Abstract
Although the effect of surface topography on fatigue life is widely accepted, the underlying role of surface roughness from first principles is still poorly understood. Currently approaches which consider the influence of surface roughness on fatigue life prediction can be broadly classified into surface corrector factors (Cs) and stress concentration factors (Kt). Those approaches describe the surface according to the manufacturing process (machined, grounded…), or using 2D height descriptor parameters (Ra, Rz…). However, these approaches are not able to correctly describe the effect of roughness on the fatigue performance where it is anticipated a richer set of surface descriptors would show correlation. The present work aims to highlight the inherent limitations of the most commonly employed 2D surface measurement and characterization techniques, and provides an insight into the application of 3D areal surface characterization processes including the use of the latest areal surface topography parameters quantifying amplitude, spatial, and hybrid topographical information which is considered to be important for fatigue performance correlation.
Highlights
The influence of surface topography on fatigue strength is widely accepted
The present work aims to highlight the inherent limitations of the most commonly employed 2D surface measurement and characterization techniques, and provides an insight into the application of 3D areal surface characterization processes including the use of the latest areal surface topography parameters quantifying amplitude, spatial, and hybrid topographical information which is considered to be important for fatigue performance correlation
This surface finish corrector factor categorizes finish in qualitative terms according to the manufacturing process, or presents the surface finish correction factor in a more quantitative way by using quantitative measure of surface roughness according to the average roughness amplitude (Ra)
Summary
The influence of surface topography on fatigue strength is widely accepted. The micro-geometrical irregularities that constitute surface roughness can be treated as microscopic notches, which promotes crack initiation through local stress concentrations, reducing life-to-firstcrack and total fatigue life [1,2]. Technical literature provides an empirical correction factor, generally known as surface factor Cs, [10] that can be used to adjust the endurance limit if surface roughness is different from standard specimen conditions. This surface finish corrector factor categorizes finish in qualitative terms according to the manufacturing process (machined, forged...), or presents the surface finish correction factor in a more quantitative way by using quantitative measure of surface roughness according to the average roughness amplitude (Ra). The present work aims at highlighting the inherent limitations of the most commonly employed 2D surface measurement and characterization techniques, and provide an insight into the 3D/areal characterization process and latest areal surface topography parameters important in fatigue performance correlation
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