Tom Lassen

Professor Tom Lassen Kontor: D3-097Campus Grimstad Email: tom.lassen@uia.no Tlf.: 3723 3249 Adresse: Fakultet for Teknologi og Realfag, Universitetet i Agder, Grimstad

Bakgrunn:

Present: Professor in Mechanical Engineering at Agder University
1997 Ph.D. in Structural Reliability Engineering, Aalborg University, Denmark 1975 Pedagogical Seminar for engineers at NTNU
1973 Master of Science in Naval Architecture at Norwegian University of Science and Technology, Trondheim, Norway

Prosjekter:

Recent and current research projects
1. Mechanical behaviour and fatigue durability of offshore loading hoses
The aim of the project is to verify the fatigue capacity of flexible loading hoses with catenary configuration used in offshore floating loading systems. The project involves a test program and the establishment of fatigue life prediction methods. The main industrial partners are Statoil and Advanced Production and Loading, Arendal, Norway. At present this technology is used to take decisions regarding retirement of installed hoses at the North Sea. Planned course with Tekna, Oslo May 2009. Final publication OMAE 2010, Shanghai, China.

2. Probabilistic Damage Tolerance Concept for Welded Joints in Steel Structure
The objective is to establish stochastic models for predicting the both random behaviour of fatigue crack growth in welded joint and the uncertainty in the performance various inspection techniques. The models include the application of Monte Carlo simulation, First and Second Order Reliability Methods and Markov Chain modelling. The final aim is to calculate fatigue reliability as a function of service time under various inspection strategies. The work is a collaboration with Professor Naman Recho, University of Paris 6, France. The project is ongoing. Publication at Fatigue Design Conference in Paris, November 2009

3. Strength and durability of mooring chains subjected to fatigue and corrosion deterioration.
In offshore oil and gas exploitation there has in the last decade been a shift from fixed installations towards the use of moored floaters. To ensure a safe and economical operation during the service life, prediction of durability and reliability levels against failure of mooring lines becomes crucial. This makes deterioration of mooring chains due to the fatigue and corrosion processes an issue of major concern. Mechanical characteristics of various steel qualities and manufacturing and statistical aspects of the initial quality are among the main topics in the planned research work. The project will be co-ordinated by Vicinay Cadenas, S.A. and the University of Basque Country, Spain.

The project is planned and described and an application for a financial founding has been presented to the Spanish government. Project start was January 2002 and finished in with presentation at OMAE 2005. Next publication at OMAE 2009.

4. Theoretical and experimental study on the strength and durability of thermally cut steel.
Joint research project between University of Maribor, Slovenia and Agder University for the period 2007-2009. The project is supported by the Slovenian Council for Research. Opponent in PhD dissertation in September 2009.

5) International book project on Fatigue behaviour of welded joints.
Publishing and maintenance of an international text book. The main issues are life predictions and damage tolerance assessment of welded joints. Hermes Lavoisier, ISTE Publishing Company, ISBN 1905209541-2006

Publikasjoner:

T. Lassen: "The Effect of the Welding Process on the Fatigue Crack Growth." American Welding Society (AWS) Welding Journal 69 (2) 1990

T. Lassen: "Markov modelling of the fatigue damage in welded structures under in-service inspection.” International Journal of Fatigue, UK. 13 (5) 1991

A. Grous, N.Recho, T. Lassen and H. P. Lieurade:"Caracterisitiques mecaniques de fissuration et defaut initial dans les soudures d'angles." Fatigue of components and welded structures. Conference proceedings CETIM, Senlis, France november 1992

T. Lassen: "Minimum Weight Design of 3D Framework Structures with Wideflange and TubularMembers." American Society of Civil Engineering (ASCE) Journal of Structural Engineering, 119 (3) pp 713-727 March 1993.

T. Lassen and N. Recho: "An expert system for design and inspection strategy of welded joints." The 5 th. International Conference on Fatigue and Fatigue Thresholds. Montreal, Canada May 1993

T. Lassen: "Reliability based design and fatigue inspection of welded structures." International short course 1993 within the framework of COMETT (European community Program for Technical training)

T. Lassen :"Optimum fracture control plan for gas turbine engine components." American Society of Testing and Materials (ASTM). Special Technical Publication, STP 1231, pp 477-490, 1994

T. Lassen and K. Syvertsen: "Fatigue Reliability and Life Cycle Cost Analysis of Mooring Chains." Proceeding of the Sixth (1996) International Offshore and Polar Engineering Conference. Los Angeles, USA, May 1996

