Tomoaki Tsuji

An atomistic study of the strength of an extended-dislocation barrier

The stress dependence of a lock consisting of a stair rod symmetrically located between two Shockley partials in face-centred cubic nickel was examined by atomistic simulation. The applied stress forced the partials into the stair rod. As the partials move into the lock with increasing strain, the separation distances are reasonably consistent with a linear elastic calculation of equilibrium separation except at the closest approach where the elastic calculation overestimates the separation. The overestimation is attributable to core overlap. The lock underwent several unstable transitions before becoming an inverted arrangement of its initial configuration. The sequence of transitions involves an asymmetric configuration at 2.3% strain containing an extrinsic fault, a transition at 4.8% strain that changes the stair rod to , and a transition that inverts the lock at 6% strain with the stair rod becoming . The evolution of the lock is not reversible.

An inverse transient thermoelastic problem for a transversely-isotropic body

Analytical method for an inverse problem of three-dimensional transient thermoelasticity in a transversely-isotropic solid. The heating temperature of a transversely-isotropic infinite circular cylinder is determined in the case where the radial displacement is given at an arbitrary cylindrical section and the radial and shear stresses are free on the lateral surface of the cylinder

THERMAL SHOCK PROBLEMS OF ELASTIC BODIES WITH A CRACK

This paper deals with thermal shock, problems of elastic bodies with a crack. The case considered is that of an infinitely long circular cylinder with an edge crack, and a homogeneous flat plate with an edge crack initially at uniform temperature and suddenly immersed into a medium of lower temperature. The thermal disturbance near the crack tip is assumed to be neglible in the analysis of the temperature field because thermal shocks occur very quickly. We analyze the transient thermal stress problems of elastic solids with a crack and determine the stress intensity factor at the crack tip. The nondimensional maximum transient stress intensity factor is expressed as a function of the Biot number and the nondimensional crack length. Then we propose simplified formulations of the nondimensional maximum transient stress intensity factor as a function of the Biot number and the nondimensional crack length.

BOUNDARY INTEGRAL EQUATION ANALYSIS FOR STEADY THERMOELASTIC PROBLEMS USING THERMOELASTIC POTENTIAL

In a boundary integral formulation to a thermoelastic problem, the temperature change is treated as an equivalent body force. Therefore, even in the case of no body force acting, the formulation involves volume integrals. In the present paper it is proved that introduction of the thermoelastic potential succeeds in eliminating the volume integrals in the three-dimensional formulation. The formulations are transformed from Cartesian coordinates into axisymmetric coordinates. All the surface integrals are replaced by line integrals along the boundary of the axisymmetric domain. By using the above formulation, the deformation and stress distributions of a bonded cylinder subjected to a uniform temperature change are analyzed numerically.

An Identification Method of the Time Dependence of the Impact Force by Using Acoustic Response and FEM Analysis

The radiated sound from the impacted body must have the information with respect to the impact force. We have proposed the method in order to identify the impact force by analyzing the radiated sound from the impacted body. Normally the impact position is unknown and important to measure the impact position. Therefore, in this study, we propose the method to identify the impact position and force by using the radiated sound from the impact body. In the present method, the relationship between the impacted force and sound pressure is obtained by FEM simulation. In order to identify the impact position, the sound pressure, which is measured at the other position, is used. The efficiency of the present method is confirmed by using the many experiments of the plate as the impacted body

Determination of Boundary Values In The Inner Surface of A Cylinder By Using Boundary Element Method

In order to obtain data for practical use, an inverse problem for determining boundary values in inner surface of a cylinder is investigated. The indirect boundary element method with fictitious boundary is applied to this problem. The pressure in the inner surface of the cylinder is obtained by using the tangential strain data in the outer surface, and the availability of this method is confirmed by the actual experiment.

Stress singularity at the bottom of a V-notch in the inner surface of a circular pipe under torsion

Abstract The torsion problem of a circular pipe including a circumferential V-notch in the inner surface is considered. Stress singularity occurs at the bottom of the V-notch and a parameter similar to the stress intensity factor for a crack is defined. The series expansion technique is used in consideration of the stress singularity. The stress field neighboring the V-notch is denoted by the above parameter and thus the order of the stress singularity is obtained. The relationship between the parameter and the geometry or the mechanical properties of the pipe is obtained by numerical calculation.

The Void Growth Simulations in the Hyper-Elastic Material with Multiple Seeds

The behaviors of a material are nonlinear in the large deformed region. The hyper elastic models can describe such non linear materials. If the hyper elastic material is applied to the hydrostatic tensile load, the void begins to grow when the load exceed the critical value. It is important to study the coalescence of the void growth in order to consider the destruction of the material. In this paper, the void growth simulations in the hyper-elastic material with multiple seeds are studied. The unit rectangular cell with small voids is subjected to the hydrostatic tensile load. This problem can be analyzed by FEM. However, the simulation with the larger number of the voids is not possible. Thus, the CA (Cellular Automaton) is used to describe the behaviors of the void coalescence and the possibility of CA is discussed.

Multiple Void Growth Simulations in the Hyper-Elastic Material

If the hydrostatic tensile load is applied to a hyper-elastic material, the void initiates when the load exceeds the critical value. On the other hand, it is important to study multiple void growth phenomena, in order to consider the fracture by coalescence of voids. In this paper, we study the growth of multiple voids in the hyper-elastic material. The material is characterized by the energy function as the compressive material. Some experiments for the rubber, as a hyper-elastic material, are proceeded, in order to obtain these mechanical properties in the energy function. A square cell with some small voids is constructed and applied with tensile deformation by moving outer surface. The large deformation and the non-linear simulations are proceeded by using FEM. If there is only one seed, one void grows from the seed. However, when there are some seeds, we observed the void growing and the void vanishing by the influence from the other voids. The influence of the initial voids scale to the void growth is studied.Copyright

An Analysis of Functional Gradient Materials by Molecular Dynamics Method

Various kinds of Functional Gradient Materials (FGM) have been developing, and many investigators have been studying in order to develop an analysis method. It is difficult to analyze FGM comparing with ordinal alloy, because mechanical properties of FGM are changing along its gradient direction. Usually, mechanical properties of FGM are decided by using the function with respect to volume mixture ratio. Such the functions were obtained by experimental methods for an alloy. Thus, accuracy of these functions are unknown when we use them in the case of designing a new FGM. Moreover, it is very difficult to obtain mechanical properties of FGM by experiments. Consequently, it is important to develop a new analysis method. On the other hand, Molecular Dynamics (MD) is one of the important simulation technique, when we struggle atom older structures. If we know only the kinds of material, we can simulate any behavior of the material as same as experimental method.