The proposed approach to model stresses in cutting tools leading to evaluation of tool temperature distribution, and to eventually model the combined thermo-elastic stress state, is primarily intended for the development of efficient cutting tools rather than process control. The highlights of the approach are the semianalytical modeling of the tool-chip and tool-work contract stresses and friction, incorporation of the role of the secondary shear effects (albeit empirical) and the use of finite element method (FEM)-based estimation of the elastic (2-D) stress field. The contact stress information is used subsequently to model the temperature distribution in the tool. This approach was successfully evaluated in the case of single point turning tools using results from the experimentally measured temperature field in the tool based on the Binder Phase Transformation (BPT) technique. The temperature distribution in the tool for both dry and wet conditions as predicted by the FEM approach agreed quite well, in general, with experimentally obtained isotherms. Deviations in the observed results in the vicinity of the flank region appears to be related to the simplifications used in modeling the contact stresses therein.
The pre-existing segregation at grain boundaries in two austenitic stainless steels has been investigated by atom probe field ion microscopy and analytical electron microscopy. In addition, the effect of radiation-induced segregation on the near-grain-boundary composition has been studied by analytical electron microscopy. Pre-existing enrichment of Cr, Mo, B, C and P and depletion of Fe and Ni near grain boundaries has been observed. Significant affinity between Mo and N in both alloys is indicated by the detection of MoN2+` molecular ions during field evaporation. The pre-existing segregation is modified by radiation-induced segregation resulting in Ni and Si enrichment near the boundary as well as depletion of chromium adjacent to the boundary resulting in a “W-shaped” Cr profile.
The out of roundness distortion of bearing rings owing to relaxation of internal stresses was investigated experimentally and numerically. Internal stresses in the rings were owing to bending of the tubes from which the rings were produced. This three point bending operation can be regarded as an idealised tube straightening operation. Bending is a typical deformation mode in real tube straightening. The experiments and simulations included the following steps: three point bending of tube, ring turning, and soft annealing heat treatment (also representing the heating in a hardening operation). The ring distortion was measured after ring turning and after soft annealing. A considerable out of roundness was found in both steps but the major contribution was owing to the elastic deformation of the ring at the ® nal stage of turning when the ring was cut off from the tube. MST/4488
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