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.

随着高强度材料在冷锻中的应用越来越多，相关的工艺压力不断增大，成形性降低，这对传统的成形工艺提出了重大挑战。一个有前途的方法，以减少成形力和扩大成形极限是在超声范围内的振荡叠加的工具运动。由于所谓的超声波辅助，材料暂时软化，工艺力显著降低。这种现象首先由Blaha和Langenecker发现，并已在各种成形工艺的几项研究中得到证实，如超声波辅助拉丝，深拉和挤压。尽管关于这种现象的原因提出了许多假设，如应力叠加，减少摩擦和加热，因果关系仍然没有解决。因此，本研究项目的目标是综合研究金属材料在压缩、拉伸和剪切载荷结合超声激励下的流动行为和成形极限。在第一个项目阶段内，分析了各种振荡频率、振幅、压力机速度和振荡持续时间对发生的工艺力降低的影响。除了临时力的减少，这是强烈的振幅依赖性，一个修改后的硬化状态后，超声激励确定。金相分析以及显微硬度测量证实了这些发现，由于更明显的剪切带和更不均匀的硬度分布。因此，超声波对加工硬化的影响的调查以及确定潜在的因果关系是第二个项目阶段的目标。在这种情况下，超声波辅助压缩测试与各种真实应变进行的材料C35，Cu-OFE和CuZn 30。通过这种方式，逐渐检查硬化过程。基于对不同材料的测量，获得可转移的知识。此外，关于基于超声的材料软化的研究延伸拉伸试验。排除任何摩擦学效应，增加了对潜在软化机制的理解。最后，将根据所研究的材料和应力状态对所识别的基于超声的效应进行评估。