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RISS 인기검색어
- 검색키워드
- 저자 : Jörg Wallaschek (검색결과 2 건)
- 무료
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Pre-stressing Piezoelectric Actuators by Using Superelastic Shape Memory Alloys
Florian Schiedeck,Sebastian Mojrzisch,Jörg Wallaschek 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.41
This work investigates and describes the use of superelastic shape memory alloys (SMAs) for pre-stressing piezoelectric actuators. The nonlinear, hysteretic stress-strain diagram of superelastic SMAs is characterized by two stress plateaus over strains of up to 8% during loading and unloading. In this range of strain, the stress is nearly constant, which yields a theoretical stiffness of 0. A superelastic SMA that is used for pre-stressing will be stretched by the piezoceramic in the range of per mill (one-tenth of a percent), which leads to minor hysteretic loops. The effective stiffness when cycling these minor loops is very small compared to conventional steel – large strokes close to the nominal displacement of the unloaded piezoelectric ceramic are reachable. This theory was experimentally proven with a piezoelectric multilayer actuator using replacable pre-stressing elements. The investigations have confirmed that the use of a superelastic SMA leads to a larger stroke in comparison to the use of steel elements.
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Quantification of the Energy Flows during Ultrasonic Wire Bonding under Different Process Parameters
Yangyang Long,Friedrich Schneider,Chun Li,Jörg Hermsdorf,Jens Twiefel,Jörg Wallaschek 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.6 No.3
Despite of its wide and long-term application for interconnections in the field of microelectronics packaging, a quantitative understanding on the mechanisms of ultrasonic (US) wire bonding is still lacked. In this work, the energy flows from the electrical input energy to the different mechanisms during the US bonding process are quantified based on real-time observations via which the relative motions at the wire/substrate and the wire/tool interfaces can be detected. The relative motions at the two interfaces are proved to be caused by both the continuous plastic deformation and the US vibration. The normal force and US power interdependently affect the relative motion amplitudes. The deduced energy flows show that the energy from the transducer mainly flows to the vibration induced friction at the two interfaces and the microwelds formation, deformation and breakage. Despite of their significance to the process, the other mechanisms receive only little amount of energy. The impacts of the process parameters including normal force, US power and time on the energy flows are quantitatively investigated. A good coupling of the normal force and the US power guides more energy to the formation of microwelds while a long process time would increase the friction induced energy consumption.
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