| 1. |
- Andreasson, Björn, et al.
(författare)
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The measurement of venous haematocrit in patients with polycythaemia vera.
- 1999
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Ingår i: Journal of internal medicine. - : Wiley. - 0954-6820 .- 1365-2796. ; 246:3, s. 293-7
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: In clinical practice, patients with polycythaemia vera (PV) are monitored by measurement of venous packed cell volume (PCV). However, whereas treatment recommendations are still based upon studies in which the results were obtained with the centrifuged microhaematocrit, currently in most instances automated blood cell counters are used to calculate PCV. In a group of patients with polycythaemia we therefore compared the results obtained by the microhaematocrit method with PCV calculated by haematology analysers. DESIGN: The study was carried out on a prospective basis. Duplicate venous blood samples were collected. The centrifuged microhaemotocrit was obtained by using an IEC Micro-MB Centrifuge. Depending on different routine methods used in the participating hospitals, the blood cell counter PCV was calculated using Coulter STKS, Bayer Technicon H2 or H3. SETTING: Patients were included from four Swedish university hospitals: Akademiska (Uppsala), Huddinge and Karolinska (Stockholm) and Sahlgrenska (Göteborg). SUBJECTS: Seventy-four patients with PV and 10 patients with secondary polycythaemia were included and a total of 150 duplicate blood samples were analysed from these subjects. RESULTS: In the 150 measurements the mean blood cell counter calculated PCV was 0.448 +/- 0.037; the mean for centrifuged microhaematocrit was 0.467 +/- 0. 037 and the difference between means was highly significant (P = 6.8 x 10-25). The means for centrifuged haematocrit and calculated PCV differed significantly in the groups of PV patients treated with phlebotomy only, hydroxyurea or radiophosphorous (P < 0.0001, respectively). In PV patients treated with alpha-interferon and in patients with secondary polycythaemia the difference in means did not reach statistical significance (P = 0.07 and P = 0.13, respectively). The groups of patients with MCV <80 fL and >/=80 fL both presented significant differences between means for calculated PCV and centrifuged haematocrit. CONCLUSIONS: If PV patients are monitored with blood cell counter calculated PCV it appears that the therapeutic goal should be to maintain the calculated PCV below 0.43, provided the local differences in calculated PCV and centrifuged haematocrit are of the same magnitude as in this study.
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| 2. |
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| 3. |
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| 4. |
- Barsoum, Zuheir, et al.
(författare)
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Fatigue Assessment of Cruciform Joints Welded with Different Methods
- 2006
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Ingår i: Steel Research International. - : Wiley. - 1611-3683. ; 77:12, s. 882-888
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Tidskriftsartikel (refereegranskat)abstract
- The advantages of the relatively new laser welding method are low welding distortions and high productivity, and it opens new opportunities for welding of steel structures in the automotive and heavy machinery industries. There is a need for understanding the fatigue strength and to develop fatigue design curves for laser welded joints. In this paper fatigue testing and weld quality of Hybrid Nd: YAG laser/MAG and MAG welded non-load carrying cruciform joints is examined. Four batches were produced, tested and the results were compared. The local weld geometry of the cruciform welded joints was measured and analysed. The measured parameters were used to calculate the stress concentration factors by implementing FE-models, in order to anticipate the influence of size of weld geometrical parameters on the stress concentrations. Residual stress measurement was carried out close to the toe region using the X-ray diffraction method and weld defects (cold laps) in the cracked specimens was measured.
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| 5. |
- Barsoum, Zuheir, et al.
(författare)
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Fatigue design of lightweight welded vehicle structures : Influence of material and production procedures
- 2012
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Ingår i: Proceedings of the Institution of mechanical engineers. Part B, journal of engineering manufacture. - : SAGE Publications. - 0954-4054 .- 2041-2975. ; 226:10, s. 1736-1744
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Tidskriftsartikel (refereegranskat)abstract
- Structural details and components in many types of products are continuously subjected to variable amplitude loading during operation. Fatigue loading and fatigue damage is thus the most common failure mode for the mentioned equipment in operation. The influence of the material grade, weld quality and fabrication procedure have a major impact on the structural durability of welded vehicle structures. The comprehensive research work within the Nordic research and development community have contained development of finite element modelling of complex structures, including crack growth in two- and three-dimensional fatigue testing of welded small-scale specimen and full-scale components, investigations of weld defects and flaws (e.g. cold laps) and weld roots. An important part of these projects is related to simulation and measurements of formation and relaxation of residual stresses. Within these projects three new quality systems, for welded and cast components and for cut edges, have been developed based on a scientific ground and a fitness for purpose design philosophy. Volvos new weld class system, which is an open standard, is now a base for the revision of the international weld quality system ISO 5817. In this article the major findings in these research activities are briefly presented and discussed.
