General Mechanical

General Mechanical

Simulation of additive manufacturing – issues with large element deformations

    • helen.durand


      I am currently creating a one-way coupled transient thermal and transient structural simulation to represent an additive manufacturing process called powder bed fusion (also known as selective laser melting). The idea is that the powder material is melted and fused to a build platform, one layer at a time.

      The transient thermal simulation applies a laser profile to determine which powder elements go above the melting point at each loadstep. In the structural simulation, I import the temperatures and the elements that are solid at each load step. In the structural simulation, EKILL and EALIVE commands are used to make sure the powder and liquid elements are killed while the solid elements are alive (I am not simulating any fluid flow). This is updated at every loadstep to represent material added to the building surface.

      The mesh I am using consists of cube elements, where elements near the bottom are assumed solid (to represent the build surface), with the underside having a fixed boundry condition. I am using nonlinear material properties and a temperature-dependent multilinear stress-strain model.

      Most aspects of the simulation are implemented in command blocks with APDL code.

      This issue if that I have had high deformations in transient structural. I have tried several methods to address this:

      • I created a second solid material with a reference temperature at the melting point (instead of at room temperature), and any elements that cool after melting are giving this alternate solid material.
      • I tried both quadratic and linear elements
      • I tried decreasing the element size, the length of each loadstep, and the number of substeps (using the auto time stepping feature)
      • I tried using line search
      • I tried both ramped and stepped loads

      Is there something I can do to appropriately deal with these high deformations?

      Thank you!

    • Ashish Khemka
      Ansys Employee
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