Rubber of high molar mass, like cis-polybutadiene, shows a stress peak on theenineering stress-strain curve during stretching at room temperature. In this work cis-polybutadiene samples were swollen in a poor solvent,...Rubber of high molar mass, like cis-polybutadiene, shows a stress peak on theenineering stress-strain curve during stretching at room temperature. In this work cis-polybutadiene samples were swollen in a poor solvent, CHCl<sub>3</sub>/EtOH （1/1 v/v）, for differenttimes. It was found that both the initial modulus and the stress peak on stretching de-creased in magnitude with increasing swelling time and the peak disappeared entirely after1 hour of swelling. On further swelling the initial modulus increased somewhat and a smallstress peak re-appeared after swelling for 2 h. The disappearance of the stress peak afterswelling is interpreted as the result of disruption of cohesional entanglements present in theinitial rubber sample. The re-appearance of a small stress peak and the increase of modu-lus on further swelling are interpreted as being of the same nature as the phenomenon ofanti-plasticization. It is the result of forming some new cohesional entanglements of largerbinding energies through longer range chain segmental motions excited after the disruptionof the previously existing cohesional entanglements in the rubber. Thus an understand-ing of the stress peak on stretching a high molar mass rubber and the phenomenon ofanti-plasticization on molecular level has been put forward.展开更多
颗粒混凝土材料在建筑结构中应用比较常见,但其冲击下的动力学性能研究欠缺.为得到颗粒混凝土的动力学特性,借助MTS实验机得出其静力学强度,其后使用直径为75 mm SHPB系统对颗粒混凝土试样做了多种加载速度下的冲击试验.结果表明,颗粒...颗粒混凝土材料在建筑结构中应用比较常见,但其冲击下的动力学性能研究欠缺.为得到颗粒混凝土的动力学特性,借助MTS实验机得出其静力学强度,其后使用直径为75 mm SHPB系统对颗粒混凝土试样做了多种加载速度下的冲击试验.结果表明,颗粒混凝土试样的毁坏模式是非脆性碎裂,呈现出延性特点;随着冲击速度的增大,破坏后的形状由试样被压扁(形态基本完整,表现出明显的可压缩性)过渡到絮状.应变率在103.88~464.71 s^(-1)时,试样的峰值应力随着应变率的变大而增大,表现出明显的应变率效应.根据实验现象和实验数据进行分析,推导建立了颗粒混凝土峰值应力前和峰值应力后应力-应变的等效本构方程,将实验数据与拟合数据进行对比,具有较为明显的一致性,验证了本构方程的准确性.展开更多
An analytical model for dynamic recrystallization (DRX) is studied based on the relative grain size model proposed by Sakai and Jonas, and the characteristic flow behaviors under DRX are analyzed and simulated. Introd...An analytical model for dynamic recrystallization (DRX) is studied based on the relative grain size model proposed by Sakai and Jonas, and the characteristic flow behaviors under DRX are analyzed and simulated. Introducing the variation of dynamic grain size and the heterogeneous distribution of disolo- cation densities densities under DRX,a simple method for modeling and simulating DRX processes is developed by using Laplace transformation theory. The results derived from the present model agree well with the experimental results in literatures. This simulation can reproduce a number of features in DRX flow behaviors, for example,single and multiple peak flow behaviors followed by a steady state flow, the transition between them, and so on.展开更多
A set of absorption curves was priorly prepared on transparent films to fit the backgroundand peak intensities in continuous scanning X-ray stress measurement.It may be betterto correct both background and absorption ...A set of absorption curves was priorly prepared on transparent films to fit the backgroundand peak intensities in continuous scanning X-ray stress measurement.It may be betterto correct both background and absorption of pure diffraction intensity.Experimentalresults revealed this to be a reliable correction method.展开更多
文摘Rubber of high molar mass, like cis-polybutadiene, shows a stress peak on theenineering stress-strain curve during stretching at room temperature. In this work cis-polybutadiene samples were swollen in a poor solvent, CHCl<sub>3</sub>/EtOH （1/1 v/v）, for differenttimes. It was found that both the initial modulus and the stress peak on stretching de-creased in magnitude with increasing swelling time and the peak disappeared entirely after1 hour of swelling. On further swelling the initial modulus increased somewhat and a smallstress peak re-appeared after swelling for 2 h. The disappearance of the stress peak afterswelling is interpreted as the result of disruption of cohesional entanglements present in theinitial rubber sample. The re-appearance of a small stress peak and the increase of modu-lus on further swelling are interpreted as being of the same nature as the phenomenon ofanti-plasticization. It is the result of forming some new cohesional entanglements of largerbinding energies through longer range chain segmental motions excited after the disruptionof the previously existing cohesional entanglements in the rubber. Thus an understand-ing of the stress peak on stretching a high molar mass rubber and the phenomenon ofanti-plasticization on molecular level has been put forward.
文摘颗粒混凝土材料在建筑结构中应用比较常见,但其冲击下的动力学性能研究欠缺.为得到颗粒混凝土的动力学特性,借助MTS实验机得出其静力学强度,其后使用直径为75 mm SHPB系统对颗粒混凝土试样做了多种加载速度下的冲击试验.结果表明,颗粒混凝土试样的毁坏模式是非脆性碎裂,呈现出延性特点;随着冲击速度的增大,破坏后的形状由试样被压扁(形态基本完整,表现出明显的可压缩性)过渡到絮状.应变率在103.88~464.71 s^(-1)时,试样的峰值应力随着应变率的变大而增大,表现出明显的应变率效应.根据实验现象和实验数据进行分析,推导建立了颗粒混凝土峰值应力前和峰值应力后应力-应变的等效本构方程,将实验数据与拟合数据进行对比,具有较为明显的一致性,验证了本构方程的准确性.
文摘An analytical model for dynamic recrystallization (DRX) is studied based on the relative grain size model proposed by Sakai and Jonas, and the characteristic flow behaviors under DRX are analyzed and simulated. Introducing the variation of dynamic grain size and the heterogeneous distribution of disolo- cation densities densities under DRX,a simple method for modeling and simulating DRX processes is developed by using Laplace transformation theory. The results derived from the present model agree well with the experimental results in literatures. This simulation can reproduce a number of features in DRX flow behaviors, for example,single and multiple peak flow behaviors followed by a steady state flow, the transition between them, and so on.
文摘A set of absorption curves was priorly prepared on transparent films to fit the backgroundand peak intensities in continuous scanning X-ray stress measurement.It may be betterto correct both background and absorption of pure diffraction intensity.Experimentalresults revealed this to be a reliable correction method.
