Solutions Of Some Elastodynamic Problems With Application To Crack Propagation

The purpose of this study is to develop a range of elastodynamic solutions that will be applicable to the investigation of crack growth and to non-destructive evaluation. A number of problems of dynamic crack propagation in brittle solids are solved by applying the Smirnov and Sobolev method of self-similar potentials and extending the method in several ways. The method of self-similar potentials in conjunction with function-theoretic approach leads to a direct approach to the solutions of two-dimensional problems of mode-I, mode-II, and mode-III cracks in homogeneous solids as well as to the solution of problem of the mode-III interface crack. The technique of self-similar with a new application of rotational superposition was used to solve dynamic problems of an expanding penny-shaped crack under torsional loading. The problem of sudden arrest of a crack is treated by the method of self-similar potentials with the aid of appropriate time delays and origin shifts and by using a scheme of weighted superposition of fundamental problems. The solutions of fundamental problems require a full of the function-theoretic approach. In all the problems considered, it is assumed that the crack-tip speed is less than that of the Rayleigh-wave speed for inplane problems and less than that of the shear-wave speed for antiplane problems. For the sub-Rayleigh cases, the singularities of velocities and stresses occurring at crack tips are always of inverse square root type. The dynamic stress intensity factor is used to describe the square root singularities at the crack tips. The asymptotic solutions at wave fronts are also obtained for some problems.

"Methods of the Classical Theory of Elastodynamics" deals not only with classical methods as developed in the past decades, but presents also very recent approaches. Applications and solutions to specific problems serve to illustrate the theoretical presentation. Keywords: Smirnov-Sobolev method with further developments; integral transforms; Wiener-Hopf technique; mixed boundary-value problems; time-dependent boundaries; solutions for unisotropic media (Willis method); 3-d dynamical problems for mixed boundary conditions.

This volume focuses on the development and analysis of mathematical models of fracture phenomena.

Numerical Solution of Partial Differential Equations—III: Synspade 1975 provides information pertinent to those difficult problems in partial differential equations exhibiting some type of singular behavior. This book covers a variety of topics, including the mathematical models and their relation to experiment as well as the behavior of solutions of the partial differential equations involved. Organized into 16 chapters, this book begins with an overview of elastodynamic results for stress intensity factors of a bifurcating crack. This text then discusses the effects of nonlinearities, such as bifurcation, which occur in problems of nonlinear mechanics. Other chapters consider the equations of changing type and those with rapidly oscillating coefficients. This book discusses as well the effective computational methods for numerical solutions. The final chapter deals with the principal results on G-convergence, such as the convergence of the Green's operators for Dirichlet's and other boundary problems. This book is a valuable resource for engineers and mathematicians.

A dynamic propagation of a finite crack of opening mode in a micropolar elastic solid was investigated. By using an integral transform method, a pair of twodimensional singular integral equations governing stress and couple stress was formulated in terms of the displacement transverse to the crack, macro- and microrotations, and microinertia. These integral equations are solved numerically. Solutions for dynamic stress intensity and couple stress intensity factors are obtained by utilizing the values of the strengths of the square root singularities in the macro-rotation and the gradient of the micro-rotation at the crack tips. The motion of the crack tips and the load on the crack surface are not prescribed in the formulation of the problem. Therefore, the method of solution is applicable to nonuniform rates of propagation of a crack under an arbitrary time-dependent load on the crack surface. The behavior of the micro-rotation field, and the dynamic couple stress intensity factor, which are influenced by microinertia, in addition to the dynamic stress intensity factor, are examined. The classical elasticity solution for the corresponding problem follows as a special case of our solution when the micropolar moduli are dropped.

Inverse and crack identification problems are of paramount importance for health monitoring and quality control purposes arising in critical applications in civil, aeronautical, nuclear, and general mechanical engineering. Mathematical modeling and the numerical study of these problems require high competence in computational mechanics and applied optimization. This is the first monograph which provides the reader with all the necessary information. Delicate computational mechanics modeling, including nonsmooth unilateral contact effects, is done using boundary element techniques, which have a certain advantage for the construction of parametrized mechanical models. Both elastostatic and harmonic or transient dynamic problems are considered. The inverse problems are formulated as output error minimization problems and they are theoretically studied as a bilevel optimization problem, also known as a mathematical problem with equilibrium constraints. Beyond classical numerical optimization, soft computing tools (neural networks and genetic algorithms) and filter algorithms are used for the numerical solution. The book provides all the required material for the mathematical and numerical modeling of crack identification testing procedures in statics and dynamics and includes several thoroughly discussed applications, for example, the impact-echo nondestructive evaluation technique. Audience: The book will be of interest to structural and mechanical engineers involved in nondestructive testing and quality control projects as well as to research engineers and applied mathematicians who study and solve related inverse problems. People working on applied optimization and soft computing will find interesting problems to apply to their methods and all necessary material to continue research in this field.

Dynamic fracture in solids has attracted much attention for over a century from engineers as well as physicists due both to its technological interest and to inherent scientific curiosity. Rapidly applied loads are encountered in a number of technical applications. In some cases such loads might be applied deliberately, as for example in problems of blasting, mining, and comminution or fragmentation; in other cases, such dynamic loads might arise from accidental conditions. Regardless of the origin of the rapid loading, it is necessary to understand the mechanisms and mechanics of fracture under dynamic loading conditions in order to design suitable procedures for assessing the susceptibility to fracture. Quite apart from its repercussions in the area of structural integrity, fundamental scientific curiosity has continued to play a large role in engendering interest in dynamic fracture problems In-depth coverage of the mechanics, experimental methods, practical applications Summary of material response of different materials Discussion of unresolved issues in dynamic fracture