FUNDAMENTAL STUDY OF MECHANICAL BONDING AND SEPARATION OF DUCTILE METALS

1)设计并安装了一台具有四个横向布置的液压执行机构的材料试验机，该试验机的容量为16吨。利用微型计算机操作和控制方便，使电流冲压载荷和冲程的直观观察和精确测量成为可能。2)为了进行铝试件在叠加静水压力作用下进行冷态自焊的试验，研制了专用的锻造工装和传压介质试验装置。还阐述了实现连接界面扩展到10的技术，以及对最小长度为6 mm的焊接试件进行拉伸试验的技术。当静水压力为30kgf时，粘接效果最好。&lt；mm^(-2)&gt；仅在镦粗的最后阶段施加在侧面，而在整个过程中或在过程的早期阶段压力的叠加会恶化结合性能。对试件纵向截面的微观观察表明，高压增加了刷丝表层的延展性，从而减少了原始金属表面的面积，同时提高了原始金属界面的结合强度。观察到的接头强度归因于压力的冲突效应。3)为了实验研究双金属焊接中由于流动应力的差异而导致的异常变形和材料破坏，开发了基于塑料的模型材料。还研制了一台脉冲电机驱动的两冲程压缩试验机和透明工具，用于侧向和正向挤压试验。实验表明，当流动应力差较大、硬质层厚度较小时，硬质材料失效。侧向挤压时较硬的坯料宽度越窄，正向挤压时的面积缩小率越大，则破坏越明显。

1) A material testing machine with four crosswise arranged hydraulic actuators of a <+]-> 16 tonf capacity was designed and installed. By the use of a microcomputer , easy operation and control of the machine, visual watch and precise measurement of current punch loads and strokes were made feasible.2) To carry out experiments in cold autogenous welding by upsetting of aluminium specimens under superimposed hydrostatic pressure, a special upsetting tooling and a test equipment for pressure transmission medium were deviced. Techniques to attain expansions of joining interface up to 10 and to conduct tensile tests of welded specimens of a minimum length of 6 mm were also elaborated. The best bonding was achieved when a hydrostatic pressure of 30 kgf. <mm^(-2)> was imposed on the side surfaces only at the final stage of upsetting, while superposition of the pressure throughout or in the early period of the process deteriorated bonding. Microscopic examination of longitudinal sections of the specimens indicated that the high pressure increased ductility of the wire-brushed surface layers thus reducing the area of virgin metal surface, while it raised the bond strength at the virgin metal interface. The observed joint strengths were thus attributable to the conflicting effect of pressure.3) For an experimental investigation of abnormal deformation and material failure in bimetallic welding due to the difference in flow stress, model materials based on plasticine were developed. A two-ram compression tester driven by pulse-motors and transparent toolings for sideways and forward extrusion experiments were also deviced. The experiments revealed that the harder material failed when the flow stress difference was large and the thickness of harder layer was small. A narrower width of the harder billet in the sideways extrusion and a higher reduction in area in the forward extrusion promoted failure.