Surface effects

Similarly, the surface roughness factor can account for differences in fatigue life from difference in surface roughness between the component and the laboratory specimen from which the basic SN-curve was determined. It has been observed that fatigue life is reduced as the surface roughness increases. Surface scratches such as machining marks can serve as stress concentrations and more quickly initiate cracks than observed in polished specimens.

This factor could also be less than or greater than one, depending on the relative roughness between the component and laboratory specimen. Again, the value of this factor to use in an analysis will depend on prior experience and insight into the component fatigue behavior.

Correction Factors due to Surface Roughness

The surface correction factor is defined as

Note:

If you previously created durability models using LMS Virtual.Lab Durability, type the product of the Surface Correction and Size Correction values from that application in the Cumulated Fatigue Correction box for the Fatigue Correction Factor durability simulation object in Specialist Durability. For example, if Surface Correction was set to 1.2 and Size Correction was set to 2 in LMS Virtual.Lab Durability, then the value for Cumulated Fatigue Correction in Specialist Durability would be 2.4.

Learn more

The fatigue notch factor

Examples for size effects

Stress gradients

Theoretical concepts

Application of the theory

Macroscopic yielding

Neuber's approach to micro-yielding

Summary for size effects

Quick links

Command reference

Pre/Post video examples

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Surface effects, Simcenter 3D 2021.1 Series

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