Shigley, Mechanical Engineering Design, Third Ed, Table A-18, McGraw-Hill, New York, 1977. V. and A. Askenazi, Building Better Products with Finite Element Analysis, OnWord Press, Santa Fe, N.M., 1999. APPENDIX A Fatigue Cracks A ductile material subjected to fatigue loading experiences structural changes. The changes occur in the following order: A crack begins to form within the material. Initiation. Local extrusions and intrusions occur at the surface of Localized crack growth. the part because plastic deformations are not completely reversible. Crack growth on planes of high tensile stress. The crack propagates across the section at those points of greatest tensile stress. Ultimate ductile failure. The sample ruptures by ductile failure when the crack reduces the effective cross to a size that cannot sustain the applied loads. Design and Environmental Variables affecting Fatigue Life The following factors decrease fatigue life. Stress concentrators. Holes, notches, fillets, steps, grooves, and other irregular features will cause highly localized regions of concentrated stress, and thus reduce fatigue life. Surface roughness. Smooth surfaces are more crack resistant because roughness creates stress concentrators. Surface conditioning. Hardening processes tend to increase fatigue strength, while plating and corrosion protection tend to diminish fatigue strength. Environment. A corrosive environment greatly reduces fatigue strength. A combination of corrosion and cyclical stresses is called corrosion fatigue.
Shigley, Mechanical Engineering Design, Third Ed, Table A-18, McGraw-Hill, New York, 1977. V. and A. Askenazi, Building Better Products with Finite Element Analysis, OnWord Press, Santa Fe, N.M., 1999. APPENDIX A Fatigue Cracks A ductile material subjected to fatigue loading experiences structural changes. The changes occur in the following order: Initiation. A crack begins to form within the material. Localized crack growth. Local extrusions and intrusions occur at the surface of the part because plastic deformations are not completely reversible. Crack growth on planes of high tensile stress. The crack propagates across the section at those points of greatest tensile stress. Ultimate ductile failure. The sample ruptures by ductile failure when the crack reduces the effective cross to a size that cannot sustain the applied loads. Design and Environmental Variables affecting Fatigue Life The following factors decrease fatigue life. Stress concentrators. Holes, notches, fillets, steps, grooves, and other irregular features will cause highly localized regions of concentrated stress, and thus reduce fatigue life. Surface roughness. Smooth surfaces are more crack resistant because roughness creates stress concentrators. Surface conditioning. Hardening processes tend to increase fatigue strength, while plating and corrosion protection tend to diminish fatigue strength. Environment. A corrosive environment greatly reduces fatigue strength. A combination of corrosion and cyclical stresses is called corrosion fatigue.
Miners_fatigue_rainflow.docx