Micromechanism Of Cleavage Fracture Of Metals

In this book the authors focus on the description of the physical nature of cleavage fracture to offer scientists, engineers and students a comprehensive physical model which vividly describes the cleavage microcracking processes operating on the local (microscopic) scale ahead of a defect. The descriptions of the critical event and the criteria for cleavage fracture will instruct readers in how to control the cleavage processes and optimize microstructure to improve fracture toughness of metallic materials. Physical (mechanical) processes of cleavage fracture operating on the local (microscopic) scale, with the focus on the crack nucleation and crack propagation across the particle/grain and grain/grain boundaries Critical event, i.e., the stage of greatest difficulty in forming the microcrack, which controls the cleavage fracture Criteria triggering the cleavage microcracking with incorporation of the actions of macroscopic loading environment into the physical model Effects of microstructure on the cleavage fracture, including the effects of grain size, second phase particles and boundary Comprehensive description of the brittle fracture emerging in TiAl alloys and TiNi memory alloys

Micromechanisms of Fracture and Fatigue forms the culmination of 20 years of research in the field of fatigue and fracture. It discusses a range of topics and comments on the state of the art for each. The first part is devoted to models of deformation and fracture of perfect crystals. Using various atomistic methods, the theoretical strength of solids under simple and complex loading is calculated for a wide range of elements and compounds, and compared with experimental data. The connection between the onset of local plasticity in nanoindentation tests and the ideal shear strength is analysed using a multi-scale approach. Moreover, the nature of intrinsic brittleness or ductility of perfect crystal lattices is demonstrated by the coupling of atomistic and mesoscopic approaches, and compared with brittle/ductile behaviour of engineering materials. The second part addresses extrinsic sources of fracture toughness of engineering materials, related to their microstructure and microstructurally-induced crack tortuosity. Micromechanisms of ductile fracture are also described, in relation to the fracture strain of materials. Results of multilevel modelling, including statistical aspects of microstructure, are used to explain remarkable phenomena discovered in experiments. In the third part of the book, basic micromechanisms of fatigue cracks propagation under uniaxial and multiaxial loading are discussed on the basis of the unified mesoscopic model of crack tip shielding and closure, taking both microstructure and statistical effects into account. Applications to failure analysis are also outlined, and an attempt is made to distinguish intrinsic and extrinsic sources of materials resistance to fracture. Micromechanisms of Fracture and Fatigue provides scientists, researchers and postgraduate students with not only a deep insight into basic micromechanisms of fracture behaviour of materials, but also a number of engineering applications.

Advances in Research on the Strength and Fracture of Materials: Volume 2As—The Physical Metallurgy of Fracture contains the proceedings of the Fourth International Conference on Fracture, held at the University of Waterloo, Canada, in June 1977. The papers review the state of the art with respect to the physical metallurgy of fracture in a wide range of materials such as metals, alloys, and structural steels. This volume is comprised of 85 chapters and opens by discussing the effect of grain size on the fracture of steel, aluminum alloys, and other materials. The influence of Mn additions on the fracture behavior of an Al-Mg-Si alloy is also considered, along with crack propagation in austenitic sheets. The next sections focus on the effect of phase transformation on the tensile fracture of austenitic stainless steel; atomistic simulation of the ductile/brittle transition; the effect of microstructure on fracture of a high toughness titanium alloy; and the effect of metallurgy on stress corrosion cracking and hydrogen embrittlement of ultra high strength steels. The remaining chapters are devoted to creep in materials such as Cr-Mo-V steels and titanium alloys. This monograph will be a useful resource for metallurgists, materials scientists, and structural and mechanical engineers.

This book is based on 40 years of research and teaching in the fields of fracture mechanics and plasticity. It will bring students and engineers from various disciplines up to date on key concepts that have become increasingly important in the design of safety-relevant engineering structures in general and in modern lightweight structures in the transportation industry in particular. Primarily intended for graduate students in the engineering sciences and practicing structural engineers, it employs a multidisciplinary approach that comprises theoretical concepts, numerical methods, and experimental techniques. In addition, it includes a wealth of analytical and numerical examples, used to illustrate the applications of the concepts discussed.

This report assesses the current state of knowledge of the 'local approach' to cleavage fracture, reviews application to ferritic steels and their weldments and addresses limitations and disadvantages of the methodology.