ALUMINUM PROFILES EXTRUSION PROCESS ANALYSIS. MECHANICAL ASPECTS
The presented paper subject is the engineering analysis of the aluminum profiles hot extrusion. Some theoretical aspects of the process as described in professional publications have unsufficient physical grounds. The imperfections of the theory supply a platform for arbitrary interpretations and distorted understanding of the process. Particularly, this relates to the billet friction problem. The paper is addressed primarily to practical engineers with the aim to give them physically consistent process imagine. Some principal solutions to the process were developed in the paper: billet friction by liner; the plastic flow model in dummy block region; the stress state and flow beginning relations in the die opening zone. General model of stable metal flow relations in the billet volume was formulated. The analysis of all mentioned above problems fulfilled by the uniform methodology with the necessity simplifications. The uniform field stress state was used as base model. Strain energy minimum principal for static relations and mass transfer energy minimum principal for plastic flow relations were used generally. Numerical estimations of given solutions were fulfilled. Principal stress component ratio in uniform stress of three dimensional compressing field was defined. Billet — liner, billet — dummy block friction forces acting model was developed. By appraisal, billet — liner friction force does not exceed about 31 % of summative press force. The region of friction force acting was defined. The region restricted as rather short distance from dummy block. Surface forces accumulation effect was revealed. Probable model of plastic flow in dummy block region is presented. Investigation of stress state in die opening region was fulfilled. Additional stresses field in the region revealed. Configuration of the field was defined with numerical estimation. The field in great degree defines the necessary stress level for metal flow start and stable process. The algorithm of maximal flow stress definition was developed. The flow model with restricted shear strain was presented. Preferable flow direction is radial, relative to die opening. Essential interdependencies and general relations of billet metal flow are presented. The analyses of press load by dummy block displacement graph was fulfilled. No contradictions with the theoretically achieved results were revealed. The results experimental confirmation and further introduction to practice are proposed.
Key words: еxtrusion, dummy block, billet, stress, force, friction, plastic flow, die, equation, solution.
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Authors: Nudelman B.