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  • 1.
    Josefson, Lennart
    et al.
    Chalmers University of Technology.
    Lindström, Per
    Chalmers University of Technology.
    Molin, Mats
    Forsmarks Kraftgrupp.
    2D and 3D Simulation of the IIW Round Robin Benchmark2010Report (Other academic)
  • 2. Lindström, Per
    Arctic Technology: Report of Committe V.62012In: Proceedings of the 18th International Ship and Offshore Structures Congress, Volume 2: Report of Committe V.6 - Arctic Technology / [ed] W. Fricke & R. Bronsart, Hamburg: Schiffbautechnische Gesellschaft , 2012, 1, p. 243-274Chapter in book (Other academic)
  • 3.
    Lindström, Per
    DNV GL Materials Laboratory, Norway ; University West.
    DNV Platform of Computational Welding Mechanics2013Report (Other academic)
    Abstract [en]

    This document presents the DNV Platform of Computational Welding Mechanics, CWM, with its associated CWM-methodology. That has been developed, validated and implemented as a part of DNV’s Technology Leadership program in the field of Structural Integrity and Materials Technology.A successful CWM implementation requires that the actual organisation has gained the knowledge and understanding of the following related topics:- Welding Engineering with an emphasis on the welding process and its thermodynamics- Weld process quality control such as calibration, validation as well as DAQ, (Data Acquisition)- Transient thermo-mechanical coupled FE-analyses and constitutive modelling- Computational platforms comprising the selection of hardware, operative system and FEM-code as well as suitable pre- and post-processing toolsFrom that perspective there is a lack of reliable and/or hands-on oriented CWM Engineering Handbooks and best recommended practices available on the market. For that sake is the DNV CWM-methodology and its hands on solutions presented.The CWM-methodology described can not only be used for residual stress assessments, as presented in this report. It can also be used for various applications such as assessment of used and/or proposed WPS, Welding Procedure Specifications as well as optimisation of the manufacturing and production process of integrated metallic structures.From the results of a parametric CWM-study have three (3) factors been identified to drive and/or contribute to the magnitude of the weld residual stresses in ship steel plate materials. The contributing and/or driving factors identified are the:- Thermal- and Mechanical Boundary Conditions during the production welding- Yield stress difference between the base- and the weld filler material- Weld heat input, Q, which affects the weld cooling time

  • 4.
    Lindström, Per
    Chalmers University of Technology.
    Heat Transfer Prediction of In Service Welding in a Forced Flow of Fluid2005Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    An algorithm for heat transfer prediction of in-service welding operations in a forcedflow of fluid is presented. The algorithm presented is derived from Rosenthal’s 3D heatflow equation and boundary layer approximations. This was possible by the introductionof an apparent thermal conductivity kPL, which is a function of the boundary layer’s heattransfer coefficient f and the base material’s thickness . This implies that a weldcooling time ΔtT1 /T2 in a forced flow of fluid can now be calculated by an ordinaryengineering calculator and thus enabling suitable welding parameters to be determined.The magnitude of kPLf , was established by regression analysis of results from aparametric finite element analysis series of a total number of 112 numerical simulations.Furthermore, the result of the regression analysis was validated and verified by a weldingexperiment series accomplished on an in-house designed and constructed in-servicewelding rig. The principle design of the welding rig as well as its instrumentation, a PCbased Data Acquisition system, is described. In addition, a method to measure the weldmetals cooling time ΔtT1 /T2 by means of thermocouple elements is described. Finally,the algorithm presented in this study proved feasible for industrial in-service weldingoperations of fine-grained Carbon and Carbon–Manganese steels with a maximum Carbon Equivalent (IIW) (CE) of 0.32.

  • 5.
    Lindström, Per
    Högskolan Väst.
    Improved CWM platform for modelling welding procedures and their effects on structural behaviour2015Doctoral thesis, monograph (Other academic)
    Abstract [en]

    A welding procedure specification is the document describing how a weld joint should be constructed. Arc weld processes are characterized by transient thermal behavior, leading to rapid changes in material properties and dynamic interaction between weld and base material. The objective of the project is to explore how the use of an improved CWM-platform affects representative stress and strain fields in order to assess welding procedure qualification records. Forthis project, the accumulated thermal and mechanical influences from the first run to the final run are brought forward, in one and the same meshed geometrical model. Both the thermal and mechanical material model of the platform are designed to be used for modelling of the base- and weld material,promoting the simulation of the intricate combination of the thermal, elastic,and plastic strains on the plastic strain hardening and the formation of residual stress fields. The output of the simulation is mainly weld cooling times, residual stresses, and deformations. This analysis is taken further by examining how residual stresses influence crack driving force under elastic and plastic loading. In addition, the output from the simulations can be used to assess the realism of the proposed welding parameters. The main experimental welding procedure examined comes from the IIW RSDP Round Robin Phase II benchmark project, where the main aim was to benchmark residual stress simulations. This work was found to contain many applicable challenges of a CWM-analysis project.

