Multiaxial Notch Fracture and Fatigue


Book Description

This book presents the unified fatigue life prediction equation for low/medium/high cycle fatigue of metallic materials relevant to plain materials and notched components. The unified fatigue life prediction equation is the Wöhler equation, in which the "stress-based intensity parameter" is calculated based on the linear-elastic analysis. A local approach for the static fracture analysis for notched components is presented based on the notch linear-elastic stress field. In the local approach, a stress intensity parameter is taken as a stress-based intensity parameter. Experimental verifications show that the local approach is also suited for the static fracture analysis for notched components made of ductile materials. The book is also concerned with a material failure problem under the multiaxial stress states. A concept of the material intensity parameter is introduced in this book. It is a material property parameter that depends on both Mode-I fracture toughness and Mode-II (or Mode-III) fracture toughness and the multiaxial parameter to characterize the variation of the material failure resistance (notch fracture toughness) with the multiaxial stresses states. The failure condition to assess mixed-mode fracture of notched (or cracked) components is stated as the stress-based intensity parameter being equal to the material intensity parameter. With respect to the traditional S-N equation, a similar S-N equation is presented and verified to have high accuracy. This book will be of interest to professionals in the field of fatigue and fracture for both brittle and ductile materials.




Multiaxial Fatigue


Book Description

This book provides practicing engineers, researchers, and students with a working knowledge of the fatigue design process and models under multiaxial states of stress and strain. Readers are introduced to the important considerations of multiaxial fatigue that differentiate it from uniaxial fatigue.




Multiaxial Notch Fatigue


Book Description

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. - 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







The Theory of Critical Distances


Book Description

Critical distance methods are extremely useful for predicting fracture and fatigue in engineering components. They also represent an important development in the theory of fracture mechanics. Despite being in use for over fifty years in some fields, there has never been a book about these methods – until now. So why now? Because the increasing use of computer-aided stress analysis (by FEA and other techniques) has made these methods extremely easy to use in practical situations. This is turn has prompted researchers to re-examine the underlying theory with renewed interest. The Theory of Critical Distances begins with a general introduction to the phenomena of mechanical failure in materials: a basic understanding of solid mechanics and materials engineering is assumed, though appropriate introductory references are provided where necessary. After a simple explanation of how to use critical distance methods, and a more detailed exposition of the methods including their history and classification, the book continues by showing examples of how critical distance approaches can be applied to predict fracture and fatigue in different classes of materials. Subsequent chapters include some more complex theoretical areas, such as multiaxial loading and contact problems, and a range of practical examples using case studies of real engineering components taken from the author's own consultancy work. The Theory of Critical Distances will be of interest to a range of readers, from academic researchers concerned with the theoretical basis of the subject, to industrial engineers who wish to incorporate the method into modern computer-aided design and analysis. - Comprehensive collection of published data, plus new data from the author's own laboratories - A simple 'how-to-do-it' exposition of the method, plus examples and case studies - Detailed theoretical treatment - Covers all classes of materials: metals, polymers, ceramics and composites - Includes fracture, fatigue, fretting, size effects and multiaxial loading




Notch Effects in Fatigue and Fracture


Book Description

As Directors of this NATO Workshop, we welcome this opportunity to record formally our thanks to the NATO Scientific Affairs Division for making our meeting possible through generous financial support and encouragement. This meeting has two purposes: the first obvious one because we have collected scientists from East, far East and west to discuss new development in the field of fracture mechanics: the notch fracture mechanics. The second is less obvious but perhaps in longer term more important that is the building of bridges between scientists in the frame of a network called Without Walls Institute on Notch Effects in Fatigue and Fracture". Physical perception of notch effects is not so easy to understand as the presence of a geometrical discontinuity as a worst effect than the simple reduction of cross section. Notch effects in fatigue and fracture is characterised by the following fundamental fact: it is not the maximum local stress or stress which governs the phenomena of fatigue and fracture. The physic shows that a process volume is needed probably to store the necessary energy for starting and propagating the phenomenon. This is a rupture of the traditional "strength of material" school which always give the prior importance of the local maximum stress. This concept of process volume was strongly affirmed during this workshop.




Applications of Automation Technology to Fatigue and Fracture Testing and Analysis


Book Description

From a November 1995 symposium in Norfolk, Virginia 11 papers report on how computers are playing an ever greater role in testing for fatigue and fracture as applications have become more sophisticated and hardware smaller and more powerful over the past few years. Covering data acquisition, simulat










Theory of Notch Stresses


Book Description