The past decade has shown that fatigue is still a great challenge facing the engineering community as one of major factors causing structural defects. The reasons of it may be, among others, the unavoidable uncertainty of physical data and shortcomings of some design approaches. Therefore in this publication, which comprises new results of the author's investigations on selected problems touched upon in his monograph entitled "Analytical Procedures of High-Cycle Fatigue Assessment of Structural Steel Elements" (1st Edition: Gdańsk University of Technology 1997, 2nd Edition revised and enlarged: Naval University of Gdynia 1999), special attention is concentrated on the design criteria. The publication title, "On Fatigue Safety of Metallic Elements...", implies that the fatigue safety is its sole subject, whereas the actual scope is wider and also includes stress modelling and fatigue lifetime predicting. In its preparation the author decided to strive for utilisation of those theories and hypotheses that are capable of dealing with complex stress patterns without too much computational effort and of those mathematical relationships that enable the comprehensive load description, stress analysis and fatigue assessment of metallic elements.
The main idea behind this work has been to formulate energy-based design criteria, with the effect of static loads as well as mean and residual stresses on fatigue performance under periodic and/or stationary random loads taken into account.
The volume consists of two Parts, each divided into two Chapters. Part I is devoted to those loading cases where the stress level lies below the fatigue "safe-life" limit. Part II is concerned with the high-cycle fatigue regime where a finite fatigue life is envisaged. Chapters 1 and 3 deal with design criteria in deterministic approach. In Chapters 2 and 4 probabilistic design criteria are developed. Satisfaction of the presented criteria should ensure that both the conditions of static strength are met and the combinations of constant and time-varying stress components will not lead to fatigue failure.
CONTENTS:
Nomenclature
Introduction
PART I. FATIGUE "SAFE-LIFE" DESIGN CRITERIA
1. PERIODIC STRESS
1.1. Uniaxial stress
1.1.1. Constant amplitude stress
1.1.2. Uniaxial periodic stress
1.2. Multiaxial stress
1.2.1. Average-distortion-energy strength hypothesis
1.2.2. In-phase stress
1.2.3. Data transformations
1.2.4. Out-of-phase stress
1.2.5. Three-dimensional periodic stress
1.2.6. Fatigue "safe-life" criterion for anisotropic metallic elements
2. STATIONARY RANDOM STRESS
2.1. Uniaxial stress
2.1.1. Random amplitude stress
2.1.2. Two-variable stress
2.1.3. Uniaxial random stress
2.2. Multiaxial stress
2.2.1. Stress in combined bending, torsion and tension-compression
2.2.2. Three-dimensional random stress
2.2.3. Fatigue "safe-life" criterion for anisotropic metallic elements Conclusions
PART II. DESIGN CRITERIA FOR HIGH-CYCLE FATIGUE
3. PERIODIC STRESS
3.1. Uniaxial stress
3.1.1. Constant amplitude stress
3.1.2. Application of Soderberg equation to biharmonic stress
3.1.3. Uniaxial periodic stress
3.1.4. Variable amplitude stress
3.2. Multiaxial stress
3.2.1. Multiaxial stress with synchronous components
3.2.2. Multiaxial stress with biharmonic components
3.2.3. Three-dimensional periodic stress
4. STATIONARY RANDOM STRESS
4.1. Uniaxial stress
4.1.1. Random amplitude stress
4.1.2. Uniaxial random stress
4.2. Multiaxial stress
4.2.1. Energy-based modelling of periodic and random stresses
4.2.2. Three-dimensional random stress
Conclusions
References
APPENDICES
A. Semiprincipal stress systems
B. On the relation between probability density functions of maximum values of original and equivalent stresses
C. Application of the theory of energy transformation systems to fatigue assessment of metallic elements under unsteady loading conditions
Summary
Streszczenie
