During the experiment of cell poking, it is required that the point of a probe is aimed at the cell with the help of a precision motion platform, and then, controlled by this motion platform, the tip of the probe pokes into the cell. When these operations are done, the driving force of this platform will be removed. But within a certain period (for example, an hour), the platform doesn’t stop moving. This kind of movement, which should be only several microns, is termed in this paper as the mechanical drift of ultrasonic linear motors. Experiments show that the forms used for clamping the stator is one of the factors that affect the mechanical drift. It is studied through experiments the impacts of several clamping forms on mechanical drift, the drift value’s relationship with the slide rail’s damping and the motor’s step size, and how the drift direction is related to the motion direction. The mechanism of mechanical drift of ultrasonic linear motors has also been explored preliminarily. This kind of research will facilitate refinements of the design and control methods for ultrasonic linear motor as well as motion platforms.
In order to simulate the rupture process of Cartridge Case, material failure constitutive model is researched. Johnson-Cook plasticity model is given as an analytical function of equivalent plastic strain, strain rate, stress triaxiality. Johnson-Cook plasticity model and Johnson-Cook Damage initiation criterion are used to describe the plastic deformation and fracture of case for the pressure of power gas. Using the implementation of this stress-displacement and characteristic length, problem of the relationship between fracture energy and the characteristic length in finite element model is solved. Finally, the simulated model which includes barrel, case, bolt and locking rigidity spring is built. Comparing the fracture shape and position in simulated test and physical experiment, the results are very similar. It proves that the rupture process of Cartridge Case can be simulated by the constitutive model which is introduced in this paper.
This paper proposes an ultrasonic knife system for MEMS packaging. The ultrasonic knife system is consisted of an ultrasonic transducer, a cutter and a gripper feeder. The ultrasonic transducer engenders high frequency vibration, which lead to the resonance of the structure. Amplitude transformer can magnify the amplitude. By the impact and collision of the cutter, the material can be cut through, and the high temperature created by high-frequency vibration can do the welding. The structure is designed and optimized by the finite element method, and a model machine is produced. According to the experimental results, the ultrasonic knife system has the virtues of high cutting force and better wedding feature, which are suitable for MEMS packaging.
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