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| 6. |
- Barsoum, Zuheir, 1978-
(författare)
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Residual Stress Analysis and Fatigue Assessment of Welded Steel Structures
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This doctoral thesis is concerned with fatigue life of welded structures. Several topics related to fatigue of welded structures are treated such as; weld defects and their influence on fatigue performance of welded structures, fatigue life prediction using LEFM (Linear Elastic Fracture Mechanics), fatigue testing, welding simulation, residual stress prediction and measurement and their influence on fatigue life. The work that is reported in this doctoral thesis is part results of the Nordic R&D project QFAB (Quality and Cost of Fabricated Advanced Welded Structures) and the Swedish R&D project LOST (Light Optimized Welded Structures). One of the main objectives is to compare different welding processes for the fatigue performance, weld quality and gain understanding of the weld defects, their appearance in different welding processes and their effect on fatigue life. Another main objective is to study welding residual stresses and their effect on fatigue. The design rules are in some cases conservative and especially on the weld root sides the knowledge about the residual stress field may improve the life prediction. The aim is to develop simplified procedures for analysis of residual stresses, their relaxation and influence on fatigue life. Fatigue testing of Hybrid Nd: YAG laser/MAG and MAG welded (tandem arc solid wire, flux cored wire, tandem flux cored wire) non-load carrying cruciform joints was carried out. Four batches were produced, tested and the results were compared. The local weld geometry of the cruciform welded joints was measured and analyzed. Residual stress measurement was carried out close to the toe region using X-ray diffraction. Weld defects, in most cases cold laps, in the cracked specimens were measured. Further fatigue testing, weld defect assessment and residual stress and local weld geometry measurements were carried out on joints welded with flux cored and metal cored arc wires. Two-and three dimensional LEFM crack growth analysis were carried out in order to predict the influence of weld defects, local weld geometry and residual stresses. Residual stresses in multi-pass welded tube-to-plates were studied for two different tubular joint configurations; a three-pass single-U weld groove for maximum weld penetration and a two-pass fillet (no groove) welded tube-to-plates for minimum weld penetration. Torsion fatigue tests were performed in order to study crack propagation from the weld root. Mode III propagation from the lower and upper weld toe on the same tubular joints was also studied. Some tubes were stress relieved (PWHT) and some were fatigue tested with internal static pressure. A three dimensional finite element welding simulation of the multi-pass welded tubular joint was carried out. The calculated temperatures in the transient thermal analysis were compared with measured temperatures. The FE predicted residual stresses in the as-welded conditions were verified with hole drilling strain gage measurements. The residual stresses were used as internal stresses in the finite element model for the torsion fatigue simulation in order to study the cycle by cycle relaxation of the residual stresses in constant amplitude torsion loading. A two dimensional finite element welding simulation procedure was developed in order to predict welding residual stress. The predicted residual stresses were used together with a developed 2D LEFM subroutine to predict the fatigue life, crack path and the effect of residual stresses on weld root defects. The developed simulation subroutines were validated with results found in the literature. Residual stresses measurement, two-and three dimensional welding simulations were carried out in fillet welded joints in order to study the three dimensional effects of the welding process, boundary conditions and modelling technique on the formation of residual stresses.
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| 7. |
- Barsoum, Zuheir, 1978-
(författare)
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Residual Stress Analysis and Fatigue of Welded Structures
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This licentiate thesis is generally concerned with the fatigue of welded structures. Several topics related to fatigue of welded structures are treated such as; weld defects and their influence on fatigue performance of welded structures, fatigue life prediction using LEFM (Linear Elastic Fracture Mechanics), fatigue testing, welding simulation, residual stress prediction and measurement and their influence on fatigue. The work that is reported in this thesis is a part result of a Nordic research project QFAB (Quality and Cost of Fabricated Advanced Welded Structures). One of the main objectives is to compare different welding processes in fatigue performance, weld quality and gain understanding of the weld defects, their appearance in different welding processes and their influence on fatigue life. Another main objective is to study welding residual stresses and their effect on fatigue. The design rules are in some cases conservative and especially on root sides the knowledge about the residual stress field may improve the life prediction. The aim is to develop simplified procedures for analysis of residual stresses, their relaxation and influence on fatigue life. In one study fatigue testing of Hybrid Nd: YAG laser/MAG and MAG welded (tandem arc solid wire, flux cored wire, tandem flux cored wire) non-load carrying cruciform joints was carried out. Four batches were produced, tested and the results were compared. The local weld geometry of the cruciform welded joints was measured and analyzed. Residual stress measurement was carried out close to the toe region using X-ray diffraction. Weld defects, in most cases cold laps, in the cracked specimens was measured. Residual stresses in multi-pass welded tube-to-plates were studied for two different tubular joint configurations; a three-pass single-U weld groove for maximum weld penetration and a two-pass fillet (no groove) welded tube-to-plates for minimum weld penetration. Torsion fatigue tests were performed in order to study crack propagation from the weld root. Mode III propagation from the lower and upper weld toe on the same tubular joints was also studied. Some tubes were stress relieved (PWHT) and some were fatigue tested with internal static pressure. A three dimensional finite element welding simulation of the 3 pass welded tubular joint was carried out. The calculated temperatures in the transient thermal analysis were compared with measured temperatures. The FE predicted residual stresses in the as-welded conditions were verified with hole drilling strain gage measurements. The residual stresses were used as internal stresses in the finite element model for the torsion fatigue simulation in order to study the cycle by cycle relaxation of the residual stresses in constant amplitude torsion loading.
