基于动态摩擦因数磨损系数的先进高强钢模具寿命研究

A Study on AHSS Die Life Based on Dynamic Friction and Wear Coefficients

为更精确地计算先进高强钢冲压模具的磨损,预测模具的寿命,和揭示冲压过程中不断变化的节点压力及相对滑动速度对摩擦因数和磨损系数的影响,以不同的压力和速度为条件进行正交摩擦磨损实验,得到对应的摩擦因数和磨损系数。再以压力和速度为自变量,摩擦因数和磨损系数为因变量分别进行曲线拟合,提出基于动态的摩擦因数和磨损系数的计算模型。由于模具表面镀层硬度随镀层厚度变化而变化,通过实验和理论推导,建立变化的模具表面硬度与磨损系数的耦合模具表面磨损方程,并以动态变化的摩擦因数模型代替库伦摩擦模型进行冲压过程的数值模拟,以耦合的模具表面磨损方程进行磨损计算,将计算结果与模具磨损型面的扫描数据进行对比。结果表明,与传统恒定摩擦因数、磨损系数计算结果相比,运用该方法计算得到磨损结果的精确度提高了15.05%,采用该方法对某先进高强钢零件拉延模具进行了寿命预测,显示该模具在冲压大约5.9万件时,模具表面局部区域镀层磨损严重,需要修模。

In order to more accurately calculate the wear of advanced high-strength steel(AHSS) stamping die, predict die life, and reveal the effects of constantly changing nodes’ pressure and relative sliding velocity during stamping on friction coefficient and wear coefficient, orthogonal experiments on friction and wear are carried out under different pressures and velocities, with corresponding friction coefficient and wear coefficient obtained. Then curve fitting is conducted with pressure and velocity as independent variables and friction coefficient and wear coefficient as dependent variables and a calculation model for dynamic friction coefficient and wear coefficient is put forward. Due to the hardness of plating layer on die surface is changed with its thickness,the coupled die face wear equations for the changing hardness and wear coefficient of die face are established based on experiments and theoretical derivation, a numerical simulation on stamping process is performed by using the model for dynamically changing friction coefficient in stead of Coulomb friction model, and die wear is calculated using coupled die face wear equations, whose results are compared with the scanning data of worn die face. The results show that compared with traditional calculation using constant friction and wear coefficients, the accuracy of wear results calculated by the method proposed is 15.05% higher, and the life prediction on an AHSS drawing die using this method indicates that after 59,000 parts are stamped, the plating layer on some areas of die face is seriously worn and need repair.