Bending Fatigue

Bending fatigue, dynamic fatigue and fatigue-related failures in gears, airfoils and other components occur after repeated loading and unloading cycles and are commonly classified as low cycle fatigue (LCF) or high cycle fatigue (HCF).  These failures always occur at the weakest point on a component where high-stress concentrations and/or surface initiation sites exist.  Surface roughness and surface texture strongly influence bending/dynamic fatigue resistance.  Machined surfaces exhibit parallel machining marks and additively manufactured surfaces commonly have sharp, v-notch surface characteristics from the building process as well as near-surface porosity.  These surface and near-surface features are common surface-initiated fatigue failure points.

REM’s isotropic superfinishing technologies have been shown to significantly increase bending/dynamic fatigue resistance by removing or remediating surface initiated failure points.  For gear applications, this benefit is achieved by the application of the ISF® Process or the Rapid ISF® Process to gear flank and root fillet regions, thereby transforming the roughly machined root and the finely ground flank into isotropic superfinished surfaces.  For additively manufactured components, the Extreme ISF® Process can remove all surface v-notch failure points generating a surface with either a flat, isotropic micro-texture or a microscopic, gently rolling, and sloping topography depending on the desired final surface finish quality.  REM’s Extreme ISF Process is capable of polishing lattice structures and internal channels allowing for fatigue improvements even for geometrically complex components. In both cases, subtractively machined components and additively manufactured components, REM’s ISF® Technology can eliminate sharp, angle, v-notch failure points on the components’ surfaces, thereby increasing bending fatigue resistance and component life.


Machined gear components commonly show >5% increases in bending fatigue life when both gear flank and root fillet isotropic superfinishing is allowed to fully remove all machining marks.[1] Additively manufactured components can see increases over as-built surfaces of 2x or more and/or significant increases to fatigue load resistance.[2]

REM’s ISF, Rapid ISF, and Extreme ISF Processes can be applied to very wide ranges of components types, sizes, and metals.  These processing technologies are available via outsourced processing at a REM facility or as technology installations at a customer site.  Contact us today to learn more or to start a project.


[1] Winkelmann, L., Michaud, M., Sroka, G., Swiglo, A., “Impact of Isotropic Superfinishing on Contact and Bending Fatigue of Carburized Steel”, SAE International Off-Highway Congress (2002), 2002-01-1391

[2] Witkin, David B., Patel, Dhruv N., Helvajian, Henry, Steffeney, Lee, Diaz, Agustin, “Surface Treatment of Powder-Bed Fusion Additive Manufactured Metals for Improved Fatigue Life”, Journal of Materials Engineering and Performance, 19 November 2018