城轨地铁用车轴强度计算分析

为了保证某城轨地铁车辆的行车安全,对其车轴强度进行了分析。参照标准EN13103中的材料力学计算方法,选取该车轴的7个截面,计算出各截面的合力矩、应力以及安全系数。结果表明,车轴危险截面位于轮座与刹车盘座圆弧过渡处和刹车盘座与轴身圆弧过渡处,且最大计算应力小于许用应力,满足车轴强度设计要求。     

装配式凸轮轴滚花连接机理及连接强度研究

装配式凸轮轴与传统凸轮轴相比具有重量轻、加工成本低、材料利用合理等优点。是新型的凸轮轴制造技术, 具有广泛的发展空间。而其连接方法是装配式凸轮轴制造的关键技术。本文基于相异材料的咬合连接理论, 提出了滚花式塑性变形连接机理, 对不同材料、尺寸的滚花式凸轮轴静连接强度及疲劳强度进行了实验研究, 同时分析了滚花连接的不同连接状况以及凸轮压装张紧应力。     

高强度结构钢的韧性启裂和稳态扩展

研究了具有一定韧度的高强度结构钢裂纹早期扩展阻力与材料的微观组织结构、应力状态、变形历史和应变特性之间的关系。结果表明:裂纹扩展阻力(指J_R阻力曲线中的J_i和dJ/da)主要决定于裂纹尖端的塑性约束程度和应力应变场中消耗的弹性能和塑性功。这与三轴应力状态函数σ_mσ~(1/2)有关。材料的流变曲线描述了形变过程中的变形历史和应变特性,有明显的阶段性,其中第Ⅱ阶段的变形历史和应变特性制约着裂纹的启裂过程,第Ⅲ阶段的变形历史和应变特性制约着裂纹的扩展过程。应变硬化率dσ/dε可以敏感地反映出材料内部的应力分布和微观断裂机制。     

碳化物在高铬铸铁高应力磨料磨损中的影响

对不同载荷作用下的高铬铸铁在耐磨实验机上进行了磨料磨损试验;对在不同的碳化物对基体的保护作用与碳化物的剥离进行了相关的分析.结果表明载荷在一定值以下磨损较为缓慢,当载荷超过一定值时,磨损急剧加剧,随着载荷的增加"尺寸较小"的碳化物首先剥离基体,当载荷继续增大时,"尺寸较大"的碳化物也剥离基体并有碎裂现象.这要求高铬铸铁中的碳化物不仅要分布均匀,碳化物的尺寸也要合适.     

X射线衍射-拉伸法测薄膜应力

薄膜应力的测量一直是一个困难的问题。本文尝试用一种新的方法——X射线衍射-拉伸法,对薄膜的应力进行检测,与侧倾法实验结果相比较,X射线衍射-拉伸法更为准确与可靠。     

AN EXPERIMENTAL-NUMERICAL METHOD FOR MEASURING CRACK PROPAGATING VELOCITIES UNDER STRESS WAVE LOADING

An experimental-numerical method for measuring dynamic crack propagating velocities under stress wave loading is established in this paper. The experiments of the three-point bend specimen are done on the improved Hopkinson bar. Deflection of loading point, dynamic load and instantaneous crack length are measured, then crack propagating velocities are calculated. Experiments on 40Cr steel show that the results given by this method have a good agreement with that obtained by the resistance fracture gage method. Therefore this method is feasible for measuring crack propagating velocities under high loading rate and will have wide application.     

AA7005铝合金的热加工变形特性

研究了AA7005合金高温压缩变形时的流变应力、动态回复与再结晶以变形组织变化特征。合金稳态变形时,应变速度、温度和流变应力之间满足包含热激活材料常数的Arrhenius项的双曲正弦关系,变形过程为受位错增殖和相互销毁速率控制的热激活过程,螺型位错的交滑移和刃型位错的攀移为主要动态回复机制。动态回复时,形成典型的变形亚晶组织,亚晶尺寸随1nZ的减小而增大。高温低速变形条件下,合金发生局部几何动态再结晶,流变曲线呈现连续下降的特征,形成与原始纤维组织不同的细小等轴大角度再结晶晶粒。     

Stress due to a moving band source of heat and mechanical load on the work surface during grinding

The grinding operation is considered to be equivalent to a moving band source of heat and mechanical load on the surface of a semi-infinite solid, producing very high temperature on the surface of the workpiece. The resulting temperature may result in high stress in the workpiece. It is thus desirable to be able to predict the stress levels expected during the grinding process.     

铸钢件准固态区域应力,应变数值模拟及热裂机制

对ＺＧ４５实验热裂试棒的数种工况进行了应力－应变的数值模拟，对热裂形成机制进行了讨论。研究认为：热裂起源于Ｂｉｎｇｈａｍ体，是塑性变形超过Ｂｉｎｇｈａｍ体塑性储备值所致。     

Analytical and experimental analysis of deep drawing process for bimetal elements

The paper presents the concepts of solving of deep drawing process for bimetal elements of sheet materials. The inertia forces, plastic hardening behaviour of the deformed material and dynamic stress are utilized in the problems of plasticity. The experimental results and general conclusion are presented at the end of the paper.