Papers by Author: Ryuji Mukai

Abstract: This paper focuses on the thermal stress and deformation analysis of the support plate of a nuclear reactor during the quenching process. A 3D finite element model of the support plate is incorporated into nonlinear coupling analysis that considers temperature, stress, and deformation. To verify the effect of cooling rate on the thermal stress and deformation of the model, we applied the heat transfer coefficients of water and heat treatment oil, depending on temperature variations, into heat conduction analysis. This analytical method enables the determination of the maximum deformation and residual stresses, so that the strength of the support plate can be identified.

Abstract: The purpose of this paper is coming thing by the neutron diffraction method in respect of inside residual stress of carburizing-nitriding quenching spur gear measure. Moreover, from Metallo-thermo-mechanical theory, simulation using the coupled analysis by finite element method is carried out, and the residual stress is predicted.

Abstract: Mechanism of transformation plasticity (TP) is discussed from continuum mechanics viewpoint, and derivation of TP law from the unified thermo-mechanical and transformation plasticity constitutive equation. Result of identified TP coefficient for a chromium steel (JIS SCr420) by use of multi-functional testing machine is introduced as one of the material data together with other data to the simulation of a quenching process by use of newly developed code COSMAP. The simulated distribution of temperature, phases and stress/distortion are compared with the experimentally measured values to verify the accuracy.

Abstract: The objective of this paper is to extend the capability of analyzing the time dependence and coupling of temperature, stress and strain effects on the macroscopic and microscopic structures subjected to quenching, and to introduce a theory of the kinetic of the phase transformation. Strain due to phase transformation, transformation plasticity and thermal expansion are the dominant factors that need to be included in the simulation of a quenching process. The evolution of the microstructure also influences the constitutive equations. In particular, as the temperature changes from the high to phase transformation, temperature and then room temperature, the stress-strain relationship changes from elastic-plastic strain. Therefore, in order to obtain a high strength and ductility in carbon steels, transformation plasticity often has a major effect in increasing of the residual stress during quenching process. In this paper, we measured temperature change and distortion occurring during the quenching process of a carbon steel(SCr420) by thermal simulation machine (Gleeble 1500) are used to determine the parameter of transformation plasticity due to the generation of martensite. The modeling of martensitic transformation plasticity is also verified by using of computational simulation of the quenching process.