The life of an engineering component is limited. Its failure may sometimes occur due to faulty design, higher level of operating and residual stresses and corrosive environment. However, in majority of cases, the failure is associated with some manufacturing defect such as higher inclusion rating, discontinuities or undesirable microstructure. It is found that almost every component contains small flaws whose size and morphology are dependent upon the material and its processing. These may range from non-metallic inclusions and microvoids to casting and forging defects, grinding cracks, quench crack, etc. Furthermore, the matrix structure may be also brittle on account of defective heat treatment, subjecting the component to plain strain condition failure leading to severe losses both in terms of money and human life. Evaluation of structural integrity and noncomitant service life of engineering components, which are primarily castings and forgings, is thus exceedingly important. The present paper discusses typical casting and forging defects and their effects on the mode of failure. The effect of inclusions and matrix structure on the plain strain fracture toughness and crack propagation rate are also discussed. The paper includes some case studies of the failure of castings and forgings.
Publication Source: Trends in NDE Science & Technology; Proceedings of the 14th World Conference on Non-Destructive Testing, New Delhi, 8-13 December 1996.Vol. 2, pages 993 - 996 Publisher:Ashgate Publishing Company
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