超声辅助微塑性成形过程超声尺度效应研究

发布时间：2018-02-15 23:22

本文关键词： 微塑性成形超声振动镦挤尺寸效应　出处：《杭州电子科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：传统的金属微塑性成形工艺由于微成形过程中尺寸效应的影响,坯料在成形过程中摩擦力变大,成形性能降低。而超声辅助微塑性镦挤成形工艺是结合超声波机械振动能,使坯料在载荷作用下发生微塑性变形的一种成形方法。超声辅助微塑性镦挤成形过程中的超声效应降低了材料流动应力,改善了工模具间接触状况。本文将超声振动引用到微塑性成形过程中,采用实验研究结合仿真分析的方法,研究当材料变形尺度较小时,超声振动对于材料变形规律的影响。针对超声辅助微镦挤成形过程,设计并搭建了浮动式超声辅助镦挤成形装置,实验研究超声辅助镦挤成形过程中超声振幅对于材料变形的影响,以及超声辅助微镦挤过程中超声尺度效应。研究表明:(1)使用浮动式实验装置进行超声辅助镦粗时,成形工件形状与固定式实验装置所得的成形工件有明显不同,超声辅助镦挤实验表明,表明浮动式实验装置的成形工件小孔填充能力更好。(2)超声振动提高了工件的成形能力,显著的提高了成形工件地的材料流动。此外,超声辅助镦挤成形工件表面出现明显的黑色物质,并且随振幅的增大,现象更加明显。(3)微塑性成形过程中,随着坯料直径的减小((1.5mm~0.5mm)),材料的流动更加困难,出现明显的尺寸效应,材料的挤出长度明显越来越小,且坯料尺寸越小,尺寸效应越明显。引入超声振动后,可以发现,随成形工件的尺寸下降,材料的成形能力上升,超声振动明显提高了材料的小孔填充能力,改善了微塑性成形过程中材料的尺寸效应。(4)基于相对增量的表征超声镦挤过程超声尺度效应研究发现相对于模具小孔直径1.5mm的相对增量,模具小孔直径1mm、0.8mm、0.5mm的相对增量有显著的增大,说明在超声辅助微塑性成形过程中,超声振动明显高了材料的成形能力,存在明显的超声尺度效应。采用有限元仿真技术,研究了超声辅助微镦挤成形过程工件的成形模式和材料变形规律:基于材料变形等效原则,采用仿真技术研究了材料应力软化效应和摩擦降低对于成形过程的影响,发现仅用两者不足以模拟超声振动对于微小孔填充能力改善的效果。
[Abstract]:The traditional metal micro-plastic forming process is due to the influence of size effect in the process of micro-forming, the friction force of the blank increases and the forming performance decreases during the forming process, while the ultrasonic assisted micro-plastic upsetting extrusion process is combined with the ultrasonic mechanical vibration energy. The ultrasonic effect of ultrasonic assisted micro-plastic upsetting extrusion reduces the flow stress of the material. The contact between die and die is improved. In this paper, ultrasonic vibration is applied to the process of micro-plastic forming, and the method of experimental research combined with simulation analysis is used to study when the material deformation scale is small. The influence of ultrasonic vibration on the deformation of materials. In view of the ultrasonic assisted micro-upsetting forming process, a floating ultrasonic assisted upsetting extrusion forming device was designed and built. The influence of ultrasonic amplitude on material deformation in ultrasonic assisted upsetting extrusion process and the ultrasonic scale effect in ultrasonic assisted micro upsetting process are studied experimentally. The results show that the floating experimental device is used for ultrasonic assisted upsetting. The shape of the formed workpiece is obviously different from that obtained by the fixed experimental device. The ultrasonic assisted upsetting experiment shows that the forming capacity of the workpiece formed by the floating experimental device is better than that of the floating-type experimental device. (2) Ultrasonic vibration improves the forming ability of the workpiece. In addition, the surface of the workpiece formed by ultrasonic assisted upsetting extrusion appears obvious black matter, and with the increase of amplitude, the phenomenon is more obvious in the process of micro-plastic forming. With the decrease of the diameter of the blank, the flow of the material becomes more difficult, the extrusion length of the material becomes smaller and smaller, and the smaller the blank size, the more obvious the size effect is. When ultrasonic vibration is introduced, it can be found that, With the decrease of the size of the workpiece, the forming ability of the material increases, and the ultrasonic vibration obviously improves the filling ability of the small hole of the material. The size effect of the material during microplastic forming is improved. (4) based on the relative increment, the ultrasonic scale effect of ultrasonic upsetting process is characterized and the relative increment is found to be 1.5 mm relative to the diameter of the small hole in the die. The relative increment of 1 mm / 0.8 mm / 0. 5 mm diameter of the small hole in the die is obviously increased, which indicates that the ultrasonic vibration obviously increases the forming ability of the material and has obvious ultrasonic scale effect in the process of ultrasonic assisted micro plastic forming. The finite element simulation technique is used. Based on the principle of equivalent deformation of materials, the effects of stress softening effect and friction reduction on the forming process were studied by simulation technology. It is found that both of them are not enough to simulate the effect of ultrasonic vibration on improving the filling capacity of tiny holes.
【学位授予单位】：杭州电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG663

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