Applied Mechanics and Materials Vols. 37-38

Abstract: In this paper, the open architecture technique is used to develop the computer numerical control (CNC) system of parallel mechanism. The personal computer (PC) with high-performance motion control card Flex-6C and virtual instrument software package are utilized as the hardware and software platforms, respectively. The interface between motion controller and servo system is designed, and the core functional module and control software is programmed. Further it is successfully applied in a series of parallel mechanisms, which serves as the foundation for achieving the high-speed and high-precision control of such kinds of parallel mechanism.

Abstract: Magnetorheological fluid torque servo (MRT) is a novel torque generating and controlling device. It converts the rotational input of active shearing disc into the torque output of passive shearing disc by controlling the rheological property of the magnetorheological fluid. In this paper, the working principle of the MRT was introduced. The effects of the input rotational speed on the shear stress of the magnetorheological fluid and then the output torque were analyzed. The model describing the relationship of the output torque with respect to the rotational speed of the active shearing disc as well as to other parameters was established. A critical rotational speed was deduced. The factors affecting the critical speed were discussed, and an experiment was conducted to ascertain the validity of the theoretical analysis.

Abstract: The quality of hole is difficult to be guaranteed and tools wear severely in the drilling process of titanium alloy. To investigate more efficient methods to improve the quality of holes, the drilling experiments of titanium alloy Ti6Al4V were carried out under different drilling speed and different feeding speed. The drilling force was achieved through the dynamometers in the experiment. Simultaneously, a series of drilling experiment of titanium alloy was carried out with the two different shape drills and three different diameter drills. The comparison of the achieved drilling force proved that the sharpened tool is better to guarantee the quality of hole for titanium alloy Ti6Al4V.

Abstract: Aspheric parts are attracting many researchers’ attention for their excellent optical properties. The commonly used manufacturing technology for aspheric parts are mainly based on dedicated high precision machines, resulting in high cost and restricted application fields. To polish this kind of parts on general CNC machine tools, however, the surface quality improvement is limited due to the problem of force-position coupling. In order to solve this issue, a force-position decoupling control method for abrasive polishing was studied, a corresponding comliant polishing tool system was developed, and the mathematical model of the tool system was established. In addition, a polishing force controller was designed, and the performance of the tool system was numerically simulated. Simulation results showed that the polishing tool system can effectively achieve the tasks of force-position decoupling and the stable control of the polishing force.

Abstract: Tolerance information plays a critical role in many steps of the product life cycle. It is especially important due to the advances in Internet technologies and increasing integration requirements from industry. In this paper, geometric tolerances information in manufacturing process (IMP) is studied, and the layered conformance level of geometric tolerances is established according to ASME Y14.5-1994, STEP and DMIS. An EXPRESS-G data model of geometric tolerance information in IMP is established. The XML language is used to represent and program the geometric tolerances information in IMP.

Abstract: A new method for identifying stable cutting speed in regenerative chatter is studied by time- varying cutting width. The model of the regenerative chatter system is established in CNC lathe. In this model, all dynamic parameters had been obtained by experimental methods. The cutting system stability is simulated and the relation curves between the limited cutting width and spindle speed are established in the experiment. Simulation and experimental results show that it can identify stable speeds range effectively and such stable speeds range make the cutting process in stable state. The method is applicable and credible to suppress chatter. The testing works were performed in a CNC lathe.

Abstract: Based on study and analysis of the advantages and disadvantages of the design methods of AD (AD, Axiomatic Design), QFD (QFD, Quality Function Development), TRIZ (TRIZ, Theory of Inventive Problem Solving) and Taguchi Method, the article established the integrated design model of the four. Taking the design of a compressor cutting machine as example, the article analyzed how to design the machine under the guidance of the integrated design method based on AD-QFD-TRIZ and Taguchi Method according to the actual needs of users. Thus, the article provides a useful reference for the design of related products to designers.

Abstract: Early breakage of tap often occurs when tapping on difficult-to-cut materials with the method of low frequency torsional vibration tapping, which decreases the technological effect and restricts its application. The effect of impact load on tap breakage in vibration tapping was analyzed, and the stress state in tap teeth was simulated by FEM, on this basis, it is concluded that too large tensile stress in tap teeth is the main cause of early breakage of tap. To reduce the tensile stress and enhance the shock resistance of tap teeth, the tap should be ground to minor negative rake angle. Experiments showed that the failure mode of grinded taps changed to wear, and thereby the service life of tap was prolonged significantly.

Abstract: The heat penetration depth of mould for Semi-solid net-shape forming affects not only the life of moulds, but also the quality of products. By integral approximate solution of temperature field and analyses of solidification process, a theoretical model of heat penetration depth for semi-solid net-shape forming mould was obtained, and in this model the influence factors such as product material thermal properties, mould material thermal properties and solidification time are given much consideration. Studies show that the heat penetration depth increases exponentially with interface thermal resistance and time respectively, and increase as a cubic curve with pouring temperature and preheating temperature.

Abstract: To reveal the cutting process of aluminum alloy 7050, the oblique cutting finite element model was established to simulate the cutting process. The key techniques including material constitutive model and temperature finite element model were investigated. The chip of aluminum alloy 7050 formed in the simulation of cutting process, and the cutting force curve and cutting temperature distribution were analyzed. The chip obtained by simulation is spiral, and the chip shape of simulation agrees well with the chip of cutting experiment. The oblique cutting finite element model of aluminum alloy 7050 can be used to investigate the optimization of cutting parameters and tool angle further.