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Modified Goodman Diagram

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Fig1.

The following table shows the bounds on regions in the modified Goodman range-of-stress diagram shown in Fig1. Region Limiting Value of σm a −σyp ≤ σm ≤ σab b σab < σm ≤ 0 c 0 < σm ≤ σcd d σcd < σm ≤ σyp

The modified Goodman range-of-stress diagram shown above is a failure locus for the case of uniaxial fatigue stressing. Any cyclic loading that produces a stress amplitude that exceeds the bounds of the locus will cause failure in fewer than N cycles. Any stress amplitude that lies within the locus will result in more than N cycles without failure. Stress amplitudes that just touch the locus produce failure in exactly N cycles.

A modified form of the Goodman relationship is recommended for general use under conditions of high-cycle fatigue. This form is represented by the modified Goodman diagram. Any given Goodman diagram is constructed for a single fatigue lifetime of N cycles. The Goodman Diagram is only good for one point on the fatigue curve. The Goodman Diagram will change for different points on the fatigue curve. The amplitude stress line σ_a represents the Goodman equation. The diagram may also be called a 'range-of-stress' diagram or a 'modified Goodman range-of-stress' diagram.

Fig2.

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Related
▪ R - Machine Design Nomenclature
▪ L - Cyclic Loading
▪ L - Mean Stress Equations

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The material and content of Engineering Archives is designed to be subject to change and alteration at all times. Therefore, it may not be assumed that any presented material herein is static. The material is constantly subject to change for the purpose of maximizing the ability of the learner to comprehend and absorb the material. The changing and alteration is conducted based on user feedback. Therefore, effective changes cannot take place without the user feedback. Please go to the forum for questions and feedback. See more…
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