Modelling the Fatigue and Creep of Weldments

Lead Research Organisation: University of Strathclyde
Department Name: Mechanical and Aerospace Engineering

Abstract

Life prediction of welded components that are subjected to creep-fatigue loading associated with the start up and shut down of power plant is a critical design issue, from the economical, environmental and safety viewpoints. However design and life assessment of welded steel structures that operate at high temperatures is particularly difficult and problematic. The current UK design and assessment approaches for weldments are still empirical and therefore tend to be rather conservative. This project focuses on the development of a new understanding of the complex fatigue and creep behaviour of weldments subjected to cyclic temperature and mechanical loads, and the formulation of novel simulation and modeling methods. Preliminary research by the applicant shows that the current Linear Matching Method (LMM) framework can assess welded components with significantly greater accuracy while still using the same fundamental assumptions and materials database as typical UK codes. This project will strengthen the LMM framework to include novel simulation techniques which capture the effects of weldments on the integrity of component with fatigue and creep-fatigue mechanisms.For the first time, this unique next-generation numerical technique and associated semi-analytic models will be developed to comprehensively investigate the fatigue and creep behaviour of high temperature weldments for a wide range of factors (e.g. different weldment type, material and geometric effects, temperature and load range), providing a degree of accuracy of prediction hitherto unavailable and without the restrictions inherent in other methodologies. The research outputs will significantly advance the internationally-leading role of the UK in the assessment of industrial and commercial welded structures, and underpin moves to high temperature structures required for emissions reduction targets.This project will also provide interdisciplinary training opportunities for both a postdoctoral researcher and a PhD student in material modeling, applied mechanics, FEA, integrity assessment, and software engineering.

Publications

10 25 50
 
Description The research outcomes of this project have been reported in more than 20 research papers in the international journals and conferences. The key findings are as follows:Theoretical and Numerical Developments1) An efficient shakedown analysis method has been developed for the assessment of welded structures subjected to cyclic thermal and mechanical loads.2) A new ratchet analysis method based upon the Linear Matching Method (LMM) has been developed for the welded structures and cracked components. 3) A novel simulation technique has been developed for the direct evaluation of the steady cyclic behavior of complicated engineering structures. The proposed numerical technique is able to capture the effects of weldments on the integrity of component with fatigue and creep-fatigue mechanisms, with great convenience and efficiency.4) In addition to the elastic-perfectly plastic material model and creep Norton's law, a more practical cyclic hardening material model (Ramberg-Osgood) and time hardening creep constitutive model have been implemented for the assessment of creep fatigue interaction of the weldments.5) All numerical developments come with Abaqus user subroutines, which provide powerful software tools for industrial users.Numerical Validations1) Numerical tests have been carried out to formulate effective numerical schemes to enhance computational performance, including efficiency and stability. 2) The developed LMM and its software have been validated by a benchmark example of holed plate and also by direct comparisons with the available experimental solutions.3) The new simulation techniques and proposed analytical models for the weldments have been validated via comparisons with experimental and R5 analytical data.Numerical Applications1) The developed novel simulation technique has been successfully applied to full penetration Type 1 and 2 weldments with a wide range of configurations including perfectly dressed, dressed, as-welded, extreme undressed and coarse-welded parameters.2) The combination of geometric strain concentration and material discontinuity effects, and the interaction of fatigue and creep behaviour of weldments have been investigated.3) Contour plots of cycles to failure (N*) depending on dwell period and the applied load intended for design application have been derived.4) Analytical functions for cycles to failure N* and residual life L* of weldments corresponding to different dwell period _t and the applied load have been derived for industrial application.5) Parametric studies of the influence of variation of weldment geometrical parameters on the number of cycles to failure have been carried out, and formulation of a mathematical relation to describe the corresponding dependence have been derived, in order to establish efficient semi-analytic models to assess failure of weldments corresponding to different weld types, geometries, material data and failure laws, applicable for a range of amplitude of loads and dwell times. Industrial impact 1) Working with industrial project partners including Rolls-Royce and EDF Energy, the developed LMM and its simulation results of the weldments have provided a new route for the assessment of the fatigue and creep-fatigue life of weldments.2) New research opportunities have arisen from the work of this project via three nuclear EngD projects funded by the industrial partners.
Exploitation Route By working with industrial partners including EDF Energy, Rolls-Royce and Siemens UK
Sectors Environment

 
Description Cited and adopted in the world leading structural integrity assessment procedure R5 and announced in the R5/R6 Newsletter. A software and user guider developed, and widely used by key industries including EDF Energy (David Tipping, david.tipping@edf-energy.com) and Rolls-Royce (Michael Martin, Michael.Martin@Rolls-Royce.com). The associated method applied by University of Oxford and Italian university for frame structures (e.g. European journal of mechanics. A. Solids, 33, 783-793 2011). Creating a new nuclear EngD project supported by the EPSRC nuclear EngD centre and the EDF energy, £118,000. A new nuclear EngD project supported by the EPSRC nuclear EngD centre and the Rolls-Royce, £118,000. A new nuclear EngD project supported by the EPSRC nuclear EngD centre and the Siemens UK, £120,000, 2012-2016. Promoting the research outcomes www.thelmm.co.uk
 