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| 8. |
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| 9. |
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| 10. |
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| 11. |
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| 12. |
- Björkblad, Anders, 1963-
(författare)
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Fatigue Assessment of Cast Components : Influence of Cast Defects
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is on the fatigue assessment of cast components with special attention to defects. The primary material in view is nodular cast iron, but also cast steel is considered. However, the fatigue behaviour is in principle valid for general use on other cast metals.The first two papers is about general cast material behaviour in fatigue loading. The materials considered are a high strength alloyed cast steel and a medium strength nodular cast iron. It is concluded that cast defects is the main fatigue initiation cause and it is only in exception that the fatigue life is not ruled by fracture mechanics. The third paper is a fracture mechanics evaluation of a nodular iron cast sleeve. The analysis of the component is based on crack initiation from cast defects and low-cycle fatigue. Fracture mechanics material parameters for Paris law, c and m, are extracted for the materials considered. In paper D design quality rules for nodular cast iron based on the Swedish standard SS 11 40 60 is presented. The quality rules regard cast defects in fatigue assessments and facilitate defect-based component design. In paper E, a finite element tool that is capable to predict and calculate 3D crack propagation for embedded cracks and defects is presented. The tool is an add-on for ANSYS finite element program. In paper F, closure equations for nodular cast iron are proposed in parallel to refined fracture mechanics material data. The paper includes crack propagation at different load ratios and in different microstructures.Summarized, the thesis composes a further development of the fatigue assessment of cast components. The central role of defects in fatigue is clarified and tools are provided for fracture mechanics evaluations of defects as well as for defect based design. The quality rules are also fit for application in manufacturing and for acceptance tests, hence covering the span from design to complete product.
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| 13. |
- Byggnevi, Magnus, 1964-
(författare)
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LEFM analysis and fatigue testing of welded structures
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fatigue design of welded structures has always been important for construction equipment manufactures. The product development and manufacturing trends are reduction of lead time, cost and LCC. In manufacturing, improved quality assurance system and automated weld processes will reduce scatter and improve the possibilities for lighter structures with improved performance. At present most fatigue analysis is done using the nominal stress method or by structural testing, sometimes with improved concepts as structural stress or effective notch stress. In this thesis methods for fatigue life assessment, with higher accuracy, have been evaluated on frame structures. The main objectives in this thesis is to investigate the utility of LEFM in fatigue assessment of typical welded structures in construction equipment; to verify the accuracy of LEFM with results from fatigue testing of a complex welded structure and to achieve an better understanding of parameters that influence on crack propagation. The purpose was also to compare different fatigue assessment methods, this has been done to some extent but main part of the work has been on LEFM. An investigation of the accuracy and efforts in connection with different life prediction methods of welded joints in a complex structure has been done. The investigated structure was a frame to a wheel loader. The life prediction was performed with nominal stress, structural stress, effective notch stress and LEFM. The investigations show a lot of scatter in predicted life for the different methods. Fatigue analysis and testing of a welded frame has been performed and discussed. The structure contained typical welds for a frame to a wheel loader. A service load spectrum with an overall stress ratio, R, of about -1 was used. The test results were correlated with LEFM including different assumptions of residual stress distributions. In literature survey information useful in fatigue crack propagation analysis are compiled. The disussed concepts are crack closure, threshold values, crack growth material parameters, mixed mode conditions, variable amplitudes, small cracks and residual stresses.
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| 14. |
- Hamberg, Kenneth, 1949, et al.
