精冲模具复合磨损机理及控制方法研究

Fine-blanking, as one of the precision plastic forming technologies, has been widely used in the field of automobile industry. Currently, majority of precise, complex and long-lifetime fine-blanking tools are still relied on importation from foreign countries due to the lack of knowledge on the working condition and tool wear mechanism, which seriously hindered the development of fine-blanking technology in China. Therefore, to clarify the fine-blanking tool wear mechanism and establish the process window oriented to tool wear control is significant to the tool optimization, life extension and part quality improvement. Under these circumstances the current study will focus on the interaction of different wear behaviors during the fine-blanking process, and the conditions of occurrence and transformation related to various wear behavior with the help of multi-scale analysis, and further on the establishment of the compound tool wear model. Then the compound wear model is introduced as well as the damage model into the fine-blanking process simulation to realize the prediction of tool wear during the production cycle. Finally the relationships of the process and tool parameters with tool wear would be investigated experimentally and numerically, so as to define a process window aiming at the fine-blanking tool wear control. The purpose of the project is not only to provide significant academic results, but also to enhance the level of fine-blanking industry in China.

精冲作为一种重要的精密塑性成形技术，已被广泛应用于汽车制造领域。然而，精冲成形过程工况复杂，模具易磨损，目前大部分精密、复杂且长寿命的精冲模具仍然依赖进口，严重制约了我国精冲技术的进一步发展。因此，厘清精冲模具磨损机理，形成面向模具磨损控制的工艺窗口，对优化精冲模具设计、提高模具寿命和产品质量具有十分重要的意义。基于上述背景，本项目旨在研究精冲成形过程中多种磨损形式的交互作用机制，借助多尺度分析确定多种磨损形式产生与转化的条件，构建精冲模具复合磨损模型；将磨损模型与损伤模型引入包含零件成形和凸模回程的精冲过程模拟，实现加工循环中精冲模具磨损的动态预测；在此基础上结合物理实验，研究工艺与模具参数对精冲模具磨损的影响规律，形成面向精冲模具磨损控制的工艺窗口。本项目的研究不仅具有重要的学术价值，而且在提升精冲成形技术水平、促进精冲技术发展方面也有重要的应用价值。

精冲成形过程中，金属板料在较大的三向静水压应力下发生剪切变形，裂纹的产生与扩展得以抑制，因而得到的零件表面有较高的垂直度和平行度，剪切面光亮平整，可直接用于装配。但是，精冲工艺条件的严苛导致精冲模具的工作环境较为恶劣，涉及较大的摩擦力、局部交变作用力以及温升情况，使得精冲模具的磨损情况较普通冲裁要严重得多。.围绕精冲成形过程中的模具磨损问题，本项目以传动板精冲凸模为研究对象，进行了传动板精冲凸模的磨损失效分析和磨损表征，发现传动板精冲凸模的磨损过程是一个复合黏着磨损、磨料磨损和疲劳磨损的复杂失效过程，三种磨损机理相互影响、相互促进。结合有限元模拟和物理试验，项目研究了传动板精冲凸模的磨损影响因素与模具磨损的量化关系，结果显示精冲凸模磨损与压边力、反顶力、冲裁速度、凹模倒斜角成正相关关系，而与精冲间隙和模具硬度成负相关关系。.由于精冲成形模具的磨损量化受制于模具频繁拆卸和装配所带来的精度损失与工况波动，本项目借助有限元分析手段，发现特定条件下板料挤压模具受力和材料流动情况与精冲成形过程近似相同。在此基础上，提出了一种新的接近精冲工况的模具磨损评估装置，通过批量板料挤压实验，测量不同挤压次数下模具的刃口轮廓，进而形成刃口轮廓的演化曲线，为实际精冲工况下模具磨损的研究提供数据支撑。.为研究不同精冲材料微观组织对模具磨损的影响，本项目建立了精冲成形过程的多尺度仿真模型，明确了精冲材料微观组织对精冲性能的影响，以及精冲成形过程中材料和模具的受力与损伤情况；建立了以Archard模型为基础的精冲模具磨损模型，考虑了精冲加工循环模拟中模具轮廓和材料磨损系数的动态更新，结合实验结果加以修正，实现了批量加工循环的模拟；此外，考虑到成形过程中的温升所带来的影响，建立了接触导热系数多变量映射关系，对精冲模具在成形过程中的温度变化进行了研究，明晰了温升对模具磨损行为的影响。