Papers by Author: Qiang Xu

Abstract: Creep damage is one of the serious problems for the high temperature industries and computational approach (such as continuum damage mechanics) has been developed and used, complementary to the experimental approach, to assist safe operation. However, there are no ready creep damage constitutive equations to be used for predicting the lifetime for this type of alloy, particularly for low stress. This paper presents an analysis of the cavity nucleation, growth and coalescence mechanism of 9Cr-1Mo-VNb steel (P91 type) under high and low stress levels and multi-axial stress state.

Abstract: The preliminary validation of in-house finite element analysis software for creep damage mechanics is reported. The Finite Element Analysis Method and the programme strcuture for creep damage problem were reported elsewhere and the validation conducted so far include plane stress, plane strain, and axisymmetric cases. Furture work is also outlined.

Abstract: There is a need for a computational tool for analyzing creep damage problems for the research community and high temperature industries, and dedicated in-house software still has its merits and advantages. This paper reports the development of such software including the development of finite element algorithms based on CDM for creep damage analysis, and the use of some standard subroutines in programming, and sample of validation.

Abstract: This paper presents a review of creep cavitation and rupture of low Cr alloy and its weldment, particular in the heat-affected zone (HAZ). Creep damage is one of the serious problems for the high temperature industry. One of the computational approaches is continuum damage mechanics which has been developed and applied complementary to the experimental approach and assists in the safe operation. However, the existing creep damage constitutive equations are not developed specifically for low stress. Therefore, in order to form the physical bases for the development of creep damage constitutive equation, it is necessary to critically review the creep cavitation and rupture characteristics of low Cr alloy and its weldment.

Abstract: This paper reported a validation of computational software system for creep damage analysis using circular notched bar. The complete computational software system for creep damage analysis consists of pre-and post-processing and the numerical solver and here the validation is primarily for the pre-and post-processing section developed by the authors. The creep damage evolution with time was post-processed interactively via FEMSYS.

Abstract: This paper reports a critical summary of literature review of creep damage constitutive equations. Firstly, it introduces the general background on the creep damage in low alloy stainless steel and weldment. Then, it summarizes the typical creep damage constitutive equations for this material available from public literature and discusses the deficiencies existed in the popular creep damage constitutive equations. Finally it outlines the approach to be used in the developing a new set of creep damage constitutive equation and the directions of future work.

Abstract: This paper presents a review of developing of creep damage constitutive equations for high chromium alloy (such as P91 alloy). Firstly, it briefly introduces the background of creep damage for P91 materials. Then, it summarizes the typical creep damage constitutive equations developed and applied for P91 alloy, and the main deficiencies of KRH (Kachanov-Robatnov-Hayhurst) type and Xus type constitutive equations. Finally it suggests the directions for future work. This paper contributes to the knowledge for the developing creep damage constitutive equations for the specific material.

Abstract: This paper reports a review on the computational (finite element) software for creep damage analysis. Firstly, it summarizes the current state of how to obtain such computational capability then it concludes with a preference of in-house software. It further reviews the validation practice. Finally, it completes with an outlines of the approach to be used in the developing in-house FE software.

Abstract: This paper reports a literature review on the development of computational software system for creep damage analysis for weldment. It starts with a brief review on the creep damage problem in weldment and the computational approach; identifies the need for computational approach and the un-availability of such computational system; further details on the preliminary development progress of a transfer programme and constitutive equation subroutines. This paper contributes to knowledge to the development of computational system for creep damage analysis.