Papers by Author: Ya Li Hou

Abstract: Abrasive machining is a widely employed finishing process for different-to-cut materials such as metals, ceramics, glass, rocks, etc to achieve close tolerances and good dimensional accuracy and surface integrity. High speed and super-high speed abrasive machining technologies are newest developed advanced machining processes to satisfy super-hardness and difficult-to-machining materials machined. In the present paper, high-speed/super-high speed abrasive machining technologies relate to ultra high speed grinding, quick-point grinding, high efficiency deep-cut grinding were analyzed. The efficiency and parameters range of these abrasive machining processes were compared. The key technologies and the newest development and current states of high speed and super-high speed abrasive machining were investigated. It is concluded that high speed and super-high speed abrasive machining are a promising technology in the future.

Abstract: In the grinding process, in order to exert the hot-roll on-line grinding (HOG) better, the on-line profile measure (OPM) is required to work steadily and reliably. Nevertheless, owing to the bad environment in the hot-roll grinding, the high distinguish ability and the high security for the OPM technology are the most difficult problems at all the time.The research on this project fits for the development of on-line profile measure for hot stripe rolling grinding. Based on the thought of the operation principle and mathematical model and characteristic analysis, associated with the HOG system, the measurement can work numerically, high efficiently and accurately. The detecting system can inspect and diagnose the potential fault of the equipment, consequently the whole system can be assured to run in the best state.

Abstract: Based on the modeling and experiments concerning the surface roughness in abrasive jet finishing with grinding wheel as restraint, the effect of abrasive size, abrasive fluid concentration, machining cycles, wheel velocity and carrier fluid on machined surface quality was investigated. Surface grinder M7120 was employed in a jet machining experiment conducted with W18Cr4V and 40Cr materials, profilometer TALYSURF was used to measure the micro geometrical parameters after machining, and SEM was used to observe surface micro-morphology. Experimental results show that with W7 Al2O3 powder at the mass fraction of 10% and antirust lubricating liquid being adopted in jet machining for 20 to 30 cycles, not only high surface shape precision can be kept or obtained, but also defect-free machined surface with the roughness of Ra0.15～1.6µm can be obtained with high efficiency. Experimental observation and experimental results proved that the experimental results agree well with a mechanism-based machining model.

Abstract: In the grinding process, conventional method of flood delivering coolant fluid by a nozzle in order to achieve good surface integrity. However, hydrodynamic fluid pressure can be generated ahead of the contact zone due to the wedge effect between wheel peripheral surface and work surface. In the paper, a theoretical hydrodynamic pressure modeling is presented for flow of coolant fluid through the grinding zone in flood delivery grinding. Moreover, coolant induced force can be calculated by integrate the hydrodynamic pressure distribution over the whole contact length. The theoretical results show that the hydrodynamic pressure was proportion to grinding wheel velocity, and inverse proportion to the minimum gap between wheel and work surface and the maximum pressure value was generated just in the minimum gap region in which higher fluid pressure gradient occuring. It can also be concluded the pressure distribution was uniform in the direction of width of wheel except at the edge of wheel because of the side-leakage.

Abstract: In order to meet the demands of high-quality talents raised by the nation, guide and inspire the college students’ hard thinking so as to get more fruits and improve their personal refinement, continuously promote the standard, systematic, and scientific construction of scientific innovation of our students, create a good atmosphere for the students’ participation into the scientific research and practice, and to cultivate high-quality comprehensive talents with innovation capability, in accordance with the reality of our college, we propose that taking the research program as the carrier, the students take part in the instructors’ scientific program. Meanwhile, the instructors are responsible for the scientific innovation activities of the students, and give evaluations in terms of working attitude, scientific quality, innovation capability, working effect. After several years’ exploration, a satisfied result is achieved.

Abstract: The development and manufacturing speed of products have become the focus of competition, at the same time the manufacturing not only has to meet user’s constantly changing needs, but also has to have a relatively strong flexibility of manufacturing technologies. Additive processes can be defined as rapid prototyping, which generate parts (prototyping) in a layered way, is gaining progress by rapid tools (RT) and rapid manufacturing (RM) for production of functional parts in small quantity and even one product without adding the cost becomes more and more critical. The paper describes which mechanism of stereo lithography (SLA) rapid prototyping can be applied to rapid tooling for production complex geometries for long-term consistency. Moreover, the paper demonstrates the application examples of rapid tooling fulfilling the required physical, mechanical and geometrical properties in precision deformation and casting process. The most notable advantage is the integration of production design and digital manufacturing within the product development period.

Abstract: In the grinding process, conventional method of flood delivering coolant fluid by a nozzle in order to achieve high performance finishing. However, hydrodynamic fluid pressure can be generated ahead of the contact zone due to the wedge effect between wheel peripheral surface and work surface. In the paper, a theoretical hydrodynamic pressure modeling is presented for flow of coolant fluid through the grinding zone in flood delivery grinding. Moreover, coolant induced force can be calculated by integrate the hydrodynamic pressure distribution over the whole contact length. The theoretical results show that the hydrodynamic pressure was proportion to grinding wheel velocity, and inverse proportion to the minimum gap between wheel and work surface and the maximum pressure value was generated just in the minimum gap region in which higher fluid pressure gradient occuring. It can also be concluded the pressure distribution was uniform in the direction of width of wheel except at the edge of wheel because of the side-leakage. Furthermore, the hydrodynamic pressure and coolant induced force at wedge-like zone were also investigated experimentally. The experimental results show the theoretical model is agreement with experimental results and the model can well forecast hydrodynamic pressure distribution at contact zone between grinding wheel and workpiece.

Abstract: In the grinding process, grinding fluid is delivered for the purposes of chip flushing, cooling, lubrication and chemical protection of work surface. Lubrication and cooling are the most important roles provided by a grinding fluid. Hence, the conventional method of flood delivering coolant fluid by a nozzle in order to achieve high process performance purposivelly. However, hydrodynamic fluid pressure can be generated ahead of the grinding zone due to the wedge effect between wheel peripheral surface and part surface. In the paper, a theoretical hydrodynamic pressure modeling is presented for flow of coolant fluid through the grinding zone in flood delivery mode in the surface grinding using resin-bonded diamond grinding wheel, which based on Navier-Stokes equation and continuous formulae. The numerical simulation results showed that the hydrodynamic pressure was proportion to grinding wheel velocity, and inverse proportion to the minimum gap between wheel and workpiece and the maximum pressure was generated just in the minimum clearance region in which higher fluid pressure gradient occur. It can also be concluded the pressure distribution was uniform in the direction of width of wheel except at the edge of wheel because of the side-leakage.

Abstract: Grinding processes are mainly technique employed widely as a finishing process in a variety of materials, such as metals, hardness and brittleness and ductile materials machining to achieve good dimensional and form accuracy of the product with acceptable surface integrity. However, grinding is associated with high specific energy requirements which may be an order higher than that required in other conventional machining processes such as turning, planning, milling etc. Therefore, 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. Therefore, grinding fluids are applied in different forms to control such high temperature, but they are ineffective, especially under high speed grinding conditions where the energy of the fluid is not sufficient to penetrate the boundary layer of air surrounding the wheel. Moreover, the conventional flood supply system demands more resources for operation, maintenance, and disposal, and results in higher environmental and health problems. Therefore, there are critical needs to reduce the use of cutting fluid in grinding process, and cryogenic cooling grinding is a promising solution. The work presented in this paper aims at evaluating the grind ability and surface integrity of the nickel base super alloy resulting from the application of cryogenic cooling.

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.