Applied Mechanics and Materials Vols. 37-38

Abstract: To improve turning process, a testing system for dynamic cutting force was established. The paper studied the dynamic cutting force theoretically and experimentally with the frequency domain analysis. Cutting experiments were conducted for new tools, worn tools, and broken tools respectively. And a comparison among three forces’ power spectrum was made. The results show that the power spectrum value of radial force in the frequency range of 2450~3100 Hz has a close relation to the state of tool wear and tool breakage, which can be used to monitor the cutting process in real time.

Abstract: The aim of this study is to get a better understanding of Micro Flat-Wire Roll Forming Technology. There are three methods for Mirco flat-wire forming, i.e., drawing, extrusion, and rolling. Without replacing the equipment, rolling method only demands to adjust the relative roll gap between the pressure and the wire deformation that it can produce different specifications of mirco flat-wire. The rolling equipment was introduced and can be divided into three parts, the mechanism section, the control part and the wire-locating device. Furthermore, the rolling process parameters were summarized as well. The effect of rolling amount and rolling speed on the wire surface quality was also discussed.

Abstract: The single factor experience of Fiber Reinforced Ceramic Matrix Composites (briefly named FCC) grinding was done on a NC optical curve grinding machine, and then the morphologie of the grinding surface was observed with an optical microscope. The effect of the grinding parameters, which include mainly grinding depth, abrasive grain size of diamond grinding wheel and grinding direction, on the grinding-induced surface damage of FCC was discussed, finally, the paper drew the conclusions that both increasing of grinding depth and increasing of abrasive grain sizes of diamond wheel can make the grinding-induced surface damage worse, and that different grinding directions also produce different effects on the grinding-induced surface damage.

Abstract: Wrinkling and tearing are major defects that usually occur in the deep-drawing process. This study presents a new sheet forming technology, together with machining small lubrication holes on the die shoulder. Deep drawing process of cylindrical cups with flange is investigated. Mechanical characteristics of die shoulder with small lubrication holes in deep drawing are analyzed. Numerical simulation and experimental methods are used to determine the influence on formability of machining small lubrication holes on the die shoulder. The results show that this new sheet forming process can improve formability and forming quality.

Abstract: In cutting experiment, high alloy antifriction cast irons were selected. Through high-speed cutting experimentation, the materials’ performance and requirement for tools were analyzed. The feasible cutting capacity and tool parameters were ascertained. The cutting defect and solving method were discussed. The results indicate that there are high hardness, high wear resistance and brittleness of high alloy antifriction cast irons. In ensuring the technical requirements of work-piece machining, PCBN is a better tool material. When the tool orthogonal rake angle =-6°, the tool’s durability is higher and machining quality is better. High cutting efficiency can be obtained, when cutting speed vc is from 75 to 100 m/min, the feedrate f is less than 8 mm/min, and the cutting depth ap is from 0.1 to 0.3 mm. These cutting dosages are appropriate in machining high alloy antifriction cast irons.

Abstract: Two-dimensional ultrasonic vibration was introduced into common rolled extrusion, effect of the process parameters including tool head radius, feed speed, preload and spindle speed on the 45 steel shaft surface roughness were analyzed through orthogonal experiments. Experimental results show that lower value of surface roughness may be obtained in the process of two-dimensional ultrasonic rolled extrusion than that of common rolled extrusion, and the influence order of process parameters on surface roughness is feed speed, spindle speed, preload and tool head radius; the influence curves of tool head radius and spindle speed on surface roughness are concave curves, and influence curves of feed speed and preload on surface roughness are convex curves, or optimizing process parameters exist. The empirical formula for surface roughness is given using multiple regression analysis based on the experimental results. This study will provide a new technique for finishing precision parts.

Abstract: MR dampers are new kind of the most promising devices for structural vibration control. In this paper, an overview of the structure and working principle of shear-valve mode magnetorheological (MR) damper is given. An experimental study was carried out to test the performance characteristics of a shear-valve mode MR damper, its dynamic testing was performed on a Material Testing System (MTS) under sinusoidal and triangle excitation. Based on experimental data, the dynamic characteristics, energy dissipation and dynamic response time were analyzed. The present work lays down a foundation for MR damper application in the semi-active vibration control system.

Abstract: As a new type of smart materials, magnetorheological elastomer (MRE) has become a hot current research focus. However, the piezoresistivity and magnetoresistivity of MRE have not been well studied. In this paper, this was done by using a test rig developed by the authors. The experimental results showed that the conductivity of the MRE responded sensitively to the applied pressure, and a linear relationship between the resistivity of the MRE and the applied pressure can be observed within a certain range. Besides, the sensitivity of piezoresistivity is different among different ratios of metal content, and it becomes more obvious when using the nickel content. And, the magnetoresistivity of MRE is not obvious in a range of low magnetic field intensity, and there is also no hysteresis phenomenon about magnetoresistivity.

Abstract: To improve the quality of the light guide plate (LGP) made by injection molding, a fabrication method based on hot embossing was proposed. The silicon mold of the LGP with micro pyramid array was fabricated by wet chemical etching. The experiments of embossing the LGP were performed with a self-designed hot embossing machine. Orthogonal method was used to analyze the imprint pressure, the holding time, the imprint temperature and the width of pyramid with respect to the accuracy of replication (AOR). The experimental results show that the imprint temperature has the greatest effect on the AOR, followed by the imprint pressure and the holding time, while the width of micro pyramid has the minimal effect on the AOR. The increase of imprint temperature can obviously improve the pattern filling quality in the lower imprint pressure (0.7MPa). At last the optimal process parameters were obtained with the imprint pressure of 0.9MPa, the holding time of 5min and the imprint temperature of 130°C.

Abstract: In order to meet the requirements of research on tension control system based on magnetorheological fluid (MRF) damper, an experimental system of tension measurement and control was developed using an industrial personal computer as hardware control center and using VC software as development tool. By applying the sensing and measuring, computer signal processing, motor speed control, and smart material technologies, the system can achieve the tasks of automatic tension measure and the automatic control of the whole running process. The system has the functions of speed measurement and control, tension measurement and control, as well as power supply control. The experimental data can be displayed and stored in real time. The system has friendly man-machine interfaces. The system can be maintained and expanded easily. Experimental test shows that the system can be effectively used for the research of the tension control based on the MRF damper.