Based on the slip-line field theory, a two-dimensional slip failure mechanism with mesh-like rigid block system was constructed to analyze the ultimate bearing capacity problems of rough foundation within the framewor...Based on the slip-line field theory, a two-dimensional slip failure mechanism with mesh-like rigid block system was constructed to analyze the ultimate bearing capacity problems of rough foundation within the framework of the upper bound limit analysis theorem. In the velocity discontinuities in transition area, the velocity changes in radial and tangent directions are allowed. The objective functions of the stability problems of geotechnical structures are obtained by equating the work rate of external force to internal dissipation along the velocity discontinuities, and then the objective functions are transformed as an upper-bound mathematic optimization model. The upper bound solutions for the objective functions are obtained by use of the nonlinear sequential quadratic programming and interior point method. From the numerical results and comparative analysis, it can be seen that the method presented in this work gives better calculation results than existing upper bound methods and can be used to establish the more accurate plastic collapse load for the ultimate bearing capacity of rough foundation.展开更多
在金属板料拉深工艺设计中,拉深力的计算通常采用经验公式,不同参考资料上的经验公式有时差别很大。而滑移线法是求解理想刚塑性金属材料塑性变形力的方法之一。介绍了用滑移线法求解拉深力的方法,通过对金属板料拉深时凸缘区进行受力分...在金属板料拉深工艺设计中,拉深力的计算通常采用经验公式,不同参考资料上的经验公式有时差别很大。而滑移线法是求解理想刚塑性金属材料塑性变形力的方法之一。介绍了用滑移线法求解拉深力的方法,通过对金属板料拉深时凸缘区进行受力分析,利用滑移线理论建立了变形区的滑移线场,依据屈服准则和滑移线的沿线特性求解出了金属板料拉深时凸缘区的单位流动拉应力的计算公式,进而能够求出总变形力。通过实例进行了验证,滑移线法得到的拉深力是61 k N,经验公式法得到的拉深力是63 k N,结果表明,根据滑移线法求解的应力计算出来的拉深力符合工程要求,能够实现设备吨位的选择。展开更多
Rolling force and rolling moment are prime process parameter of external spline cold rolling. However, the precise theoretical formulae of rolling force and rolling moment are still very fewer, and the determination o...Rolling force and rolling moment are prime process parameter of external spline cold rolling. However, the precise theoretical formulae of rolling force and rolling moment are still very fewer, and the determination of them depends on experience. In the present study, the mathematical models of rolling force and rolling moment are established based on stress field theory of slip-line. And the isotropic hardening is used to improve the yield criterion. Based on MATLAB program language environment, calculation program is developed according to mathematical models established. The rolling force and rolling moment could be predicted quickly via the calculation program, and then the reliability of the models is validated by FEM. Within the range of module of spline m=0.5-1.5 mm, pressure angle of reference circle α=30.0°-45.0°, and number of spline teeth Z=19-54, the rolling force and rolling moment in rolling process （finishing rolling is excluded） are researched by means of virtualizing orthogonal experiment design. The results of the present study indicate that： the influences of module and number of spline teeth on the maximum rolling force and rolling moment in the process are remarkable; in the case of pressure angle of reference circle is little, module of spline is great, and number of spline teeth is little, the peak value of rolling force in rolling process may appear in the midst of the process; the peak value of rolling moment in rolling process appears in the midst of the process, and then oscillator weaken to a stable value. The results of the present study may provide guidelines for the determination of power of the motor and the design of hydraulic system of special machine, and provide basis for the farther researches on the precise forming process of external spline cold rolling.展开更多
基金Projects(51078359, 51208522) supported by the National Natural Science Foundation of ChinaProjects(20110491269, 2012T50708) supported by China Postdoctoral Science FoundationProject supported by Postdoctoral Science Foundation of Central South University, China
文摘Based on the slip-line field theory, a two-dimensional slip failure mechanism with mesh-like rigid block system was constructed to analyze the ultimate bearing capacity problems of rough foundation within the framework of the upper bound limit analysis theorem. In the velocity discontinuities in transition area, the velocity changes in radial and tangent directions are allowed. The objective functions of the stability problems of geotechnical structures are obtained by equating the work rate of external force to internal dissipation along the velocity discontinuities, and then the objective functions are transformed as an upper-bound mathematic optimization model. The upper bound solutions for the objective functions are obtained by use of the nonlinear sequential quadratic programming and interior point method. From the numerical results and comparative analysis, it can be seen that the method presented in this work gives better calculation results than existing upper bound methods and can be used to establish the more accurate plastic collapse load for the ultimate bearing capacity of rough foundation.
文摘在金属板料拉深工艺设计中,拉深力的计算通常采用经验公式,不同参考资料上的经验公式有时差别很大。而滑移线法是求解理想刚塑性金属材料塑性变形力的方法之一。介绍了用滑移线法求解拉深力的方法,通过对金属板料拉深时凸缘区进行受力分析,利用滑移线理论建立了变形区的滑移线场,依据屈服准则和滑移线的沿线特性求解出了金属板料拉深时凸缘区的单位流动拉应力的计算公式,进而能够求出总变形力。通过实例进行了验证,滑移线法得到的拉深力是61 k N,经验公式法得到的拉深力是63 k N,结果表明,根据滑移线法求解的应力计算出来的拉深力符合工程要求,能够实现设备吨位的选择。
基金supported by National Natural Science Foundation of China (Grant No. 50675145)Shanxi Provincial Key Project of Science and Technology of China (Grant No. 2006031147)+1 种基金Shanxi Provincial Innovation Project for Graduate Students of China (Grant No. 20061027)Shanxi Provincial Key Project for Studied-abroad Returnee of China
文摘Rolling force and rolling moment are prime process parameter of external spline cold rolling. However, the precise theoretical formulae of rolling force and rolling moment are still very fewer, and the determination of them depends on experience. In the present study, the mathematical models of rolling force and rolling moment are established based on stress field theory of slip-line. And the isotropic hardening is used to improve the yield criterion. Based on MATLAB program language environment, calculation program is developed according to mathematical models established. The rolling force and rolling moment could be predicted quickly via the calculation program, and then the reliability of the models is validated by FEM. Within the range of module of spline m=0.5-1.5 mm, pressure angle of reference circle α=30.0°-45.0°, and number of spline teeth Z=19-54, the rolling force and rolling moment in rolling process （finishing rolling is excluded） are researched by means of virtualizing orthogonal experiment design. The results of the present study indicate that： the influences of module and number of spline teeth on the maximum rolling force and rolling moment in the process are remarkable; in the case of pressure angle of reference circle is little, module of spline is great, and number of spline teeth is little, the peak value of rolling force in rolling process may appear in the midst of the process; the peak value of rolling moment in rolling process appears in the midst of the process, and then oscillator weaken to a stable value. The results of the present study may provide guidelines for the determination of power of the motor and the design of hydraulic system of special machine, and provide basis for the farther researches on the precise forming process of external spline cold rolling.
