Problem6_10 - MACHINE DESIGN An Integrated Approach 6-10-1...

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MACHINE DESIGN - An Integrated Approach 6-10-1 W 980.7 N = (a) 3. Figure D-3 a in Appendix D shows that the maximum bending moment occurs at the right-hand support and is M max WL b () := M max 1.275 10 6 × Nmm = This is repeated bending so M a M max 2 := and M m M a := 4. The stress in the board at the point of maximum bending moment is Area moment of inertia I wt 3 12 := I 8.329 10 5 × mm 4 = (b) Alternating stress σ a M a t 2 I := a 12.2 MPa = (c) Mean stress m M m t 2 I := m 12.2 MPa = (d) 5. For repeated (fluctuating) bending, the factor of safety for Case 3 loading is N f S f5E8 S ut a S ut m S f5E8 + := N f 2.4 = (e) PROBLEM 6-10 Statement: An overhung diving board is shown in Figure P6-4a. A 100-kg person is standing on the free end. Assume cross-sectional dimensions of 305 mm x 32 mm. What is the fatigue safety factor for infinite life if the material is brittle fiberglass with Sf = 39 MPa @ N = 5E8 cycles and Sut = 130 MPa in the longitudinal direction? 700 = a 2000 = L R R 1 2 P Units:
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This note was uploaded on 05/19/2011 for the course EML 2005 taught by Professor Arakere during the Spring '05 term at University of Florida.

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