Yohei Sonobe

Accurate SIF Analysis of a Partially Cylindrical Side Crack Opened by Far-Field Tension

In recent years, due to a remarkable progress of qualified mesh generation algorithms combinedwith computational image processing technologies, a complex shaped 3D crack analysis has been carried out more and more easily by finite element method. Generally speaking, in order to assess thereliability of numerical solution, existence of a closed-form solution or a practically exact numericalsolution is important and thank-worthy. In contrast with 2D problems, however, there are very fewnumber of closed form solutions regarding to 3D crack problems. In the present analysis, we examineda highly accurate body force method (BFM) analysis for a partially cylindrical 3D surface crackin which a suitable basic density function can be supposed reasonably by taking account the crackgeometry. The present SIF solution could be used effectively for the purpose of benchmark the finiteelement solution for general non-planar crack problems.

Analysis of Planar Crack Coalescence by Mesh-Free Body Force Method

In a standard body force method analysis, a mesh division is required to define the boundary of a problem and to solve a governing equation using discretization procedure. However, in the present study, a moving least square strategy is introduced to define a weight function for the density of body force doublet and therefore a crack analysis is carried out without providing a standard mesh-division. Hence, the standard crack face elements are not required at all. A variety of 3D crack problems can be analyzed simply by providing a data that only de nes a crack front. Besides the nodal points for crack front, several internal nodes are generated on the crack face to represent a distribution of unknown function. At the internal nodes, an unknown variable is assigned which uniquely de ne a distribution of the relative crack face displacement. In the present approach, a crack problem is formulated as a singular integral equation whose unknown is a value of the weight function at the internal nodal points. A crack growth can be simulated directly by changing the shape of crack front, by means of adding a new nodal point in the vicinity of the current crack front. In the present paper, the proposed method is used to simulate a coalescence of interacting planar cracks.

Improvement of Stress Intensity Factor Analysis Using Overall Defined Basic Density Function on Crack Face

In this study, an improved technique for the evaluation of stress intensity factor (SIF) along the 3D planar crack front is proposed. In the present analysis, a planar triangular element is used to cover the total crack face. The stress field induced by a body force doublet in an infinite body is used for a fundamental solution. In the present analysis, overall defined basic density function of body force doublet is introduced. The crack problem is formulated as hypersingular boundary integral equations and the magnitudes of distributed point force doublets are determined through boundary conditions. The numerical SIF solution obtained using the present approach was compared with the solution obtained using the conventional basic density function. The results indicate that the proposed technique improves the accuracy of SIF. In addition, some numerical examples were examined to verify the effectiveness and the robustness of the proposed technique.

Basic Research on Simulation for 3D Crack Growth by Mesh Free BFM

A new methodology that enables us to compute the arbitrary shaped 3D crack problems is studied. In the present method, it is possible to analyze the 3D crack problems without preparing mesh data as in ordinary boundary elements but with defining a sequence of nodal points representing the crack front and the internal nodal points that define a crack surface as well as a shape function used for determining unknown variables. The present method has special potential for analyzing a complicated 3D crack geometry which is generally difficult to treat in usual element based methods. In the present research, we apply mesh-free body force method to analyze the growth of 3D planar cracks. In concrete, a crack growth analysis for initially rectangular or elliptical crack existing in an infinite solid under uniform tensile stress perpendicular to the crack surface at infinity is demonstrated