基于动态模型的冲压模具磨损寿命研究

为了准确预测模具磨损深度，提高模具使用寿命，通过研究冲压模具磨损机理，建立了混合磨损动态模型，提出一种新的模具磨损寿命预测方法。由于前次冲压对后次冲压模具磨损具有显著影响，模具的总磨损深度并不与单次冲压磨损深度呈简单的线性关系，该方法考虑了镀铬层和火焰淬火层厚向磨损系数、粗糙度的影响以及模具表面到芯部材料硬度的梯度变化关系。通过试验得到火焰淬火和电镀铬2种不同处理方式下模具材料磨损的相关参数，将其运用到混合磨损动态模型中。运用节点移动来不断更新磨损型面，获得当前磨损深度下的新参数，使用新参数计算当次冲压的磨损深度，确保随着磨损的增加，磨损参数不断更新，使得磨损预测更符合实际磨损的物理过程，弥补了经典Archard模型忽略因磨损而导致接触应力和滑移速度改变的不足。用壳单元提取冲压接触型面建立有限元模型，不需表达整个模具，降低了问题的复杂性，极大提高了计算效率。建立了磨损深度与冲压次数之间的确切关系，得到了模具磨损深度的定量预测方法。使用该方法对某车型发动机盖外板冲压模具进行磨损分析，将结果与实际模具磨损情况以及经典Archard方法预测结果进行对比。结果表明：所提出的冲压模具磨损寿命预测方法更接近实际磨损，误差比经典Archard方法小18.60%，预测精度明显高于经典的Archard方法。

Research on Stamping Die Wear Life Based on Dynamic Model

In order to accurately predict the die wear depth and to improve the service life of the stamping die, a dynamic mixed wear model was established by investigating the stamping die wear mechanisms, whilst a new method for predicting die wear life was proposed. On account of the significant influence of the previous stamping on the die wear of the after stamping, the relationship between the gross die wear depth and the single stamping die wear depth is not simple linear. The influence of wear coefficient and roughness coefficient of the chromium plating layer and flame hardening along the thickness direction, and the material hardness gradient change from the mould surface to the core were taken into consideration. The wear parameters of stamping die material with processing methods of flame hardening and electroplating chromium were obtained through the wear experiments. Such parameters were applied to the dynamic mixed wear model. The new parameters of the current wear depth which acquired by constantly updating the wear geometric profile via moving mesh nodes were used to calculate the wear depth of current stamping, to ensure that with the increase of wear, the wear parameters can be constantly updated and the wear prediction can be more accordant with the actual physical process. The deployment of new parameters made up for the shortage of the classical Archard's model in which the contact stress and sliding speed changed due to the ignorance of the wear. The finite element model was established through extracting contact surface by shell elements instead of expressing the whole stamping die. Hence, with the low complexity of the problem, the computational efficiency was improved. In this project, on the basis of an accurate relationship between wear depth and stamping times, a quantitative prediction method of the stamping die wear depth was acquired. The wear analysis on the stamping die of a certain hood outer was carried out, and the results were compared with values predicted by the classical Archard method and the actual die wear pattern. The result shows that the value predicted by the new method is close to the actual wear, and the deviation is 18.60% lower than the value predicted by classical Archard method. The accuracy of the new method is obviously higher than that of the classical Archard method.