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Amer Darvishvand,Asghar Zajkani 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.6
Present study investigates a comparative study of lower and higher-order strain gradient plasticity (SGP) theories involvingthe size-dependent micromechanically flexural behaviors of crystalline thin plates. The investigation includes the Mechanism-Based and the Chen–Wang SGP models established on the Taylor dislocation hardening by evoking the statistically storeddislocations and geometrically necessary dislocations. In addition, these models are conjugated with a multiple plasticwork-hardening law proposed for the microstructural applications of the SGP. An analytical approach based on energyminimizing method is used for obtaining deflection values in terms of the length scale, exponent of the work-hardening andthe tangential module. The obtained results indicate a meaningful dependence of the deflections to the length scale, plasticwork hardening and other parameters as well.
Amer Darvishvand,Asghar Zajkani 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.71 No.3
Since the actuators with small- scale structures may be exposed to external reciprocal actions lead to create undesirable loads causing instability, the buckling behaviors of them are interested to make reliable or accurate actions. Therefore, the purpose of this paper is to analyze plastic buckling behavior of the micro beam structures by adopting a Conventional Mechanism-based Strain Gradient plasticity (CMSG) theory. The effect of length scale on critical force is considered for three types of boundary conditions, i.e. the simply supported, cantilever and clamped - simply supported micro beams. For each case, the stability equations of the buckling are calculated to obtain related critical forces. The constitutive equation involves work hardening phenomenon through defining an index of multiple plastic hardening exponent. In addition, the Euler-Bernoulli hypothesis is used for kinematic of deflection. Corresponding to each length scale and index of the plastic work hardening, the critical forces are determined to compare them together.