超声波辅助中高碳钢精冲成形技术基础研究

As an advanced plastic forming process, fine blanking has been widely applied in the industry area. Because of the increasing of the carbon content, the material plasticity will be decreased and the strength will be increased, which lead to the medium-high carbon steel is very difficult to be fine blanked. Therefore, present studies of the fine blanking process are mainly focused on the low carbon steel. Based on the active demand of the medium-high carbon steel fine blanked components during the industrial application, the ultrasonic vibration is applied in the fine blanking process to improve the formability of the material. By using the theoretical calculation, finite element modeling (FEM) and experiment methods, the metal flow, shearing area initiation and propagation, stress and strain distribution and temperature variation within the shearing area, crack initiation and spreading during the ultrasonic vibration assisted medium-high carbon steel fine blanking (UAFB) process are investigated. The mechanisms of the plastic deformation and the die wear during the UAFB process are revealed. According to the research of the fabrication of the outer-gear of the steel synchronizing ring, the cooperative control method is created for the UAFB process, which is cooperated by the part quality, geometric dimensional precision and die wear. This method can provide science direction for the forming process design and control of the UAFB. This project is great significant to build the engineering science theory for the medium-high carbon steel fine blanking process, and hence to improve the formability of the material and enhance the quality of the fine blanking parts.

精冲作为一种先进的塑性加工方法在工业领域中得到了广泛应用。由于随着材料碳含量升高，材料塑性降低和强度升高，精冲难以进行，所以现有研究主要为低碳钢材料。基于中高碳钢精冲件在工业应用中的强烈需求，本项目将超声波应用到中高碳钢精冲成形工艺中,以提高其精冲成形性能。通过理论计算、有限元模拟、超声波辅助精冲成形实验，以及精冲件断面形貌和内部组织测试分析，综合研究超声波辅助精冲成形中的金属流动规律、剪切区萌生和演变机理、剪切区里应力应变以及温度分布、裂纹萌生和扩张机理，揭示超声波辅助中高碳钢精冲成形塑性变形和模具磨损机制与规律。针对具体的汽车钢质同步环外齿圈精冲成形研究，建立超声波辅助中高碳钢精冲成形精冲件质量、几何尺寸精度和模具磨损协同控制方法，为超声波辅助中高碳钢精冲成形工艺设计及过程控制提供科学依据。本研究对于建立中高碳钢精冲成形工程科学理论，提高中高碳钢精冲性能和精冲件质量具有重要意义。

精冲作为一种先进的塑性加工方法在工业领域中得到了广泛应用。与普通冲裁相比，一次精冲成形既可得到冲裁断面光洁、表面平整、尺寸精度高的可直接互换性装配的零件。精冲原理是材料在三向静水压应力作用下，在狭窄的冲裁间隙里以纯剪切塑性变形的方式实现分离。由于超声波的高频振动能够改变材料的金属流动方式，因此本项目将超声波应用到精冲成形过程中，开展超声波辅助中高碳钢的精冲成形基础研究。. 本项目首先建立了超声波辅助精冲的有限元模拟模型，制造了超声波辅助精冲实验装置，通过实验验证了有限元模型的正确性。利用有限元模拟和物理实验研究，对超声波辅助精冲过程中的塌角与光亮带形成机理进行了研究。研究结果表明与传统精冲相比在相同的精冲工艺条件下，超声波高频振动能够极大的减小精冲件塌角尺寸，实现小无塌角成形。而对于光亮带，由于超声波的高频振动，变形非常剧烈，剪切变形区内的应力交替变换，从而使裂纹萌生提前发生。进而，研究了冲裁间隙、凹模圆角半径、压边力、反顶力等工艺参数对于超声波辅助精冲断面质量的影响，通过工艺优化能够获得塌角接近于零，全光亮带的精冲件。. 本项目对于超声波辅助精冲的凸模磨损进行了研究，研究表明虽然超声波辅助精冲能够降低成形载荷，有益于模具寿命,但是由于冲头的端面粒子高频振动，因此冲头在高的交变成形载荷作用下，磨损反而比普通精冲严重。. 借助本项目支助对于精冲成形装备进行研究，提出了一种两步拓扑优化设计方法，是大吨位精冲机机架的刚度得到了提升而质量减小了13.6%。采用机械结合面接触特性理论建立了1200吨精冲机的模型，通过动态力学分析与性能优化，提高了大吨位精冲的运动精度与抗偏载能力，降低了振动。. 通过本项目研究，揭示了超声波辅助精冲成形机理，为超声波在精冲领域的应用提供了理论指导；同时通过精冲装备研究，为高性能大吨位精冲装备的研发制造提供理论指导。