One-dimensional tensile constitutive equation cannot be directly generalized to deal with two-dimensional bulging mechanical problems

Superplastic forming has been extensively applied to manufacture parts and components with complex shapes or high-precisions. However, superplastic formation is in multi-stress state. In a long time, uniaxial tensile constitutive equation has been directly generalized to deal with multi-stress state. Whether so doing is feasible or not needs to be proved in theory. This paper first summarizes the establishing processes of superplastic tensile and bulging constitutive equation with variable m, and, using the analytical expressions of equivalent stress a and equivalent strain rate ε of free bulge based on the fundamentals of continuum medium plastic mechanics, derives the analytical expressions of optimum loading rules for superplastic free bulge. By comparing the quantitative results on typical superplastic alloy ZnAI22, it is shown that one-dimensional tensile constitutive equations cannot be directly generalized to deal with two-dimensional bulging quantitative mechanical problems; only superplastic b     

超塑性拉伸变形应变速率敏感性指数的试验测量及其精细分析

从理论上导出不同典型变形路径下用试验参数F(变形载荷 )、v(十字头速度 )和l(试样标距长度 )表达的应变速率 ( ε)敏感性指数m的一组公式 ,并由此建立了在一组恒 ε试验、恒v试验和定F试验曲线上测量定长度应变速率敏感性指数ml、恒速度应变速率敏感性指数mv 和定载荷应变速率敏感性指数mF 的统一方法。在同一组恒 ε(恒v或定F)曲线上测得ml、mv 和mF,而且测得的ml、mv 和mF 是不相同的 ,这说明超塑性变形具有较强的结构敏感性。但是在不同组的恒 ε、恒v和定F试验曲线上用相同的测量公式测得的ml、mv 或mF 的值也各不相同 ,便是应分析的问题 ,于是又对m值的结构敏感性作了精细分析。     

超塑拉伸变形应变速率敏感性指数的力学解析

从拉伸变形的状态方程和力学基本理论出发,导出了塑性和超塑性拉伸变形ｍξ、ｍｖ　和ｍＦ（ｍξ、ｍｖ。和Ｆ分别为恒应变ξ、恒变形速度ｖ和恒载荷Ｆ的应变速率敏感性指数）的函数表达式,而且理论计算值与典型超塑性合金ＺｎＡ１５的试验数据吻合,这便从理论上解答了“拉伸变形应变速率敏感性指数的力学涵义及其规范测量”一文从试验上提出的问题,即：为什么ｍξ、ｍｖ和ｍＦ随应变速率ξ的变化规律互不相同,甚至出现了ｍＦ会大于１,ｍｖ会是负值的反常结果。对这些问题的理论解答便进一步揭示了ｍ值的力学本质。     

IC厌氧反应器内上升流速对钙离子截留量的影响

IC反应器钙化问题是造纸废水处理中面临的重大问题,钙离子截留量的高低是判断污泥钙化快慢的主要依据。本文针对某造纸企业3个IC反应器的进出水各项指标及进水量、循环量、上升流速等工艺指标进行分析,探讨了上升流速的高低对钙离子截留量的影响。