MACHINE DESIGN - An Integrated Approach6-10-1W980.7N=(a)3. Figure D-3a in Appendix D shows that the maximum bending moment occurs at the right-hand support and isMmaxWL b−()⋅:=Mmax1.275106×Nmm⋅=This is repeated bending soMaMmax2:=andMmMa:=4. The stress in the board at the point of maximum bending moment isArea moment of inertiaIwt3⋅12:=I8.329105×mm4=(b)Alternating stressσaMat⋅2I⋅:=a12.2MPa=(c)Mean stressmMmt⋅2I⋅:=m12.2MPa=(d)5. For repeated (fluctuating) bending, the factor of safety for Case 3 loading isNfSf5E8Sut⋅aSut⋅mSf5E8⋅+:=Nf2.4=(e)PROBLEM 6-10 Statement: An overhung diving board is shown in Figure P6-4a. A 100-kg person is standing on the freeend. Assume cross-sectional dimensions of 305 mm x 32 mm. What is the fatigue safety factor for infinite life ifthe material is brittle fiberglass with Sf = 39 MPa @ N = 5E8 cycles and Sut = 130 MPa in the longitudinaldirection?700 = a2000 = LRR12P 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.