CREEP/FATIGUE CRACK GROWTH TESTING IN RESIDUAL LIFE ASSESSMENT OF WELDED COMPONENTS
K M Nikbin
Mechanical Engineering Department,
Imperial College,
Lonndon SW7 2BX.
UK
ABSTRACT
Weldments in components are regions where failures are most likely to occur either by fast fracture, creep or fatigue. These regions could exhibit microstructural inhomogeneity as well as the presence of micro-cracks and residual stresses. Understanding their behaviour is of major source of interest for a range of industries. Creep and creep/fatigue crack growth models as well as residual defect assessment codes need reliable and verifiable material properties data and validated fracture mechanics parameters for use in their predictive methodologies. The research to develop an overall methodology for deriving acceptable data and validated parameters for life assessment analysis has been developing in Europe through a number of collaborative European projects. These have covered both parent as well as weld material of a range of alloys and conditions. Although there is substantial information and data on weld tests available, due to an absence of validated information the industrial community cannot easily use this information with confidence. The present standards, also, do not deal directly with testing of welded specimens and therefore. The Analysis of the results from these projects have been continuing and furthermore have been used to assist in the development of testing standards as well as life assessment codes of practice. As a result a VAMAS (Versailles Agreement for Materials And Standards) Round Robin weld testing programme has been initiated to address the issues of testing and analysis of weld related materials. The paper presents the methodology that will lead to recommendations for a code of practice (CoP) of welded materials.
Curriculum Vitae
Full Name and Title: Dr Kamran Nikbin
Date of Birth: 06-01-1951
Department/Division: Mechanical Engineering, Strength of Materials
Email Address: k.nikbin@ic.ac.uk
Daytime Phone Number: 020-7594-7133
Title of Current Appointment: Principal Research Fellow
Higher Education: 1973 – 1977 Imperial College: PhD, DIC (Applied Mechanics)
1970 – 1973 Queen Mary College: BSc (Eng.) (Upper-2nd Honours)
Membership of Professional Bodies, Learned Societies, etc.:
2002- Chairman, ASTM E08-06 Committee
1999- Chairman VAMAS (Versailles Agreement on Materials and Standards) TWA25 Committee
1999- ASME- American Society of Mechanical Engineers
-
1994- American Society for Testing and Materials (ASTM)
E08 Committee.
Appointments:
-
1998- Imperial College Principal Research Fellow
In charge of Section Computing Resources
- 1997- Appointment as a Royal Academy of Engineering/British Energy Senior sponsored Research Fellow
1987- 1997 Imperial College: Research Fellow, RAII
In charge of Section Computing Resources
1979 - 1987 Imperial College: Research Assistant, RAI
1977 - 1979 National Iranian Steel Industry: Consultant Engineer
Short Description of Responsibilities:
Since 1979 till the present time Dr Nikbin has been working on a range of research topics at the Mechanics of Material’s Section at Imperial College. From the beginning and more so since his appointment as a Royal Academy of Engineering/British Energy Senior sponsored Research Fellow in 1998 his target has been to direct the group’s research in achieving an overall goal of developing predictive techniques of failure using fracture mechanics methods. He has been involved with industry and research establishments on numerous multi-disciplinary projects dealing with different aspects of fracture ranging from cryogenic to very high temperature. In particular his main impetus has been in the field of high temperature creep/fatigue crack growth, by considering the experimental, metallurgical, micro-modelling and numerical predictions associated with it.
In addition to the research he has worked continuously with both undergraduate and graduate students in tutoring, teaching computing related studies as well as giving post-experience teaching courses both at Imperial College and at institutions abroad.
Links to Industrial Activities
Dr Nikbin has worked closely for his entire career with industrial and other research sponsors both by direct and with joint funding backed by EPSRC, DTI and EU related grants. The main sponsors have included CEGB and MOD (Ministry of Defence), EXXON, British Energy, Powergen, DERA, QINETIQ, Rolls Royce, ALsthom, NPL, UKAEA, EFDA, ITER, (International Thermo Nuclear Reactor), MHI (Mitsubishi Heavy Industries), IHI (Ishikawa Heavy Industries).
Dr Nikbin’s collaboration in four European Projects has also allowed him to work with a number of European Industries and research institutes such as MPA, Max-Planck Institute GKSS, SPG, (Germany), ENEL (Italy), JRC, Metsearch (Holland), CEA, EDF (France), ISQ (Portugal), VTT (Finland), SIMR (Sweden).
Dr Nikbin’s involvement in the ASTM E08 and the VAMAS Committees and the European COST and Brite/Euram collaborative projects since 1985 has ensured that the group’s methodologies have been adopted by Industry and incorporated into appropriate procedures and standards. He has taken a leading role, both technically and at the organisation level, in a number of European sponsored projects in recent years. Dr Nikbin has been instrumental in incorporating the group’s research work into new international standards and codes of practice such as the British Energy R5, ASTM E1457, BS 7910, ASME and API 597 codes. In addition he has been involved in
- • Developing computer procedures which have been incorporated into the commercial computer code ABAQUS and validated in the course of time through his computational work.
More recently, his Chairmanship of VAMAS TWA25 and ASTM E08.06 Committees in 1998 and 2002 respectively has allowed him to influence edit and re-write the contents of the respective documents. This has resulted in the following deliverables;
- • New ASTM standards E1457-01 on Creep Crack Growth Testing’, completed 2000’
In all these he has been the key person in developing organising the particular international group and editing the collected information towards producing a technical document for use by Industry. It is now the likely course of action that the documents mentioned above will find their way into appropriate ISO documents. This will give in the long term a wider acceptability of the work at the International Level.
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