Papers by Keyword: Boss

Abstract: Effective detection of software defects is an important activity of software development process. In this paper, we propose an approach to predict residual defects for BOSS project, which applies defect distribution model. Experiment results show that this approach can effectively improve the accuracy of defect prediction.

Abstract: Magnesium alloys are light weight and highly recyclable. To use magnesium alloys as parts of products such as automobiles, it is very effective make bosses by using plastic workings because this can reduce material loss and welding for producing parts. The bosses can be produced by a press cylindrical tool with rotation to the surface of the magnesium alloy sheet. To reduce the period of development of the tools in forming condition investigations, numerical simulation with FEM is very useful. FEM technologies have been developed for making bosses with plastic working. Because of the symmetry of the tool, the axisymmetrical FEM is applied as the first step. Bosses were found to increase in height as the friction coefficient increased. To investigate the friction between the tool and the alloy sheets, a ring compression test was conducted. The temperature of the alloy sheets increases as the bosses are formed. Therefore, the compression test was conducted at an elevated temperature. The heat transfer rate also affects the results of the forming simulation. To improve the shape of bosses from the simulation results, 3D simulation was performed. The shape of bosses in the 3D simulation is better than that in the 2D simulation by taking into account the traction at the contact area of the cylindrical tool.

Abstract: The shrinkage cavity defect of the extruded boss is harmful to the quality of fine blanking workpiece and process. To suppress the shrinkage cavity defect, firstly, the boss extrusion is simulated to analyze main features of metal flow and the causes of the shrinkage cavity defects; secondly, some parameters affecting the material flow, such as the size of die and punch, blank holder force, friction coefficient, sheet thickness and counter force, are studied to figure out their influences on the depth of shrinkage cavities respectively; finally, the process parameters of a special workpiece are selected according to research results above, and experiment verified that the selected parameters can suppress the shrinkage cavity defect pertinently. In the paper, the shrinkage cavity defect is systematically studied for the first time, and this provides the base to design and optimize the extruded boss feature in fine blanking process.

Abstract: This study aims to produce magnesium alloy strip with boss and rib directly from molten metal. Magnesium alloy is the lightest structural material, so it is expected to widely use for small electronic device and etc. We studied about melt drag process. Melt drag process is one of single roll strip casting process. We use model melt drag experimental device to produce rapid solidified magnesium strip with boss and rib. Substrate is used on model experimental device instead of roll to easily research shape of substrate. Diameter of boss is 5 mm, 7.5 mm and 10 mm. Height of boss is 6 mm. We revealed on this study that the experimental conditions to get good shape boss and rib, improvement substrate shape for good boss and rib, microstructure and etc.

Abstract: Press forging of magnesium alloy AZ31 sheets was investigated in this paper. The typical component, a rectangular box with bosses at the bottom was formed. The experimental results show that the magnesium alloy sheets are suitable for press forging. The bosses and the rectangular box can be formed synchronously for 2 mm or 3 mm thick sheets when the punch temperature is 250 °C. By experimentation and numerical simulation, the effects of process parameters on material flow were analyzed, including the temperature, the die shape, the blank size, the lubrication manners and the friction condition.