Abstract
The present work deals with the development of a finite element methodology for obtaining the stress distributions in thick cylindrical HK40 stainless steel pipe that carries high-temperature fluids. The material properties and loading were assumed to be random variables. Thermal stresses that are generated along radial, axial, and tangential directions are generally computed using very complex analytical expressions. To circumvent such an issue, probability theory and mathematical statistics have been applied to many engineering problems, which allows determination of the safety both quantitatively and objectively based on the concepts of reliability. Monte Carlo simulation methodology is used to study the probabilistic characteristics of thermal stresses, and was implemented to estimate the probabilistic distributions of stresses against the variations arising due to material properties and load. A 2-D probabilistic finite element code was developed in MATLAB, and the deterministic solution was compared with ABAQUS solutions. The values of stresses obtained from the variation of elastic modulus were found to be low compared to the case where the load alone was varying. The probability of failure of the pipe structure was predicted against the variations in internal pressure and thermal gradient. These finite element framework developments are useful for the life estimation of piping structures in high-temperature applications and for the subsequent quantification of the uncertainties in loading and material properties.
Highlights
Axisymmetric pressurized thick cylindrical pipes are widely used in chemical, petroleum, and military industries, in fluid transfer plants and power plants, as well as in nuclear power plants due to ever-increasing industrial demand
The finite element framework was enhanced to find the effects of uncertainties in pipe structure due to material properties and loading
Random variable models were used to model the variabilities in material properties and load by using Monte Carlo simulations
Summary
Axisymmetric pressurized thick cylindrical pipes are widely used in chemical, petroleum, and military industries, in fluid transfer plants and power plants, as well as in nuclear power plants due to ever-increasing industrial demand. The stress distribution in nuclear power plant piping systems remains a main concern, and deterministic structural integrity assessment needs to be combined with probabilistic approaches in order to consider uncertainties in material and load properties. The objective was to compile statistical information and data based on literature review regarding both strength and load random variables relevant to thick pipe structure for the quantification of the probabilistic characteristics of these variables. The quantification of random variables of loads and material properties in terms of their means, standard deviations, or coefficients of variation and probability distributions can be achieved by data collection and analysis. Zhou and Tu [1] carried out a work to estimate the service life of a high-temperature furnace, which is very difficult due to the variability of creep data. The stress induced by thermal gradient through the wall is given by [9]: σrT
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