帯板のレーザ割断における温度上昇の抑制

A non-uniform temperature rise in the vicinity of crack tip often causes crack propagation. Taking advantage of this phenomenon, some brittle materials can be cleaved without any cutting tools but with an adequate controlling of a temperature distribution in the body.In the present paper, based on the linear fracture mechanics, a possibility of the thermal stress cleaving is discussed for a brittle rectangular plate which is heated along its symmetrical axis. A time dependent thermal stress intensity factor of an edge crack was analyzed systematically by changing the plate dimensions and crack length. Experimental findings were compared with the analytical results and good agreements were found.Especially, the crack extension characteristics in a cleaving test of a lime-soda glass can be well understood through the dependence of stress intensity factor on heating time and crack tip location.

A general solution to the thermoelastic problem of a circular inhomogeneity in an infinite matrix is provided. The thermal loadings considered in this note include a point heat source located either in the matrix or in the inclusion and a uniform heat flow applied at infinity. The proposed analysis is based upon the use of Laurent series expansion of the corresponding complex potentials and the method of analytical continuation. The general expressions of the temperature and stress functions are derived explicitly in both the inclusion and the surrounding matrix. Comparison is made with some special cases such as a circular hole under remote uniform heat flow and a circular disk under a point heat source, which shows that the results presented here are exact and general.

A boundary element procedure is formulated to treat frictional contact problems of thermally stressed structures. The aim is the computation of steady‐state and time‐dependent thermal stress intensity factors of interfacial cracks in two‐dimensional bimaterial structures when crack closure conditions are present. The effect of friction between the crack faces is taken into consideration. The problems considered are formulated in an incremental and iterative fashion because of their non‐linear nature. Near crack tip singularities of temperature and displacement fields are modelled through appropriate quarter‐point singular elements. Fracture parameters are evaluated from nodal displacements of singular elements utilizing proper formulas. Numerical results are compared with available solutions from the literature, where possible. Good agreement between them can be found. Copyright © 2005 John Wiley & Sons, Ltd.

In this paper, the sensitive mechanism of airflow level posture sensor is explained. By using the finite element method, the stream field by two point heat sources, when the two-dimensional enclosure is inclined, has been obtained by a series of procedure, such as model building, meshing, loads applying and equation solving. In the process ANSYS - FLOTRAN CFD program is applied .The numerical results are as follows: (1) In horizontal status, velocities of airflow at two point heat sources are equal, so currents of both hot wires are also equal. The output of the Bridge circuit is zero. (2)In tilting status, the velocity difference of airflow at two point heat sources changes with the tilt angle, which leads to changing of the current difference of both hot wires, the Bridge outputs a voltage signal of corresponding to the tilt angle. This calculated method provides a new road for optimization of airflow level posture sensor.

SUMMARY We derive closed analytical solutions for quasi-static thermoelastic deformation in response to instantaneous point and spherical heat sources in an elastic half-space. Since we can take advantage of the solutions for an infinite medium, the derivation of solutions for a semi-infinite medium is straightforward. We examine the spatial and temporal evolution of thermoelastic deformation for point and spherical heat sources. We applied the solution to a radar interferometric observation of post-eruptive deformation associated with the 1986 fissure eruption at Izu-Oshima volcano, Japan. Assuming a spherical heat source at a depth of 240 m with a volume of 1.15 × 10 7 m 3 and a temperature step 10 3 K, the predicted rate of post-eruptive ground movement agrees with the observed rate within observational errors. Also, the same parameter values allow us to compute the co-eruptive ground displacement by the effect of mass intrusion, whose amplitude is consistent with the observed height (45 m) of the newly formed cone. The derived solutions can be applied to transient ground displacements observed at active volcanoes, and allow us to evaluate the heat amount of magma intruded at very shallow depths.

