Creep-Fatigue Damage: An International Perspective

2007 ◽  
Author(s):  
David W. Gandy ◽  
Jonathan Parker
Keyword(s):  
Fatigue Damage ◽  
Impact Damage ◽  
International Perspective ◽  
Test Methods ◽  
Future Research ◽  
International Expert ◽  
Damage Initiation ◽  
Cyclic Operation ◽  
Creep Fatigue ◽  
Expert Workshop

Improved knowledge of creep and fatigue interactions is necessary today more than ever as power-generating plants are exposed to cyclic operation. Understanding factors that impact damage initiation and propagation, as well as technologies to predict accumulation of damage in systems and components are required. This paper summarizes the primary results of an International Expert Workshop on Creep-Fatigue Damage Interaction that was held in Amsterdam in July 2006. The purpose of the Expert Workshop was to bring together key industry experts from around the world to do the following: • Assess and document current creep-fatigue test methods; • Evaluate analytical methodologies with respect to crack initiation and growth; • Discuss life prediction methodologies for different applications; • Assess deficiencies that exist in the area of creep-fatigue damage; • Identify future research and development requirements. The International Expert Workshop resulted in 16 action items which are delineated in this paper. Updates will be provided on progress made to date toward addressing these 16 items.

Micro-Mechanics of Creep-Fatigue Damage in PB-SN Solder Due to Thermal Cycling—Part I: Formulation

2002 ◽  
Vol 124 (3) ◽  
pp. 292-297 ◽  
Author(s):  
Pradeep Sharma ◽  
Abhijit Dasgupta
Keyword(s):  
Fatigue Damage ◽  
Damage Mechanics ◽  
Void Nucleation ◽  
Cyclic Creep ◽  
Diffusional Creep ◽  
Void Coalescence ◽  
Second Phase ◽  
Structural Stress ◽  
Damage Initiation ◽  
Creep Fatigue

This paper presents a micro-mechanistic approach for modeling fatigue damage initiation due to cyclic creep in eutectic Pb-Sn solder. Damage mechanics due to cyclic creep is modeled with void nucleation, void growth, and void coalescence model based on micro-structural stress fields. Micro-structural stress states are estimated under viscoplastic phenomena like grain boundary sliding, its blocking at second-phase particles, and diffusional creep relaxation. In Part II of this paper, the developed creep-fatigue damage model is quantified and parametric studies are provided to better illustrate the utility of the developed model.

Micro-Mechanics of Creep-Fatigue Damage in Pb-Sn Solder Due to Thermal Cycling

2000 ◽  
Author(s):  
Pradeep Sharma ◽  
Abhijit Dasgupta
Keyword(s):  
Fatigue Damage ◽  
Damage Mechanics ◽  
Void Nucleation ◽  
Cyclic Creep ◽  
Diffusional Creep ◽  
Void Coalescence ◽  
Structural Stress ◽  
Damage Initiation ◽  
Mechanical Cycling ◽  
Creep Fatigue

Abstract This paper presents a micro-mechanistic approach for modeling fatigue damage initiation due to cyclic creep in eutectic Pb-Sn solder. Damage mechanics due to cyclic creep is modeled with void nucleation, void growth and void coalescence model based on micro-structural stress fields. Micro-structural stress states are estimated under viscoplastic phenomena like grain boundary sliding and its blocking at 2nd phase particles, and diffusional creep relaxation. A conceptual framework is provided to quantify the creep-fatigue damage due to thermo-mechanical cycling. Some parametric studies are provided to better illustrate the utility of the developed model.

