Multiaxial fatigue criterion accounting for anisotropy in forged components

Abstract

Numerical modelling of fatigue behavior for anisotropic structures has become critical for design applications. This is particularly true for forged components due to the intrinsic anisotropy of the material resulting from the process. The aim of this study is to relate the microstructure scale to the process scale, i.e. the engineer scale. Anisotropy induced by the forming process and the most relevant feature which results from forging, is the preferential orientation of structural defects and grains in the direction of the deformation. Grain flow is modelled using a fiber vector at the level of the representative elementary volume. It can then be used to improve and refine the Papadopoulos fatigue criterion by taking into account fatigue limits for each direction of anisotropy. In practice, it is very tedious to determine precisely these fatigue limits and impossible to obtain experimentally all of them for each direction of uniaxial loading. To circumvent this difficulty, we simulate the problem at the microstructure scale by considering fiber vector as the result of the inclusion and grain orientation. Microstructures are then precisely modelled using DIGIMICRO software. A representative elementary volume including inclusions is meshed and high cycle fatigue simulation is performed. The results can be used in order to optimize the preform of the component before simulation.

Extension of strain–life equation for low‐cycle fatigue of sheet metals using anisotropic yield criteria and distortional hardening model

“…The present work addresses the second issue of lack of orientation specific fatigue life curves. Once the critical plane of failure is identified, the equivalent damage should be compared against the fatigue life curves along the orientation of critical plane and not the rolling direction. The modification of Coffin–Manson equation proposed in the present work can be used effectively to generate the orientation specific fatigue life curves along the direction of critical plane.…”

“…Both the earlier models require extensive experimental data along every orientation of interest. Milesi et al . proposed a mesoscopic approach to determine the orientation dependent fatigue constants of a critical plane multiaxial fatigue criterion to avoid extensive experiments.…”

“…The orientation dependence of monotonic yield strength in materials can be modelled using anisotropic yield criterion based on octahedral shear stress . The equivalent stress computed using octahedral shear stress cannot be directly used for multiaxial fatigue calculation as it is applicable only under proportional fatigue loading . The uniaxial strain controlled or stress controlled tests to calculate the fatigue strength of materials, however, are subjected to proportional loading, and their orientation dependence could be modelled using anisotropic yield criteria.…”

“…Both the earlier models require extensive experimental data along every orientation of interest. Milesi et al 19 proposed a mesoscopic approach to determine the orientation dependent fatigue constants of a critical plane multiaxial fatigue criterion to avoid extensive experiments. A constitutive model relating the orientation specific fatigue properties would reduce the experimental efforts to incorporate the anisotropic effect in fatigue damage models.…”

A multi-scale approach for high cycle anisotropic fatigue resistance: Application to forged components

“…For inclusion generation, all statistical parameters described previously were used. A software dedicated to microstructure representation was specially developed [2,15]. The localized cluster method [16] has been properly adapted to separate the statistical parameters of cluster and inclusions.…”