Advanced Materials Research Vol. 1017

Abstract: An experimental study was undertaken to explore the conditions and performance on rough and finish grinding fir-tree root forms of turbine blades made of a nickel-based alloy using vitrified CBN wheels and water-based grinding fluid. This work was motivated by switching the grinding of fir-tree root forms from grinding with conventional abrasive wheels to vitrified CBN wheels for reducing overall production cost and enhancing productivity. Grinding experiments were conducted to measure grinding forces, power, surface roughness, and stress near the blade roots under various dressing and grinding conditions. Wheel re-dressing life in terms of the total number of good parts ground between dressing was tested with the condition producing the maximum material removal rate while satisfying preset part quality and process requirements. It was found that the maximum material removal rate achievable in rough grinding was restricted by the stress limit and the wheel re-dressing life was dominated by the radial wheel wear limit. The targeting part quality and process requirements were achieved. It was proved that vitrified CBN grinding process is feasible and very promising to machine fir-tree root forms.

Abstract: The deformation and removal mechanism of a multilayered thin film structure involved in nanoscratching and diamond lapping processes were investigated. The results obtained from the two processes were compared, in terms of deformation characteristics and surface finish. It was found that both nanoscratching and lapping demonstrated similar characteristics. This work provides insight into the deformation and removal of a thin film multilayered structure under mechanical loading, and thus the outcome is of value for developing the efficient machining process for such structures.

Abstract: Rapid Rotation Mirror-like surface Grinding (RRMG), in which combine Rapid Rotation Grinding (RRG) and Truncate Truing with Micro Dressing (TTMD) are combined, is a suitable method for mirror-like surface finishing with high efficiency. The surface roughness of a workpiece decreased with increasing work speed of RRMG, contradicting the conventional grinding principle on grinding geometry and kinematics. Furthermore, it was analyzed that a heat-affected layer and subsurface microstructure of the workpiece having a surface roughness Ra of less than 0.05 μm were obtained by RRMG. As a result, it was clarified that the thickness of the heat-affected layer was decreased and the subsurface microstructure was nanocrystallized, because the grinding temperature was suppressed with increasing peripheral work speed of RRMG.

Abstract: In the grinding process, due to the elastic deformations of grinding machine and grinding wheel, the ground depth of cut is smaller than the applied depth of cut. Consequently, the ground depth of cut has to be controlled in spark-out grinding process. However, the cycle time in spark-out grinding process is not easy to be estimated. From such a viewpoint, in this study, using specific grinding force obtained by measured grinding force in the first spark-out pass, a calculating method of the real ground depth in continuous pass process is proposed. And, this method is experimentally evaluated.

Abstract: In cylindrical traverse grinding of a long workpiece with high aspect ratio, the shape accuracy of a workpiece worsens due to its low stiffness. In this study, the grinding force was measured during grinding process to calculate the elastic deformation of a workpiece caused by the normal grinding force. By comparing calculated elastic deformation with the measured shape error of ground workpiece, the cause for the shape error in case of grinding a long workpiece was investigated experimentally. From experimental results, it is confirmed that the main factor of the shape error of the long workpiece is its elastic deformation during grinding process.

Abstract: Grinding process can be considered as micro-cutting processes with irregular abrasive grits on the surface of grinding wheel. The study of grit-workpiece interaction through single grit cutting was an important contribution to describe material removal process in the grinding process. This paper presented a finite element simulation model for the analysis of AISI D2 cutting process using alumina abrasive grit. Finite element simulations of AISI D2 single grit cutting processes were performed using Advantedge^TM software. Results of material deformation, forces, the critical depth of cut, temperature and material removal rate were discussed.

Abstract: This study aimed to investigate the effect of grinding conditions, including depth of cut and grinding direction, on the material removal and surface finish of multilayered thin film structures. It was found that the increase in depth of cut improved the material removal rate, but worsened the ground surface finish. The grinding perpendicular to the thin films caused less damage and produced better surface than that parallel to the films. The characteristics of wheel wear were also studied. Grit pull-out and micro-fracture should be attributed to the wheel wear.

Abstract: Abrasive belt grinding experiments of ZrO₂ Engineering Ceramics are carried out by using 4 different abrasive belts. The orthogonal test with zirconia-corundum belt was to get the best grinding parameter, the amount of material removal workpiece surface roughness and belt wear were measured to get the best grinding parameter.In this paper,the influence of abrasive belt granularity and different grinding parameters to grinding efficiency and workpiece surface quality throughout the process of grinding ZrO₂ Engineering Ceramics was analyzed. Analysis wear mechanism of engineering ceramics based on the Abrasive cutting model by observing the surface morphology. The results show that increasing the grinding force or the abrasive belt granularity can decrease the workpiece surface roughness;With the abrasive belt speed or grinding force increasing,the material removal rate and the wear ratio to some extent, but brittle fracture is occued easily on its surface when exceeds the critical value; When the abrasive belt speed is 19m/s,the grinding force is 15N and the abrasive belt granularity is 120#, ZrO₂ Engineering Ceramics grinding effects reach the best.

Abstract: With silicon particles reinforced aluminum matrix composites with high volume fraction becoming a new hotspot on research and application in the aerospace materials and electronic packaging materials, the machinability of this material needs to be explored. This paper reports research results obtained from the surface grinding experiment of silicon particles reinforced aluminum matrix composites using black silicon carbide wheel, green silicon carbide wheel, white fused alumina wheel and chromium alumina wheel. The issues discussed are grinding force, surface roughness, the comparison of different grinding wheels, the micro-morphology of the work piece. The results showed that the grinding force was related with the grinding depth and the grinding wheel material, the grinding force was increasing as the grinding depth growing. The surface roughness was between 0.29μm and 0.48μm using the silicon carbide wheel. The surface of the work piece had concaves caused by silicon particles shedding and grooves caused by the grains observed by the SEM and CLSM.

Abstract: YL10.2 and YF06 are ultrafine-grained cemented carbides, and grinding experiments were carried out with resin-bonded diamond grinding wheel. Based on measured grinding force, surface roughness and SEM topography, experimental results were analyzed; grinding forces and depth of grinding approach linear correlation; and the grinding force of YF06 is greater than that of YL10.2 in rough grinding, but the grinding force increases significantly if depth of cut is greater than a certain value in finish grinding. The trend of machined surface roughness looks like “V” type with the increasing of depth of cut; the material removal behavior of ultrafine-grained cemented carbides in grinding was observed; the ploughing and fragmentation exist simultaneously on the ground surface, and the dominated material removal behavior depends on the grinding parameters or chemical composition of workpiece.