A new equivalent approach for additive manufacturing (ALM) numerical simulation

Abstract

As the layer additive manufacturing processes exhibit currently a huge growth in industrial applications, more and more simulation researches have been carried out recently. Nevertheless, the scale factor between the grains sizes (several tens of micrometers) and the piece sizes (couple of centimeters at least) leads to the use of too large numerical resources. For this reason, two simulation methodologies can be envisaged. The first (microscale) aims to simulate the realistic laser-material interaction and the powder coalescence inside the fusion zone. In this configuration each grain of the powder is considered which is prohibitive to multilayer simulation and three dimensional analysis. The second (macroscale) is built in order to compute residual mechanical behaviors (stress and strain). In this case, the whole piece is taken into account but the simulated physics are reduced to heat transfers and solid mechanics. Usually, too heavy assumptions are made concerning the layers addition.In the present paper, a numerical simulation of selective laser melting process is developed. This intermediate methodology is based on the representation of the powder as a third dense material with “equivalent” properties. These equivalent properties are calculated from a densification rate based on the material properties. The objective here is to provide a satisfactory computation of the weld pool shape (just like in the microscale case) in a three- dimensional domain and with layer additions. Indeed, the assumption related to the powder simulation reduces widely the size of the numerical problem.Nevertheless, the main key points of the process, like the densification effect or the powder denudation around the fusion zone, are considered.As the present study corresponds to the first step of this numerical methodology, this preliminary development takes place in a reduced axisymmetric domain.As the layer additive manufacturing processes exhibit currently a huge growth in industrial applications, more and more simulation researches have been carried out recently. Nevertheless, the scale factor between the grains sizes (several tens of micrometers) and the piece sizes (couple of centimeters at least) leads to the use of too large numerical resources. For this reason, two simulation methodologies can be envisaged. The first (microscale) aims to simulate the realistic laser-material interaction and the powder coalescence inside the fusion zone. In this configuration each grain of the powder is considered which is prohibitive to multilayer simulation and three dimensional analysis. The second (macroscale) is built in order to compute residual mechanical behaviors (stress and strain). In this case, the whole piece is taken into account but the simulated physics are reduced to heat transfers and solid mechanics. Usually, too heavy assumptions are made concerning the layers addition.In the present pa...