# Homework Help: Stress strain laboratory question

1. Oct 8, 2012

### xzibition8612

1. The problem statement, all variables and given/known data
Establish the constitutive relationship for the cantilever beam material, i.e., provide an empirical formula for the relationship σxxxxxx) and generate a plot of this relationship. What is the cantilever beam material?
2. Relevant equations
This is a pure beam bending theory lab, rosette gauge on beam with loads and displacements from a precision micrometer.

3. The attempt at a solution
Not really sure what this question is asking. Also I'm confused about the equation. Wouldn't the stress xx just cancel out and εxx=1?? I got a bunch of data on the beam from the rosette gauge, but I don't really get this question. Any help on shedding what its asking would be great. thanks.

2. Oct 8, 2012

### Undoubtedly0

Greetings xzibition8612! The notation $\sigma_{xx}(\epsilon_{xx})$ means "find $\sigma_{xx}$ as a function of $\epsilon_{xx}$". For example, a beam under uniaxial tension might obey $\sigma_{xx}(\epsilon_{xx}) = E\epsilon_{xx}$, where $E$ is the elastic modulus.

3. Oct 8, 2012

### xzibition8612

alright i figured it out using your formula. So this is my result. Now the question is what kind of material follows this graph? Anyone know or where can i find this info? By the way strain is in micro strain, or 10^-6.

thanks

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4. Oct 9, 2012

### Undoubtedly0

Given your graph you should be able to find the elastic modulus of the material. Then you may need to consult some tables to see which material has that same elastic modulus.