Material Properties: Stress Strain Curve Analysis

[vm2007]

Hi,

I need to use a load deflection curve to determine the material properties of a elastic material. The stress strain is far from being linear. Any suggestions??

 

[FredGarvin]

I'd have to see the curve. Is it for something like copper?

 

[Astronuc]

Hi,

I need to use a load deflection curve to determine the material properties of a elastic material. The stress strain is far from being linear. Any suggestions??

What material - metal, ceramic, polymer, . . . ?

Metals are exhibit linear elasticity up to the point where yielding occurs, however there is always some small amount of plasticity, or permanent deformation.

Besides the elastic modulus (Young's modulus), yield point (yield strength), and possibly Poisson's ratio, ultimate tensile strength, uniform and total elongation, what material property is one wishing to determine?

 

[vm2007]

its actually for a elastic polymer. I recived the load deflection curve (compression). and I need to obtain the material properties from it. ie. youngs modulus and poisson's ratio. any advice?
the curve is initially fairly linear, then rapidly increaces exponentially. I have the sectionally properties of the test piece.

 

[Vanechka]

... you can determine Young's modulus from the slope of the initial linear part, but other than that - especially the Poisson's ratio - you need some complementary information like for example about deformation in another principal-direction, or the shear modulus or so on (take a look at the "basic" equations of elasticity theory and the relations between these properties - so far it doesn't seem like you should be doing anything with the nonlinearities of the curve but they're there for "realistic feel" ). Like Fred said, seeing the information you've available would help get deeper in getting to the roots of it all.

 

[vm2007]

thanks Vanechka... I think it might be wise for me to try to contact the manufacturer of the polymer to get a little more information.

 

[Gokul43201]

1. What is the exact material?
2. Can you attach the load deflection curve?
3. If you can, also include the testing specs.
4. What is the end use - include typical loading conditions.

 

[tospok]

It may not be safe to get the first portion to calculate Youngs moduslus, there can be some distortion in the first part due to test machines internal dynamics. First be sure that graph is free from that.