Tailoring the theory of critical distances to better assess the combined effect of complex geometries and process-inherent defects during the fatigue assessment of SLM Ti-6Al-4V

Gillham B. Yankin A. McNamara F. Tomonto C. Huang C. Soete J. ODonnell G. Trimble D. Yin S. Taylor D. Lupoi R.
July 2023 Elsevier Ltd

International Journal of Fatigue
2023 #172

This work aims to apply the Theory of Critical Distances (TCD) to the fatigue assessment of additively manufactured (AM) Ti-6Al-4V material produced via the selective laser melting (SLM) process. Modified alternatives to traditional TCD methods are considered. In this sense, it is sought to develop a fatigue prediction model that is better suited to assessing the impact of multiple stress-rising features which are located in close proximity to each other. Hereby, consideration has been given to modelling process-inherent surface roughness in combination with an internally positioned artificial defect, shaped as a feature that is reminiscent of a pore. Simultaneously, the research also seeks to circumnavigate a potential issue with respect to the current TCD methodology. This concerns the matter of applying TCD practices to components whereby the area of interest for conducting stress-distance analytics is on a size scale that is smaller than that of the critical distance length parameter itself. Several different strategies were attempted as a way to try and achieve meaningful modifications to the TCD process. Results show that it is possible to overcome such challenges that can often present themselves during the fatigue appraisal of AM metal parts. In this sense, the optimal novel strategy that was experimented with returned average error margins of 13.7% or better. It is anticipated that such models may assist in further optimising the accuracy of service life evaluation for metallic AM components that are intended for industry.

Critical distance , Defects , Fatigue design , LEFM , SLM

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Trinity College Dublin, The University of Dublin, Department of Mechanical, Manufacturing and Biomedical Engineering, Parsons Building, Dublin 2, Ireland
3D Printing Innovation & Customer Solutions, Johnson & Johnson Services Inc., Loughbeg, Ringaskiddy, Co. Cork, P43 ED82, Ireland
3D Printing Innovation & Customer Solutions, Johnson & Johnson Services Inc., Miami, 33126, FL, United States
Institute of Materials Technology, Helmut-Schmidt-University/University of the Federal Armed Forces Hamburg, Hamburg, 22043, Germany
Department of Materials Engineering, KU Leuven, Heverlee, 3001, Belgium
AMBER, the SFI Research Centre for Advanced Materials and BioEngineering Research, Ireland
Department of Mechanical and Aerospace Engineering, School of Engineering & Digital Sciences, Nazarbayev University, Astana, 010000, Kazakhstan

Trinity College Dublin
3D Printing Innovation & Customer Solutions
3D Printing Innovation & Customer Solutions
Institute of Materials Technology
Department of Materials Engineering
AMBER
Department of Mechanical and Aerospace Engineering

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