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Material Selection for a Pressure Vessel ABSTRACT

Pressure vessels are designed to contain pressure and withstand the operating mechanical and thermal transients for a specified design life. In addition they are designed to safety to leak before break (LBB). LBB describes the situation in which a leak occurs before a complete double-ended break of a component. Ductile and tough materials are widely used in nuclear pressure vessels, because of their high resistance to catastrophic rupture. The design process involves fatigue analysis to demonstrate that there is insignificant crack growth a postulated surface crack during the entire design life. However in terms of LBB the significant parameter is the elastic-plastic fracture toughness, and the material strength. However based on assessment based on linear elastic fracture mechanics, the candidate materials are carbon steels, low alloy steels and stainless steels, which interestingly are the materials that are used for pressure vessels. In terms of the fatigue crack initiation, the appropriate parameters are the threshold stress intensity factor range and the endurance limit and the material selection is based on these parameters.

INTRODUCTION

Selection of materials and manufacturing processes are important activities that are essential for structural design. Ashby (2005) was the first to demonstrate that a wide range of material properties could be collected and plotted on the same curve, where two individual material variables appear on the abscissa and the ordinate. Using this concept Granta Design (2007) has developed a software package CES EduPack which includes a wide range of data on materials, manufacturing processes and shapes for over 3000 engineering materials. The objective of the present study is explore the use of the software CES EduPack in the selection of material for a pressure vessel where competing requirements of strength and resistance to crack extension have to be met.

Traditional treatment of pressure vessels in undergraduate engineering and engineering technology curricula appears typically in the course on strength of materials where only the strength design is emphasized. The elastic analyses are invoked and deformations beyond the elastic limit are not considered. In addition there is very limited reference to fracture mechanics. There have been incidences of failure of pressure vessels that could not be attributed to strength but to brittle and ductile fracture. In addition a large number of vessels fail in fatigue for which design codes exist.

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Chattopadhyay, S. (2008, June), Material Selection For A Pressure Vessel Paper presented at 2008 Annual Conference & Exposition, Pittsburgh, Pennsylvania. 10.18260/1-2--4471