基于多尺度分析的先进高强度钢板冲压成形粘模机理研究

In sheet metal forming process, galling behavior is one of the most significant influencing factors on die failure and surface damage. It is an urgent problem in plastic processing industry to reduce or even eliminate galling behavior in sheet metal forming process. At present, since the high strength steel sheets are the key materials for the lightweight of automobiles, the contact interface in sheet metal forming processes become worse and more complex, the traditional wear methods can not solve these galling problems. In the present project, based on the theories of friction and wear, metallography, contact mechanics and stamping technology, our project aims to construct the prediction frame of galling behavior under the consideration of formability by synthesis methods such as experiments, derivation of theoretical model, FEM, First principles calculation and advanced test technology. Multi-scales method, namely macro-scale, miro-scale and atomic scale are used to clarify the initial galling mechanism and evolution law, where the macro contact pressure model, micro initial galling model and semicoherent die/workpiece interface model with consideration of misfit dislocation would be established to realize the accurate and effective control of galling behavior in sheet metal forming process. Our studies will provide scientific basis for solving the galling behavior in sheet metal forming process and promote the engineering application of ultra high strength steel sheets in the future.

在板料冲压成形中，成形界面间的粘模行为是引发产品表面损伤与模具失效的关键因素之一，如何减小甚至消除成形粘模问题是塑性加工行业迫切需要解决的课题。目前，随着高强度钢板成为汽车轻量化结构的关键材料，其成形接触界面发生了根本性变化，传统的摩擦磨损方法不能有效地解决该类成形粘模问题。本课题基于摩擦学、金属学、接触力学及冲压工艺学等理论，采用面向可成形性的几种典型冲压成形工艺方法，综合运用工艺试验、理论模型推导、有限元模拟、第一性原理计算及先进检测技术等手段，构建面向可成形性的汽车用先进高强度钢板成形粘模预测框架，从宏观、微观、原子尺度三方面揭示成形粘模的产生机理及演化规律，建立成形界面接触压力的宏观力学模型、微观粘模初始模型及考虑界面失配位错的模具/板料半共格界面模型，实现冲压成形粘模的准确、有效控制。本项目研究将为解决冲压成形粘模现象提供科学依据，并促进超高强度钢板在工程上的应用。

随着高性能成形制造的要求，先进高强度钢板以其良好的综合性能成为轻量化材料的主要发展方向之一。然而，随着先进高强度钢板强度的增加，其冷冲压成形性能变差，成形界面接触压力增大，粘模行为成为影响冲压模具失效与零件表面质量的关键问题。因此，系统研究冲压成形过程中的粘模产生机理及演化规律，并构建面向可成形性的粘模行为预测框架，是解决冲压成形粘模行为的首要问题。. 项目以双相高强度钢板为研究对象，结合运用冲压工艺试验、有限元数值模拟、第一性原理计算及先进检测技术，从宏观、微观、原子尺度三方面揭示成形粘模的产生机理及演化规律。研究结果表明：冲压类模具圆角接触压力分布区域与数值大小极其不均匀，局部瞬态接触压力较大且对粘模产生影响最大。U型弯曲模式中凹模圆角为偏差圆弧结构时的粘模倾向，较标准圆弧与椭圆弧时小。方盒拉深变形模式下粘模区域主要集中在拉深圆角与弯曲直边相接的直壁区域，且随着凹模高度的增加，滑移距离增大，粘模越严重；同时合理的分块压边对控制界面成形粘模倾向具有一定的积极作用。双相高强度钢板成形粘模的表现形式依次为微观划痕，犁沟与微裂纹，粘着磨损，磨粒磨损，宏观粘模行为。原子尺度下bcc-Fe(100)/VC(100)界面电荷密度分布存在很强的C-Fe共价键，且界面分离功大于bcc-Fe表面能，bcc-Fe(100)/VC(100)界面容易发生原子粘着行为。此外，先进高强度钢板塑性变形时表面发生粗化，随着应变值的增大，Ra与Ry值线性增大、Rsm值减小。. 本项目的研究结果可为实际冲压成形工艺提供一定的理论指导意义，并促进超高强度钢板及无润滑/微量润滑工艺在工程上的应用。