T. Lassen : "Analysis of the Uncertainties in Time to Crack Initiation and Propagation of Fatigue Surface cracks in welded Joints." International conference on fatigue of welded components and structures, Senlis, France 12-14 June 1996

T. Lassen and K. Syvertsen: "Fatigue Reliability and Life Cycle Cost Analysis of Mooring Chains." International Journal of Offshore and Polar Engineering Vol 7 No 2 June 1997

T. Lassen: "Experimental Investigation and Stochastic Modelling of the Fatigue Behaviour of Steel welded Joints." Ph.D. Thesis at Aalborg University, Denmark, September 1997

T. Lassen: “Damage Tolerance Assessment of Welded Joints Subjected to Fatigue Crack Growth.” Proceedings of the Eight International Offshore and Polar Engineering Conference, Montreal, Canada 1998

T. Lassen: Fatigue Durability and Damage Tolerance Verification of Welded Joints.” Proceeding of the Seventh International Fatigue Congress. Higher Education Press, 55 Shatan Houjie, Beijing, China 1999

T. Lassen, Jan Vidar Aarsnes: "Experimental Investigation on the Fatigue of Loading Hoses."

Results from a joint research work between Advanced Production and Loading, Arendal and Kleber Industries, Clermont-Ferrand. The report is on the publication list of The French-Norwegian Research Foundation, June 2000.

J.Cognard, N. Recho and T. Lassen: "Offshore loading Hoses made of Steel Reinforced Rubber-Applications, Behaviour and Durability" Advanced Production and Loading International Conference, Arendal, Norway, July 2000.

T. Lassen and J.D. Sørensen: “A Probabilistic Damage Tolerance Concept for Welded joints Part 1: Data Base and Stochastic Modelling.” Journal of Marine Structures, December 2002.

T. Lassen and J.D. Sørensen: “Probabilistic Damage Tolerance Concept for Welded Joints Part 2: A Supplement to Rule Based S-N Approach.” Journal of Marine Structures December 2002

P. Lazzarin, T. Lassen, P. Livieri : "A Notch Stress Intensity approach applied to fatigue strength predictions of welded joints with different weld toe radii." International Journal of Fatigue & Fracture of Engineering Materials & Structures January 2003 (Publication together with Department of Management and Engineering - University of Padova, Italy).

Philippe Darcis, Diego Santarosa, T Lassen, Naman Recho: “A fracture mechancis approach for the crack growth in welded joints with reference to BS 7910” Presented at the 15th European Conference on of Fracture, Stockholm, 11-13 august 2004

Tom Lassen, Jose Luis Arana, Luis Canada:”Crack growth in high strength steel subjected to fatigue loading in a corrosive environment. ” Published at the 24th international conference of Offshore Mechanics and Artic Engineering, Halkidiki, Greece, June 2005

Lassen,T, Darcis, Ph. and Recho, N. 2005: Fatigue behavior of Welded Joints Part 1- Statistical Methods for Fatigue Life Predictions. Welding Journal 84 (12): 183-s to187-s.

Darcis, Ph., Lassen,T, and Recho, N. 2006: Fatigue behavior of Welded Joints Part 2: Physical Modeling of the Fatigue Process Welding Journal 85 (1): 19-s to 26-s.

T. Lassen and N. Recho: Re-assessment of the Fatigue Life of a riser steel pipe in an offshore loading buoy. 11th international spring meeting Paris 29-30 May 2006. Société Française de Métallurgie et de Matériaux (SF2M)

T. Lassen and N. Recho: The Fatigue Process in Welded joint-Practical Consequences of Refined Modelling. 16th European Conference on Fracture, Alexandroupolis, Greece 3-7 July 2006

T. Lassen and A. Spagnoli: Fatigue Crack Paths in Shafts Subjected to Bending and Torsion.

International conference on crack paths, Parma, Italy 14-16 September 2006

T. Lassen and N. Recho: Re-assessment of the Fatigue Life of a riser steel pipe in an offshore loading buoy. Revue de Metallurgie, Paris September 2007, pp 411

T. Lassen and N. Recho: Proposal for a more accurate physically based S-N curve for welded steel joints. International Journal of Fatigue, Elsevier, - January 2009, pp70-78.

Books

T. Lassen and N. Recho: Fatigue Life Analyses of Welded Structures (FLAWS) A book on life predictions and damage tolerance assessment of welded joints Hermes Lavoisier, ISTE Publishing Company, ISBN 1905209541-2006

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