Fundamental investigation of ultrasonic-assisted forming of metallic materials under compression and shear loading

压缩和剪切载荷下金属材料超声辅助成形的基础研究

• 批准号: 393723186
• 负责人: Professorin Dr.-Ing. Marion Merklein
• 金额: --
• 依托单位: Lehrstuhl für Fertigungstechnologie (LFT)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/393723186?language=en
• 关键词: Fundamental; investigation; ultrasonic; assisted; forming

The increasing use of high strength materials in cold forging and the associated rising process forces as well as the reduced formability present a major challenge for conventional forming processes. A promising approach to reduce forming forces and expand the forming limits is the superposition of oscillations in the ultrasonic range to the tool motion. Due to the so-called ultrasonic-assistance the material is softened temporarily and process forces are reduced significantly. This phenomenon was first discovered by Blaha and Langenecker and has been confirmed in several investigations for various forming processes, such as ultrasonic-assisted wire drawing, deep drawing and extrusion. Despite the proposition of numerous hypotheses regarding the causes of this phenomenon, such as stress superposition, reduced friction and heating, the cause-effect relationships remain unsettled. Therefore, the objective of this research project is the comprehensive investigation of the flow behavior and forming limits of metallic materials during compression, tensile and shear loading in combination with ultrasonic excitation. Within the first project phase the effects of various oscillation frequencies, amplitudes, press velocities and oscillation durations were analyzed with regard to the occurring process force reduction. Besides the temporary force reduction, which is strongly amplitude dependent, a modified hardening state was determined after ultrasonic excitation. Metallographic analyses as well as micro hardness measurements confirmed these findings due to more pronounced shear bands and more inhomogeneous hardness distribution. Thus, the investigation of ultrasonic-based influences on the work-hardening as well as the determination underlying cause-effect relationships are objectives of the second project phase. In this context, ultrasonic-assisted compression tests with various true strain are carried out for the materials C35, Cu-OFE and CuZn30. This way, the hardening process is examined gradually. Based on the measurements for the different materials transferable knowledge is acquired. Moreover, the investigations regarding the ultrasonic-based material softening are extended by tensile tests. Excluding any tribological effect, the understanding of the underlying softening mechanisms is increased. Finally, the identified ultrasonic-based effects will be evaluated with respect to the investigated materials and stress states.

高强度材料在冷锻造和相关的上升工艺力以及可降低的外观上的使用越来越多，对常规形成过程带来了主要的挑战。一种有希望的方法来减少形成力并扩大形成极限的方法是超声范围内振荡的叠加到工具运动中。由于所谓的超声辅助，该材料暂时软化，并且过程力显着降低。这种现象最初是由Blaha和Langenecker发现的，在几项研究中已经确认了各种形成过程，例如超声辅助的线图，深度绘图和挤出。尽管有许多关于这种现象原因的假设的主张，例如应力叠加，减少摩擦和加热，但原因效应的关系仍未解决。因此，该研究项目的目的是对压缩，拉伸和剪切负荷在结合使用超声激发期间的流动行为和形成金属材料的限制的全面研究。在第一个项目阶段，分析了各种振荡频率，幅度，压力速度和振荡持续时间的影响。除了临时性减少（强烈依赖性临时）外，超声激发后确定了修改的硬化状态。金属学分析以及微硬度测量结果证实了这些发现，由于更明显的剪切带和更不均匀的硬度分布。因此，研究基于超声波的影响对工作硬化以及基本原因效应关系的确定是第二个项目阶段的目标。在这种情况下，对材料C35，Cu-Ofe和Cuzn30进行了各种真实应变的超声辅助压缩测试。这样，逐渐检查了硬化过程。根据对不同材料转移知识的测量结果。此外，通过拉伸测试扩展了有关基于超声的材料软化的研究。除了任何摩擦学效果外，对潜在软化机制的理解增加了。最后，将根据研究的材料和应力状态评估所鉴定的基于超声波的效应。