超声波在拔丝加工中减摩降载作用的研究

为了搞清超声波在拔丝加工中产生降载效应的机理，在自制的超声波拔丝装置上对黄铜丝进行了一系列冷拔加工的实验。结果表明，在模具上施加超声波，可以有效地降低拉拔力，超声波输出功率愈大，拉拔力的降低幅度愈大，在本实验的工况范围内，最大可降低３７％。超声波的降载效果与拔丝速度有关，在相同的超声波功率作用下，拉拔速度愈小，拉拔力的减少幅度愈大。通过对拉拔丝材表面的扫描电镜观察，表明施加超声波还可改善线材的表面质量，减少表层损伤，降低表面粗糙度。提出了一个简化的超声波拔丝拉拔力的计算模型。根据这一模型所得出的超声功率和拔丝速度对拉拔力影响的计算结果与实验结果能较好的吻合，从而初步说明了超声波所产生的减摩降载作用主要是由于模具和线材之间的断续接触和冲击造成的。

Investigation on the effect of ultrasonic vibration on reduction in drawing force

In order to clarify the effects of ultrasonic vibration on wire drawing process, an experimental research of copper wire drawing with utilization of ultrasonic vibration was conducted. It has been shown that the drawing force can be effectively reduced by applying ultrasonic vibration to the drawing die. The greater the output power of the ultrasonic vibration, the more the reduction in drawing force. A force reduction was obtained as more as 37% under the experimental conditions. Experiment results indicated that the effect of ultrasonic vibration on reduction in drawing force was influenced by drawing speed. It is more effective at lower speeds. Examination of the wire surface under SEM (scanning electron microscope) revealed that the copper wire drawn under ultrasonic vibration conditions has a more smooth and flaw less surface compared with those obtained under no ultrasonic vibration. The mechanism of ultrasonic vibration effect on force reduction has been discussed, and a simple theoretical model has been proposed. The prediction given by the model agrees well with the experiment results. It is concluded that the force reduction effect was mainly attributed to the superposition of ultrasonic impact force on the drawing force rather than to Blacha effect, heat or reduction in friction.