Die stress and friction behaviour analysis in bolt farming

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Date

2006

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Aygen, Mert

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In cold forming operations, tool geometry has a direct influence on the product quality, forming force, load acting on dies and tool life. Finite element method provides a means to analyse these parameters to predict forming defects and die failures. In this study, shrink fitting the components of a bolt forming die is modelled and the finite element results are compared with the analytical solutions and experiments. In order to perform die stress analyses, deformable die models are implemented in the forging simulations. Furthermore, effect of using rigid and deformable dies on the stress distributions in the tools, forming force and product dimensions are examined. Some applications of tool geometry improvements and optimization of prestressing are presented in the case studies. In the second part of the study, the appropriate friction model for the cold forming operation of bolts is investigated. For this purpose, ring compression and forward rod extrusion tests are conducted. Dimensional variations and deformation forces are compared with the finite element simulations performed for different friction models and constants. The results of shrink fit analyses of die prestressing are in good agreement with the elasticity formulations and real applications. In the studied bolt production cases, after improving the die stress distributions by using FE simulations, longer tool lives are achieved. Finally, for more accurate results, Coulomb friction model is determined as an appropiate model for bolt forming analyses.

Subject Keywords

Mechanical Engineering.

URI

http://etd.lib.metu.edu.tr/upload/3/12607910/index.pdf
https://hdl.handle.net/11511/16480

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

M. Aygen, “Die stress and friction behaviour analysis in bolt farming,” M.S. - Master of Science, Middle East Technical University, 2006.