响应曲面法优化气体淬火过程中的工艺参数

以轴对称问题气体淬火过程为研究对象，提出了阶段换热系数模型，进行了五因子三水平Box-Behnken实验设计．根据实验设计结果，将设计的变量水平代入本文开发的淬火过程有限元分析软件进行计算，用逐步回归法和响应曲面方法对实验结果进行拟合，建立了拟合变形程度、表面单元平均等效残余应力、等效残余应力标准差、平均表面硬度和表面硬度标准差的响应曲面公式．以变形程度为目标，建立了相应的优化目标函数，用Lagrange乘子法对优化目标函数进行了带上下限及约束函数的非线性优化．优化后，五项目标中的四项得到了有利的结果，使用优化后工艺参数进行气体淬火，可以提高零件的淬火质量．

OPTIMIZATION OF PARAMETER IN GAS QUENCHING PROCESS USING RESPONSE SURFACE METHOD

A step function model with time is presented, and an axisymmetric component is regarded as the study objective in this model. Heat transfer coefficient during the gas quenching process is described as a function of time, and five design variables are selected to do the design of Box-Behnken experiment with five factors and three levels. The levels of design variables attained from the result of Box-Behnken experiment design are regard as the technical parameters of gas quenching to simulate the gas quenching process using the FEM software developed in the paper. Some mathematical models of response surface are attained using the stepwise regression method and the response surface method. These mathematical models show the releationship between the quenching results and the design variables. An optimization model is presented in the paper, the distortion is regarded as the optimization objective in the model. An optimization process is done using the non-linear method and the Lagrange multiplier method. After optimization, four items of evaluation objectives are improved. The quenching quality using technical parameters technical parameters before optimization. after optimization is much better than that using