Browsing by Author "Mugwagwa, L."

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    Influence of process parameters on residual stress related distortions in selective laser melting
    (Elsevier, 2018) Mugwagwa, L.; Dimitrov, D.; Matope, S.; Yadroitsev, I.
    ENGLISH ABSTRACT: Residual stresses pose a major setback in Selective Laser Melting (SLM) and limit the applicability of the process, particularly from the standpoint of form accuracy and mechanical strength. The purpose of this paper is to investigate the influence of SLM parameters namely laser power and scanning speed on thermal stress related warping distortions and porosity. In this study, residual stress related distortions and achievable density for different process parameter combinations are presented simultaneously due to the profound influence of the porosity on residual stress relaxation. The paper also discusses the implications of the process parameters on the sustainability of the SLM process.
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    A methodology to evaluate the influence of part geometry on residual stresses in selective laser melting
    (Faculty of Engineering, Department of Industrial Engineering, Stellenbosch University, 2016) Mugwagwa, L.; Dimitrov, D.; Matope, S.; Becker, T. H.
    ENGLISH ABSTRACT: The subject of residual stresses induced by the Selective Laser Melting (SLM) process has been one of the main focus areas in literature over the past decade. It has been reported that residual stresses can be responsible for shape and dimensional distortions, cracking and compromised mechanical properties (reduced yield and fatigue strength). These shortfalls limit the applicability of SLM components in industry, particularly for the aerospace industry where part lifetime and hence fatigue life is of utmost concern. High temperature gradients have been reported to be responsible for the residual stress build up. A key aspect that has not been considered in literature is part geometry and orientation and its influence on residual stress levels. Thus, this study proposes a methodology for investigating this influence for different geometric features. In this work, samples were built from tool steel powders. The Hole Drilling Method (HDM) and X-Ray Diffraction (XRD) techniques are proposed for measuring residual stresses. Preliminary results show that the geometry of a part influences residual stress magnitudes and distributions, with sharper ends exhibiting higher stresses than less sharp specimen ends.