Interfacial Stresses Induced by a Point Heat Source in an Isotropic Plate with a Reinforced Elliptical Hole

This work presents the closed-form solutions of the long-term thermal stresses, displacements and temperature increment of the cross-anisotropic strata subjected to a point heat source at great depth. The medium is initially modeled with cross-anisotropic mechanical and thermal properties. Under this assumption, the properties of the materials are different between the planes on and normal to the isotropic plane. Using Hankel and Fourier transforms, this paper presents the analytic solutions to soils or rocks affected by the point heat source, such as the repositories of nuclear wastes. The general solutions are further simplified to cases of materials with isotropic mechanical properties, and they are finally extended to fully isotropic in each property of the strata. Based on numerical results, the thermal stresses, displacements and temperature change of the thermoelastic half space are significantly affected by the anisotropy of mechanical and thermal properties of the strata.

The thermoelastic problem associated with a point heat source embedded in an anisotropic body containing an elliptic hole or a rigid inclusion is considered in this paper. By using the formalism of Stroh [1], the approach of analytic function continuation and the technique of conformal mapping, the expression for the temperature, displacements and stress functions is expressed in explicit matrix form. The present derived solutions are also valid for some special problems such as a crack or a rigid line inclusion if one lets the minor axis of the ellipse approach to zero. The stress intensity factors induced by a point heat source are also obtained.

Thermo-osmosis and mechano-caloric couplings on THM responses of porous medium under point heat source

Interface crack in bi-piezothermoelastic media and the interaction with a point heat source

Temperature compensation is a common treatment to eliminate the influence of temperature-dependent physical and mechanical properties of medium on measurement results. To investigate the effects of ambient temperature on seepage identification results using the point heat source (PHS) method, Considering the temperature nonlinearity of hydrothermal parameters, numerical simulation was conducted on the cooling pattern of a PHS in porous medium. Then, an experimental system for calibrating the relationship between seepage velocity and its discriminant index (ξ) was established. This system can create a uniform seepage field with controllable flow velocity in porous medium. The thermal response laws of the PHS in porous medium were investigated under different ambient temperatures and seepage velocities using the quasi-distributed seepage monitoring system with a mobile PHS. The results show that ambient temperature and seepage velocity have negligible effects on the heating phase of the PHS when heating voltage and duration remain constant, making temperature rise amplitude unsuitable as a discriminant index of seepage velocity. Both ambient temperature and seepage velocity influence the cooling phase of the PHS. The absolute value of ξ decreases with the increase of ambient temperature when the seepage velocity is constant. A multilayer neural network incorporating both ambient temperature and ξ as input parameters, with seepage velocity as output parameter, achieves satisfactory identification performance.

This paper discusses the predictive modeling of a scribing process. The diamond tool geometry is important for this process. As a prototype for the diamond tool, a four-sided pyramid is taken. Some minor changes are made in its geometry in purpose to make the modified tools. The tool geometry is a factor which affects greatly the quality of a final product, its forming, and overall efficiency of the scribing process. Scribing a brittle sheet with the modified tool is studied via parametric finite element modeling (FEM) with aid of the ANSYS software package for computer-aided engineering. The heterogeneous mesh is generated using solid finite elements with a quadratic form function. To obtain more precise simulation and decrease singular effect under force loading conditions, the contact elements and increased density of knots near the tooltip are added in this mesh. The modified variants of the tools are developed to provide a necessary groove quality on a brittle material surface regardless of movement direction. Finally, the algorithm and the corresponding program module for the parametric solution have been created using internal ANSYS APDL programming language. The computation results sufficiently agree with the experimental data obtained in this work and earlier. The calculated stress intensity in the sheet along the normal direction to the surface has large value up to 15 μm from cutting tool tip and decreases more sharply on the surface than in the cross section. So, the approach presented in this paper helps to understand the cutting process and improve machining technology of brittle materials.

The transient analysis of a subsurface inclined crack subjected to a buried dynamic dilatational source

A comparative study on FeAl and NiAl bonded diamond tools for dry grinding based on wear characteristics at elevated temperature

A rectangular surface crack perpendicular to the free surface of a three-dimensional solid is assumed and numerically analyzed when the solid surface is heated by an instantaneous point heat source. In particular, the effect of Poisson’s ratio on the distribution characteristics of the stress intensity factor along the crack front is clarified by the body force method. The present analysis is a numerical model for thermal stress laser cleaving of a brittle materials like Si wafer.