tailieunhanh - Theory and Problems of Strength of Materials Part 4

Tham khảo tài liệu 'theory and problems of strength of materials part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 86 DIRECT SHEAR STRESSES CHAP 4 For equilibrium in the vertical direction we have 2 F . 9000 - 7 2 sin 75 - ơ 2 sin 15 0 Substituting Ơ and solving we find T 2900 lb in2. . The shearing stress in a piece of structural steel is 100 MPa. If the modulus of rigidity G is 85 GPa find the shearing strain y. By definition G -ĩỉy. Then the shearing strain y - r G - 100 X 10f 85 X 109 rad. . A single rivet is used to join two plates as shown in Fig. 4-6. If the diameter of the rivet is 20 mm and the load p is 30 kN what is the average shearing stress developed in the rivet Fig. 4-6 Here the average shear stress in the rivet is P A where A is the cross-sectional area of the rivet. However rivet holes are usually mm larger in diameter than the rivet and it is customary to assume that the rivet fills the hole completely. Hence the shearing stress is given by T 12 8-26 x N m2 or MPa rr 4 m 2 . One common type of weld for joining two plates is the fillet weld. This weld undergoes shear as well as tension or compression and frequently bending in addition. For the two plates shown in Fig. 4-7 determine the allowable tensile force p that may be applied using an allowable working stress of lb in7 for shear loading as indicated by the Code for Fusion Welding of the American Welding Society. Consider only shearing stresses in the weld. The load is applied midway between the two welds. The minimum dimension of the weld cross section is termed the throat which in this case is J sin 45 in. The effective weld area that resists shearing is given by the length of the weld times the throat dimension or weld area 7 in2 for each of the two welds. Thus the allowable Fig. 4-7 CHAP. 4 DIRECT SHEAR STRESSES 87 tensile load p is given by the product of the working stress in shear times the area resisting shear or p 11 300 2 56 000 lb. . Shafts and pulleys are usually fastened together by means of a key as shown in Fig.