Creep-fatigue interaction on estimation of lifetime and fatigue damage of F82H

2021 ◽  
Vol 173 ◽  
pp. 112830
Author(s):  
Wenhai Guan ◽  
Hyoseong Gwon ◽  
Takanori Hirose ◽  
Hisashi Tanigawa ◽  
Yoshinori Kawamura ◽  
...  
Keyword(s):  
Fatigue Damage ◽  
Creep Fatigue

Management of Complex Loading Histories for Use in Probabilistic Creep-Fatigue Damage Assessments

2018 ◽  
Author(s):  
N. A. Zentuti ◽  
J. D. Booker ◽  
R. A. W. Bradford ◽  
C. E. Truman
Keyword(s):  
Fatigue Damage ◽  
Input Parameter ◽  
Three Dimensional ◽  
Complex Loading ◽  
Fe Model ◽  
Plant Component ◽  
Fatigue Lifetime ◽  
Wide Range ◽  
Stress Components ◽  
Creep Fatigue

An approach is outlined for the treatment of stresses in complex three-dimensional components for the purpose of conducting probabilistic creep-fatigue lifetime assessments. For conventional deterministic assessments, the stress state in a plant component is found using thermal and mechanical (elastic) finite element (FE) models. Key inputs are typically steam temperatures and pressures, with the three principal stress components (PSCs) at the assessment location(s) being the outputs. This paper presents an approach which was developed based on application experience with a tube-plate ligament (TPL) component, for which historical data was available. Though both transient as well as steady-state conditions can have large contributions towards the creep-fatigue damage, this work is mainly concerned with the latter. In a probabilistic assessment, the aim of this approach is to replace time intensive FE runs with a predictive model to approximate stresses at various assessment locations. This is achieved by firstly modelling a wide range of typical loading conditions using FE models to obtain the desire stresses. Based on the results from these FE runs, a probability map is produced and input(s)-output(s) functions are fitted (either using a Response Surface Method or Linear Regression). These models are thereafter used to predict stresses as functions of the input parameter(s) directly. This mitigates running an FE model for every probabilistic trial (of which there typically may be more than 104), an approach which would be computationally prohibitive.

scholarly journals Vulnerability of bridges to scour: insights from an international expert elicitation workshop

2017 ◽  
Vol 17 (8) ◽  
pp. 1393-1409 ◽  
Author(s):  
Rob Lamb ◽  
Willy Aspinall ◽  
Henry Odbert ◽  
Thorsten Wagener
Keyword(s):  
Risk Mitigation ◽  
Good Practice ◽  
Expert Elicitation ◽  
Residual Risk ◽  
Bridge Scour ◽  
International Expert ◽  
Quantitative Estimates ◽  
Bridge Failure ◽  
Expert Workshop ◽  
Failure Probabilities

Abstract. Scour (localised erosion) during flood events is one of the most significant threats to bridges over rivers and estuaries, and has been the cause of numerous bridge failures, with damaging consequences. Mitigation of the risk of bridges being damaged by scour is therefore important to many infrastructure owners, and is supported by industry guidance. Even after mitigation, some residual risk remains, though its extent is difficult to quantify because of the uncertainties inherent in the prediction of scour and the assessment of the scour risk. This paper summarises findings from an international expert workshop on bridge scour risk assessment that explores uncertainties about the vulnerability of bridges to scour. Two specialised structured elicitation methods were applied to explore the factors that experts in the field consider important when assessing scour risk and to derive pooled expert judgements of bridge failure probabilities that are conditional on a range of assumed scenarios describing flood event severity, bridge and watercourse types and risk mitigation protocols. The experts' judgements broadly align with industry good practice, but indicate significant uncertainty about quantitative estimates of bridge failure probabilities, reflecting the difficulty in assessing the residual risk of failure. The data and findings presented here could provide a useful context for the development of generic scour fragility models and their associated uncertainties.

