Several methods have been proposed to calculate the critical stress for initiation of dynamic recrystallization （σc） on the basis of mathematical methods. One＇ of them is proposed by Stewart et al. in which this c...Several methods have been proposed to calculate the critical stress for initiation of dynamic recrystallization （σc） on the basis of mathematical methods. One＇ of them is proposed by Stewart et al. in which this critical point appears as a distinct minimum in the （-dθ/dσ vs σ） through differentiating from θ vs σ. Another one is presented by Najafizadeh and Jonas by modifying the Poliak and Jonas method. According to this method, the strain hardening rate was plotted against flow stress, and the value of σc was attained numerically from the coefficients of the third-order equation that was the best fit from the experimental θ-σ data. Hot compression tests were used in the range of 1000 to 1100℃ with strain rates of 0.01^-1 s^-1 and strain of I on 316 stainless steel. The result shows that Najafizadeh and Jonas method is simpler than the previous one, and has a good agreement with microstructures. Furthermore, the value of normalized critical stress for this steel was obtained uc=σc/σp=0.92.展开更多
The main objective of this research is to investigate the hygroelastic behavior of a non-homogeneous circular plate made up of porous metamaterial resting on an auxetic material plate.The mechanical properties of the ...The main objective of this research is to investigate the hygroelastic behavior of a non-homogeneous circular plate made up of porous metamaterial resting on an auxetic material plate.The mechanical properties of the main plate,as well as moisture concentration,vary as an exponential function in the transverse direction.Poisson’s ratio is constant.The elastic supporting medium is developed by considering the structurestructure coupling.Based on the linear hygroelasticity theory,the governing state equations in terms of displacements and moisture concentration are acquired.At first,the Fickian equation is solved to compute the nonlinear distribution of moisture through the plate thickness,and then the state equations are semi-analytically solved using the statespace(SS)method and the differential quadrature(DQ)rule to predict the elastic field quantities.A comprehensive parametric analysis is accomplished to elucidate the effects of key parameters on the steady-state response of the plate under the mechanical and hygral loads.展开更多
文摘Several methods have been proposed to calculate the critical stress for initiation of dynamic recrystallization （σc） on the basis of mathematical methods. One＇ of them is proposed by Stewart et al. in which this critical point appears as a distinct minimum in the （-dθ/dσ vs σ） through differentiating from θ vs σ. Another one is presented by Najafizadeh and Jonas by modifying the Poliak and Jonas method. According to this method, the strain hardening rate was plotted against flow stress, and the value of σc was attained numerically from the coefficients of the third-order equation that was the best fit from the experimental θ-σ data. Hot compression tests were used in the range of 1000 to 1100℃ with strain rates of 0.01^-1 s^-1 and strain of I on 316 stainless steel. The result shows that Najafizadeh and Jonas method is simpler than the previous one, and has a good agreement with microstructures. Furthermore, the value of normalized critical stress for this steel was obtained uc=σc/σp=0.92.
文摘The main objective of this research is to investigate the hygroelastic behavior of a non-homogeneous circular plate made up of porous metamaterial resting on an auxetic material plate.The mechanical properties of the main plate,as well as moisture concentration,vary as an exponential function in the transverse direction.Poisson’s ratio is constant.The elastic supporting medium is developed by considering the structurestructure coupling.Based on the linear hygroelasticity theory,the governing state equations in terms of displacements and moisture concentration are acquired.At first,the Fickian equation is solved to compute the nonlinear distribution of moisture through the plate thickness,and then the state equations are semi-analytically solved using the statespace(SS)method and the differential quadrature(DQ)rule to predict the elastic field quantities.A comprehensive parametric analysis is accomplished to elucidate the effects of key parameters on the steady-state response of the plate under the mechanical and hygral loads.
