Papers by Author: Shi Ming Ji

Abstract: The milling vibration affects machined surface quality and the size of the error, and has an important impact on the machining accuracy. This paper studies the different cutting parameters on cutting conditions on milling vibration during ball end milling Cr12MoV hardened steel assembled with different hardness steels, and use LMS. Test. Lab software to analyze the vibration signal on the condition of different spindle speed milling direction, axial depth of cut, and the vibration signal of transitional zone and the non-transitional zone are compared, providing the basis for a reasonable choice of milling parameters.

Abstract: Because of the liquid phase’s driving action, particles would be collided the surface and impacted with each other in the flow passage, the surface will be machined though the continuous action of impact force and friction force. The finishing results of structural surface is related to the collision frequency and the pressure, abrasion situation in different area of the structural surface can be analyzed obviously by investigating dynamic characteristic and distribution of particle group. Based on coupled wave theory of liquid-solid two phases flow, using mixture model which belongs to Euler-Euler multiphase flow model and realizable turbulence model, turbulence effects of liquid-solid two-phase flow in the wall is numerical simulated and some parameters such as turbulent velocity and turbulent energy are calculated with different particles concentration in the flow passage which has V-shaped texture and semicircular cross-section. The simulation results show that the disorder degree of turbulence can be improved by assembling V-shaped constrained component, because V-shaped passage is benefit of eddy current’s generation. As the concentration of particles being enhanced, the velocity of particle would be increased in a certain range, turbulence energy reduces gradually, fluctuation margin of particle volume fraction is smaller and smaller, and curves of every kind of parameters change as continuous oscillation, area of surface corresponded with crest of the curve. The concentration of particles should be selected properly and different particles distribution and finishing performance would be obtained with different particles concentration.

Abstract: Analytical and experimental identifications on the characteristics of the acceleration signal in high speed milling (HSM) process using ball end mill were studied. Three parts of harden steel with different hardness were assembled together, as opposed to the single harden steel in general HSM process. Dynamic model of ball end milling was established, tests with new and worn cutter were carried out respectively. Time domain analysis on the acceleration signal showed that the amplitude varies with the hardness through the whole cutting path. Furthermore, frequency domain analysis using fast Fourier transform (FFT) technique shows that the spectrum of the vibration signal using new cutter contain the tool spindle rotation speed as fundamental frequency and its harmonics. On the other hand, the spectrum of vibration signal under tool wear state contain other frequencies in addition to the fundamental frequency and harmonics, and this feature of spectrum can be used to monitor the state of the cutter during HSM.

Abstract: As it was difficult to solve the near wall characteristics of flow field in softness abrasive flow machining (SAFM) on mould structural surface, a method for simulation the flow characteristics based on the low Re number k-ε model was proposed in this paper. The U-shaped tube was used as specific simulation object. The motion law of particles and related parameters were calculated and the precision machining mechanism of SAFM was discussed. Simulation results show that the micro cutting of abrasive flow mainly appears as the transposition of cutting location influenced by the particle pressure, and as the variation of machining efficiency influenced by near-wall particle velocity. Thus via control of the inlet velocity and its corresponding machining time, it is supposed to work out the machining process according with the machining requirements. By tracking near-wall particles, it can be confirm that the movement of near-wall abrasive particles is similar to stream-wise vortices. The cutting traces on workpiece surfaces assume disorderly arrangement, so the feasibility of SAFM method can be reaffirmed.

Abstract: Autonomous nodes distribution, including their relations, real time quality and network communication in abrasive flow precision machining (AFPM) was studied. Autonomous nodes are arranged according to their function. Control program of motor speed is copied into liquid level nodes, pressure nodes, temperature nodes, flux nodes and input/output nodes. If nodes failure has happened, competition algorithm is enabled automatically to select a new node to run important program. Reliability of autonomous control system can be calculated utilizing the formula derived from probability theory. ARM 9 embedded systems with 32 bit CPU and real time embedded operating system are adopted to realize real time quality and reliability of nodes which run independently. CAN field bus and message type flag are used in network communication structure to ensure the real time quality and reliability of nodes connection. Results reveal that using autonomous decentralized control in AFPM possesses not only the characteristic of real time quality, but also the online fault tolerance, which can ensure that system runs continuously even if some nodes break down. The method can avoid system destruction and improve whole system reliability.

