A Topology Optimization Framework considering Sintering in Design for Additive Manufacturing
Authors
Elmstrøm, Frederik Tobias ; Troelsgaard, Christian
Term
4. term
Education
Publication year
2024
Abstract
Metal binder jetting (MBJ) is a promising route for additive manufacturing, but parts shrink and distort during post-processing sintering, challenging dimensional tolerances. This thesis investigates whether accounting for sintering during structural design can reduce the need for geometric compensation and improve accuracy after sintering. A custom topology optimization framework is developed in which sintering-induced deformation is modeled by a 3D geometrically nonlinear finite element analysis coupled to a nonlinear viscoplastic, semi-implicit material model. A Newton-Raphson solver with a consistent tangent ensures convergence, and the MATLAB implementation is verified against a 1D analytical solution and ANSYS. Optimization uses the gradient-based MMA algorithm with linear and projection filtering and continuation; design sensitivities are derived analytically using a path-dependent adjoint method and validated by forward difference. The framework is tested on the MBB beam benchmark and an industrial component, and four objective functions are proposed. Three objectives reduce deformation and distortion for the MBB beam; for the industrial case, two objectives yield similar designs with only minor differences. Selecting a preferred objective may require further experimental study. The work demonstrates how to integrate sintering behavior into design for additive manufacturing to achieve more dimensionally stable metal parts.
Metal binder jetting (MBJ) er en lovende vej til additiv fremstilling, men emner krymper og deformerer under den efterfølgende sintring, hvilket udfordrer dimensionstolerancer. Dette speciale undersøger, om man ved at indregne sintring i selve designprocessen kan mindske behovet for geometrisk kompensation og forbedre nøjagtigheden efter sintring. Der udvikles en skræddersyet topologioptimeringsramme, hvor sintringsdeformation modelleres med en 3D geometrisk ikke-lineær finit element analyse koblet til en ikke-lineær viskoplastisk, semi-implicit materialemodel. En Newton-Raphson-løser med konsistent tangent sikrer konvergens, og MATLAB-implementeringen verificeres mod en 1D analytisk løsning og ANSYS. Optimeringen anvender den gradientbaserede MMA-algoritme, lineær og projektionfiltrering samt continuation; designfølsomheder udledes analytisk med en baneafhængig adjointmetode og valideres med fremadrettet differens. Rammeværket afprøves på MBB-beam benchmarken og en industriel komponent, og der foreslås fire målfunktioner. Tre af disse reducerer deformation og forvrængning for MBB-beamet; i den industrielle sag giver to valgte målfunktioner lignende design med kun små forskelle. Valg af endelig målfunktion kan kræve yderligere eksperimentel afklaring. Arbejdet demonstrerer en måde at integrere sintring i design for additiv fremstilling for at opnå mere dimensionsstabile metaldele.
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