Advanced Materials Research Vol. 1017

Abstract: Grinding-hardening is a thermo-mechanical process capable of simultaneous material removal and surface enhancement. However, there are difficulties in dealing with cylindrical workpieces, because of the complex 3D-helical movement of the grinding-induced heat source. This paper investigates the effects of some key grinding parameters on the profile and microstructure variations of the hardened layer generated by a traverse cylindrical grinding, both experimentally and numerically. It was found that the ratio of the longitudinal wheel feed to the rotational speed of the workpiece R is most influential on the hardened layer profile. A larger R results in a thicker hardened layer but a more pronounced discontinuity of two adjacent hardening zones. Although a smaller R yields a relatively thinner hardened layer, the non-uniformity could be minimised by the overlapping of the grinding heating. The microstructure of the hardened layer can be altered by the tempering in subsequent grinding heating. A thermal analysis with the aid of the finite element method in conjunction with an experimental microstructural examination showed that the temperature distribution in the tempered region would lead to a variation of the precipitated carbide, and that a higher tempering temperature could result in a higher degree of the carbide precipitation and a more significant reduction of hardness.

Abstract: In order to establish a high performance grinding method of cemented carbide, the grinding force distribution on the working surface of the cup type electroplated diamond grinding wheel is experimentally analyzed with the grinding force variation of face grinding, which is carried out on the narrow workpiece. The grinding force distribution is obtained by the successive difference of the grinding force variation. The grinding state becomes steady as soon as beginning of the interference of grinding wheel in workpiece, because the edge profile of workpiece is formed as same as the envelope of the grinding wheel. Main conclusions obtained in this study are as follows. In the region of the front edge of the grinding wheel, relatively large grinding force occurs, then in the region of the rear edge of the grinding wheel, the grinding force becomes smaller. In the left right-side end of the wheel, the grinding forces are larger than the center of the wheel. It is made clear that the grinding force distribution shows the peak value near the outer part of the wheel, and the peak value is larger in the center part of the wheel, on the contrary, the peak width become broad in both the left and right-side end of the wheel.

Abstract: The majority of aero-engine components are designed and manufactured with nickel-based superalloy GH4169 in mind. There is little information available in the literature related to belt grinding processes of aero-engine components. Up to now, limited research has been reported in the use of belt for grinding aero-engine components made of nickel-based superalloy GH4169. A case study of an abrasive belt grinding performance applied on nickel-based superalloy GH4169 in manufacturing processes is presented, aiming to investigate the possibility of using belt grinding as a operation for components made of nickel-based superalloy GH4169. For the ‘optimised’ grinding conditions, the belt service life is evaluated by changing grinding parameters (grinding speed, contact force and oscillation frequency), and the following output measures are obtained: material removal, belt wear and grinding ratio. As a result, the maximum grinding ratio of G is 8.8, it could be concluded that belt grinding might be considered as a viable process for grinding aero-engine components.

Abstract: The demand for large aperture lenses with high surface quality and form accuracy used for single-lens reflex cameras has been increasing. Generally, large aperture glass lenses are produced by ultra-precision grinding. Considering the increasing global competition, the grinding process has to be improved. However, highly efficient grinding causes worse surface quality, which leads to much polishing and ultimately results in lower form accuracy. Thus in this study, aiming at the realization of highly efficient and precise grinding of glass lenses, cross grinding of optical glass BK7 is carried out. As a first step of the study, the influence of grinding conditions on the surface quality is investigated experimentally.

Abstract: Soft magnetic powder cores are made by pressurizing and molding pure iron powder covered with insulation film. The material is used as a component of electro-magnetic converter parts essential for automobiles, home electric appliances and electronic equipment. The material permits downsizing and higher performance of such equipment. The recent severer requirements for performance and dimensional accuracy need a new processing technology that warrants the required level of both magnetic performance and surface quality of the material. However in general, processing - grinding - soft magnetic powder cores can give rise to degradation of magnetic performance and/or chipping or plucking of the ground surface due to the mechanical damage of the insulation film and/or loss of structural particles from the material due to the increase in grinding resistance. The authors performed basic studies for various grinding conditions and wheels that could possibly affect the quality of the material with a view to eliminating these problems. As a result, factors that affect the surface quality were identified, and a method that warrants a higher surface quality was proposed.

Abstract: We explored the effect of supplying coolant from the inner side of a grinding wheel on the residual stress caused by grinding. Effect of depth of cut on grinding temperature and residual stress was also studied. Results clarified that grinding with an internal coolant supply induced a larger compressive residual stress compared to a conventional external grinding fluid supply when depth of cut was large. In addition, grinding temperature in the internal grinding fluid supply was lower than in the external grinding fluid supply, as measured by infrared thermograph camera. Findings suggested that large compressive residual stress was obtained in the case of the coolant supplied from the inner side of the grinding wheel because temperature was lower than external coolant supply.

Abstract: Composite materials, such as CFRP, are hard-to-cut materials but their specific strength is useful. Drill tools are usually used to generate small holes of 1-2 mm diameter, but tool abrasion occurs early, causing problems of processing costs. Comparing other processing methods, it was revealed in the previous report that it was possible to effectively generate large quantities of small size holes using blasting. However, there have been many unknown mechanisms about this blast processing. In the present report, we investigated the material-removing mechanisms of the blast from the viewpoint of the erosion abrasion, considering the most suitable method through changing work materials and processing conditions such as abrasive and pressure.

Abstract: Belt grinding is characterized by elastic contact grinding. Generally, the non-uniform material in complex machining area could be removed by repeated grinding or longer dwell-time grinding to obtain the required grinding capacity, which leads to low efficiency, difficult dimension accuracy control and poor surface quality. It should be considered thoroughly surface geometry, grinding force and system stiffness in surface belt grinding. Belt grinding parameters can be then dynamically adjusted. This paper focuses on controlling material removal efficiently and uniformly in marine propeller belt grinding. The material removal process is modelled considering elastic contact between grinding wheel and workpiece. Then, a grinding depth and grinding dwell time control strategy of surface belt grinding is proposed based on rigid-flexible coupled analysis. The variable feed grinding experiments were carried out on the developed five-axis CNC belt grinding machine integrated measuring and machining. The marine propeller with cast aluminum bronze (ZCuAl₈Mn₁₃Fe₃Ni₂) was employed to validate the proposed controllable material removal strategy. It is shown that the proposed strategy is feasible and efficient.

Abstract: Generally, grinding fluid is supplied from a nozzle to a grinding point. However, it is difficult to supply sufficient coolant to the deep grinding point of a hole. Therefore, we have proposed an alternative coolant system that supplies grinding fluid from the inner side of the grinding wheel utilizing the spindle through the supply system of the machining center. In this study, a new tool for small and deep holes was developed to supply grinding fluid in this way. The inside of a 0.45%C steel cylinder was then machined under various grinding conditions. Higher form accuracy and surface roughness were obtained under all conditions by supplying grinding coolant from the inner side of the grinding wheel. In addition, the system prevented tears on the machined surface and loading on the grinding wheel.