Liesegang Moritz, Daniel Tobias, Jäckels Benedikt, Smaga Marek, Beck Tilmann
Institute of Materials Science and Engineering, Technische Universität Kaiserslautern, 67653 Kaiserslautern, Germany.
Materials (Basel). 2022 Aug 30;15(17):6002. doi: 10.3390/ma15176002.
Ultrasonic processes such as ultrasonic welding or ultrasonic fatigue testing use power ultrasound to stimulate materials with amplitudes in the range of 1-100 µm. The ultrasonic welding process is sensitive to any changes in the system or even the environment that may result in lower joint quality. The welding tools, so called sonotrodes, have to be accurately designed to endure high mechanical and thermal loads while inducing a sufficient amount of welding energy into the joining zone by oscillation with the Eigenfrequency of the whole system. Such sonotrodes are often made of thermally treated metals where the heat treatment is accompanied by microstructural changes. During ultrasonic stimulation, the material may further change its properties and microstructure due to cyclic loading. Both are expected to be recognized and identified by loss coefficients. Therefore, the loss coefficient was determined by modal analysis of rods and fatigue specimen made of different materials to correlate microstructural changes to attenuation. The determined loss coefficients indicated microstructural changes in all materials investigated, confirming results from previous investigations that showed an increasing attenuation due to cyclic loading for AISI 347. For the sonotrode materials Z-M4 PM and Ferrotitanit WFN, the loss coefficients decreased due to thermal treatments. Technically most relevant, changes in elastic modulus due to thermal treatments were quantitatively related to frequency changes, which can significantly simplify future sonotrode development.
诸如超声焊接或超声疲劳测试等超声工艺使用功率超声来激励振幅在1-100微米范围内的材料。超声焊接工艺对系统甚至环境中的任何变化都很敏感，这些变化可能导致接头质量降低。焊接工具，即所谓的超声变幅杆，必须经过精确设计，以承受高机械和热负荷，同时通过与整个系统的固有频率振荡，将足够量的焊接能量引入连接区域。这种超声变幅杆通常由经过热处理的金属制成，热处理会伴随微观结构的变化。在超声激励过程中，材料可能会由于循环加载而进一步改变其性能和微观结构。两者都有望通过损耗系数来识别和鉴定。因此，通过对由不同材料制成的杆和疲劳试样进行模态分析来确定损耗系数，以将微观结构变化与衰减相关联。所确定的损耗系数表明了所有研究材料中的微观结构变化，证实了先前研究的结果，即AISI 347由于循环加载而导致衰减增加。对于超声变幅杆材料Z-M4 PM和Ferrotitanit WFN，损耗系数由于热处理而降低。在技术上最相关的是，热处理引起的弹性模量变化与频率变化在定量上相关，这可以显著简化未来超声变幅杆的开发。