(författare)
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Fatigue Crack Growth in Ductile Iron
- 2005
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Ingår i: Component Design by Castings, VTT Symposium 237. - 9513862984
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Konferensbidrag (refereegranskat)
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| 15. |
- Jonsson, B., et al.
(författare)
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DEVELOPMENT OF WELD QUALITY CRITERIA BASED ON FATIGUE PERFORMANCE
- 2011
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Ingår i: Welding in the World. - 0043-2288 .- 1878-6669. ; 55:11-12, s. 79-88
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Tidskriftsartikel (refereegranskat)abstract
- Historically, production technology researchers and structural design researchers have had only limited dialogue and each group has focused on their own narrow field of interest. This has led to inconsistencies in the definition of so-called "weld class systems" which have been primarily developed based on concepts related to good workmanship but have little or no relation to the actual performance of the welded structure. Additionally, some of the quality measures in existing systems are qualitative and, thus, subjective. In recent years, Commission XIII of the International Institute of Welding (IIW) has been promoting research and developing the technical background needed to develop a weld quality guideline which quantitatively relates weld acceptance criteria to the expected structural performance (primarily fatigue strength). A new weld class system with this same objective has recently been developed as a Volvo Group Standard. This system is described in this paper. The new standard has three quality levels for fatigue; as-welded normal quality, as-welded high quality and post-weld treated quality. It contains acceptance limits which are consistent with the expected fatigue strength and which can more objectively handle revisions. This new system will help in the development of new structures with lower weight and increased reliability.
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| 16. |
- Martinsson, Johan, 1974-
(författare)
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Fatigue assessment of complex welded steel structures
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- To improve the usage of material in fatigue loaded complex welded structures a better calculation method (based on FEA) is needed than what is available on the market and an improved management of weld quality. Improved FE-procedures are directly applicable to design of generic structural components within virtually all industries using CAD and FEtools, irrespective of industrial sector. More and more welded structures are created as 3D models from the design offices and the FE-work will be easier but the requirement of being accurate from the beginning and the reduction of lead times create a great need to substantially reduce calculation time. The main objectives in this thesis is to develop novel procedures to extract design data from finite element stress analyses of complex fatigue loaded welded structures, to achieve a better understanding of the limits of the different fatigue design methods and to investigate the influence of fatigue strength due to the weld quality. An investigation of how weld geometry and different type of defects influence fatigue life of the weld has been made on a non-load carrying cruciform joint. The weld geometries were measured and the stress distributions were computed using FEA. Fatigue tests have been performed and the initial defects were analysed. Life predictions with LEFM based on the stress distributions and defects were performed with good agreement with the test results. The different fatigue design methods Nominal stress, Structural stress, Effective Notch stress and LEFM proposed by the International Institute of Welding (IIW) have been investigated and applied on a welded link. In order to verify the accuracy of the prediction methods, fatigue tests of the link were made. Structural optimisations based FEA, using different objectives regarding the fatigue properties of the welded link were also carried out to increase the performance of the link. Comparison and investigations of the advantages and disadvantage of the two different LEFM approaches, weight function technique and FEA solutions is made on welded structures. Based on the conclusions of the investigations an automatic 3D FE based LEFM program was developed. The program was successfully implemented and verified on two welded structures.
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| 17. |
- Palmblad, Jan, et al.
(författare)
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TPO, but not soluble-IL-6 receptor, levels increase after anagrelide treatment of thrombocythemia in chronic myeloproliferative disorders
- 2008
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Ingår i: International Journal of Medical Sciences. - Lake Haven : Ivyspring international publishers. - 1449-1907. ; 5:2, s. 87-91
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Tidskriftsartikel (refereegranskat)abstract
- Anagrelide is often used in the treatment of thrombocythemia in myeloproliferative disease (MPD), but information concerning effects of treatment on cytokines involved in regulation of blood platelet levels is limited. Here, we investigated serum levels of thrombopoietin (TPO) and soluble IL-6 receptor (sIL-6R) in relation to response to treatment with and plasma concentrations of anagrelide. Samples from 45 patients with thrombocythemia due to MPD (ET=31, PV=14), being treated with anagrelide for 6 months, were analyzed for TPO, sIL-6R and anagrelide levels. The mean baseline platelet count was 983x10(9)/L. A reduction of platelets to <600 in asymptomatic or <400 x 10(9)/L in symptomatic patients was defined as a complete remission (CR), a reduction with >50% of baseline as partial remission, and <50% reduction as failure. At 6 months, 35 patients were in CR, 1 had a partial remission and 9 were treatment failures. For all patients, there was an increase in TPO of 44% from baseline; this change was more pronounced for patients with partial remission and failure. sIL-6R levels did not change significantly. There was no correlation between levels of anagrelide and cytokine levels at 6 months, and changes of cytokine levels did not relate to changes of platelet counts. Thus, a pronounced increase of TPO levels after 6 months of anagrelide treatment indicated that this treatment affected a major regulatory mechanism for megakaryocyte and platelet formation in MPD.
