Date of Award

Fall 1994

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Mechanical Engineering - (Ph.D.)

Department

Mechanical and Industrial Engineering

First Advisor

Benedict C. Sun

Second Advisor

Rong-Yaw Chen

Third Advisor

Bernard Koplik

Fourth Advisor

Nouri Levy

Fifth Advisor

C.T. Thomas Hsu

Abstract

A comprehensive study of local thermal stresses at the juncture of pipe-nozzle is presented in this thesis. The thermal loading is assumed to be a linear thermal gradient across the thickness of the pipe and nozzle. Currently, there exists neither experimental nor analytical data that is sufficient for pressure vessel designers to analyze the local thermal stresses at the juncture of pipe-nozzle. In order to provide a comprehensive database to calculate these thermal stresses, the finite element technique is used to provide a series of local thermal stress factor plots as a function of pipe-nozzle geometrical parameters.

For the local thermal stresses on the juncture of pipe-nozzle, the longitudinal and circumferential thermal stress factors due to the thermal loading are presented in a series of plots as functions of gamma, γ (pipe mean radis/pipe thickness) and beta, f3 (nozzle mean radius/pipe radius). The gamma values vary from 10 to 300 and beta values vary from 0.1 to 1.0. These stress factors would complement the welding Research Council Bulletin 107 method in pipe-nozzle stress analysis which did not include the effect of local thermal stresses.

To ensure the convergence of the finite element results, two major parameters were thoroughly studied. First, to minimize the influence of boundary conditions on the thermal stresses around the juncture of the pipe-nozzle, the geometrical parameter alphap, αp , (pipe length/pipe mean radius) is found to be at least equal to 8.0 as well as alphan , αn, (nozzle length/nozzle mean radius) at least to be 4.0. Next, 96 node points must be assigned at the juncture of pipe-nozzle. As a result, approximately 5000 node points and 3000 plus elements were needed for the computation. Numerical examples are also presented in this thesis to demonstrate how the thermal stress components complement the WRC 107 local stress computation due to external loadings.

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