The Effect of Multiaxial States of Stress on Creep Failure of Type 316H Under Displacement Control

2009 ◽  
Author(s):  
Michael W. Spindler ◽  
Michael C. Smith
Keyword(s):  
Damage Model ◽  
Creep Damage ◽  
Good Prediction ◽  
Displacement Control ◽  
Creep Failure ◽  
Element Analysis ◽  
Reheat Cracking ◽  
Simplified Method ◽  
Multiaxial Creep ◽  
Creep Damage Model

Reheat cracking in the heat affected zones (HAZ) of Type 316H welds has been observed in the UK’s Advanced Gas cooled Reactors after 15–50k hours service at 490 to 520°C. These cracks are caused by creep damage from the relaxation of a triaxial residual stress. To validate a model for multiaxial creep damage under triaxial states of stress, notch bar specimens have been tested under displacement control. The test programme included the effects of different notch geometries, test temperatures (475 to 550°C) and both Type 316H parent and HAZ materials. Finite element analysis was used to develop a simplified method to calculate creep damage in the test specimens and this simplified method was then used to analyse the results of the notched bar stress relaxation tests. It was found that the multiaxial creep damage model gave a good prediction of failure in the tests particularly for the levels of triaxiality relevant to welds and at temperatures relevant to service.

An improved nonlinear damage model of rocks considering initial damage and damage evolution

2020 ◽  
Vol 29 (7) ◽  
pp. 1117-1137 ◽  
Author(s):  
Wenlin Feng ◽  
Chunsheng Qiao ◽  
Shuangjian Niu ◽  
Zhao Yang ◽  
Tan Wang
Keyword(s):  
Damage Evolution ◽  
Least Squares Method ◽  
Damage Model ◽  
Creep Damage ◽  
Secondary Creep ◽  
Nonlinear Creep ◽  
Creep Failure ◽  
Initial Damage ◽  
Nonlinear Damage Model ◽  
Creep Damage Model

The experimental results show that the creep properties of the rocks are affected by the initial damage, and the damage evolution also has a significant impact on the time-dependent properties of the rocks during the creep. However, the effects of the initial damage and the damage evolution are seldom considered in the current study of the rocks' creep models. In this paper, a new nonlinear creep damage model is proposed based on the multistage creep test results of the sandstones with different damage degrees. The new nonlinear creep damage model is improved based on the Nishihara model. The influences of the initial damage and the damage evolution on the components in the Nishihara model are considered. The creep damage model can not only describe the changes in three creep stages, namely, the primary creep, the secondary creep, and the tertiary creep, but also reflect the influence of the initial damage and the damage evolution on creep failure. The nonlinear least squares method is used to determine the parameters in the nonlinear creep damage model. The consistency between the experimental data and the predicted results indicates the applicability of the nonlinear damage model to accurately predict the creep deformation of the rocks with initial damage.

Creep Failure Simulations for 316H at 550°C

2012 ◽  
Author(s):  
Nak Hyun Kim ◽  
Yun Jae Kim ◽  
Catrin M. Davies ◽  
Kamran M. Nikbin ◽  
David W. Dean
Keyword(s):  
Experimental Data ◽  
Damage Model ◽  
Creep Damage ◽  
Inelastic Strain ◽  
Compact Tension ◽  
Creep Failure ◽  
Creep Ductility ◽  
Summation Rule ◽  
Creep Damage Model ◽  
Damage Summation

In this work a method to simulate failure due to creep is proposed using finite element damage analysis. The creep damage model is based on the creep ductility exhaustion concept. Incremental damage is defined by the ratio of incremental inelastic (plastic & creep) strain and multi-axial ductility. A simple linear damage summation rule is applied. When accumulated damage becomes unity, element stresses are reduced to almost zero to simulate progressive crack growth. The model is validated through comparison with experimental data on various sized compact tension, C(T), specimens of 316H stainless steel at 550 °C. The influence of the inelastic strain rate on the uniaxial ductility is considered. Good agreement is found between the simulated results and the experimental data.

A Novel and Simple Approach for Predicting Creep Life Based on Tertiary Creep Behavior

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Khosrow Zarrabi ◽  
Lawrence Ng
Keyword(s):  
Gas Turbines ◽  
Damage Model ◽  
Creep Damage ◽  
Life Assessment ◽  
Advanced Technology ◽  
Creep Life ◽  
Practical Applications ◽  
Damage Models ◽  
Multiaxial Creep ◽  
Creep Damage Model

The creep of materials is a research topic of major significance in the life assessment and design of many modern engineering components of advanced technology such as power generation plant, chemical plant, gas turbines, jet engines, spacecrafts, and components made of plastics and polymers. To predict the creep life of such components, one necessary ingredient is a creep damage model. The current creep damage models are either too cumbersome to be readily employed and/or not sufficiently accurate for practical applications. This paper describes a new multiaxial creep damage model that alleviates the major shortcomings of the existing models. Yet it is relatively simple and accurate and is readily applicable to industrial cases.

