January 2018, № 1 (213), pages 92–111
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.
1. Predip K. Saha Aluminum Extrusion Technology. Ohio: ASM International, 2000, 259 p.
2. Aluminium-guide.ru — sajt dlya professionalov alyuminievoj promyshlennosti [Aluminium-guide.ru — site for professionals of the aluminum industry]. Available at: http://aluminium-guide.ru/.
3. Danchenko V.N., Milenin A.A., Golovko A.N. Proizvodstvo profilej iz alyuminievyh splavov [Production of profiles from aluminum alloys]. Dnepropetrovsk, 2002, 448 p.
4. George E. Tollen, D. Scott Mackenzie (Eds) Handbook of Aluminum V.1. Marcel Dekker. Inc., New York Basel, CRC Press, 2003, 1310 p.
5. Sheppard T. Extrusion of Aluminum Alloys. KLUWER ACADEMIC PUBLISHERS, Dortrecht, Boston, London, 1999, 420 p.
6. Flitta I., Sheppard T. Nature of Friction in Extrusion Process and its Effect on Material Flow. Materials Science and Technology, IoM Communications Ltd, 2003, volume 19, issue 7, pp. 837–846.
7. L.S. Polak (Ed) Variacionnye principy mekhaniki. Sbornik statej klassikov nauki [Variational principles of mechanics. Collection of articles of the classics of science]. Fizmatlit, 1959, 930 p.
8. Smolyanskij M.L. Tablicy Neopredelennyh Integralov [Tables of Uncertain Integrals]. M.,1965, 112 p.
9. Vlasov A.K. Kurs vysshej matematiki [Course of Higher Mathematics]. Leningrad, OGIZ, Gosudarstvennoe izdatel'stvo tekhniko-teoreticheskoj literatury, 1946, 1000 p.
10. Online Materials Information Resource. Available at: www.asm.matweb.com.
11. Castool Tooling Systems. Available at: http://www.castool.com/product/clean-out-block.
12. Paul Robbins et al. Today's Understanding of the Function and Benefit of Dummy Block Design. ET Dummy Block Paper, 2016, pp. 2, 4, 9. Available at: http://www.castool.com/sites/default/files/publications/ET%20Dummy%20Block%20Paper%20-%20May%202016.pdf.
13. Aluminum Extrusion Council. Available at: www.aec.org.
14. Mirkin L.I. Fizicheskie osnovy prochnosti i plastichnosti [Physical basis of strength and plasticity]. Izd. MGU, M, 1968, pp. 184–241.
15. Malinin N.N. Prikladnaya teoriya plastichnosti i polzuchesti: uchebnik dlya studentov vuzov [Applied theory of plasticity and creep: a textbook for university students]. M., Mashinostroenie, 1975, 400 p.
16. E.A. de Souza Neto, D. Peric, D.R.J. Owen Computational Methods for Plasticity: Theory and Applications. Publ. John Wiley&Sons, 2009, 814 p. ISBN0470694521.
17. Available at: http://www.egr.msu.edu/~pkwon/me477/bulkforming2.pdf.
18. J.X. Liu, T. ElSayed A strain gradient plasticity theory with application to wire torsion. International Journal of Damage Mechanics, 2014, vol. 24, issue 4, pp. 512–528. Available at: https://doi.org/10.1177/1056789514537920.
19. Lilian Wang Modelling of friction for high temperature extrusion of aluminium alloys. Doctor's thesis. Delft University of Technology, 2012, 131 p. ISBN978-94-6182-07855.
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Author: Nudelman B.