Review of creep deformation and rupture mechanism of P91 alloy for the development of creep damage constitutive equations under low stress level

This paper presents a review of creep deformation and rupture mechanism of P91 alloy for the development of its creep damage constitutive equations under lower stress level. 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 prediction the lifetime for this type of alloy, partially under low stress. The paper reports a critical review on the deformation and damage evolution characteristics of this alloy, particularly under low stress, to form the physical base for the development of creep damage constitutive equations. It covers the influence of the stress level, states of stress, and the failure criterion

Preliminary analysing of experimental data for the development of high Cr Alloy Creep damage Constitutive Equations

This conference paper presents the current research of preliminary analysing of experimental data for the development of high Cr Alloy Creep damage Constitutive Equations (such as P91 alloy). Firstly, it briefly introduces the background of general creep deformation, rupture and continuum damage mechanics. Secondly, it illustrates the constitutive equations used for P91 alloy or its weldment, especially of the form and deficiencies of two kinds of most widely used typical creep damage constitutive equations Kachanov-Rabotnov-Hayhurst (KRH) and Xu’s formations. And then, the methodology for development of new set constitutive equation proposed by Xu (2004) has been followed in this research. Fourthly, there is a critically analysis of the specific experiment data for P91 alloy and its weldment. Afterwards, the specific requirements for developing a new set constitutive equation have been reported

Analyzing the characteristics of the cavity nucleation, growth and coalescence mechanism of 9Cr-1Mo-VNb steel (P91) steel

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

Review on the current state of developing of advanced Creep Damage Constitutive Equations for high Chromium Alloy

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

Condensation - warming up to mitotic DNA architecture

During interphase, chromatin is in a state of least condensation and most accessible to transcription factors. When cells enter mitosis, replicated chromosomes are compacted, and sister chromatids are cohered to form specific mitotic architectures, which are essential for appropriate chromosome segregation. Disruption of the formation, regulation and maintenance of mitotic chromosome structure results in aneuploidy, which is tightly correlated with severe developmental maladies, aging and tumorigenesis. To understand how cells achieve mitotic condensed DNA architectures, we focus on the regulation of helicase activity and also the impact of site-specific condensation events. We report that helicase the Chl1 acts a novel regulator of mitotic chromosome condensation through cohesin-based mechanisms, revealing an exciting interface between native DNA structure that relies on helicase activity and higher-ordered chromosome compaction that requires cohesin complex. We also report for the first time that the condensed rDNA locus retains great plasticity during mitosis and responds to elevated temperature through a novel hypercondensation activity. This hyperthermic-induced rDNA hypercondensation is based on heat shock chaperone Hsp82, revealing a new role for chaperones in regulating mitotic DNA architecture