Surface roughness evolution in hardened steel disks: an integrated profilometry and ansys-fea approach to assess contact conditions and residual stress profiles

Elsheltat, Salem ORCID: https://orcid.org/0000-0002-8459-9078 2024. Surface roughness evolution in hardened steel disks: an integrated profilometry and ansys-fea approach to assess contact conditions and residual stress profiles. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

This thesis investigates the impact of the running-in process on the surface roughness of hardened and ground steel disks, which simulate gear tooth contact conditions. The focus is on the changes in asperity shape due to plastic deformation and the associated residual stresses at the asperity scale. In-situ profilometry quantifies these shape changes, particularly in areas with high plastic deformation and tensile residual stress, which could lead to surface micropitting during further use. A novel method for repositioning and aligning measured surface profiles from mixed lubrication experiments is presented. Finite element analysis (FEA) using ANSYS software is central to this study, encompassing both elastic and plastic contact analyses. The analysis starts with standard smooth elastic body contacts, validated against Hertzian elastic solutions, and extends to include plastic behaviour, aligning with established models. Various numerical case studies improved the predictive accuracy of FEA, with increased mesh resolutions enhancing result precision and scaled-down loading conditions managing convergence issues effectively. The FEA simulations incorporate real surface profiles to assess how ground steel disk surfaces react under different loads. By comparing profiles before and after loading, a detailed representation of elastic/plastic interactions on real rough surfaces is achieved within the ANSYS environment. This method predicts residual stress profiles beneath select asperities. Validation of the FEA analysis is conducted through a comparative study using an innovative depth-profiling residual stress measurement technique. This technique utilizes Focused Ion Beam (FIB) milling and digital image correlation to measure near-surface residual stresses within asperities up to a depth of 3 microns, providing accurate validation and aligning with experimental measurements. Additionally, the thesis includes an appendix with detailed, step-by-step instructions for conducting FEA contact modelling using ANSYS software, supported by visual figures. The appendix also contains extensive comparative analyses to validate the FEA results against analytical solutions.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Engineering
Date of First Compliant Deposit:	1 July 2024
Last Modified:	01 Jul 2024 14:48
URI:	https://orca.cardiff.ac.uk/id/eprint/170189

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