Abstract: Damping in built-up structures is often caused by energy dissipation or energy loss due to micro-slip along frictional interfaces interaction, which provides a beneficial damping mechanism and plays an important role in the dynamics vibration behavior of such structures, especially the contact stiffness and damping coefficient accounting for the kinematics joint. A detailed study the mechanics derived from the interaction interface between the different components has some embarrassment. And a careful study on the micro-slip phenomenon has been carried out using the finite element method. A classical joint configuration, the plane translation joint, has been used as the model problems. The focus of this paper is to evaluate the effect of dry friction coefficient, the external mechanics on the damping response of frictional joint interfaces interaction, to understand the evolution of the slip-stick regions along a joint interface during loading, and to quantify the amount of energy dissipation/loss during cyclic loading and its dependence on structural and loading parameters.

Abstract: This paper focuses on the dynamics characteristic difference on the two kinds of broading machine, the workpiece moving and the cutting-tool moving. There is 0.002mm thickness of oil-film clearance between the mobile and immobile components of the broading machine. Hydraulic pressure derived from the driving oil cylinder drives the workpiece or cutting-tool moving, while the material on the workpiece is cutting. Cutting-tool of the machine is an external expand cutter with the groove for breaking the cutting waste, the manufacturing phase is a pulse impact cutting exciting applying on the broading machine correspondingly. On manufacturing, natural characteristic of the broading machine is approximately the pulse impulsion frequency of the machine;response amplitude of the lather is increasing manifesting. The study is focused on the dynamics characteristic of two kinds of broading machine, the difference is workpiece or cutter moving, to predict the manufacturing performance.

Abstract: As it was difficult to solve the near wall characteristics of flow field in softness abrasive flow machining (SAFM) on mould structural surface, a method for simulation the flow characteristics based on the low Re number k-ε model was proposed in this paper. The greater curvature of small size tube was used as specific simulation object. The motion law of particles and related parameters were calculated and the precision machining mechanism of SAFM was discussed. Simulation results show that the micro cutting of abrasive flow mainly appears as the transposition of cutting location influenced by the particle pressure, and as the variation of machining efficiency influenced by near-wall particle velocity. Thus via control of the inlet velocity and its corresponding machining time, it is supposed to work out the machining process according with the machining requirements. By tracking near-wall particles, it can be confirm that the movement of near-wall abrasive particles is similar to stream-wise vortices. The cutting traces on workpiece surfaces assume disorderly arrangement, so the feasibility of SAFM method can be reaffirmed.

Abstract: Nowadays, researches concerned magnetic abrasive finishing (MAF) are becoming increasingly popular. Polishing head is one of the most important factors in the whole polishing system in which magnetic abrasive act directly on the workpiece. In this paper, two kinds of polishing heads applied in the polishing of free form surface are proposed. They are hard polishing head and soft polishing head, respectively. And some important factors are contrasted such as selfsharpening capacity, morphology distribution, and removal uniformity. Moreover, the finishing force is the key factor which is different between the two polishing heads having a great influence on polishing effect. Through comparison and analysis, the soft polishing head is better to finish free form surface. And the experimental results reflect its superiority in polishing free form surface.

Abstract: This paper brought forward an intelligent computer aided instruction (ICAI) modeling method oriented to parallel robot instruction. According to the learning-origin structure of mechanical specialty students, the study process and cognition characteristics were analyzed, and the comparative research on their quality performance in parallel robot direction was carried out. The ICAI model was established oriented to parallel robot practical instruction combining machine learning and artificial intelligence method. Aiming at the basic instruction requirements of mechanical engineering specialty, the innovation mechanism of this area was researched, and the instruction strategies optimized and realization method were provided. Experiments proved that this method can simulate the implementation course of parallel robot instruction, and improve the instruction effects validly.