  • 6. Lindström, Per
    et al.
    Caprace, J.-D
    Mishra, B.
    Pires, F.
    Roland, F.
    Schipperen, I.
    Andric, J.
    Li, L
    Osawa, N
    Doig, R.
    Remes, H.
    Kim, M. H.
    Materials and Fabrication Technology: Committee v.32015In: Proceedings of the 19th International Ship and Offshore Structures Congress, Volume 2: Committee v.3 Materials and Fabrication Technology / [ed] Carlos Guedes Soares & Yordan Garbatov, EH Leiden, Nederlands: CRC Press, 2015, 1, Vol. 2, p. 619-698, article id V.3Chapter in book (Other academic)
    Abstract [en]

    Due to the past crises, the shipbuilding and offshore industry has realised that new innovative designs and design and production methods are necessary to decrease operational costs, production costs and emissions,while meeting the changing rules and regulations. This ISSC-V.3 report is discussing recent developmentin materials and fabrication technology applied to ship and offshore structures.Chapter 2 focuses on worldwide trends in materials and fabrication methods. Developments in metallicand non-metallic structural materials are dealt in Chapter 3. Advances in fabrication and joining technologiessuch as welding are increasing. Some main areas of applications and research in those areas aredescribed in Chapter 4. Innovative development about corrosion protection systems are presented inChapter 5 while Chapter 6 give an overview about the application of production simulation and virtualreality to improve the production management of ship and offshore structures.The ISSC-V.3 technical committee has performed a benchmark to define a Best Practice Guideline touse Computational Welding Mechanics tools (CWM) in shipbuilding and offshore industry. To achievethis objective various experimental welding tests have been performed in order to give a reference point.Both the residual welding distortions and residual stresses have been compared between numerical simulationsand welding experiments for a common “T” welded assembly used in the shipbuilding industry.However, it has been decided to publish the results of this study in a separate document. Nevertheless, Chapter 7 of this report presents the state of the art as well as the experimental test case that has been analysed.

  • 7.
    Lindström, Per
    et al.
    DNV Materials Laboratory, Norway ; University West.
    de Blanche, Andreas
    University West.
    Integration and Optimization of a 64-core HPC for FEM- and/or CFD Welding Simulations2013In: NAFEMS NORDIC Seminar: Improving SimulationPrediction by Using Advanced Material Models / [ed] Roger Oswald, München: NAFEMS Deutschland, Österreich, Schweiz - DACH , 2013Conference paper (Other academic)
  • 8.
    Lindström, Per
    et al.
    Chalmers University of Technology.
    Faraji, Maneli
    Chalmers University of Technology.
    Review and Selection of a Finite Element Simulation Platform For Academic and Industrial Analyses of In-Service Welding Operations2004In: Proceedings of OMAE’04 23rd International Conference on Offshore Mechanics and Arctic Engineering, June 20-25, 2004, Vancouver, British Columbia, Canada, ASME Press, 2004, Vol. 2, p. 801-806, article id 51246Conference paper (Refereed)
    Abstract [en]

    In order find a general platform/environment forsimulation of in-service welding operations, a review andanalysis of non-linear Finite Element Analysis, FEA, programshave been performed. Free and commercial softwares havebeen considered and the programs that have been reviewed andevaluated are ABAQUS, CALCULIX, CODE-ASTER, MARCand SYSWELD. Different platforms, i.e. workstation configurationswith the associated Operative System, OS, has alsobeen investigated to find an optimised simulation platformsolution. To facilitate the selection of a suitable simulationplatform, the performance and durability of ABAQUS has beenevaluated by means of an in-service weld simulation.The residual weld hoop stresses of the weld simulationhave been compared with the results of girth weld experimentsfrom bibliographic sources. To enhance the evaluation processas well as gain experiences of measuring residual weld stresses,two (2) girth welds with measurement of the weld hoop stresseshave been carried out. The maximum solving performance ofABAQUS was obtained by means of a tailor-made workstation,configured with the OS Slackware Linux 9.1 and a speciallycompiled Linux kernel.The findings of the research will be utilized on selection ofa FEA-simulation platform that will be used for the purpose ofscientific research and industrial development in the field of inservicewelding operations.

