| 1. |
- Atif, Yacine, 1967-, et al.
(författare)
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Cyber-Threat Intelligence Architecture for Smart-Grid Critical Infrastructures Protection
- 2017
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Konferensbidrag (refereegranskat)abstract
- Critical infrastructures (CIs) are becoming increasingly sophisticated with embedded cyber-physical systems (CPSs) that provide managerial automation and autonomic controls. Yet these advances expose CI components to new cyber-threats, leading to a chain of dysfunctionalities with catastrophic socio-economical implications. We propose a comprehensive architectural model to support the development of incident management tools that provide situation-awareness and cyber-threats intelligence for CI protection, with a special focus on smart-grid CI. The goal is to unleash forensic data from CPS-based CIs to perform some predictive analytics. In doing so, we use some AI (Artificial Intelligence) paradigms for both data collection, threat detection, and cascade-effects prediction.
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| 2. |
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| 3. |
- Lindström, Per, 1967-
(författare)
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Approximation of maximum weld induced residual stress magnitude by the use of meyer hardness
- 2016
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Ingår i: Maritime Transportation and Harvesting of Sea Resources. - : CRC Press. - 9780815379935 ; , s. 625-632
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Konferensbidrag (refereegranskat)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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| 4. |
- Lindström, Per, 1967-
(författare)
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Improved CWM platform for modelling welding procedures and their effects on structural behaviour
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)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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| 5. |
- Lindström, Per, 1967-, et al.
(författare)
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Materials and Fabrication Technology : Committee v.3
- 2015. - 1
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Ingår i: Proceedings of the 19th International Ship and Offshore Structures Congress, Volume 2. - EH Leiden, Nederlands : CRC Press. - 9781138028975 - 9781138028968 ; , s. 619-698
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 6. |
- Lindström, Per, 1967-, et al.
(författare)
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Non-linear fracture mechanics in LS-DYNA and LS-PrePost
- 2015
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Ingår i: European LS-DYNA Conference 2015. - Würzburg : DYNAmore GmbH.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 7. |
- Lindström, Per, 1967-, et al.
(författare)
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Nonlinear fea of weld residual stress influence on the crack driving force
- 2016
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Ingår i: Maritime Transportation and Harvesting of Sea Resources. - : CRC Press. - 9780815379935 ; , s. 633-644
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Konferensbidrag (refereegranskat)abstract
- Weld joints play a very important role in the assessment of structural integrity of steel structures. The likelihood of defects is significantly higher in the weld joint compared to the unaffected base material. Here the Computational Welding Mechanics platform developed by Lindström (2015) has been used to model representative residual stress fields by the use of the IIW RSDP Phase II Initiative documentation (Janosch 2001). Where the CWM-platform includes an option for tracking the welding’s influences on the evolution of the base and weld material’s tensile properties. A detectable defect is introduced in the weld metal and the crack driving force in terms of the CTOD is extracted from the FEA. The loading applied covers both globally elastic and fully plastic conditions. The analysis allows evaluation of the influence of both residual stresses and changes in the tensile properties on the crack driving force as a function of applied global load.
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| 8. |
- Rahman, Hafizur, et al.
(författare)
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The effect of increased pulp yield using additives in the softwood kraft cook on the physical properties of low-grammage handsheets
- 2017
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Ingår i: Nordic Pulp & Paper Research Journal. - : AB SVENSK PAPPERSTIDNING. - 0283-2631 .- 2000-0669. ; 32:3, s. 317-323
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Tidskriftsartikel (refereegranskat)abstract
- The effect of increasing the pulp yield by the addition of sodium borohydride (NaBH4) or polysulfide (PS) in softwood kraft cooking, i.e. enhancing the retention of glucomannan, on the physical properties of low-grammage handsheets was studied. In addition to the yield improvement, an increase in tensile index was observed, especially at lower degrees of beating. These higher yield pulps showed an increase in pore volume, indicating an increased degree of swelling of the fibres. Presumably, the increased flexibility of the fibres affects the bonding strength and leads to the higher tensile index observed.
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