60.00.00 CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
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- 2022 (1)
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- VHCF (1)
- cyclic load (1)
- loss coefficient (1)
- modal analysis (1)
- phase transformation (1)
- sonotrodes (1)
- ultrasonic processes (1)
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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.