TiNi形状记忆合金的电火花加工性能

TiNi形状记忆合金由于具有优异的超弹性和形状记忆效应等性能而被大量地应用于工业生产中。然而,形状记忆合金的传统加工相当复杂。因此,研究TiNi形状记忆合金的电火花线切割加工（WEDM）性能。采用L27正交阵列以尽量减少实验。在不同的脉冲持续时间、脉冲关断时间、伺服电压、冲洗压力和线速度条件下进行实验。为同步优化提出一种利用Taguchi设计与实用理念的多响应优化方法。通过对信噪比（S/N）的均值分析和方差分析,确定最佳参数水平。Taguchi分析表明：1μs脉冲持续时间、3.8μs脉冲关断时间、40 V伺服电压、1.8×105Pa冲洗压强和8 m/min线速度,有利于同时使材料去除率最大化和表面粗糙度最小化。TiNi形状记忆合金电火花线切割加工的优化结果表明：脉冲持续时间显著影响材料去除率和表面粗糙度。在较长的脉冲持续时间时,在加工表面可观察到放电坑、微裂纹和重铸层。

Wire electric discharge machining characteristics of titanium nickel shape memory alloy

Ti Ni shape memory alloys（SMAs） have been normally used as the competent elements in large part of the industries due to outstanding properties, such as super elasticity and shape memory effects. However, traditional machining of SMAs is quite complex due to these properties. Hence, the wire electric discharge machining（WEDM） characteristics of Ti Ni SMA was studied. The experiments were planned as per L27 orthogonal array to minimize the experiments, each experiment was performed under different conditions of pulse duration, pulse off time, servo voltage, flushing pressure and wire speed. A multi-response optimization method using Taguchi design with utility concept has been proposed for simultaneous optimization. The analysis of means（ANOM） and analysis of variance（ANOVA） on signal to noise（S/N） ratio were performed for determining the optimal parameter levels. Taguchi analysis reveals that a combination of 1 μs pulse duration, 3.8 μs pulse off time, 40 V servo voltage, 1.8×105 Pa flushing pressure and 8 m/min wire speed is beneficial for simultaneously maximizing the material removal rate（MRR） and minimizing the surface roughness. The optimization results of WEDM of Ti Ni SMA also indicate that pulse duration significantly affects the material removal rate and surface roughness. The discharged craters, micro cracks and recast layer were observed on the machined surface at large pulse duration.