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1 Journal of Achievements in Materials and Manufacturing Engineering

1 2007

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Sensitivity analysis in life prediction of extrusion dies

Qamar S. Z., Pervez T., Siddiqui R. A., Sheikh A. K., Arif A. F. M.

Journal of Achievements in Materials and Manufacturing Engineering

2007

Vol. 25, nr 1

49-54

Purpose: Building up on the fracture mechanics (Paris law for crack propagation) based fatigue life prediction model developed earlier by the authors, Monte Carlo simulation has been performed to evaluate sensitivity of die life related to important geometrical and material parameters. Stochastic nature of various fatigue-related die parameters is used to reflect their variability. Design/methodology/approach: Life of the die is one of the most important factors affecting productivity and profitability in hot extrusion of metals. It has been reported in earlier works by the authors that extrusion dies most often fail by fatigue fracture. Experimental studies have shown that cracks preexist in dies due to various factors including heat treatment, machining, and surface hardening. High levels of repeated mechanical and thermal loads result in crack propagation leading to ultimate fracture failure. Findings: Findings of the sensitivity analysis are that fracture life of an extrusion die is very sensitive to initial crack size, section thickness, profile outer diameter and billet length; moderately sensitive to Paris constant and extrusion ratio; and only slightly sensitive to fracture toughness and ram speed. Practical implications: The study can be of direct utility in extrusion die design improvement, formulation of an optimum die replacement strategy, etc. Originality/value: The paper provides basis for a deeper understanding of the factors responsible for fracture failure of an extrusion die exposed to thermo-mechanical fatigue environment.