Rosetta gauge for stress strain

Mechaman · Nov 6, 2015

Homework Statement

Typed lab procedure sheet titled Principal Strains and Stresses - Strain Rosette, listing objective, equipment and twelve numbered procedure steps for a cantilever beam experiment.

Homework Equations

Printed page showing two strain equations for a rosette gauge: equation (1) for the three-element rosette with principal strains from measured strains e1, e2, e3, and equation (2) for the rectangular rosette, with variable definitions below.

Scanned lab manual page titled E-103 Principal Strains and Stresses, Flexure, with yellow highlighting on the principal strain and stress equations and a list of equipment and procedure text.

The Attempt at a Solution

Handwritten working on lined paper finding principal strain εp from strains ε1 = 348, ε2 = 482, ε3 = 18 using a square-root formula, ending with εp = 357 με + 341.5 με = 698.5 με.

I'm trying to find the principal strain, then from that find stress. The poisons ratio should be around 0.3 for this experiment. My result is about 100 micro strain higher than what my class mates got. Can anyone see where I'm going wrong?

JBA · Nov 6, 2015

In the first element of your calculation you give the result of : (348 + 18) /2 to be 357; the result should be 183.

Mechaman · Nov 6, 2015

JBA said:

In the first element of your calculation you give the result of : (348 + 18) /2 to be 357; the result should be 183.

Amazing, I forgot to enclose the whole top line with brackets on my calculator and divide by 2. Thanks a lot for looking over it and seeing that.

Rosetta gauge for stress strain

Homework Statement

Homework Equations

The Attempt at a Solution

Discussion

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