Abstract: This paper discusses the mechanism behind the grinding force decrease associated with ultrasonication of the grinding wheel in constant-depth-of-cut ultrasonically assisted grinding (UAG). By introducing a grinding model describing the cutting trace of an abrasive grain, an equation relating the grinding
force decrease to such process parameters as the amplitude and frequency of vibration and the grinding wheel speed, is established. Experiments are conducted to confirm the theoretical prediction. Theoretical and empirical results both indicate that the decrease in grinding force is due to the grinding chips becoming smaller and fracturing more easily under ultrasonication. The results also suggest that the grinding force decrease is greater at higher vibration amplitudes and at lower grinding wheel speeds.
Abstract: One of key approaches to improve the productivity is to control with constant force in the milling process by adjusting the feed rate. In order to overcome the mismatch model occurred in adaptive control and inaccurate deducing regulation in fuzzy logic control, a three-layer BP neural network is designed for tracing reference force. First of all, control arithmetic is given, and a series of simulation work is achieved to determine the study factor. At last, aimed at two working conditions with abrupt and gradual change of cutting depth, the correctness and effectiveness of the neural network controller are proved by experiments.
Abstract: This paper attempts to correlate surface functionality generation with machining
conditions by computer simulation and machining trials. The linear and nonlinear machining conditions, such as feed rate, built-up-edge, shear- localized chip formation, regenerative chatter are modelled in the light of their physical features. They are the inputs to the integrated surface topography generation model. The dynamic tool path is calculated through the dynamic cutting force model and surface response model. The surface is generated by transforming the tool profile onto the workpiece surface along the dynamic tool path. All of these models are integrated in a user-friendly Matlab Simulink environment. On the basis of the Simulink model, the dynamic simulation is performed to predict the 3D machined surface topography and its functionality. The simulation results have been validated by precision turning trials. The spectrum analysis of the machining dynamics and surface topography shows that surface generation is highly affected by the nonlinear factors in precision turning process. A case study shows the feasibility of generating some
functional surface for some product/component through controlling machining variables.
Abstract: The diamond wire-saw is a kind of stone machining equipment with flexible cutters. It is widely used in quarrying granite, machining of quarry stones and various special-shaped stones. Experiment has been carried out on the parametric relations among wear form, cutting liner speed and tightening force of diamond wire according to the experimental result of diamond wire-saw in quarrying Shidao Red granite with high efficiency. The suitable working parameters of diamond wire-saw in granite cutting are discussed in the paper, the purpose of which is to improve productivity and quality, and to reduce the cost of the diamond wire-saw as well as to make good
use of advantages of diamond wire-saws. Practice proves that diamond wire-saw is an ideal equipment with high economy index in quarrying granite.
Abstract: This paper presents a model to predict the cutting forces for flat end milling as machining gear indexing cam. Rotation feeding makes axial depth of cut and uncut chip thickness change during cutting process. The development of the model is based on the analysis of cutting edge expression. According to the existing the relationship of the local cutting force and chip load and assuming the cutter to be divided into a number of differential elements in the axial direction of the cutter, the model is derived by summarising the cutting forces produced by each differential cutter disc engaged in the cut. The equation for calculating uncut chip thickness of differential disc is educed. In order to avoid the complex computing for axial depth of cut of the entire edge, a unit square window function and its criterion are introduced to estimate whether a segment of edge is in engaging range.
Abstract: The cutting vibration is one of the main factors to affect precision machining. In this
paper, the influence of tool rake angle on cutting vibration is studied at different cutting speed in turning operation, and corresponding theoretical analysis is made. The experiment results show that: the amplitude of machining vibration gradually decreases with tool rake angle increasing; while rake angle o g <0°, the biggest amplitude occurs at V=50~70m/min; While o g ≥0°, it is at V=160~180m/min. Moreover, theory and experiment foundation is presented on avoiding the biggest amplitude range so as to guarantee quality of precision machining at high speed.
Abstract: Evaluation system of grindability was proposed for advanced ceramics. Grinding forces and material removals of SiC, Al2O3, Si3N4 and ZrO2 were measured. Grindabilities of ceramics were evaluated with property parameters based on fuzzy comprehensive evaluation theory. The experimental results suggest that grindabilities of SiC and Al2O3 are better than those of Si3N4 and ZrO2. The fuzzy evaluation results show grindabilities of SiC and Al2O3 ceramics are classified as
grade of very easy to grind, and Si3N4 and ZrO2 are classified as grade of difficult to grind. The ranking of maximum grinding principal stresses of ceramics considering Poisson’s ratio is SiC, Al2O3, ZrO2 and Si3N4. Theoretical analysis calculated with property parameters is consistent with experimental results in comparison of grinding output parameters. The proposed evaluation system for ceramic grindability is feasible, and the evaluated results are comprehensive and reasonable.
Abstract: By virtue of the technology characteristics of liquid-phase sintering ternary boride hard alloy cladding material, two steel plates were bonded together by a ternary boride hard alloy cladding material through a liquid phase sintering procedure. The bonding strength between a hard alloy cladding layer and a steel substrate was characterized by means of measuring the bonding strength of two steel plates bonded by the hard alloy cladding layer. The bonding strength between hard alloy cladding layer and the steel substrate was measured by transverse rupture strength
method, tensile fracture method and single side shear method, respectively. The results show that a firm metallurgical bonding is formed during the liquid phase sintering.
Abstract: Gas cooled cutting is an important branch of green machining technology with its
excellent cooling performance and is used more and more widely in field of machining. A new method of developing cooling gas generator using semiconductor refrigeration is presented in this paper. Then the main principle, structure and performance of the generator are introduced. In addition, the experiments of high speed milling of Ti Alloy using cooled nitrogen gas were conducted and satisfactory results were achieved. These researches show that the new cooling gas generator has a series of merits such as simple structure, excellent performance, handy operation, low cost and significant spreading value etc.