ratio in order to calculate Bulk modulus, then youngs modulus, then finally stress (stress= E * stain)

I have calculated Shear modulus to be 0.37

 

[scottdave]

Strain is dimensionless (change in length) ÷ (original length). If it is Engineering Stress, the original cross-sectional area is used.