True strain distribution profile on sheet metal using different punch geometries
Changes are often necessary during the tryout of stamping tools. These changes may range from adjustments on die and punch designs to the selection of a new material with better formability characteristics. All these actions, however, require time and money creating the need for better initial sheet metal evaluation. Hence, increasing attention has focused on the development of laboratory tests that enable stamping companies to know more about the sheet metal stampability or that can, at least in part, ensure that their stamped products are produced without major problems. Identification of high stress region on stamping may allow for better tool stamping adjustment during tests, rendering a more uniform materials deformation and leading to the production of higher quality parts. Increasing attention has focused on the material evaluation based on the tool geometries in order to calculate the strain distribution. This study deals with an evaluation of four punch models with varied geometries in addition to the traditional Nakazima test tool. An evaluation was also made of the major true strain distribution profile at points distributed linearly from the region close to the die shoulder to the punch center.
Analysis of numerically simulated true strain on high stampability sheets
The sheet metal forming is a manufacturing process widely used industrially. The quality and efficiency of the process is dependent on the correct choice of the process parameters and the correct understanding of the sheet metal behavior. The identification of the regions where stretching and/or deep drawing occurred during the forming process can aid the process through the tools design optimization. This work consisted of evaluating three punch models with varied geometries. The purpose of this work was to simulate different punch geometries using the ANSYS/LS_DYNA program and to compare the results with those reported in the literature. An evaluation was also made of the chosen program's response quality (validation). The material model chosen was the Barlat's model. The friction coefficient influence was also investigated. A comparison of the major true strain (e1) obtained by simulation compared with the experimental results indicated that this material model is able to satisfactorily reproduce the major true strain found in practice for the DC 06 steel.
SR topography of plastically deformed Fe-Si bicrystals - observation in situ and post mortem
SR reflection topography was applied to study the interaction of slip dislocations with the grain boundaries in Fe-4at%Si bicrystals deformed by compression. Three experimental settings with either a white or monochromatic beam were used and the corresponding orientation contrast analysed. Dislocation transmission through the grain boundary was observed in bicrystals with favourable geometry of the slip systems.