| 11. |
- Lindström, Per, 1967-, et al.
(author)
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An Experimental Rig For Verification of The Mechanical Properties of Welds Produced at In-Service Welding
- 2003
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In: Proceedings of OMAE’03 22nd International Conference on Offshore Mechanics and Arctic Engineering, June 8 – 13, 2003, Cancun, Mexico. - : ASME Press. - 0791836835 - 079183672X ; , s. 57-65
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Conference paper (peer-reviewed)abstract
- 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 calculatedvalues 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.
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| 12. |
- Lindström, Per, 1967-
(author)
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Approximation of maximum weld induced residual stress magnitude by the use of meyer hardness
- 2016
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In: Maritime Transportation and Harvesting of Sea Resources. - : CRC Press. - 9780815379935 ; , s. 625-632
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Conference paper (peer-reviewed)abstract
- Weld joints play a very important role in assessment of structural integrity of steel structures. The weld joint region is the location of weld induced residual stress and strain fields (WRS). For the time being there is a lack of engineering methods to be used for approximations of the maximum WRS magnitudes in the way of a weld joint proposed to be produced with a specific Welding Procedure Specification (WPS). Or screening of residual stress measurement results obtained by various measuring methods. This report describes how one can proceed to establish best estimate material data by the use of the Meyer’s hardness. The Meyer’s hardness can also be used to determine the maximum physically possible WRS magnitude.
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| 13. |
- Lindström, Per, 1967-
(author)
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Arctic Technology : Report of Committe V.6
- 2012. - 1
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In: Proceedings of the 18th International Ship and Offshore Structures Congress, Volume 2: Report of Committe V.6 - Arctic Technology. - Hamburg : Schiffbautechnische Gesellschaft. - 9783877001325 ; , s. 243-274
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Book chapter (other academic/artistic)
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| 14. |
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| 15. |
- Lindström, Per, 1967-
(author)
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DNV Platform of Computational Welding Mechanics
- 2013
-
Reports (other academic/artistic)abstract
- 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
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| 16. |
- Lindström, Per, 1967-
(author)
-
Heat Transfer Prediction of In-Service Welding in a Forced Flow of Fluid
- 2009
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In: Journal of Offshore Mechanics and Arctic Engineering-Transactions of The Asme. - : ASME International. - 0892-7219 .- 1528-896X. ; 131:3, s. 1-6
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Journal article (peer-reviewed)abstract
- 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 tT1 /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 tT1 /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 CarbonEquivalent (IIW) (CE) of 0.32.
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| 17. |
- Lindström, Per, 1967-
(author)
-
Heat Transfer Prediction of In Service Welding in a Forced Flow of Fluid
- 2005
-
Licentiate thesis (other academic/artistic)abstract
- 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.
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| 18. |
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| 19. |
- Lindström, Per, 1967-
(author)
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Improved CWM platform for modelling welding procedures and their effects on structural behaviour
- 2015
-
Doctoral thesis (other academic/artistic)abstract
- 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.
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| 20. |
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