Residual Stress Modeling with Phase Transformation for Wire Arc Additive Manufacturing of B91 Steel
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https://doi.org/10.1007/s11837-020-04424-w 2020 The Minerals, Metals & Materials Society
ADDITIVE MANUFACTURING FOR ENERGY APPLICATIONS
Residual Stress Modeling with Phase Transformation for Wire Arc Additive Manufacturing of B91 Steel XAVIER JIMENEZ,1 WEN DONG,1 SANTANU PAUL,1 MICHAEL A. KLECKA,2 and ALBERT C. TO1,3 1.—Department of Mechanical Engineering and Material Sciences, University of Pittsburgh, Pittsburgh, PA, USA. 2.—Raytheon Technologies Research Center, 411 Silver Lane, East Hartford, CT, USA. 3.—e-mail: [email protected]
Wire arc additive manufacturing (WAAM) is an energy-efficient manufacturing technique used for near-net-shape production of functional industrial components. However, heat accumulation during deposition and the associated mechanical and metallurgical changes result in complex residual stress profiles across the cross section of the fabricated components. These residual stresses are detrimental to the service life of the components. In this study, sequentially coupled thermomechanical analysis of WAAM B91 steel is conducted to quantify the residual stress variation across the component. The thermomechanical analysis includes a transient heat transfer model and a static stress model that incorporates the transformation-induced plasticity due to martensitic phase transformation. The experimentally calibrated heat transfer model mirrors the temperature variation of the system during the deposition. The results from the stress model are validated via x-ray diffraction measurements, and the numerical results are in good agreement with the experimental data.
INTRODUCTION Directed energy deposition (DED) is a type of additive manufacturing technique that dispenses and melts a feedstock on top of the workpiece or substrate plate on a layer-by-layer basis. Different energy sources, types of feedstock, and motion systems can be used to obtain different print speeds and qualities. A common DED technique, mostly suited for large parts with medium to low complexity, is wire arc additive manufacturing (WAAM). This technique takes advantage of different welding processes along with metal wire feedstock deposit to create near-net shapes. The most common welding processes are gas metal arc welding (GMAW), gas tungsten arc welding (GTAW), and plasma arc welding (PAW). The welding system can be mounted on a computer numerical control (CNC) table or a six-axis robotic arm to deposit the material based on a three-dimensional (3D) model. The main advantages of WAAM are its high deposition rate and simpler machine setup that allows (Received July 21, 2020; accepted September 29, 2020)
the creation of large parts, up to several meters long, in a considerable short time when compared with other DED techniques. Low capital investment is also a major benefit of the WAAM process, since the components of a WAAM machine can be derived from open-source equipment from a range of suppliers in the mature welding industry.1 WAAM does not need the vacuum environment commonly applied in electron beam-based methods
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