Effect of surface/interface stress on the plastic deformation of nanoporous materials and nanocomposites |
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Authors: | WX Zhang TJ Wang X Chen |
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Institution: | 1. MOE Key Laboratory for Strength and Vibration, Department of Engineering Mechanics, Xi’an Jiaotong University, Xi’an 710049, China;2. Department of Earth and Environmental Engineering, Columbia University, 500 W 120th Street, New York, NY 10027, USA;3. Department of Civil & Environmental Engineering, Hanyang University, Seoul 133-791, Republic of Korea |
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Abstract: | Surface and interface play an important role on the overall mechanical behaviors of nanostructured materials. We investigate the effect of surface/interface stress on the macroscopic plastic behaviors of nanoporous materials and nanocomposites, where both the surface/interface residual stress and surface/interface elasticity are taken into account. A new second-order moment nonlinear micromechanics theory is developed and then reduced to macroscopically isotropic materials. It is found that the effect of surface/interface residual stress is much more prominent than that of the surface/interface elasticity, causing strong size effect as well as asymmetric plastic deformation for tension and compression. The variation of yield strength is more prominent with smaller pore/inclusion size or higher pore/inclusion volume fraction. For a representative nanoporous aluminum, the surface effect becomes significant when the pore radius is smaller than about 50 nm. When hard inclusions are embedded in a ductile metal matrix, the interface effect and resulting size effect are much smaller than that of nanoporous materials. The results may be useful for evaluating the mechanical integrity of nanostructured materials. |
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Keywords: | Surface stress Plasticity Nanoporous material Nanocomposite Size effect |
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