Papers by Author: Bing Heng Lu

Abstract: The abrasive jet finishing process with wheel as restraint is a kind of compound precision finishing process that combined grinding with abrasive jet machining, in which inject slurry of abrasive and liquid solvent to grinding zone between grinding wheel and work surface under no radial feed condition when workpiece grinding were accomplished. The abrasive particles are driven and energized by the rotating grinding wheel and liquid hydrodynamic pressure and increased slurry speed between grinding wheel and work surface to achieve micro removal finishing.In the paper,the finished surface morphology was studied using Scanning Electron Microscope (SEM) and microscope and microcosmic geometry parameters were measured with TALYSURF5 instrument respectively. According to the metrical results, the surface topographical characteristics were evaluated with correlation function and PSD (Power Spectral Density) of random process about machined surface before and after finishing. The results show that longitudinal geometry parameter values of finishing machining surface were diminished comparing with ground surface,and the mean ripple distance was decreased and, ripple and peak density were increased. Furthermore, the finished surface has little comparability compared to grinding machining surface.The isotropy surface and uniformity veins at parallel and perpendicular machining direction were attained by abrasive jet precision finishing with grinding wheel as restraint and the surface quality is improved obviously.

Abstract: In the grinding process, grinding fluid is delivered for the purposes of chip flushing, cooling, lubrication and chemical protection of work surface. Due to high speed rotating grinding wheel, the boundary layer of air around the grinding wheel restricts most of the grinding fluid away from the grinding zone. Hence, conventional method of delivering grinding fluid that flood delivery is not believed to fully penetrate this boundary layer and, thus, the majority of the grinding fluid is deflected away from the grinding zone. The flood grinding typically delivers large volumes of grinding fluid was ineffective, especially under high speed grinding conditions. In the paper, a theoretical model is presented for flow of grinding fluid through the grinding zone. The model shows that the flow rate through the contact zone between the wheel and the work surface depends on wheel porosity and wheel speed as well as depends on nozzle volumetric flow rate and fluid jet velocity. Furthermore, the model was tested by a surface grinding machine in order to correlate between experiment and theory. Consequently, the effective flow-rate model was found to give a good description of the experimental results and the model can well forecast the effective flow-rate in flood delivery grinding.

Abstract: Grinding processes are mainly technique employed widely as a finishing and difficult-to machine such as hardness and brittleness materials machining. However in grinding process, high grinding zone temperature may lead to thermal damage to the work surface, induces micro-cracks and tensile residual stresses at the ground surfaces, which deteriorate surface quality and integrality of the ground surface. The work presented in this paper aims at evaluating the grindability and surface integrity of the nickel base superalloy resulting from the application of cryogenic cooling. Grinding experiments were conducted under three different environments: dry, mineral oil and cryogenic cooling jet. The grindability results have shown that while the cryogenic cooling generates the lowest grinding temperature, no significant differences over the specific grinding force components were observed. As for the ground surface integrity, however, substantial improvements were realized. The novel process not only obviously enhances surface quality and integrality of grinding surface, but also enables retention of the wheel sharpness for a longer period and reduces pollution of grinding fluid to nature.

Abstract: The process technique on abrasive jet finishing process with wheel as restrain was investigated by experimental. The effects of different particle size, abrasive concentration, machining cycles, the velocity of grinding wheel and medium type on surface quality were analyzed. Experiments were performed with plane grinder M7120 and workpiece material 40Cr steel. The machined surface morphology was studied using Scanning Electron Microscope (SEM) and microscope and microcosmic geometry parameters were measured with TALYSYURF5 instrument respectively. The experimental results under percentage 10 abrasive concentration, Al2O3 abrasive particle with W7 size and machining 20～30 circles showing the novelty process method, not only to attain higher surface form accuracy, to diminish grinding defects such as severely deformation, surface layer pollution and ground burnout, but also to can acquire efficiently free defects finishing surface with Ra0.15～1.6µm and finally achieve high efficiency, high precision and low roughness values. Furthermore, integrate grinding process and abrasive jet finishing process into one feature.

Abstract: The traditional method to manufacture the medical implant or prosthesis is based on sculpting and on the tissue site,or takes impressions of the entire face about human. The accuracy and efficiency of medical implant or prosthesis produced by conventional method is heavily relied on the skill and experience of both designer and manufacturer. In this paper, an integrated method of medical implant manufacture is approached. This integrated strategy was to establish a system that allows fabrication of facial prosthesis from digital information, and integrates the rapid prototyping with modeling technology of complex three-dimensional geometry from high-resolution non-invasive imaging, reverse engineering and computer aided design. The research results have shown that the integrated method can produce more exact-fit medical implant, that is, the physical model of the implant is more exactly fitted on the skull model. The advantages of this method are that the surgeon can plan and rehearse the surgery in advance, and a less invasive surgical procedure, and less time-consuming reconstructive, and an adequate esthetic can result.

Abstract: A direct metal RP (rapid prototyping) process based on micro-plasma arc welding (MPAW) is presented. The impact of R (ratio of width to height of the deposited track’s cross-section) on part quality is investigated. Taguchi method is adopted to analyze the effect of each process parameter on R, and the optimized process parameters are obtained. The results show that the quality of the parts with larger R is better than that with smaller R, and the peak current, duty cycle of pulse duration, wire-feeding speed, scanning speed and plasma gas flow rate all exert significant effects on R. The overlapped surface smoothness, tensile strength and elongation of the parts fabricated with optimized parameters are measured to show obviously better performances than those of the parts fabricated with ordinary process parameters.

Abstract: Self-hardening calcium phosphate cement (CPC) could not be used to repair a large segmental defect in a load-bearing bone because of its brittleness and weak shock resistance as well as ultra-minute pores. Recent studies incorporated fibers into CPC to improve its strength. A novel approach by rapid prototyping and rapid tool technique (RP/RT) was used in this paper to fabricate fibre-reinforced CPC composite artificial bone. The subsequent mechanical experiments demonstrated that the compressive strength of the CPC-fiber artificial bone was 24MPa, which was significantly higher than 6MPa for CPC control without fiber. And in-vivo experiment about canine radius repair proved that the implanted CPC-fiber artificial bone enabled to provide short-time reinforced mechanical strength, while the degraded fibers created new macropores for new tissue ingrowth. In summary, the CPC-fiber artificial bone may facilitate bone ingrowth and its four times increase in strength may help extend the use of CPC to larger bone repairs in moderately stress-bearing locations.

Abstract: A precision 6-degree-of-freedom measurement system has been developed for simultaneous on-line measurements of imprint lithography stage. To successfully accomplish nanometer-scale pattern transfer from mold to resist film on the wafer, two types of positioning methods, static and dynamic, are used in this system. Two laser interferometers, two optical reflection mirrors and special structure on the stage with 3 elastic tracks are employed in this system to detect the positions and rotations of the stage. Through an algorithm, measurements of pitch, yaw and roll motions can be achieved. This system can realize on-line position detecting. Based on adjusting of PZTs, the detecting precision can reach 10nm and ±3 milli-arcsec, respectively. The measuring range can reach 100mm and ±10 arcsec, respectively.