Knowledge-Based System For Computer-Aided Process Planning With Finite Element Predictions
The knowledge-based system COFEX (Cold Forging Expert) has been developed to assist in the planning of the cold forging of a wide variety of tubular steel components. Following user-input of the required shape and dimensions of the finished forging, together with as many different sequences as desired, each operation is examined by the system by consulting the knowledge-base process rules and data. Messages give the reason if any of the operations is unacceptable. If manufacture by cold forging is feasible, the dimensioned drawings of the finished and semi-finished forgings, together with the process parameters are displayed. Subsequently the suitability of existing presses are checked or new ones specified, the cost of the forging is computed and the sensitivity of the costs to various factors assesses. If heading is included in the sequence it can be checked by the finite element analysis whether or not plastic buckling and subsequent folding defect is likely to occur, and forging loads, stresses and strains predicted.
Cold Extrusion of Flanges on Cylindrical Hollows
Flanges on hollow cylindrical engineering components are often made by free upsetting when under certain conditions a bulge is formed in the unsupported portion, which on further deformation appears as a fold in the finished flange.
A bifunctional Cr/Yb/Tm:Ca3Ga2Ge3O12 phosphor with near-infrared long-lasting phosphorescence and upconversion luminescence.
Currently, upconversion nanocrystals and long-lasting phosphorescent particles have attracted extensive research interest for their possible applications as bioimaging probes. However, there are few reports concerning the achievement of both upconversion luminescence of lanthanide ions and long-lasting phosphorescence of transition metal ions in a sole host so far. Herein, we demonstrate a novel calcium gallium germanium garnet (Ca3Ga2Ge3O12) host where lanthanide ions such as Tm(3+)/Yb(3+) and transition metal ions such as Cr(3+) can be easily incorporated through substituting the Ca(2+) and Ga(3+) respectively. This Cr/Yb/Tm:Ca3Ga2Ge3O12 phosphor exhibits both broadband near-infrared long-lasting phosphorescence of Cr(3+) with an afterglow time of more than 7000 s and near-infrared to near-infrared upconversion luminescence of Tm(3+). Impressively, it is evidenced that the addition of Yb(3+)/Tm(3+) into Cr:Ca3Ga2Ge3O12 not only results in Tm(3+) upconversion luminescence but also greatly increases Cr(3+) afterglow time. Based on excitation/emission, three-dimensional thermoluminescence, and time-resolved luminescence spectra, the related long-lasting phosphorescence and upconversion luminescent mechanisms are systematically discussed as well.