Revealing the tribological stress field by using deformation twins as probes

TL;DR

This study combines experimental observations and modeling to understand the complex, position-dependent stress fields in tribologically loaded metals, emphasizing the importance of plasticity in accurate stress prediction.

Contribution

It demonstrates that incorporating plasticity into stress models improves the prediction of deformation twin activation under tribological conditions.

Findings

Plasticity-inclusive models better match experimental data.

Elastic-only models are insufficient for accurate stress prediction.

Model parameters critically influence stress field accuracy.

Abstract

Microstructural evolution in metallic materials feedbacks with the loading conditions and influences the life time of parts and components. Therefore, the deformation mechanisms have to be fundamentally understood. Tribological loading causes a non-trivial, position-dependent, moving stress field. We present a systematic study on the influence of the complexity of the implemented material models on the calculated stress field. For the stress field validation, results of tribological experiments on single crystals with the activation of deformation twins are used. The resolved shear stresses calculated with the stress field models have to be highest on the experimentally identified twin systems. From this combination of modelling and experiment, it clearly follows that a stress field model considering plasticity is required. The widely used Hamilton stress field for tribological loading is limited due to only considering elastic strains. Here, the predictive quality of the stress field is sensitive to the assumed yield strength, work hardening and plastic anisotropy. Certain stress field models are close to the experimental data, but none completely replicate them. These results highlight that the model type and parameters have to be carefully determined in order to be able to predict how a metallic material deforms due to a sliding load.