In order to solve the problem of ineffective utilization of waste heat generated by energy consumption in industrial production and life, a low-frequency thermal energy conversion type piezoelectric energy trap is proposed, and relevant theoretical analysis and experimental research are conducted. The device utilizes a piezoelectric film (polyvinylidene fluoride) combined with a shape memory alloy and features a simple green structure that can supply energy to microelectronic devices. First, the structural design and working principle of the device are analyzed and the dynamics model is built. Second, COMSOL Multiphysics simulation software (Version 5.6) is used to analyze and calculate the output voltage of shape memory alloy shrinkage, piezoelectric film shape and parameters. Finally, the experimental prototype is machined and fabricated by the fine engraving machine, and the experimental platform is built for relevant performance tests. The experimental results show that when the temperature is 100 °C, the maximum strain of shape memory alloy with 1 mm diameter is 0.148 mm. When the shape of the piezoelectric film is triangular, the length of the bottom edge is equal to the height of the triangle and the thickness ratio is 0.5, the maximum output voltage is 2.12 V. The experimental results verify the feasibility of the designed device and provide new ideas for subsequent research on piezoelectric energy capture.

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It is a very complex and difficult technology to fabricate micro-texture on tool surface. At present, available technology such as laser marking, femtosecond laser, ion beam and WEDM can be used to fabricate micro texture. However, little research has been done on the fabrication of micro-texture by WEDM. In this experiment, micro-texture was fabricated on surface of cemented carbide tool by NC WEDM technology. The effect of WEDM parameters (pulse width, pulse stop and current) on the width of micro-texture was studied, so as to control the size of micro-texture fabricated by WEDM. At the same time, the least square method was used to establish the prediction model between the width of micro-texture and the WEDM parameters. The experimental results showed that the micro-texture size fabricated by WEDM technology was in the micron scale, which met the requirements of micro-texture tool size in the field of cutting. Pulse width, pulse stop and current affected the width of micro-texture, but pulse width was the main factor affecting the width of micro-texture. The prediction model of micro-texture width was successfully established by least square method.

To explore the effect of vibration drilling on bit rigidity, the motion characteristics of the bit during vibration drilling were analyzed theoretically. According to the change of the minimum cutting thickness hmin, the bit rigidity theory was deduced, and the bit rigidity theory was verified by the drilling test of Carbon fiber reinforced polymer/aluminum alloy laminated structure. The experimental results show that; Compared with ordinary drilling, the machining accuracy of upper and lower aperture in vibration drilling is increased by 46.6% and 28.5% respectively, which makes the bit rigid and improves the stability and drilling accuracy.

<abstract> <p>Bone cutting is a complicated surgical operation. It is very important to establish a kind of gradient porous bone model in vitro which is close to human bone for the research of bone cutting. Due to the existing bone cutting researches are based on solid bone model, which is quite different from human bone tissue structure. Therefore, Voronoi method was used to establish a gradient porous bone model similar to real bone tissue to simulate the process of bone drilling in this paper. High temperature and large cutting force during bone drilling can cause serious damage to bone tissue. Urgent research on bone drilling parameters is necessary to reduce cutting temperature and cutting force. The finite element analysis (FEA) of Voronoi bone models with different gradients is carried out, and a Voronoi model which is similar to real bone tissue is obtained and verified by combining the cutting experiment of pig bone. Then orthogonal experiments are designed to optimize the cutting parameters of Voronoi bone model. The range method is used to analyze the influence weights of cutting speed, feed speed and tip angle on cutting temperature and cutting force, and the least square method was used to predict the cutting temperature and cutting force, respectively. The gradient porous bone model constructed by Voronoi method was studied in detail in this paper. This study can provide theoretical guidance for clinical bone drilling surgery, and the prediction model of bone drilling has practical significance.</p> </abstract>