A survivability model for ejection of green compacts in powder metallurgy technology

Abstract: Reliability and quality assurance have become major considerations in the design and manufacture of today’s parts and products. Survivability of green compact using powder metallurgy technology is considered as one of the major quality attributes in manufacturing systems today. During powder metallurgy (PM) production, the compaction conditions and behavior of the metal powder dictate the stress and density distribution in the green compact prior to sintering. These parameters greatly influence the mechanical properties and overall strength of the final component. In order to improve these properties, higher compaction pressures are usually employed, which make unloading and ejection of green compacts more challenging, especially for the powder-compacted parts with relatively complicated shapes. This study looked at a mathematical survivability model concerning green compact characteristics in PM technology and the stress-strength failure model in reliability engineering. This model depicts the relationship between mechanical loads (stress) during ejection, experimentally determined green strength and survivability of green compact. The resulting survivability is the probability that a green compact survives during and after ejection. This survivability model can be used as an efficient tool for selecting the appropriate parameters for the process planning stage in PM technology. A case study is presented here in order to demonstrate the application of the proposed survivability model.

How to cite this paper

 Ahi, P., Jenab, K., Ghasempoor, A & Rajabi, M. (2012). A survivability model for ejection of green compacts in powder metallurgy technology.International Journal of Industrial Engineering Computations , 3(1), 15-24.

Refrences

Briscoe, B.J. and Rough, S.L. (1998). The effects of wall friction in powder compaction. Colloids and Surfaces, A: Physicochemical and Engineering Aspects, 137(1-3), 103-116.

Dasgupta, A. and Pecht, M. (1991). Materials Failure Mechanisms and Damage Models. IEEE Transactions on Reliability, 40 (5), 531-536.

DeWolf, I. (2003). MEMS reliability. Microelectronics Reliability, 43 (7), 1047-1048.

ISO7438. (1985). Metallic Materials – Bend Test.

Korachkin, D., Gethin, D.T., Lewis, R.W., Tweed, J.H., & Guyoncourt, D. M.M. (2008). Measurement of Young’s modulus and tensile failure properties of green powder compacts. Powder Metallurgy, 51 (2), 150-159.

Lefebvre, L.P. and Mongeon, P.E. (2003). Effect of tool coatings on ejection characteristics of iron powder compacts. Powder Metallurgy, 46 (1), 43-48.

Lewis, E.E. and Chen, H.C. (1994). Load-Capacity Interference and the Bathtub Curve. IEEE Transactions on Reliability, 43 (3), 470-475.

Poquillon, D., Baco-Carles, V., Tailhades, Ph., & 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 (1), 75-84.

Redanz, P. (1998). Numerical modeling of cold compaction of metal powder. International Journal of Mechanical Science, 40 (11), 1175-1189.

Redanz, P. (2001). A study of stresses in powder compacted components during and after ejection. International Journal of Solids and Structures, 38 (5), 759-775.

Senthilvelan, T., Raghukandan, K., & Venkatraman, A. (2003a). Testing and Quality Standards for Powder Metallurgy Products. Materials and Manufacturing Processes, 18 (1), 105-112.

Senthilvelan, T., Raghukandan, K., & Venkatraman, A. (2003b). Tooling Design and Compaction Analysis on P/M Copper Bushes. Materials and Manufacturing Processes, 18 (1), 113-122.

Smith, L.N., Midha, R.P., & Graham, A.D. (1998). Simulation of metal powder compaction, for the development of a knowledge based powder metallurgy process advisor. Journal of Materials Processing Technology, 79 (1-3), 94-100.

Sopchak, N. D. and Misiolek , W. Z. (2000). Density Gradients in Multilayer Compacted Iron Powder Parts. Materials and Manufacturing Processes, 15 (1), 65-79.

Straffelini, G. and Molinari, A. (1996). Microstructure and mechanical reliability of powder metallurgy (P/M) Ferrous Alloys. Journal of Materials Engineering and Performance, 5 (1), 27-33.