Investigation of the effects of geometric parameters on temperature distribution, residual stress and deformation in selective laser melting (SLM)

Residual stresses are known as one of the main problems of additive manufacturing and can cause problems such as cracks and dimensional distortions. Residual stresses are affected by manufacturing parameters, temperature, part geometries, and placement of parts on the platform. In this study, the effects of temperatures, part geometries and orientation on the platform, residual stresses and dimensional deflection were investigated by keeping the manufacturing parameters constant. Parameters such as geometry types, heights and cooling modulus of the samples were considered and the changes on the part were correlated. First, the situation of producing a large number of parts on the platform was evaluated by producing 1, 5 and 13 cubic samples. Then, the differences occurring in parts with different geometries were observed on cubic, cylindrical and hollow prismatic geometries at heights of 5, 10 and 15 mm. Finally, the verification sample, in which the fins with a complex structure with critical geometric properties and cooling features were placed on one side, was investigated in the scope of geometric parameters. Temperature, residual stress and dimensional deviations are obtained by experimental studies, finite element approaches and modeled by programming with genetic expressions. In addition, a unique hybrid residual stress measurement method has been developed instead of the existing residual stress measurement methods that do not give results in additive manufacturing with the desired precision. Critical parameters affecting the residual stresses were determined depending on the geometric properties. It has been determined that the measurement accuracy in the developed residual stress measurement method is over 94.7%. The residual stresses measured within the scope of the study were modeled with an accuracy of 83% and temperatures with an accuracy of 96%. The most critical parameters for residual stresses and dimensional deviations were sudden cross-sectional changes, high cooling modulus and part height. In addition, with the help of additional cooling elements, the problems in the part could be reduced by 70%.