Forming and joining of semitubular self-piercing rivets made of high strength steel with adapted mechanical properties and numerical analysis of the process chain

具有适当机械性能的高强度钢半管自冲铆钉的成型和连接以及工艺链的数值分析

• 批准号: 328853593
• 负责人: Professorin Dr.-Ing. Marion Merklein
• 金额: --
• 依托单位: Laboratorium für Werkstoff- und Fügetechnik (LWF)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/328853593?language=en
• 关键词: Forming; joining; semitubular; self; piercing

The goal of the research project is the identification of cause‑effect relationships between the joinability of different material combinations and the geometric and mechanical properties of semi‑tubular self‑pericing rivets after forming using high strain hardening materials. For this purpose, influencing factors are identified and effects on the dimensional accuracy, the local strengthening due to forming and the resulting impacts on the joining process are investigated. The correlation of the occurring effects allows for developing methods for increasing the dimensional accuracy and influencing the mechanical properties of the rivets according to the requirements of the joints. In this way, the joint strength and the reliability of the joining process are improved. Dimensional deviations due to process variations or due to the limited loadability of the forming tools generally have a negative impact on the required joint parameters like the interlock. Therefore, the influence of process parameters like the forming temperature on the rivet geometry is investigated. Knowing the impact of volume variations is necessary to separate the effects. Regarding the cross process analysis, the correlation between variations related to the forming process, the joint quality and the joint behaviour under different loading conditions is of importance. The influence of corrosive environments and the combination of riveting with adhesive bonding must also be considered. Besides the geometry of rivet and die, the mechanical properties of the rivet are a decisive factor for the joint quality, especially for the defined flaring of the rivet, which is indispensable for improving the joint strength. The use of high strain hardening material leads to a non‑homogeneous strength distribution, as the usual hardening and tempering of the rivets is not necessary anymore. Hence, there is the potential for directly influencing the mechanical properties during forming. The prerequisite for this is a deeper understanding of the local strengthening. Thus, the mutual influence of process parameters and material specific characteristics regarding the mechanical properties is investigated. Correlating the strength of the rivets, the rivet geometry and the strength and thickness of the joined sheets is the basis for identifying a strength distribution of the rivet, which results in an improved joint strength.

该研究项目的目标是确定不同材料组合的可连接性与使用高应变硬化材料成形后半管状自融铆钉的几何和机械性能之间的因果关系。为此目的，影响因素的识别和尺寸精度的影响，由于形成和连接过程中产生的影响的局部强化进行了调查。发生的影响的相关性允许开发用于增加尺寸精度和根据接头的要求影响铆钉的机械性能的方法。这样，提高了接合强度和接合过程的可靠性。由于工艺变化或由于成形工具的有限负载能力而导致的尺寸偏差通常会对所需的接头参数（如互锁）产生负面影响。因此，工艺参数如成形温度对铆钉几何形状的影响进行了研究。了解体积变化的影响对于分离影响是必要的。关于交叉过程分析，与成形过程相关的变化之间的相关性、接头质量和不同载荷条件下的接头行为是重要的。还必须考虑腐蚀环境的影响以及铆接与粘接的结合。除了铆钉和模具的几何形状外，铆钉的机械性能是连接质量的决定性因素，特别是对于铆钉的限定扩口，这对于提高连接强度是不可或缺的。使用高应变硬化材料会导致强度分布不均匀，因为不再需要对铆钉进行通常的硬化和回火。因此，在成型过程中有可能直接影响机械性能。其前提是对局部强化有更深的认识。因此，工艺参数和材料的具体特性的机械性能的相互影响进行了研究。将铆钉的强度、铆钉的几何形状以及连接板的强度和厚度相关联是用于识别铆钉的强度分布的基础，这导致改进的连接强度。