Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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Wear of abrasive media and its effect on abrasive flow machining results

2015 , Bremerstein, Tina , Potthoff, Annegret , Michaelis, Alexander , Schmiedel, Christian , Uhlmann, Eckart , Blug, Bernhard , Amann, Tobias

Abrasive media were examined before and after application in abrasive flow machining to evaluate the wear of media due to the machining process. Both media were tested on workpieces under the same working conditions to study the effect of abrasive media wear on the results of the machining process. With the help of rheological and granulometric characterisation methods, it has been shown that alterations of rheological behaviour and composition of the abrasive medium as well as particle shape and size are responsible for the degradation of the abrasive efficiency. The increasing viscosity of the abrasive medium and progressing rounding of the large abrasive particles as a result of the machining process are the main factors that cause a decreased material removal rate and reduced surface quality.

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Development of a material model for visco-elastic abrasive medium in abrasive flow machining

2013 , Uhlmann, Eckart , Doits, M. , Schmiedel, Christian

Abrasive Flow Machining (AFM) uses the visco-elastic properties of a polymeric carrier, combined with abrasive grains, as a tool for machining of difficult to reach geometries, such as holes or cavities. Due to the design of the workpiece holding device and variable flow rates, the complex shear modulus of the polymer can locally be influenced and thus a targeted removal on the workpiece can be produced. As a result there is a reproducible material removal, causing requested polishing, deburring or edge rounding. Due to shear thinning and visco-elastic behavior of the tool, the process simulation for AFM is very complex and has not been implemented yet including an exact physical material model. Initial machining parameters so far are based on experience and extensive experiment al research. This publication gives an insight into the investigation of modeling the abrasive media in AFM by adapting the standard Maxwell model of elastomers and extending it to the Generalized Maxwell model. Assuming the material removal of the process being caused by the shear stressed dependent bonding of the abrasive grains, a fundamental material model, easy to be integrated in conventional simulation programs, is developed and presented in this paper.

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