scholarly journals Modeling of cavity nucleation, early‐stage growth, and sintering in polycrystal under creep–fatigue interaction

2022 ◽  
Author(s):  
Jingdong Hu ◽  
Changjun Liu ◽  
Fuzhen Xuan ◽  
Bo Chen
Keyword(s):  
Early Stage ◽  
Cavity Nucleation ◽  
Creep Fatigue

scholarly journals Modelling of Cavity Nucleation, Early-stage Growth and Sintering in Polycrystal under Creep-fatigue Interaction

2021 ◽  
Author(s):  
J.-D. Hu ◽  
C.-J. Liu ◽  
Fuzhen Xuan ◽  
Bo Chen
Keyword(s):  
Early Stage ◽  
Hold Time ◽  
Fatigue Loading ◽  
Initial Tension ◽  
Stress Variation ◽  
Compression Phase ◽  
Cavity Nucleation ◽  
Sliding Mechanism ◽  
Creep Fatigue ◽  
Variation Rate

A mechanistic based cavitation model that considers nucleation, early-stage growth and sintering under creep-fatigue interaction is proposed. The number density of cavities ρ and their evolution during multi-cycle creep-fatigue loading are predicted. Both the cavity nucleation and early-stage growth rates, controlled by grain boundary (GB) sliding mechanism during the tension phase, are formulised as a function of local normal stress σ. The cavity sintering that occurs during the compression phase is described as a function of σ, but the mechanism switches to the unconstrained GB diffusion. By examining various load waveform parameters, results provide important insights into experimental design of studying the creep-dominated cavitation process under creep-fatigue interaction. First, creep-fatigue test with initial compression will promote higher ρ value compared to that with initial tension, if the unbalanced stress hold time in favour of tension is satisfied. Second, the ρ value does not have a monotonic dependence on either the compressive hold time or stress level, because of their competing effect on nucleation and sintering. Third, the optimum value of stress variation rate exists in terms of obtaining the highest ρ value due to sintering effect.

scholarly journals Modelling of cavity nucleation under creep-fatigue interaction

2021 ◽  
pp. 103799
Author(s):  
J.-D. Hu ◽  
F.-Z. Xuan ◽  
C.-J. Liu ◽  
B. Chen
Keyword(s):  
Cavity Nucleation ◽  
Creep Fatigue

Creep-Fatigue Damage and Life Evaluation for Boiler Header Stub Weldment

2002 ◽  
Author(s):  
Takuya Ito ◽  
Isamu Nonaka ◽  
Hideo Umaki ◽  
Hidetaka Nishida ◽  
Shizuma Shintani
Keyword(s):  
Fatigue Damage ◽  
Early Stage ◽  
Crack Depth ◽  
Prediction Method ◽  
Fatigue Tests ◽  
Short Cracks ◽  
Micro Cracks ◽  
Creep Fatigue ◽  
Damage Process ◽  
Maximum Crack

In order to clarify the creep-fatigue damage process and to evaluate the creep-fatigue life for boiler 2.25Cr-1Mo header stub welds, a series of creep-fatigue tests were performed on partial mock-up specimens of actual plant under simulated plant loading conditions. Creep voids and micro-cracks occurred along the weld toes at an early stage of life and grew to form many short cracks. These short cracks grew both on the surface and through the wall of the stub tube and later coalesced to form one crack. It was proved that there was a correlation between the maximum crack depth and life ratio and also that there was a correlation between the maximum crack depth and the maximum crack length on the surface. A life prediction method was proposed based on these two correlations.

Characterization of the cavity nucleation factor for life prediction under creep-fatigue interaction

1996 ◽  
Vol 31 (18) ◽  
pp. 4957-4966 ◽  
Author(s):  
Baig Gyu Choi ◽  
Soo Woo Nam ◽  
Young Cheol Yoon ◽  
Joong Jae Kim
Keyword(s):  
Life Prediction ◽  
Cavity Nucleation ◽  
Creep Fatigue

Alterations in the number of motoneurons containing immunoreactive calcitonin gene-related peptide(CGRP)& choline acetyltransferase(ChAT) in the cervical spinal cord of the wobbler mouse during the development of the motoneuron disease

1995 ◽  
Vol 53 ◽  
pp. 970-971
Author(s):  
L. Vacca-Galloway ◽  
Y.Q. Zhang ◽  
P. Bose ◽  
S.H. Zhang
Keyword(s):  
Spinal Cord ◽  
Early Stage ◽  
Cervical Spinal Cord ◽  
Wild Type Mouse ◽  
Reflex Response ◽  
Mouse Strains ◽  
Behavioral Tests ◽  
Wobbler Mouse ◽  
Stage 4 ◽  
Stage 1

The Wobbler mouse (wr) has been studied as a model for inherited human motoneuron diseases (MNDs). Using behavioral tests for forelimb power, walking, climbing, and the “clasp-like reflex” response, the progress of the MND can be categorized into early (Stage 1, age 21 days) and late (Stage 4, age 3 months) stages. Age-and sex-matched normal phenotype littermates (NFR/wr) were used as controls (Stage 0), as well as mice from two related wild-type mouse strains: NFR/N and a C57BI/6N. Using behavioral tests, we also detected pre-symptomatic Wobblers at postnatal ages 7 and 14 days. The mice were anesthetized and perfusion-fixed for immunocytochemical (ICC) of CGRP and ChAT in the spinal cord (C3 to C5).Using computerized morphomety (Vidas, Zeiss), the numbers of IR-CGRP labelled motoneurons were significantly lower in 14 day old Wobbler specimens compared with the controls (Fig. 1). The same trend was observed at 21 days (Stage 1) and 3 months (Stage 4). The IR-CGRP-containing motoneurons in the Wobbler specimens declined progressively with age.

Automated high-resolution microscopy: the approaches so far

1987 ◽  
Vol 45 ◽  
pp. 58-61
Author(s):  
W. O. Saxton
Keyword(s):  
High Resolution ◽  
Early Stage ◽  
Automatic Recording ◽  
Microprocessor Control ◽  
Alternative Systems ◽  
Electron Image ◽  
Complete Automation ◽  
Analysis System ◽  
High Resolution Microscopy

Recent commercial microscopes with internal microprocessor control of all major functions have already demonstrated some of the benefits anticipated from such systems, such as continuous magnification, rotation-free diffraction and magnification, automatic recording of mutually registered focal series, and fewer control knobs. Complete automation of the focusing, stigmating and alignment of a high resolution microscope, allowing focal series to be recorded at preselected focus values as well, is still imminent rather than accomplished, however; some kind of image pick-up and analysis system, fed with the electron image via a TV camera, is clearly essential for this, but several alternative systems and algorithms are still being explored. This paper reviews the options critically in turn, and stresses the need to consider alignment and focusing at an early stage, and not merely as an optional extension to a basic proposal.

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