Multiaxial Notch Fatigue: From nominal to local stress/strain quantities

Here is a nice book written by a friend of mine. 

Multiaxial notch fatigue

Luca Susmel

 - summarises methods devised by the author to design real components against multiaxial fatigue
 - reviews definitions suitable for calculating the stress-strain quantities commonly used to perform fatigue assessment
 - includes an in-depth explanation of both the Modified Wöhler Curve and Modified Manson-Coffin Curve Method
 - contains 4500 experimental fatigue results generated by testing plain, notched and welded specimens under multiaxial fatigue loading

Metal and composite components used in structural engineering not only contain geometrical features resulting in stress concentration phenomena, but they are also subjected to in-service multiaxial fatigue loading. To address the problem, structural engineers need reliable methodologies which allow for an adequate margin of safety. The book summarises methods devised by the author to design real components against multiaxial fatigue by taking full advantage not only of nominal but also of local stress-strain quantities.

The book begins by reviewing definitions suitable for calculating the stress-strain quantities commonly used to perform fatigue assessment. The Modified Wöhler Curve Method is then explained in detail, by focusing attention on both the high- and the medium-cycle fatigue regime. The existing links between the multiaxial fatigue criterion and physical properties are also discussed. A procedure suitable for employing the method developed by the author to estimate fatigue damage both in notched and in welded components is explained. The Modified Manson-Coffin Curve method is investigated in depth, by reviewing those concepts playing a fundamental role in the so-called strain based approach. Lastly, the problem of performing the fatigue assessment of composite materials is addressed by considering design parameters influencing composite behaviour under complex cyclic loading paths and those criteria suitable for designing real components against multiaxial fatigue. The book also contains two appendices summarising experimental data from the technical literature. These appendices provide a unique and highly valuable resource for engineers. The appendices summarise around 100 values of the material characteristic length L, experimentally determined by testing specimens made of different engineering materials and about 4500 experimental fatigue results generated by testing plain, notched and welded specimens under constant-amplitude proportional and non-proportional multiaxial fatigue loading are listed.

About the author

Luca Susmel is an Associate Professor in Structural Integrity at the University of Ferrara, Italy.

Contents

Useful stress quantities used in fatigue problems
 - Introduction
 - Stress state
 - Mohr’s circles under plane stress
 - Amplitude, mean value, range and load ratio, R, under uniaxial cyclic loading
 - Stress components relative to a generic material plane: the tridimensional problem
 - Amplitude, mean and maximum value of the stress normal to a given material plane
 - Amplitude and mean value of the shear stress relative to a given material plane
 - Stress concentration factor, Kt
 - Singular stress fields
 - References

Fundamentals of fatigue assessment
 - Introduction
 - Fatigue strength and Wöhler curves
 - The mean stress effect under uniaxial fatigue loading
 - The notch effect in fatigue
 - Linear Elastic Fracture Mechanics to predict fatigue damage in cracked bodies
 - Different links between linear elastic fracture mechanics and continuum mechanics
 - The theory of critical distances (TCD)
 - Fatigue assessment under torsional loading
 - Fatigue damage under multiaxial fatigue loading
 - References

The Modified Wöhler Curve Method in fatigue assessment
 - Introduction
 - Fatigue damage model
 - Degree of multiaxiality of the stress field damaging the fatigue process zone according to the MWCM
 - The modified Wöhler curve method
 - Use of the MWCM to estimate high-cycle multiaxial fatigue strength
 - Use of the MWCM to estimate finite life under multiaxial fatigue loading
 - References

Fatigue assessment of notched components according to the modified Wöhler curve method
 - Introduction
 - Inherent and external multiaxiality
 - The MWCM applied in terms of nominal stresses
 - The MWCM applied along with the Theory of Critical Distances TCD to estimate notch fatigue strength
 - References

Multiaxial fatigue assessment of welded structures
 - Introduction
 - Stress quantities used to assess welded structures
 - Preliminary assumptions
 - MWCM and nominal stresses
 - MWCM and hot-spot stresses
 - The MWCM applied in terms of the Point Method PM to perform the fatigue assessment of weldments
 - References

The modified Wöhler curve method and metallic materials cracking behaviour under fatigue loading
 - Introduction
 - Crack initiation in single crystals
 - Stage I and Stage II in polycrystals subjected to uniaxial fatigue loading
 - Mesoscopic cracking behaviour of metallic materials under multiaxial fatigue loading
 - The MWCM and structural volume
 - The problem of estimating fatigue limits
 - Concluding remarks
 - References

The modified Manson-Coffin curve method in fatigue assessment
 - Introduction
 - Strain quantities used in low-cycle fatigue problems
 - Stress-strain behaviour of metallic materials
 - Uniaxial and torsional fatigue assessment according to Manson and Coffin’s idea
 - The modified Manson-Coffin curve method
 - Low-cycle fatigue assessment of notched components
 - References

Multiaxial fatigue of composite materials
 - Introduction
 - Stress quantities used to assess composite materials subjected to cyclic loading
 - Design parameters affecting multiaxial fatigue strength of composites
 - Multiaxial fatigue assessment of composite materials
 - Concluding remarks
 - References

Appendix A Experimental values of the material characteristic length, L
 - Introduction
 - Steel
 - Cast iron
 - Aluminium alloy
 - Other materials
 - References

Appendix B Experimental results generated under multiaxial fatigue loading
 - Introduction
 - Adopted symbolism and nomenclature
 - High-cycle fatigue strength of plain specimens
 - High-cycle fatigue strength of notched specimens
 - Fatigue results generated by testing plain and notched specimens under strain control
 - Low/medium-cycle fatigue results under stress control
 - Fatigue results generated by testing steel and aluminium welded specimens under multiaxial fatigue loading
 - Multiaxial fatigue strength of composite materials
 - Geometries of the notched/welded samples
 - References