Finite Element Analysis for Optimal Heating Condition in Thermal Stress Cleaving of Brittle Materials Using Laser Irradiation

An optimal condition of thermal stress cleaving was investigated by assuming the element-by-element temperature rise situation using finite element method. The obtained thermal stress cleaving condition is found to be optimal for the symmetrical cleaving of a rectangular plate.9th International Conference on Fracture and Damage Mechanics, FDM 2010; Nagasaki; 20 September 2009 through 22 September 200

Versatile analysis of limited plasticity by body force method

A problem of thermally induced residual stress under plane strain constraint is considered based on a body force method (BFM). As a numerical example, a simple problem of limited plasticity due to a uniform strength of transient line heat source of finite width, which is applied to a surface of a semi-infinite solid for a short duration of time, was considered. Although the out-of-plane component of normal stress (σzz) can be simply estimated from the in-plane normal stress components σxx, σyy and the Poisson\u27s ratio ν as σzz = ν(σxx + σyy) for elastic plane strain problems, this relation is violated when plasticity is considered. As a result, the residual stress in the direction of out-of-plane found to be a major component in the present problem

Analysis of 3D Planar Crack Problems by Body Force Method

Derivation of the integral equation for general 3D crack problems was examined based on the theory of body force method. In the present analysis, stress intensity factors (SIFs) along a front of arbitrary shaped 3D planar crack are obtained directly only by solving simultaneous equations expressing a boundary condition. The crack surface is discretized using number of triangular elements and the variation of the force doublet embedded in each triangle is assumed at constant. The derived boundary integral equation was transformed into a set of simultaneous equations and was solved computationally. In order to improve the accuracy of the numerically examined boundary integral, a polar transformation scheme combined with Tayler expansion of the fundamental solutions is introduced. Not only a single crack problem but also an interference among coplanar cracks can be calculated using the unique program developed in this research. It was verified that as the number of triangular elements increases, the evaluated SIF converges to the reference solution.13th International Conference on Fracture and Damage Mechanics, FDM 2014; Hotel Marina AtlanticoRua Joao de Melo AbreuPonta Delgada, Azores; Portugal; 23 September 2014 through 25 September 201

Interference Analysis between Crack and General Inclusion in an Infinite Plate by Body Force Method

A continously embedded force doublet over the particular region can be regarded as the distributing eigen strain. This fact implies that many sorts of inelastic strain can be replaced by the force doublet. In the present paper, the force doublet is used to alter the local constitutive relationship. As a result, a method for analyzing the general inclusion problem in which the material properties of the inclusion are not only different from those of the matrix material but also can be even a function of spacial coordinate variables is proposed. The theoretical background of the present analysis is explained followed by some representative numerical results.12th International Conference on Fracture and Damage Mechanics, FDM 2013; Sardinia; Italy; 17 September 2013 through 19 September 201

Compression induced shear damage in brittle solids by scattered microcracking

Failure observation and numerical analysis were conducted to understand how shear damage develops in brittle solids under biaxial compression. A biaxial compression often induces shear damaged in brittle solids, which is preceded by a formation of huge number of array cracks. Cracks in the array appeared gradually as applied compression increased. They were almost similar in shape; gently curved but were possible to approximate a troop of straight cracks almost parallel to each other without loss of essential characteristics. Under a uniaxial compression, a brittle material tends to fail exhibiting a crack growth almost parallel to the loading axis. In this situation, the crack propagates rather in a stable fashion since the stress intensity factor at crack tip generally decreases with crack extension. Under a biaxial compression, however, such a stable crack growth is strongly inhibited. Consequently, an array of microcracks often appears as a presage of the macroscopic shear failure. A mechanism of the appearance of damaged zone with increase of applied compression was discussed using a scattered cracking model. It was found that each crack composing the damaged zone has a possibility to open due to crack-to-crack interaction and a localized tensile stress appeared both in the interior and in the exterior of the damaged zone. The localized tension appeared in the interior of the damaged zone may increase a crack density, while that appeared in the exterior of the damaged zone would bring an enlargement of the damaged zone

Simulation of Crack Growth in Thermal Stress Cleaving Using Line Heat Source

The crack growing behavior in a brittle rectangular plate under transient thermal stress is studied. The transient thermal stress imposed to the rectangle here is that of due to a line heater such as an electric resistance wire which supposed to be perfectly contact to the surface of material. When the heater is placed on the symmetrical axis of the rectangle, the crack propagates just along the heating line, therefore, this situation can be used for dividing a thin rectangular plate into equal two pieces. Contrast to the symmetrical case, on the other hand, the warping of crack propagation path is observed when the heater is placed other than the symmetrical position. The main objective of the present study is to clarify the mechanism of crack path warping in the case of unsymmetrical cleaving through the crack propagation simulation. The simulated and the observed crack path show good agreement with each other and factors which make the crack path warp are understood

Accurate Solutions of Stress Intensity Factors of Standard Fracture Test Specimens

Practically exact solutions of stress intensity factor for several two-dimensional standard specimens were calculated and shown in numeric tables. The solutions were confirmed to converge until 6 significant figures through a systematical computation of discretization analysis. The convergence analyses were carried out by using a general purpose program based on a body force method.9th International Conference on Fracture and Damage Mechanics, FDM 2010; Nagasaki; 20 September 2009 through 22 September 200