Papers by Author: Jian Ping Liu

Abstract: The sound source of violin is string vibration. By the stick–slip friction action between bow and string of violin, string and bridge form a complicated vibration system. The interaction mechanism of bowstring is very intricacy. In this paper, through theoretical analysis and experiment, the vibration behavior of violin string is investigated. We measured the vibration images of bowing and plucking violin string on a high-speed photography optical platform and got two different character of string vibration, including vibration displacement, velocity and space trajectory of the mark point on string. By comparing the displacement curves of the different points among on string, the variety of the ratio of positive process time to negative one of vibration sawtooth waveform are studied, and also the formation process of string vibration enveloping curve. On this basis, the Helmholtz motion of string vibration which is presented at 1862 is studied.

Abstract: Parabolic trough solar thermal power generation system is always restricted by high drive torque, low thermal efficiency and high investment cost. In this paper, the parabolic trough solar collector in a solar energy application base is taken as the research object and FEM was used to realizing its structural light-weighting design. The structural overall performance is improved to lay a foundation for innovating drive mode and expanding the rotation scope. Beginning of the paper, the wind load characteristic was analyzed and its computational formula was provided the magnitude of wind load was computed; then, the static performance of the solar collector was analyzed by using ANSYS Workbench and the worst working condition of each static characteristic was confirmed to service for the later structural optimization; last, the overall optimization scheme of the solar collector was put forward, the position of the reflectors supporting point and the structure of the solar collectors cantilever was optimized.

Abstract: Pre-stress Hard Cutting, known as a new machining technology, is the combination of hard cutting and pre-stress cutting. Some reports show pre-stress machining can improve residual stress state of machined surface and prolong fatigue life of mechanical part, such as drive shaft, bearing and engine vane etc. Based on the principle of this technology, this paper take aero-screw shaft machining as object, investigated the pre-stress loading method, experimental device and implementation process of pre-stress hard cutting. Experiment is carried out for aero-screw shaft with PCBN tool, cutting force, machined surface residual stress state and distribution are measured. The experimental results show that by using this method, residual compressive stress is got on machined surface and good surface finish is gained, hence it can control machined surface residual stress state actively and improve the fatigue life of aero-screw shaft..

Abstract: The import mechanical components and burden part in aeronautic and automobile industry, such as screw shaft, aero-bearing and engine vane etc. are often found fatigue failure cased by their residual stress state on machined surface. Aiming at the problem, this paper presents a new green machining technology by integrating pre-stress cutting and hard machining method. The principle of pre-stress hard cutting of shaft part is introduced together with its implementary process in this paper. Pre-stress loading method on screw shaft is investigated and device for actualizing the process is designed. Experiment of pre-stress hard cutting is carried out for screw shaft with PCBN tool. The experimental results show that by using this method, residual compressive stress is got on machined surface and hence increase the quality and fatigue life of screw shaft.

Abstract: To solve the problems of automotive wheel’ design by using traditional methods, application of finite element analysis in modern automotive wheel design is presented. Then, for example of SU0011-typed aluminum alloy wheel, this paper illustrates in detail the application in its hub structure design, mold design and casting process. By using the ANSYS software, structural design of wheel is optimized according to the CAE results of fatigue strength. In the meanwhile, the casting mold of wheel hub is also designed. Using the ProCAST software, casting process optimization and casting defects elimination can be realized based on simulating the process of filling and solidification of low-pressure casting. Experimental analysis shows that, with the help of finite element analysis, design accuracy and product reliability can be effectively improved and product development cycles can be greatly shorten. So the application has a very good prospect in the automotive industry.

Abstract: This paper puts forward a new method of pre-stress hard cutting which integrates pre-stress and hard cutting technology. A thermo-mechanical coupling model of Finite Element Analysis (FEA) for pre-stress hard cutting on material 42CrMo steel is established. In this model, chip-work separating is made by applying shear fracture failure criterion, element deletion and adaptive mesh technique based on arbitrary Lagrangian Eulerian (ALE) method. The key technology for FEA, such as intrinsic equation of workpiece material, chip separating criterion and friction model of tool-chip interface and thermal conduction equation are researched respectively. Then FE simulation of chip forming and cutting force in pre-stress hard cutting is made and relationship between pre-stress and residual stress on machined surface under various cutting conditions is got. Simulation result is compared with that of experiment and found they are good in accordance.