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1、1Annals of CIRP Vol.47/2/1998:p651-665Grinding Process Achievements and their Consequence on Machine Tools Challenges and OpportunitiesH.K. Toenshoff , B. Karpuschewski AbstractThe dynamic states of temperature field and temperature history of points in various model placements are investigated by s
2、imulation. It has been demonstrated that the simulation results are in accordance with measurement results due to the reliable simulation method and the accurate heat model. Therefore the simulation may be studied instead of experiment.Usually, crank have to be grinded using several positioning and
3、clamping operations because of the differences in axes orientations of the main journal and the connecting rod journal. In the operation, there are many problems such as relatively excessive errors of positioning and clamping, low productivity, large investment of equipment and workshops, long perio
4、d in the adjustment of the machine tool and fixtures and poor surface finish of the ground part etc.Keywords Crank Coordinated grinding Grinding temperature Grind-hardening is a new technology which utilizes grinding heat to induce martensitic phase transformation and strengthen workpiece surface in
5、 grinding process by raising surface temperature above Ac3 instantaneously and cooling quickly. The application of this new technology can reduce production cycle, improve working efficiency, and decrease manufacturing cost by integrating the two operations of grinding and surface heat treatment int
6、o one, which has the great social and economical benefits. Grind-hardening experiments for external grinding mode are carried out. The results indicate that the 2hardened workpiece surface consists of three parts of hardened layer, transition layer, and body. The metallurgical structures of the part
7、s are martensite, mixture of martensite and ferrite, and mixture of ferrite and pearlite respectively. Under the experiment condition, the top value of hardness and hardened depth is HV824.1 and 1.1mm respectively, which achieves the effect of high-frequency hardening. The orthogonal experiments wit
8、h different cut depths, workpiece speeds and wheel characteristic are performed, contribution and pattern of the factors influence to hardening effect are analyzed. The results show that hardened layer thickness rises with increasing cut depth, and rises and falls with increasing workpiece speed. Wh
9、ite alundum wheel increased more hardened layer thickness than pink alundum, while small grain granularity products more hardened layer thickness than big one. The order of factors is cut depth, workpiece speed, and wheel characteristic according to the contribution. The results also indicate that s
10、urface hardness 3is only affected by cut depth, and the hardness value rises with increasing cut depth. Under the present experiment condition, the adoption of 0.4mm cut depth, 0.5m/s workpiece speed and wheel WA46L8V may achieve good comprehensive grind-hardening results of both hardened layer thic
11、kness and surface hardness.40Cr steel and 45 steel are adopted simultaneously in the experiments to research hardening effects with different materials. The results show good hardened effectiveness of both materials as well as the similar pattern of metallurgical structure and hardness distribution.
12、 It has been found that 40Cr steel has more hardened layer thickness while 45 steel has higher surface hardness. The difference derives from the material property. The observation of the metallurgical structure and test of hardness distribution for the overlap hardened zone demonstrate the rehardeni
13、ng is occurred and the metallurgical structure or hardness distribution changes little. Due to the inertance of conductivity, the residual heat in the zone tempered the material at its end part. A little tempered sorbite appears while the hardness value drops accordingly. However, because the temper
14、ed area is small in size (1.0mm) and even the bottom value (HV479.6) can satisfy the hardness requirement, it has little influence to the total hardened effectiveness. Fine grinding stage is taken for the surface roughness and quality after the hardened layer is obtained in the coarse grinding stage
15、, and the fine grinded sample is analyzed. The result indicates the same metallurgical structures and surface hardness to the sample of coarse stage. Therefore, with rational choiced grinding parameters and condition, requirement of surface hardness and machining precision may be met simultaneously.
16、 Grinding force and temperature are measured in the experiments by adopting elastic core clampers and infrared thermometer, which provides data for theory study. Moreover, the variation regularity and influence factors are analyzed. The results indicate that grinding force is proportional to workpiece speed and cut depth in external grind-hardening process, and the ratio of normal force to tangential force is more than that of common grinding. Grinding temperature is influenced by cut depth,
