Problem 7.2-18The surface of an airplane wing is subjected to planestresswith normal stresses xand yand shear stress xy, as shown in the figure. At a counterclockwise angle 30° from the xaxis thenormal stress is 35 MPa tension, and at an angle 50° it is 10 MPacompression. If the stress xequals 100 MPa tension, what are the stresses yand xy?Solution 7.2-18Plane stress434CHAPTER 7Analysis of Stress and StrainyxOxyyx= 100 MPax100 MPay?xy?At 30 , (tension)At 50 , (compression)Find yand xyFOR30 :or0.25y0.86603xy40 MPa (1)100sy2100sy2cos60txysin60sx135sx1sxsy2sxsy2cos2utxysin2usx110 MPasx135 MPaFOR50 :or0.58682y0.98481xy51.318 MPa (2)SOLVEEQS. (1) AND(2):y19.3 MPaxy40.6 MPa100sy2100sy2cos100txysin100sx110Problem 7.2-19At a point in a structure subjected to plane stress, the stresses are x4000 psi, y2500 psi, and xy2800 psi (the sign convention for these stresses is shown in Fig. 7-1). A stresselement located at the same point in the structure, but oriented at a
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