Chapter Eleven - Residual stress analysis and geometrical tolerances in powder bed fusion and direct energy deposition processes

Abstract

Metal additive manufacturing is a growing and maturing technology, especially with its two leading approaches of powder bed fusion and direct energy deposition. Next to the possible advantages of metal AM-like design freedom, decreased lead time, and lower costs for small lots, there are also manufacturing-specific challenges. These are mainly to meet the required geometrical tolerances and to avoid too high stresses and failures during the manufacturing. Instead of costly trial-and-error iterations with the real manufacturing process, numerical simulation can be used to predict distortion and stresses of parts to be additively manufactured. These results can then be used to find optimized and issue-mitigating process conditions. In order to do so, different simulation approaches exist like classical thermomechanically coupled analyses or an accelerated approach, which is reduced to the mechanical physical problem while maintaining accuracy. The basic principles of these approaches are explained, and exhaustive examples are provided. These show how manufacturing issues resulting from distortion or high stresses can be predicted and which mitigation strategies can be derived.