A rectangular rosette (Figure 2.20b), is cemented to the free surface of an airplane wing...

A rectangular rosette (Figure 2.20b), is cemented to the free surface of an airplane wing made of an aluminum alloy 7075 T6 (see Appendix A). Under load, the strain readings are ϵa = ϵxx = 0.00250, ϵh = 0.00140, ϵc = ϵyy = −0.00125.

a. Determine the principal stresses. Note that the stress components on the free surface are zero.

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b. Show the orientation of the volume element on which the principal stresses in the plane of the rosette act.

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c. Determine the maximum shear stress τmax•

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d. Show the orientation of the volume element on which τmax acts.

FIGURE 2.20 Rosette strain gages. (a) Delta rosette. (b) Rectangular rosette.