The Stress Model for the Assessment of Fatigue Life Under Uniaxial Loading
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Tadeusz Łagoda
Lifetime Estimation of Welded Joints
Tadeusz Łagoda Politechnika Opolska Katedra Mechaniki I Podstaw Konstrukcji Maszyn 45-271 OPOLE, ul. St. Mikolajszyka 5 Poland [email protected]
ISBN: 978-3-540-77061-9
e-ISBN: 978-3-540-77062-6
Library of Congress Control Number: 2007940901 c 2008 Springer-Verlag Berlin Heidelberg This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer. Violations are liable to prosecution under the German Copyright Law. The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Cover design: WMXDesign GmbH Printed on acid-free paper 9 8 7 6 5 4 3 2 1 springer.com
Preface
In the paper the author attempts to assess the fatigue life of chosen welded joints. It focuses especially on chosen problems that accompany determination of the fatigue life of welded joints, taking into consideration the strain energy density parameter. Chapter 2 describes the welded joint as a stress concentrator. The state of stress and strain in the notch are described and theoretical and fatigue coefficients are indicated. The fatigue coefficient of the notch effect is estimated on the basis of fictitious radius in the notch root. Chapter 3 presents a model of fatigue life assessment under uniaxial stress state with statistical handling of data presented. The new energy model of fatigue life assessment, which rests upon the analysis of stress and strain in the critical plane, is described in detail in chapter 4. The principle of such a description is presented in the uniaxial as well as in biaxial state of loading. Chapter 5 contains the analysis of tests of four materials subjected to different loadings: cyclic, variable-amplitude with Gaussian distribution, and variable amplitude with Gaussian distribution and overloading for symmetric and pulsating loading. The analysis is based on the determined fatigue characteristics for all the considered materials. Chapter 6 shows the application of the model in the fatigue life assessment in the complex state of loading (bending with torsion of flange-tube and tube-tube joints) based on fatigue research of steel and aluminum welded joints carried out in well-known German centres. Proportional and out-ofproportional cyclic research are carried out. Additionally, the influence of various bending and torsion frequencies and proportional and out-ofproportional variable amplitude loadings are analysed.
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