Numerical Simulation of hot forging with an integrated heat treatment considering the impact of unsteady stress state on the transformation induced plasticity

考虑非稳态应力状态对相变诱发塑性影响的热锻集成热处理数值模拟

• 批准号: 212963651
• 负责人: Professor Dr.-Ing. Bernd-Arno Behrens
• 金额: --
• 依托单位: Institut für Umformtechnik und Umformmaschinen (IFUM)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2012
• 资助国家: 德国
• 起止时间: 2011-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/212963651?language=en
• 关键词: Numerical; Simulation; hot; forging; integrated

In the course of a subsequent cooling after a hot bulk metal forming process, a structural phase transformation of austenite into secondary phases (e.g. martensite) occurs. In addition to elastic, plastic and thermal expansion strains, transformation induced volumetric changes as well as transformation induced plasticity (TRIP) arises. Transformation volumetric strain results from the change in the lattice structure of austenite to another phase, which leads to an accompanying change in the material volume. Transformation plasticity strains arise from the micro-plasticity phenomena at the phase boundary during the formation of e.g. martensite particles in an austenitic matrix. They have a decisive impact on the resulting residual stress state and can be the reason for undesirable distortion in the hot forged component. The aim of this project is a further development of the established numerical approaches for the prediction of residual stress state and transformation related distortions. Hereby, the load-dependent influence of transformation plasticity (back flow effect of TRIP) has been taken into account. Based on the fundamental experimental investigations, required material data regarding the load-dependent TRIP-behavior for two typical hot forging steels is to be determined. This data will be used to extend the models developed in the first application period, which will subsequently be implemented in a commercial FE system using user-defined subroutines. Finally, the extended material model will be tested and validated on the basis of a demonstrator component in the context of a closed die forging process chain with an integrated heat treatment. The forming process will be furthermore extended by e. g. a deflashing or a trimming stage. Within the scope of this research proposal, the investigations are focused on the diffusion-controlled transformation types. Therefore, the integrated cooling under moderate or slow cooling rates will be carried out in calm air or in sand bath. To implement the deflashing stage, the corresponding tool system will be redesigned and manufactured. As a final point, the validation of the developed numerical methods is performed by the comparison of calculated distortions and residual stresses with the ones measured on real components within experimental metallographic and XRD investigations.

在热量金属形成过程后随后的冷却过程中，会发生奥氏体变成二期（例如马氏体）的结构相变。除了弹性，塑料和热膨胀菌株外，转化引起的体积变化以及转化诱导的可塑性（TRIP）。转化体积应变是由于奥氏体的晶格结构变化到另一个阶段的原因，这导致材料体积的变化。转化塑性菌株由在例如形成期间的相边界处的微塑性现象产生。奥氏体基质中的马氏体颗粒。它们对由此产生的残留应力状态产生决定性影响，可能是热锻造组件中不良失真的原因。该项目的目的是进一步发展，用于预测残留应力状态和相关扭曲的既定数值方法。因此，已经考虑了转化可塑性（TRIP的后流效应）的负载依赖性影响。基于基本的实验研究，要确定有关两个典型热锻造钢的负载依赖性跳闸行为所需的物质数据。该数据将用于扩展在第一个申请期内开发的模型，随后将使用用户定义的子例程在商业FE系统中实现。最后，将在封闭的模具锻造过程链的背景下，通过综合热处理进行测试和验证扩展的材料模型。形成过程将由e扩展。 g。缩放或修剪阶段。在这项研究建议的范围内，研究集中在扩散控制的转换类型上。因此，将在平静的空气或沙浴中进行中等或缓慢的冷却速率下的集成冷却。为了实现缩放阶段，将重新设计和制造相应的工具系统。最后，通过比较计算出的扭曲和残余应力与在实验成熟和XRD研究中的实际成分中测量的差异应力的比较，对开发的数值方法的验证进行了验证。