Papers by Keyword: Traverse Cylindrical Grinding

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: A finite element heat transfer model incorporating a moving heat source has been developed to predict the temperature field in traverse cylindrical grinding. The model was then applied to analyse the grinding-hardening of quenchable steel 1045. It was found that in the region where the grinding wheel had an entire contact with the workpiece, material would experience a heating-cooling cycle, enabling the generation of a uniform hardened layer. In the transient regions at the two ends of the workpiece where the wheel-workpiece contacts were partial, the material was not hardened but experienced an annealing process. The results were in good agreement with the experimental observations.