Browsing by Subject "thermal distortion"

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    Optimization of Build Orientation for Minimum Thermal Distortion in DMLS Metallic Additive Manufacturing
    (University of Texas at Austin, 2017) Peng, Hao; Ghasri-Khouzani, Morteza; Gong, Shan; Attardo, Ross; Ostiguy, Pierre; Aboud Gatrell, Bernice; Budzinski, Joseph; Tomonto, Charles; Neidig, Joel; Shankar, M. Ravi; Billo, Richard; Go, David B.; Hoelzle, David
    The additive manufacturing (AM) process direct metal laser sintering (DMLS) can quickly produce complex parts. However, thermal stress in DMLS may induce thermal distortion and cause build failure. This manuscript presents an optimization algorithm for the build orientation in DMLS to minimize thermal distortion. The algorithm is built on the foundation of two coupled thermal and thermo-mechanical models developed in our previous work. The DIRECT search method and a universal objective function for thermal distortion were used. Constraints were included to rule out build orientations resulting in overheating or excessive oxidation. The optimization algorithm was tested on a rectangular bar and a complex, contoured part. Both parts were printed using an EOS M290 machine, and measured by a coordinate measuring machine. In comparison to build orientations chosen by two novice operators, the optimized build orientations gave significant reduction in the thermal distortion and number of print trials before print success.
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    Part-Scale Model for Fast Prediction of Thermal Distortion in DMLS Additive Manufacturing Part 2: A Quasi-Static Thermomechanical Model
    (University of Texas at Austin, 2016) Peng, Hao; Go, David B.; Billo, Rick; Gong, Shan; Ravi Shankar, M.; Aboud Gatrell, Bernice; Budzinski, Joseph; Ostiguy, Pierre; Attardo, Ross; Tomonto, Charles; Neidig, Joel; Hoelzle, David
    The direct metal laser sintering (DMLS) additive manufacturing process can quickly produce complex parts with excellent mechanical properties. However, thermal stress accumulated in the layer-by-layer build cycles of DMLS may induce part distortion and even cause the failure of the whole build process. This paper is the second part of two companion papers that present a part-scale model for fast prediction of temperature history and part distortion in DMLS. In this paper, a quasi-static thermomechanical (QTM) model is built to estimate the thermal distortion of entire parts in DMLS. Firstly, the thermal contraction in each build cycle is modeled as a quasi-static loading process; the final thermal stress accumulated in the parts is the superposition of thermal stress generated in each build cycle. Secondly, the stress relaxation process after the parts are cut off from the substrate is modeled, and final distortion of the parts is predicted with thermal stress calculated from the thermal contraction processes. In comparison to existing transient thermomechanical models, the QTM can predict thermal distortion in DMLS with much faster computational speed, and a comparison against experiment shows less than 10% error.