A parametric-experimental study of void growth in superplastic deformation |
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| Institution: | 1. School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164-2920, USA;1. Center for Thorium Molten Salt Reactor System, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China;2. Zhangjiang Lab, Shanghai Advanced Research Institute, Chinese Academy of Sciences, 201210, China;3. Key Laboratory of Interfacial Physics and Technology and Laboratory of Physical Biology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China;4. University of Chinese Academy of Sciences, Beijing 100049, China;5. State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China;6. Los Alamos National Laboratory, Los Alamos, NM 87545, USA;1. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, 710072 Xi’an, PR China;2. School of Materials Science and Engineering, Nanjing University of Science and Technology, 210094 Nanjing, PR China;3. School of Aeronautics, Northwestern Polytechnical University, Xi’an 710072, Shaanxi, PR China |
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| Abstract: | Substantial void growth in metals constitutes a problem in many industrial operations that utilize superplastic deformation. This is because of the likelihood of material failure due to such growth. Hence, there is a need to study void growth mechanisms in an effort to understand the parameters governing it. In this work, numerical and experimental studies of void growth, and the parameters that affect it, in a superplastically deforming (SPD) metal have been performed. In the numerical studies, using the finite-element method, a 1×2 sized thin plate (i.e. plane stress conditions) of a viscoplastic material with pre-existing holes has been subjected to a constant extension rate. The experimental studies were performed under similar conditions to the numerical ones and provided for qualitative comparison. The parameters affecting void growth in SPD are: m (the strain-rate sensitivity), void size (i.e. diameter) and the number (density) of existing voids. The results showed that increased m values produced strengthening and decreased the rate of void growth. In addition, larger initial void size (or, equivalently, a larger initial void fraction) had the effect of weakening the specimen through causing accelerated void growth. Finally, multiple holes had the effect of increasing the metal ductility by reducing the extent of necking and its onset. This was realized through diffusing the plastic deformation at the different hole sites and reducing the stress concentration. The numerical results were in good qualitative agreement with the experiment and suggested the need to refine existing phenomenological void growth models to include the dependence on the void fraction. |
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