  • 9.
    Lindström, Per
    et al.
    University West ; DNV GL Materials Laboratory, Norway.
    Jonsson, Anders
    DYNAmore Nordic AB .
    Jernberg, Anders
    DYNAmore Nordic AB .
    Östby, Erling
    DNV GL Materials Laboratory, Norway.
    Non-linear fracture mechanics in LS-DYNA and LS-PrePost2015In: European LS-DYNA Conference 2015: Conference Papers, Würzburg: DYNAmore GmbH , 2015Conference paper (Other academic)
    Abstract [en]

    Fracture mechanics provides an engineering framework for assessing the consequences of defects instructures. In linear elastic fracture mechanics (LEFM), stress intensity factors KI, KII and KIII are usedfor characterizing the stress singularity at the crack tip, which arises from the theory of linear elasticity.Crack growth is assumed to occur when KI exceeds the fracture toughness KC. LEFM can be usefulfor brittle materials, or when the size of the plastic zone is small compared to global dimensions. In non-linear fracture mechanics (EPFM), an energy based criterion is used for assessing the risk forcrack growth: if the energy release rate at the crack tip exceeds what is required for creating newsurfaces in the material, crack growth will occur. Under certain assumptions the energy release rate atthe crack tip can be calculated by a path independent integral, the so-called J-integral. In modernFE-based fracture mechanics applied to practical design, the structure under consideration ismodelled, including cracks at specific locations, and the J-integral values are computed and used asdesign criteria. From a numerics viewpoint, the J-integral has many appealing properties: it can beevaluated from the far-field solution, which reduces numerical errors that may arise close to the cracktip, and the expected path-independence can to some extent be used as a quick check on solutionvalidity.Evaluation of the J-integral from LS-DYNA simulation results has been implemented as a postprocessingtool in LS-PrePost, including consistent treatment of residual stresses. The implementationcovers both 2D (plane stress / plane strain) and 3D applications, using the virtual crack-tip extension(VCE) method. The tool is accessible both via the LS-PrePost GUI and via command file interface.

  • 10.
    Lindström, Per
    et al.
    DNV Materials Laboratory ; Chalmers University of Technology.
    Josefson, Lennart
    Chalmers University of Technology.
    2D, Axisymmetric and 3D Finite Element Analysis Assessment of the IIW RSDP Round Robin Initiative, Phase 1 and Phase 22012Report (Other academic)
    Abstract [en]

    A further assessment of the IIW numerical and experimental test RSDP Round Robin Initiative, Phase 1 and Phase 2 is presented. Focus is on the weld process specification, and the importance ofuse of as realistic as possible weld process parameters in the weld simulations. Considerable interpretation is often required of the weld designer and of the FE modeller when simulatinga weld process. The paper demonstrates, on the IIW RSDP round Robin benchmarks, that with interpretation and judgement, Computational Welding Mechanics using a variety of models and approaches is possible. Difficulties in interpretation could be substantially reduced through the use of industrial methods of specification, weld process specifications (WPS). For this reason, the authors recommend that all benchmarks follow the standards and definitions used in internationally recognised industrial standards. For the Phase 1 benchmark three-pass butt welded pipe case, which was a designed case for weld simulations, rotationally symmetric and fully 3D results are presented for temperatures, deformations and stresses. These results are compared with IIW benchmark results, and differences caused by weld process parameters and material modelling (for the mechanical analysis) are discussed.For the Phase 2 benchmark two pass butt welded coupon plate case, experimental results are available. The incomplete documentation from the weld experiment compared to realistic WPS is discussed. 3D thermal results coupled with generalised plane strain 2D results for temperatures, deformations and stresses using correct WPS and realistic material data are presented and compared with IIW benchmark results. SFor both Benchmarks the LS-Dyna FE software was used, with a major modification being a modified Goldak heat source model.

  • 11. Lindström, Per
    et al.
    Josefson, Lennart
    Schill, Mikael
    Borrvall, Mikael
    Constitutive Modelling and Finite Element Simulation of Multi Pass Girth Welds2012In: NAFEMS NORDIC Conference: Engineering Simulation: Best Practices, New Developments, Future Trends / [ed] Roger Oswald, München, Germany: NAFEMS Deutschland, Österreich, Schweiz - DACH , 2012Conference paper (Other academic)
  • 12.
    Lindström, Per
    et al.
    Chalmers University of Technology.
    Ulfvarson, Anders
    Chalmers University of Technology.
    An Experimental Rig For Verification of The Mechanical Properties of Welds Produced at In-Service Welding2003In: Proceedings of OMAE’03 22nd International Conference on Offshore Mechanics and Arctic Engineering, June 8 – 13, 2003, Cancun, Mexico, ASME Press, 2003, Vol. 3, p. 57-65, article id 37105Conference paper (Refereed)
    Abstract [en]

