Effect of Mean Stress on Fatigue

In engineering service a component is often subject to both dynamic alternating stresses and static steady-state stresses. A static steady-state stress resembles a mean stress upon which the cyclical stress is imposed. The alternating stress range, o ,ax ymin/ that can be imposed onto a mean stress without fatigue failure decreases when the value of the tensile mean stress [Pg.114]

respectively. There are two sets of coordinate systems in this diagram. The inside one is established by turning the referenced Goodman diagram 45° counterclockwise. The y-axis of the internal coordinate system represents the alternating stress. It is coincident with the R = -1 ( 1 = ) line where min = o , = 0. The x-axis of the internal coordinate sys- [Pg.117]

Master Goodman diagram of AISI4340 steel. Data from Military Handbook 5, U.S. Department of Defense (Dieter, G. R, Mechanical Metallurgy, McGraw-Hill, New York, 1986, p. 386). [Pg.117]

This master Goodman diagram is useful for predicting fatigue life with any two independent parameters. If the mean stress is 80 ksi and R = 0 (or A = 1), the estimated fatigue life for a smooth unnotched specimen can be predicted at the intersection of the two lines of constant = 80 ksi and R = 0 (or A = 1). In this case, the estimated fatigue life will be less than W cycles. [Pg.118]

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