(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Determine x and y strains in order to construct a Mohr's circle of strain.

A 2-gauge Wheatstone (the third/middle gauge was not working), with gauges 90-degrees apart, was attached to a specimen steel plate 15-degrees offset from the x and y axes. An axial load was applied to the plate on an Olsen tensile testing machine.

2. Relevant equations

Strain 1 = ((strain-x + strain-y)/2) + ((strain-x - strain-y)/2) cos (2theta) + ((shear strain-xy)/2) sin (2theta) = -65 micro strain

Strain 2 = ((strain-x + strain-y)/2) + ((strain-x - strain-y)/2) cos (2theta) + ((shear strain-xy)/2) sin (2theta) = 278 micro strain

These equations are usually used when a three-gauge rosette is used. The lecturer who set this assignment has moved to another university, and I am unable to reach him at the moment. The lecturer who took his place told me, over the telephone, that these equations only apply to a 3-gauge rosette and cannot be used for this problem. The new lecturer uses all three gauges for his experiment.

There is nothing in my notes explaining how to determine x and y strains where only two gauges of a rosette were used. Please could you help me to work out the x and y strains?

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# Strain gauge - determination of x and y strains

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