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| 18. |
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| 19. |
- Samuelsson, Jenny
(författare)
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På väg från ingenstans : kritik och emancipation av kunskapsorganisation för feministisk forskning
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This study deals with knowledge organization of feminist research, in bibliographic catalogues and in a Swedish context. The thesis develops a definition of feminist discourse which incorporates but is not limited to feminist research. Feminist research, in turn, is understood as articulating a critical approach aimed at critiquing and changing inequitable gender relations. The thesis analyzes the meaning of a range of feminist perspectives through a close text analysis of feminist PhD-dissertations. Two universal knowledge organization systems: Svenska ämnesord and Klassifikationssystem för svenska bibliotek; and one subject-specific system: Kvinnohistoriska samlingarnas ämnesord, are studied in order to discuss the extent to which they are able to articulate feminist perspectives, as well as how they actually articulate such perspectives in practice. The two universal systems studied tend to marginalize feminist perspectives as forms of knowledge. This thesis interprets this marginalization in the light of these systems’ putative objectivistic and universalistic epistemology and ontology. It is suggested that they privilege disciplinary knowledge over interdisciplinary knowledge forms, and substantive topics over conceptual perspectives. Guidelines for knowledge organizatory practice tend to encourage indexers and classifiers to search for central substantive themes. In this schema, feminism is understood as a field relating to socio-political women’s issues. Feminist knowledge qua knowledge is marginalized by the systems studied, and is at times given a plain wrong classifycation. further, this thesis suggests that the subject-specific knowledge organization system studied: Kvinnohistoriska samlingarnas ämnesord, is only able to deal with feminist research in an incomplete and inadequate way. Although this index is designed to classify texts within the broad subject field of: women’s studies, masculinity studies and gender research, as well as other material relevant to the field, the structure of the index is too simple and does not allow for associative relationships between terms; nor does it define feminist discourse. The premises and guidelines for knowledge organization practice are also under-developed or not well defined. Successful organization of feminist knowledge needs instead to be based on a particular understanding of knowledge and knowledge organization as contextually shaped (and shaping). Feminist literature is first and foremost about expressing feminist discourse qua theme, perspective, and part of the feminist tradition (such as critical, women-centring, and reflexive feminisms) – an observation that needs to be reflected in the knowledge organization.
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| 20. |
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| 21. |
- Samuelsson, Jack, et al.
(författare)
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Service fatigue design of complex welded construction equipment
- 2008
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Ingår i: Materialwissenschaft und Werkstofftechnik. - : Wiley. - 0933-5137 .- 1521-4052. ; 39:10, s. 734-739
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Tidskriftsartikel (refereegranskat)abstract
- Many steel structures and components are fabricated from steel plates and steel castings. The dominating joining method is welding for all kinds of transport vehicles and this paper describes briefly main problems in connection with design and fabrication of fatigue loaded structures. Design and fabrication has developed during the last 30 years and today we have tools, methods and knowledge to produce more optimised structures. Some of the work has been performed as joint work within Nordic projects and within IIW (International Institute of Welding). FE-modelling, improved design rules, knowledge about influence from defects and residual stresses, new manufacturing methods and scientific based weld quality rules are briefly discussed in this paper.
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| 22. |
- Ventorp, Filip, et al.
(författare)
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The CD44 ligand hyaluronic acid is elevated in the cerebrospinal fluid of suicide attempters and is associated with increased blood-brain barrier permeability.
- 2016
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Ingår i: Journal of Affective Disorders. - : Elsevier BV. - 1573-2517 .- 0165-0327. ; 193, s. 349-354
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Tidskriftsartikel (refereegranskat)abstract
- The glycosaminoglycan hyaluronic acid (HA) is an important component of the extracellular matrix (ECM) in the brain. CD44 is a cell adhesion molecule that binds to HA in the ECM and is present on astrocytes, microglia and certain neurons. Cell adhesion molecules have been reported to be involved in anxiety and mood disorders. CD44 levels are decreased in the cerebrospinal fluid (CSF) of depressed individuals, and the CD44 gene has been identified in brain GWAS studies as a possible risk gene for suicidal behavior.
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