A Direct Method on the Evaluation of Cyclic Steady State of Structures With Creep Effect

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Haofeng Chen ◽  
Weihang Chen ◽  
James Ure
Keyword(s):  
Fatigue Damage ◽  
Mechanical Load ◽  
Direct Method ◽  
Load Condition ◽  
Hysteresis Loops ◽  
Strain Range ◽  
Cyclic Behavior ◽  
Direct Evaluation ◽  
Plastic Strain Range ◽  
Creep Fatigue

This paper describes a new extension of the linear matching method (LMM) for the direct evaluation of cyclic behavior with creep effects of structures subjected to a general load condition in the steady cyclic state, with the new implementation of the cyclic hardening model and time hardening creep constitutive model. A benchmark example of a Bree cylinder and a more complicated three-dimensional (3D) plate with a center hole subjected to cyclic thermal load and constant mechanical load are analyzed to verify the applicability of the new LMM to deal with the creep fatigue damage. For both examples, the stabilized cyclic responses for different loading conditions and dwell time periods are obtained and validated. The effects of creep behavior on the cyclic responses are investigated. The new LMM procedure provides a general purpose technique, which is able to generate both the closed and nonclosed hysteresis loops depending upon the applied load condition, providing details of creep strain and plastic strain range for creep and fatigue damage assessments with creep fatigue interaction.

Passive Damage Detection of Natural Fibre Reinforced Composites Using Sensor Response Data

2014 ◽  
Vol 534 ◽  
pp. 17-23 ◽  
Author(s):  
M. Zaleha ◽  
Shahruddin Mahzan ◽  
M.I. Idris
Keyword(s):  
Lead Zirconate Titanate ◽  
Impact Damage ◽  
Lead Zirconate ◽  
Optical Microscope ◽  
Natural Fibre ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Damage Initiation ◽  
Response Data ◽  
Sensor Signals

This paper presents the detection of impact damage in a natural fibre reinforced composite plate under low velocity impact damage. Lead Zirconate Titanate (PZT) sensors were placed at ten different positions on each plate in order to record the response signals. The response signals captured from each sensor were collected for impacts performed by a data acquisition system. The impacted plates were examined with optical microscope to examine the damaged areas. It was found that the damaged size grew proportionally with impact force. The results also revealed that PZT sensors can be used to detect the damage extent with the waveform of sensor signals implying the damage initiation and propagation which detected above the damage force of 150N.

Is institutional investor a supervisor or cooperator?

2018 ◽  
Vol 9 (1) ◽  
pp. 2-18 ◽  
Author(s):  
Yuedong Li ◽  
Xianbing Liu ◽  
Qing Yan
Keyword(s):  
Institutional Investors ◽  
Institutional Investor ◽  
Test Methods ◽  
Future Research ◽  
Management Turnover ◽  
Content Type ◽  
Financial Restatement ◽  
Strategic Cooperation ◽  
Financial Restatements ◽  
The Relationship

Purpose The purpose of this paper is to discuss whether top management will assume their liabilities especially when financial restatement occurs, and,based on the “effective supervision theory” and “strategic cooperation theory,” to examine whether an institutional investor is a supervisor or a cooperator considering the management turnover caused by financial restatement in the companies. Design/methodology/approach Using a sample of the A-share-listed companies from year 2010 to year 2014 and dividing financial restatement into fraudulent financial restatement and other financial restatement, the authors examine the relationship between financial restatement and abnormal management turnover, which usually is related to the management integrity or capacity. By using group test methods, the authors test the influence of the institutional investors’ shareholding on the relation between financial restatements and management turnover. Findings This paper finds that financial restatement can result in abnormal management turnover, especially the fraudulent financial restatement. The institutional investors usually are supervisors but when the shareholding of institutional investor is too high and the management turnover results from fraudulent financial restatement, the institutional investors may become cooperators with management in the companies. Besides, the institutional investors play the supervisory function more significantly in non-state-owned enterprises. Originality/value This paper expands literature of the institutional investors in the corporate governance area and provides a basis for future research in the area of the institutional investors’ governance effect. It divides financial restatements into fraudulent financial restatement and other financial restatement and examines the relationship between financial restatement and abnormal management turnover so as to provide evidence about whether the management will assume their responsibilities when there is financial restatement in the company. It also tests whether the institutional investors will play supervisor’s or cooperator’s function in state-owned and non-state-owned enterprises.

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