本文關(guān)鍵詞： 微塑性成形 超聲振動 鐓擠 尺寸效應(yīng)　出處：《杭州電子科技大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：傳統(tǒng)的金屬微塑性成形工藝由于微成形過程中尺寸效應(yīng)的影響,坯料在成形過程中摩擦力變大,成形性能降低。而超聲輔助微塑性鐓擠成形工藝是結(jié)合超聲波機械振動能,使坯料在載荷作用下發(fā)生微塑性變形的一種成形方法。超聲輔助微塑性鐓擠成形過程中的超聲效應(yīng)降低了材料流動應(yīng)力,改善了工模具間接觸狀況。本文將超聲振動引用到微塑性成形過程中,采用實驗研究結(jié)合仿真分析的方法,研究當(dāng)材料變形尺度較小時,超聲振動對于材料變形規(guī)律的影響。針對超聲輔助微鐓擠成形過程,設(shè)計并搭建了浮動式超聲輔助鐓擠成形裝置,實驗研究超聲輔助鐓擠成形過程中超聲振幅對于材料變形的影響,以及超聲輔助微鐓擠過程中超聲尺度效應(yīng)。研究表明:(1)使用浮動式實驗裝置進(jìn)行超聲輔助鐓粗時,成形工件形狀與固定式實驗裝置所得的成形工件有明顯不同,超聲輔助鐓擠實驗表明,表明浮動式實驗裝置的成形工件小孔填充能力更好。(2)超聲振動提高了工件的成形能力,顯著的提高了成形工件地的材料流動。此外,超聲輔助鐓擠成形工件表面出現(xiàn)明顯的黑色物質(zhì),并且隨振幅的增大,現(xiàn)象更加明顯。(3)微塑性成形過程中,隨著坯料直徑的減小((1.5mm~0.5mm)),材料的流動更加困難,出現(xiàn)明顯的尺寸效應(yīng),材料的擠出長度明顯越來越小,且坯料尺寸越小,尺寸效應(yīng)越明顯。引入超聲振動后,可以發(fā)現(xiàn),隨成形工件的尺寸下降,材料的成形能力上升,超聲振動明顯提高了材料的小孔填充能力,改善了微塑性成形過程中材料的尺寸效應(yīng)。(4)基于相對增量的表征超聲鐓擠過程超聲尺度效應(yīng)研究發(fā)現(xiàn)相對于模具小孔直徑1.5mm的相對增量,模具小孔直徑1mm、0.8mm、0.5mm的相對增量有顯著的增大,說明在超聲輔助微塑性成形過程中,超聲振動明顯高了材料的成形能力,存在明顯的超聲尺度效應(yīng)。采用有限元仿真技術(shù),研究了超聲輔助微鐓擠成形過程工件的成形模式和材料變形規(guī)律:基于材料變形等效原則,采用仿真技術(shù)研究了材料應(yīng)力軟化效應(yīng)和摩擦降低對于成形過程的影響,發(fā)現(xiàn)僅用兩者不足以模擬超聲振動對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.
【學(xué)位授予單位】：杭州電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG663

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