FUNDAMENTAL STUDY OF MECHANICAL BONDING AND SEPARATION OF DUCTILE METALS

1)设计并安装了一台容量为<+]-> 16 tonf的四个并列布置的液压致动器的材料试验机。由于采用了微型计算机，操作和控制方便，可直观观察和精确测量当前冲头的载荷和冲程。2）为了进行铝件在附加静水压力下的镦粗冷自焊试验，研制了专用镦粗工装和传压介质试验装置。还阐述了实现连接界面膨胀达10倍和对最小长度为6 mm的焊接试样进行拉伸试验的技术。当静水压力为30 kgf时，达到最佳结合。<mm^（-2）>仅在镦粗的最后阶段施加在侧表面上，而在整个过程中或在过程的早期阶段的压力叠加使结合劣化。对试样纵截面的显微观察表明，高压提高了钢丝刷镀层的延展性，从而减小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。因此，所观察到的接头强度归因于压力的冲突效应。3）为了对由于流动应力差异而导致的点焊中的异常变形和材料失效进行实验研究，开发了基于橡皮泥的模型材料。研制了一台由脉冲电机和透明工装驱动的双压头挤压试验机，可进行侧向和正向挤压试验。实验结果表明，当流动应力差较大且硬化层厚度较小时，较硬材料失效。侧向挤压时较硬坯料的宽度较窄，而正向挤压时较大的断面收缩率促进了失效。

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.