    The strength of a weld joint is determined by its geometry and its metallurgic structure, which is dependent on the cooling rate, its chemical composition and the original grain size of the base material. During in-service welding of structures affected by a forced flow of fluid on its reversed side the cooling rate depends on the fluid’s boundary layer, the material’s thickness and the heat input of the welding process. Currently, the calculation of the cooling rate during in-service welding is made by means of numerical methods such as the Finite Element Method, FEM. Through the introduction of an apparent thermal conductivity, kPL, it possible to determine the cooling rate for specific welding parameters by means of Rosenthal’s equation. This can be done with a standard pocket calculator.An experimental rig for measurement of the heat transfer during the in-service welding of structures affected by a forced flow of fluid on its reversed side has been designed and built. The physical principles of welding on plates affected by a forced flow of fluid on their reverse side are the same as for welding on the circumference of a pipe containing a forced flow of fluid. In the rig, the required boundary layer is built up in a pipe system by means of a pump. As the flow and the temperature of the fluid can be controlled to simulate the specific heat transfer, it is now possible to verify the values of the apparent thermal conductivity, kPL, that were calculated

    values of the apparent thermal conductivity, kPL, for various configurations.For the purpose of evaluation and qualification of in-service Welding Procedures Specifications, WPS, the sponsors of the research project use the experimental rig.

  • 13.
    Lindström, Per
    et al.
    Chalmers University of Technology.
    Ulfvarson, Anders
    Chalmers University of Technology.
    Weld Repair of Shell Plates During Seagoing Operations2002In: Proceedings of OMAE’02; 21st International Conference on Offshore Mechanics and Artic Engineering: June 23-28, 2002, Oslo, Norway, ASME Press, 2002, Vol. 3, p. 499-506Conference paper (Refereed)
    Abstract [en]

    An algorithm to estimate the cooling rate of welding seamson the shell plating of a ship, below the waterline, while it is onvoyage has been derived. The demand for this technique hasarisen from the wish of ship operators to make it possible forthe safe repair of ship structures without taking them out ofoperation. [1] The strength of the shell plating after welding isdetermined by its metallurgic structure, which is dependent onthe cooling rate, its chemical composition and the original grainsize of the base material. [2] The cooling rate for this type ofwelding seam depends on the velocity of the water flow, thedistance from the bow, the thickness of the plate, and the heatfrom the heat input of the welding. The algorithm makes itpossible to calculate the cooling rate for a base material affectedby a forced flow of fluid by means of Rosenthal’s equation andthus enabling suitable welding parameters to be determined.As the welding parameters can be chosen to fit the specificrepair to be made, it is now possible to determine the suitabilityof a welding procedure in advance. The algorithm is applicablewhen determining welding parameters at Hot-Tappingoperations as well, where the base material is affected by aforced flow of fluid. A number of experiments have beenperformed and the results support the theoretical model. Theresearch project continues with the aim of finding an algorithmto include the enhanced cooling rate due to the layer of boilingfluid on the back of the base material. A method to improve themeasurements of the most important parameter in the algorithmhas been developed and makes it possible to build up aquantitative database of typical values for various configurations.

  • 14. Soares, C. G
    et al.
    Basu, R.
    Cerup Simonsen, B.
    Egorov, G. V.
    Hung, C. F.
    Lindström, Per
    Samuelides, E.
    Vredeveldt, A.
    Yoshikawa, T.
    Damage Assessment After Accidental Events: Report of Committee V.12009In: Proceedings of the 17th International Ship and Offshore Structures Congress: Volume 2 / [ed] C.D. Jang & S.Y. Hong, Seoul, Korea: Seoul National University , 2009, 1, p. 1-72Chapter in book (Other academic)
    Abstract [en]

    This paper contains the report of the Committee, which is a new one that was created todeal with the methods to assess damage and residual strength after accidental events.The name of the committee, being a short one may give a wrong impression about itsscope as it mentions damage assessment while the mandate refers that there should beconcern for the extent of damage and local and global residual strength of shipstructures, after accidental events. Therefore the contents of the report deal also withmethods to determine local and global residual strength, including the specification ofthe appropriate loads.It starts by providing a description of the type of damages that can be found in thevarious accidental events. Representative scenarios are described and the typicaldamages that results from the specific accidents are indicated. Next section describeshow in real situations the damaged state is perceived. Thus, inspection methods aredescribed as well as the available approaches to derive information about the status ofthe structure from indirect measurements.Loads on the structure are treated afterwards, including the loads that are generatedduring the accidental situation itself and also after the accident when the ship is indamaged state, often listed and with non symmetric sections. The loads are used todetermine ship strength using the assessment methods described in section 5, whichdeals with various types of components.If the ship is considered not having enough strength for temporary voyage to repairyard local repairs are necessary. Otherwise she will travel to a repair shipyard and berepaired there. The various types of problems raised in repair are dealt with in thefollowing section.Finally last section deals with salvage and recovery strategies which are necessary inthe cases of very large damage in ships.

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