A Novel and Simple Approach for Predicting Creep Life Based on Tertiary Creep Behaviour

2006 ◽  
Author(s):  
Khosrow Zarrabi ◽  
Lawrence Ng
Keyword(s):  
Gas Turbines ◽  
Creep Behaviour ◽  
Damage Model ◽  
Creep Damage ◽  
Life Assessment ◽  
Creep Life ◽  
Practical Applications ◽  
Damage Models ◽  
Multiaxial Creep ◽  
Creep Damage Model

The creep of materials is a research topic of major significance in the life assessment and design of many modern engineering components of advance technology such as: power generation plant, chemical plant, gas turbines, jet engines, spacecrafts, components made of plastics and polymers, etc. To predict the creep life of such components, one necessary ingredient is a creep damage model. The current creep damage models are either too cumbersome to be readily employed and/or not sufficiently accurate for practical applications. This paper describes a new multiaxial creep damage model that alleviates the major shortcomings of the existing models yet it is simple and accurate enough to be readily applicable to industrial cases.

Non-linear creep damage model of sandstone under freeze-thaw cycle

2021 ◽  
Vol 28 (3) ◽  
pp. 954-967
Author(s):  
Jie-lin Li ◽  
Long-yin Zhu ◽  
Ke-ping Zhou ◽  
Hui Chen ◽  
Le Gao ◽  
...  
Keyword(s):  
Damage Model ◽  
Creep Damage ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Linear Creep ◽  
Non Linear ◽  
Freeze Thaw Cycle ◽  
Creep Damage Model

scholarly journals The Creep-Damage Model of Salt Rock Based on Fractional Derivative

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2349 ◽  
Author(s):  
Hongwei Zhou ◽  
Di Liu ◽  
Gang Lei ◽  
Dongjie Xue ◽  
Yang Zhao
Keyword(s):  
Fractional Derivative ◽  
Creep Test ◽  
Damage Model ◽  
Creep Damage ◽  
Uniaxial Stress ◽  
Radioactive Waste Disposal ◽  
Creep Process ◽  
Salt Rock ◽  
Damage Process ◽  
Creep Damage Model

The use of salt rock for underground radioactive waste disposal facilities requires a comprehensive analysis of the creep-damage process in salt rock. A computer-controlled creep setup was employed to carry out a creep test of salt rock that lasted as long as 359 days under a constant uniaxial stress. The acoustic emission (AE) space-time evolution and energy-releasing characteristics during the creep test were studied in the meantime. A new creep-damage model is proposed on the basis of a fractional derivative by combining the AE statistical regularity. It indicates that the AE data in the non-decay creep process of salt rock can be divided into three stages. Furthermore, the authors propose a new creep-damage model of salt rock based on a fractional derivative. The parameters in the model were determined by the Quasi-Newton method. The fitting analysis suggests that the new creep-damage model provides a precise description of full creep regions in salt rock.

A nonlinear creep damage model for salt rock

2018 ◽  
Vol 28 (5) ◽  
pp. 758-771 ◽  
Author(s):  
Fei Wu ◽  
Jie Chen ◽  
Quanle Zou
Keyword(s):  
Test Data ◽  
Damage Model ◽  
Creep Damage ◽  
Nonlinear Creep ◽  
Salt Rock ◽  
Creep Tests ◽  
Nonlinear Constitutive Equation ◽  
Damage Constitutive Model ◽  
Creep Damage Model ◽  
Actual Stress

In the creep tests, stress is no longer a constant and increases gradually under the influence of damage occurring during accelerating creep, which is a slow-loading process rather than a conventional creep. With the accumulation of the damage over time, the actual stress increases greatly. The increased actual stress not only generates loading strain but also causes the steady creep rate to rise. This coupling possibly explains why salt rock presents nonlinear accelerating characteristics at the accelerating creep stage. In this work, the constraint of the present creep concept was overcome by assuming that the acceleration creep phase is a coupling process of loading and creeping. Furthermore, we demonstrate that the total strain in this phase is equal to the sum of loading strain and creeping strain. A new nonlinear constitutive equation for creep was then derived, and the mechanisms underlying the nonlinear accelerating characteristics emerging at the stage of accelerating creep are further explained. A step-loading experiment on salt rock was performed for a period of six months. The characteristics of accelerating creep appeared in the last step of loading. This new nonlinear creep damage constitutive model was used to fit and analyze the test data. Obtained results show that this model fits well to these test data and also favorably represents the nonlinear characteristics of accelerating creep, thus supporting the model’s validity.

Sign in / Sign up

Export Citation Format

Share Document