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This study is focused on the description of ductile fracture initiation, which is needed to predict product shapes in the blanking process. Two approaches are elaborated using a local ductile fracture model. According to literature, characterization of such a model should take place under loading conditions, comparable to the application. Therefore, the first approach incorporates the characterization of a ductile fracture model in a blanking experiment. The second approach is more favorable for industry. In this approach a tensile test is used to characterize the fracture model, instead of a complex and elaborate blanking experiment. Finite element simulations and blanking experiments are performed for five different clearances to validate both approaches. In conclusion it can be stated that for the investigated material, the first approach gives very good results within the experimental error. The second approach, the more favorable one for industry, yields results within 6 percent of the experiments over a wide, industrial range of clearances, when a newly proposed criterion is used. [S1087-1357(00)02202-4]

This study is focussed on the evaluation of ductile fracture methodologies, which are needed to predict product shapes in the blanking process. In an earlier publication [Goijaerts et al., J. Manuf. Sci. Eng., Trans. ASME 122 (2000) 476], two approaches were elaborated using local ductile fracture models. The ®rst strategy incorporates the characterisation of a ductile fracture model in a blanking experiment. The second methodology is more favourable for industry. In this approach, instead of a complex and elaborate blanking experiment, a tensile test is used to characterise a newly proposed criterion, which was shown to predict accurately the ductile fracture for different loading conditions. In this paper, ®nite element simulations and experiments are performed on both tensile testing and blanking to evaluate the validity of both approaches with corresponding criteria for ®ve different metals. In the blanking process, different clearances as well as different cutting radii of the tools are considered. In conclusion, it can be stated that the ®rst approach gives very good results close to, or within the experimental error for all ®ve materials. The second approach, the more favourable one for industry, yields good results that deviate slightly more over the range of metals. #

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SynopsisThe absence of a model to predict near wall viscosity of complex suspensions instigated an investigation for a new method to determine the wall shear stress. If the inner wall of a flow model is covered with a highly flexible gel layer, the local wall shear stress will deform this gel layer. Through the known properties of the gel layer, the measured deformation can be transformed to the wall shear stress. To measure the deformation of the gel layer, speckle pattern interferometry was applied. The performance of the developed speckle apparatus was evaluated using a well-controlled benchmark experiment, and a resolution of 50 nm was achieved. The deformation of a gel layer was measured in a two-dimensional rectangular duct, using a Newtonian and a non-Newtonian measuring fluid. The wall shear stresses were measured as a function of the flow rate and compared to theoretical predictions, and the results demonstrated the potential of the method.