Fracture Behaviour of Metal Powder Compact
S.M. Tahir, A.K. Ariffin & N. Muhamad
ABSTRACT
This paper is intended to establish a fracture criterion for metal powder compact during the cold compaction process. Based on the fracture criterion of granular materials in compression, a displacement based finite element model has been developed to analyse fracture initiation and crack growth in iron powder compact. Estimation of fracture toughness variation with relative density is established in order to provide the fracture parameter as compaction proceeds. A crack initiated from the boundary of iron powder compact is considered in this work. The finite element simulation of the crack propagation reveals that crack propagates in the direction of higher shear stress and higher relative density. This also implies that the crack grows in the direction where the compaction pressure is much higher, which is in line with the conclusion made by previous researchers on shear crack growth in materials under compression.
Keywords: Powder compact, Fracture criteria, Fracture toughness, Finite element.
References
[1] Chtourou, H., Guillot, M. & Gakwaya, A. (2002). Modelling of the metal powder compaction process using the cap model. Part 1: Experimental material characterisation and validation . International Journal of Solids and Structures 39, 1059-1075.
[2] Mori, K., Sato, Y., Shiomi, M. & Osakada, K. (1999). Prediction of fracture generated by elastic recoveries of tools in multi-level powder compaction using finite element simulation . Int. J. of Machine Tools & Manufacture 39, 1031-1045.
[3] Gollion, J., Bouvard, D. & Stutz, P. (1989). On the rheology of metal powder during cold compaction . Proc. Int. Conf. Micromechanics of Granular Media, Powder and Grains. Ed. J. Biarez and R. Gourves, 433-438.
[4] Ariffin, A. K. (1995). Powder compaction, finite element modelling and experimental validation . PhD Thesis. University of Wales Swansea, United Kingdom.
[5] Hauck, E. T., Rose, L. J. Won-Joon, S. & Heaney, D. F. (2003). A surface wave mediator technique for crack detection in green parts . Proceeding of The 2003 International Conference on Powder Metallurgy & Particulate Materials.
[6] Frederick, K., Zetec, Inc. (2003). Eddy current testing of powder metal components . www.zetec.com/documents/pwdr_met_insp(1).pdf.
[7] Bobet, A. (2000). The initiation of secondary cracks in compression . Engineering Fracture Mechanics 66, 187-219. 14 Fracture Behaviour of Metal Powder Compact
[8] Melin, S. (1986). When does a crack grow under mode II conditions? . Int. Journal of Fracture 30, 103-114.
[9] Melin, S. (1987). Fracture from a straight crack subjected to mixed-mode loading . Int. Journal of Fracture 32, 257-263.
[10] Mao, H. Y., Zan, Y. W., Zhao, J. & Yoshimine, M. (2002). A unified strength criterion for rock material . Int. Journal of Rock Mechanics & Mining Science 39, 975-989.
[11] Isaksson, P. & Stahle, P. (2002). Mode II crack paths under compression in brittle solids -A theory and experimental Comparison . International Journal of Solids and Structures 39, 2281-2297.
[12] De Bremaecker, J.Cl. & Ferris, M.C. (2004). Numerical models of shear fracture propagation . Engineering Fracture Mechanics 71, 2161-2178.
[13] Liu, A.F. (1974). Crack growth failure of aluminium plate under in-plane shear . AIAA Journal 12, 180-185.
[14] Hallback, N. (1998). Mixed mode I/II fracture behaviour of high strength steel . International Journal of Fracture 87, 363-388.
[15] Roy, Y. A., Narasimhan, R. & Arora, P.R. (1999). An experimental investigation of constraint effects on mixed mode fracture initiation in a ductile aluminium alloy . Acta Mater. 47, 1587-1596.
[16] Isaksson, P. & Stahle, P. (2003). A directional crack path criterion for crack growth in ductile materials subjected to shear and compressive loading under plane strain conditions . International Journal of Solids and Structures 40, 3523-3536.
[17] Rao, Q., Sun, Z., Stephansson, O., Li, C. & Stillborg, B. (2003). Shear fracture (mode II) of brittle rock . Int. Journal of Rock Mechanics & Mining Sciences 40, 355-375.
[18] Tran, D.V. , Lewis, R.W., Gethin, D.T. & Ariffin, A.K. (1993). Numerical modelling of powder compaction process: displacement based finite element method . Powder Metallurgy Vol. 36, No. 9, 257-266.
[19] Zienkiewicz, O.C & Zhu, J.Z. (1989). Error estimates and adaptive refinement for plate bending problems . Int. Journal for Numerical Methods in Engineering. 28, 2839-2853.
[20] Bouchard, P.O., Bay, F., Chastel, Y. & Tovena, I. (2000). Crack propagation modelling using an advance remeshing technique . Comput. Methods. Appl. Mech. Engineering 189, 723-724.
[21] Gibson, L.J. & Ashby, M.F. (1998). Cellular solids: structure and properties. 2nd ed. (Cambridge University press, United Kingdom). 15
Journal of Mechanical Engineering
[22] Choi, S. & Sankar, B.V. (2003). Fracture toughness of carbon foam . Journal
of Composite Materials. 37(23), 2101-2116.
[23] Poquillon, D., Baco-Carles, V., Tailhades, P. & Andrieu, E. (2002). Cold
compaction of iron powders-Relations between powder morphology and
mechanical properties Part II. Bending tests: results and analysis . Powder
Technology 126, 75- 84.
[24] Jumahat, A. (2001). Analysis of thermo-mechanical behaviour of warm
compaction process (In Malay language), Master of Science Thesis.
Universiti Kebangsaan Malaysia, Malaysia.
