Key Engineering Materials Vols. 304-305

Abstract: The smart fluid abrasive (SFA) is a suspension of magnetically soft ferromagnetic particles and nonmagnetic abrasives in a carrier liquid. When the SFA is exposed to a magnetic field, a rapid and reversible fluid-to-solid phase transition occurs. Based on these distinctive features of SFA, a new type of precision finishing technology that can be used in the finishing of the revolved surface has been developed, and the finishing results have been proved in our experiments. In this paper, the SFA finishing mechanism and finishing process are presented, the influence of some basic parameters such as magnetic strength, size of abrasives, time of processing and relative motion between abrasives and working surface of work pieces are discussed as well.

Abstract: The grinding fluid is typically used to provide functions such as lubrication and cooling in order to reduce surface grinding temperatures effectively in order to achieve better work-piece surface integrity and higher wheel life. This paper investigates the convection heat transfer coefficient of fluid based on the fluid dynamic and thermal modelling within the grinding zone under different grinding condition. This work makes it possible to determine a suitable value of the useful flowrate fluid through the grinding contact arc under optimization of the wheel speed, work speed and jet velocity of nozzle. Its simplicity and accuracy allow application to a wide range of grinding situations from shallow to high efficiency deep grinding.

Abstract: We had done the two-pass grind-hardening experiment on 40Cr steel using the conventional aluminum grinding wheel on a surface grinder, compared the structure and performance of the hardened layer of one-pass grinding with those of two-pass grinding and analyzed the forming mechanism of two-pass grinding hardened layers. The results show that there are a similar martensite structure and change rules of hardened layer of one-pass grinding and two-pass grinding in spite of the different of initial structures, for martensite has tempered by the action of the creep feed grinding temperature field. The depths of hardened layer, microhardness and wear resistance have further improved, but the maximal compressive residual stress and its influencing depth of hardened layer have decreased. The forming mechanism of the two-pass grinding hardened layer is the same as that of the grinding hardened layer of quenched steel.

Abstract: Gearlike cylindrical structure can be used as outer ring of linear bearing for saving material, but the machined surface quality and roundness of this kind of bearing is beyond control in cylindrical grinding and machining efficiency is low. To solve these problems, a new method of pre-stress grinding for gearlike cylindrical surface of linear bearing is put forward based on analysis on the principle of cylindrical centerless grinding. For implementing this process, a set of device with expanding mandrel for loading tensile pre-stress on bearing ring is designed and experiment of through-feed grinding is carried out on centerless grinder. The experimental results show that this method can get fine quality of machined surface and increase the grinding efficiency greatly.