Lifetime Estimation of Welded Joints





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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