Description Dalton Nuclear Institute
Amount £118,000 (GBP)
Funding ID NE44 (co-funded by Rolls-Royce) 
Organisation University of Manchester 
Department Dalton Nuclear Institute
Sector Academic/University
Country United Kingdom
Start 10/2010 
End 09/2014
 
Description Dalton Nuclear Institute
Amount £118,000 (GBP)
Funding ID NE44 (co-funded by Rolls-Royce) 
Organisation University of Manchester 
Department Dalton Nuclear Institute
Sector Academic/University
Country United Kingdom
Start 10/2010 
End 09/2014
 
Description Dalton Nuclear Institute
Amount £128,000 (GBP)
Funding ID NE89 (co-funded by Siemens) 
Organisation University of Manchester 
Department Dalton Nuclear Institute
Sector Academic/University
Country United Kingdom
Start 10/2012 
End 09/2016
 
Description Dalton Nuclear Institute
Amount £128,000 (GBP)
Funding ID NE89 (co-funded by Siemens) 
Organisation University of Manchester 
Department Dalton Nuclear Institute
Sector Academic/University
Country United Kingdom
Start 10/2012 
End 09/2016
 
Description Bob Ainsworth visit 
Organisation EDF Energy
Country United Kingdom 
Sector Private 
PI Contribution Member : Hosting of external, non-academic visitor : Have a meeting and discussion with Bob regarding project progress
Start Year 2010
 
Description Consultancy on the fatigue creep assessment of the welded joint 
Organisation SERCO
Country United Kingdom 
Sector Private 
PI Contribution Advisor : Consultancy (in kind)
Start Year 2012
 
Description EDF Energy Visit 
Organisation EDF Energy
Department EDF Innovation and Research
Country France 
Sector Private 
PI Contribution Participant : Hosting of external, non-academic visitor : Giving a talk on latest research outcomes and future plan
Start Year 2010
 
Description Host- Visiting researcher from France 
Organisation Cetim
Country France 
Sector Private 
PI Contribution Host : Hosting academic visitor : Development of a direct analytical method to estimate welded joint modifications generated by high frequency hammering.
Start Year 2010
 
Description Nuclear capability visit - Rolls-Royce 
Organisation Rolls Royce Group Plc
Country United Kingdom 
Sector Private 
PI Contribution Contributor : Hosting of external, non-academic visitor : Introducing departmental and personal research capacities
Start Year 2009
 
Description On the development and application of the Linear Matching Method within R5 Panel 
Organisation EDF Energy
Country United Kingdom 
Sector Private 
PI Contribution Member : Consultancy (in kind)
Start Year 2008
 
Description Partnership with EDF Energy High Temperature Centre 
Organisation EDF Energy
Country United Kingdom 
Sector Private 
PI Contribution Member : Work on advisory panel to industry or government or non-gov organisation
Start Year 2009
 
Description Prof Alan Ponter's 2 day visit at Strathclyde 
Organisation University of Leicester
Country United Kingdom 
Sector Academic/University 
PI Contribution Host : Hosting academic visitor : During Prof Ponter's visit, a meeting was arranged between Prof Ponter and Dr Chen's research team member.
Start Year 2010
 
Description Prof Alan Ponter's academic visit 
Organisation University of Leicester
Country United Kingdom 
Sector Academic/University 
PI Contribution Member : Hosting academic visitor : A thorough discussion on research projects during Prof Ponter's 2 day visit
Start Year 2009
 
Description Project seminar in Rolls-Royce Derby 
Organisation Rolls Royce Group Plc
Country United Kingdom 
Sector Private 
PI Contribution Member : Participation in workshop/networks with non-academic organisation : One day seminar. My students and I had 3 main presentations (4 hours) regarding project progress, results and future plan.
Start Year 2012
 
Description Visitors from NNL 
Organisation National Nuclear Laboratory
Country United Kingdom 
Sector Public 
PI Contribution Contributor : Participation in workshop/networks with non-academic organisation
Start Year 2011
 
Description Direct methods on the design limits in plasticity and creep 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Contributor : Invited talk : Presentation on the recent research outcomes.
Year(s) Of Engagement Activity 2012
 
Description Invited talk on the latest development of the Linear Matching Method 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Contributor : Invited talk.
Year(s) Of Engagement Activity 2012
 
Description Invited talks on the Creep Fatigue analysis and the Linear Matching Method 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Invited talks on the Creep Fatigue analysis and the Linear Matching Method


Not recorded
Year(s) Of Engagement Activity 2014
 
Description Project seminar in Rolls-Royce Derby 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact One day seminar. My students and I had 3 main presentations (4 hours) regarding project progress, results and future plan.


Not recorded
Year(s) Of Engagement Activity 2012
 
Description Technical Forum on High Temperature Materials and Lifetime Issues 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Contributor : Invited talk.
Year(s) Of Engagement Activity 2009