Toshio Furukawa

Analysis of the stress-focusing effect in a solid cylinder subjected to instantaneous heating based on the generalized thermoelasticity

This article investigates the stress-focusing effect in an infinitely long cylinder on the basis of the Lord-Shulman (L-S) theory and the Green-Lindsay (G-L) theory, which are referred to as the generalized thermoelasticity theories. The combined forms of the governing equations of both theories are used. The solution for the symmetrical and instantaneous heating is derived in the Laplace transform domain. Then, using the numerical inversion of the Laplace transform, the temperature and the thermal stress fields in the cylinder and obtained. The numerical results of the thermal stress wave based on the L-S theory are discussed. It is shown that the stress-focusing effect occurs and the order of the stress singularity is 1/ρ 2 The effects of the thermomechanical coupling and the relaxation time on the stress-focusing phenomena are examined.This article investigates the stress-focusing effect in an in¢nitely long cylinder on the basis of the Lord^Shulman (L^S) theory and the Green^Lindsay (G^L) theory, which are referred to as the generalized thermoelasticity theories. The combined forms of the governing equations of both theories are used. The solution for the symmetrical and instantaneous heating is derived in the Laplace transform domain. Then, using the numerical inversion of the Laplace transform, the temperature and the thermal stress ¢elds in the cylinder and obtained. The numerical results of the thermal stress wave based on the L^S theory are discussed. It is shown that the stress-focusing effect occurs and the order of the stress singularity is 1/r2. The effects of the thermomechanical coupling and the relaxation time on the stress-focusing phenomena are examined.

Analysis of the Generalized Thermoelastic Problem in an Infinitely Long Cylinder Subjected to an Asymmetrically Instantaneous Heating.

This work considers the two-dimensional thermoelastic problem in an infinitely long cylinder with free surface subjected to an asymmetrically instantaneous heating on the basis of the generalized thermoelastic theories, i. e. the Lord-Shulman (L-S) and the Green-Lindsay (G-L) theories. The combined forms of the governing equations of both theories are used. The solution in the Laplace transform domain is derived analytically. Using the numerical inversion of Laplace transform has made it possible to obtain the two-dimensional thermal stress and temperature in physical domain for all time scales. Calculations have been performed on the basis of the L-S theory. The behavior of the thermal stress wave is exhibited. The effects of the relaxation time and the thermomechanical coupling on the thermal stress are discussed.

Transient thermoelastic analysis for two-dimensional dissimilar materials by the boundary element method

This article deals with the transient thermoelastic analysis for dissimilar materials under the plane strain condition. In the process of the boundary element formulation, the time-dependent fundamental solution for the transient heat conduction problem and the thermoelastic displacement potential for the transient thermal stress problem are introduced. Consequently, domain integrals are completely eliminated. The discretization based on the domain combination method for these boundary integral equations is implemented, and the transient temperature and stress fields are analyzed numerically. The transient temperature at the lateral surface and the transient thermal stress at the interface are investigated for the three categories that have been determined according to the characteristic equation expressed by Dundurs parameters.

Elastic Analysis of Modeled Fiber-Reinforced Composite Material by Finite Difference Method.

Stress intensity factors of modeled fiber-reinforced composite materials are calculated by the finite difference method based on the linear two-dimensional theory of elasticity. In order to bound the region to be analyzed, cracks and fibers are periodically arrayed in an infinite region. The bounded region is conceptually divided into two regions by a square boundary centered at the crack tip. The general solution about the crack tip is employed to describe the displacement on and within the square boundary. The region outside the square is devided into finite differences. The effects of several parameters such as fiber length and crack length on the stress intensity factors are examined for two kinds of configuration.

Minor Special Issue on Corrosion. Effect on Specimen Size on the Behavior of Fast Crack Propagation and Arrest.

The dynamic stress intensity factor of fast propagating cracks was calculated from the measured data of crack tip position versus time, through numerical simulation with an improved finite difference method. The data were obtained with a measuring system consisting of ladder gages and a digital wave memory unit. The cracks were propagated in the double-cantilever beam type specimens machined from the model material, polymethyl methacrylate(PMMA). The specimens were in various sizes where the ratio of initial crack length to specimen size was kept constant. The dynamic stress intensity factor decreased at the beginning of the crack propagation phase, remained almost unchanged in the next stage, and increased in the third stage. The above mentioned result appeared in all sizes of specimens, in common. But, after the third stage the behavior of the stress intensity factor varied with the specimen geometry. The characteristic values of the dynamic stress intensity factor in the process of the crack propagation and arrest were illustrated and investigated with respect to the following parameters: the specimen size, the initiation stress intensity factor, and the crack jump distance. The specimen size mainly affects the scatter of the results: the larger specimen gives the result with a smaller scatter.

Constitutive relations between stress, strain-rate and temperature of mild steel.

Strain-rate and temperature dependence on the flow stress of mild steel is discussed. To investigate the influence of grain size and carbon content, low carbon steel S 15 C and S 35 C annealed at different temperatures were prepared. Tensile tests were made ranging in strain-rate from 2.78 × 10Z s-1 to 1.39 × 10-1 s-1 and temperature from -33°C to 700°C with an Instron-type testing machine. Experimental results were compared with a theory proposed previously by the first author for constitutive relationship of elastic/viscoplastic materials. The proposed equation represented well experimental results of constitutive relations except the blue brittleness region. Elongation, reduction in area and superplasticity of materials were discussed in connection with deformation mechanism regions.

Coupled thermal stress in solid cylinder due to limited heating.

The present paper deals with temperature and stress in a solid cylinder due to limited heating. Thermomechanical coupling was taken into account in the analysis. Numerical calculations were performed for various heating time and thermomechanical coupling parameters.The results obtained are summarized as follows:(1) The coupled temperature at the surface after a limited heating time becomes higher than the uncoupled one.(2) A long heating time causes large axial tensile stress at the surface after the limited heating time. The coupled axial tensile stress is smaller than the uncoupled one.(3) Any maximum axial tensile stress at the surface after a limited heating time does not become larger than the maximum axial compressive stress at the surface during the heating period.