Toshio Takeuchi

Bio: Toshio Takeuchi is an academic researcher. The author has contributed to research in topics: Creep. The author has an hindex of 1, co-authored 1 publications receiving 6 citations.

Modelling of high-temperature mechanical behaviour of a single crystal superalloy

Abstract: A model describing the anisotropic creep deformation of single crystal superalloys has been developed and evaluated using both a database of creep tests and validatory experiments on the alloy SRR9...

Modeling of high-temperature creep for structural analysis applications

Abstract: For many structures designed for high temperature applicat ions, e.g. piping systems and pressure vessels, an important problem is the life time a ss ssment in the creep range. The objective of this work is to present an extensive o verview about the theoretical modeling and numerical analysis of creep and longterm strength of structures. The study deals with three principal topics includin g constitutive equations for creep in structural materials under multi-axial stress states, structural mechanics models of beams, plates, shells and three-dimensional soli ds, and numerical procedures for the solution of initial-boundary value problems o f creep mechanics. Within the framework of the constitutive modeling we discus s various extensions of the von Mises-Odqvist type creep theory to take into account stress state effects, anisotropy as well as hardening and damage process es. For several cases of material symmetries appropriate invariants of the stres t nsor, equivalent stress and strain expressions as well as creep constitutive equati ons are derived. Primary creep and transient creep effects can be described by the int roduc ion of hardening state variables. Models of time, strain and kinematic ha rdening are examined as they characterize multi-axial creep behavior under simp le and non-proportional loading conditions. A systematic review and evaluation of c nstitutive equations with damage variables and corresponding evolution equatio ns recently applied to describe tertiary creep and long term strength is presented . Stress state effects of tertiary creep and the damage induced anisotropy are discus sed in detail. For several structural materials creep curves, constituti ve equations, response functions and material constants are summarized according to recently published data. Furthermore, a new model describing anisotropic cree p in a multi-pass weld metal is presented. Governing equations for creep in three-dimensional solids are introduced to formulate initial-boundary value problems, variational proc edures and time step algorithms. Various structural mechanics models of beams, plat es nd shells are discussed in context of their applicability to creep problems. Emphasis is placed on effects of transverse shear deformations, boundary layers and geometrical nonlinearities. A model with a scalar damage variable is incorporated into th e ANSYS finite element code by means of a user defined material subroutine. T o verify the subroutine several benchmark problems are developed and solve d by special numerical methods. Results of finite element analysis for the same prob lems illustrate the applicability of the developed subroutine over a wide range of lement types including shell and solid elements. Furthermore, they show the influen ce of the mesh size on the accuracy of solutions. Finally an example for long term s trength analysis of a spatial steam pipeline is presented. The results show that t he developed approach is capable to reproduce basic features of creep and damage proc sses in engineering structures.

Modelling the Anisotropic and Biaxial Creep Behaviour of Ni-Base Single Crystal Superalloys CMSX-4 and SRR99 at 1223K

Abstract: The use of single crystal turbine blade components has made many traditional models for creep unsuitable for application in certain loading situations. Such models generally assume deformation is isotropic. Since the introduction of single crystal components a generation of crystal plasticity or slip system models has emerged. Amongst the challenges of such models is to explain the orientation dependence of uniaxial creep behaviour and to attempt to make correlation between uniaxial and multiaxial stress states so that confidence can be’gained as to the performance of a model when it is applied to complex loading conditions. In this paper an attempt is made to address these issues. A slip system based finite element creep model has been fitted to uniaxial data at 1223 K in a range of crystallographic orientations. Based on experimental evidence the operative slip systems incorporated are the {111} and {111}412> families of slip system. Analysis of the data and a consideration of the dislocation mechanisms likely to occur suggest that the significant component of the hardening matrix is latent hardening by the {111} systems on the { 11 1} systems, although hardening between the { 11 l} systems may also occur. The model can describe creep deformation as a function of orientation to a reasonable degree of accuracy. It is also shown to have reasonable predictive capability when used to analyse the results of thin cylinder biaxial creep tests on CMSX-4 and SRR99. The reason for this success is explained in terms of activated slip systems and the magnitude of the cumulative shear strain rate on different types of slip system as a function of orientation and stress state. Superanoys zoo0 @ited by T.M. Pollock, R.D. Kissinger, R.R. Bowman, K.A. Green, M. M&an, S. Olson, and J.J. Schirra TMS (The h4inemls. Metals & Materials Society), 2ooO

Effects of the Cross-Sectional In-Plane Crystal Orientation on the Structural Strength of Single-Crystal Turbine Vanes

Abstract: This paper presents the effects of the cross-sectional in-plane crystal orientation (θ) on the structural strength of single crystal turbine vanes using the finite element method (FEM). The material of the turbine vanes is the single crystal superalloy TMS-75. The obtained results show that the elastic constant matrix (c'44) changes were by above 60% due to the orientation variation (0° < θ < 90°). The dependency of the structural strength of the turbine vane on the crystal orientation was calculated using von Mises stress equation. The strength of the turbine vane was strongly related to θ, and also related to the model shape and load. This influence becomes more significant near the leading edge of the turbine vane where it is most likely to fracture.

Analysis of Inelastic Behavior for High Temperature Materials and Structures

Abstract: This review provides a current status in modeling and analysis of structures for high-temperature applications. Basic features of inelastic behavior of heat resistant alloys are discussed. Typical responses for stationary and varying loading and temperature are presented and classified. Microstructural features and microstructural changes in the course of inelastic deformation at high temperature are discussed. The state of the art on material modeling and structural analysis in the inelastic range at high temperature is resented.