Metal additive-manufacturing process and residual stress modeling

Abstract

Additive manufacturing (AM), widely known as 3D printing, is a direct digital manufacturing process, where a component can be produced layer by layer from 3D digital data with no or minimal use of machining, molding, or casting. AM has developed rapidly in the last 10 years and has demonstrated significant potential in cost reduction of performance-critical components. This can be realized through improved design freedom, reduced material waste, and reduced post processing steps. Modeling AM processes not only provides important insight in competing physical phenomena that lead to final material properties and product quality but also provides the means to exploit the design space towards functional products and materials. The length-and timescales required to model AM processes and to predict the final workpiece characteristics are very challenging. Models must span length scales resolving powder particle diameters, the build chamber dimensions, and several hundreds or thousands of meters of heat source trajectories. Depending on the scan speed, the heat source interaction time with feedstock can be as short as a few microseconds, whereas the build time can span several hours or days depending on the size of the workpiece and the AM process used. Models also have to deal with multiple physical aspects such as heat transfer and phase changes as well as the evolution of the material properties and residual stresses throughout the build time. The modeling task is therefore a multi-scale, multi-physics endeavor calling for a complex interaction of multiple algorithms. This paper discusses models required to span the scope of AM processes with a particular focus towards predicting as-built material characteristics and residual stresses of the final build. Verification and validation examples are presented, the over-spanning goal is to provide an overview of currently available modeling tools and how they can contribute to maturing additive manufacturing.

Towards rapid qualification of powder-bed laser additively manufactured parts

“…The laser traverses the pyrometer field of view several times, and it is able to detect a temperature rise even when the laser is outside but near the field of view of the pyrometer. Details of macro-modeling and corresponding work- piece thermal history calculations as well as the theoretical background of mechanical analysis are discussed in [8].…”

“…VOF calculates the free surface curvature using a second order reconstruction scheme (PLIC) to provide the surface tension forces required in the momentum equations. The details of the micro-model, corresponding validation, and coupling with macro-models are available in [7,8]. Porosity predictions and how models are used to identify ideal process window towards fully dense material were presented by Mindt et al [9].…”

Influence of Powder Bed Characteristics on Material Quality in Additive Manufacturing

“…Once the powder bed geometry is obtained, either via script or via modelling of the racking process, the particle distribution on the powder bed is provided to a computational fluid dynamics model that accounts for laser interaction with the feed stock providing more insight about the phase changes and solidification behaviour of the material [2,8]. The momentum equations are extended using source terms to account for gravitational body forces, recoil pressure, and surface tension.…”

“…We study the influence of the powder bed characteristics (particle size distribution and spatial arrangement) on the SLM process using high fidelity models recently developed and validated [2][3][4][5]. Since the spatial arrangement of the particles in the powder bed cannot be manipulated or easily measured in a production 3D printer, the study of the impact of those parameters on the SLM process is investigated by comparing the melting behaviour of a BCC arrangement of powder particles with that of a powder bed obtained by modelling the racking process [6].…”

Discussing of Deformation of Additive Manufacturing due to External Bending

“…Based on different of material was used for AM, the produce of process can be widely different. For metal additive manufacturing, the processes contain power bed process, blown powder and wire feed processes [1].…”