| 1. |
|
|
| 2. |
- Isaksson, Per, et al.
(författare)
-
Crack kinking under high pressure in an elastic-plastic material
- 2001
-
Ingår i: International Journal of Fracture. - 0376-9429 .- 1573-2673. ; 108:4, s. 351-366
-
Tidskriftsartikel (refereegranskat)abstract
- Directional crack growth criteria in compressed elastic–plastic materials are considered. The conditions at the crack tip are evaluated for a straight stationary crack. Remote load is a combined hydrostatic stress and pure shear, applied via a boundary layer assuming small scale yielding. Strains and deformations are assumed to be small. Different candidates for crack path criteria are examined. Maximum non-negative hoop stress to judge the risk of mode I and maximum shear stress for mode II extension of the crack are examined in some detail. Crack surfaces in contact are assumed to develop Coulumb friction from the very beginning. Hence, a condition of slip occurs throughout the crack faces. The plane in which the crack extends is calculated using a finite element method. Slip-line solutions are derived for comparison with the numerically computed asymptotic field. An excellent agreement between numerical and analytical solutions is found. The agreement is good in the region from the crack tip to around halfway to the elastic–plastic boundary. The relation between friction stress and yield stress is varied. The crack is found to extend in a direction straight ahead in shear mode for sufficiently high compressive pressure. At a limit pressure a kink is formed at a finite angle to the crack plane. For lower pressures the crack extends via a kink forming an angle to the parent crack plane that increases with decreasing pressure.
|
|
| 3. |
- Isaksson, Per, et al.
(författare)
-
Directional crack path criterion for crack growth in ductile materials subjected to shear and compressive loading under plane strain conditions
- 2003
-
Ingår i: International Journal of Solids and Structures. - 0020-7683 .- 1879-2146. ; 40:13-14, s. 3523-3536
-
Tidskriftsartikel (refereegranskat)abstract
- A directional crack growth criterion in a compressed elastic perfectly plastic material is considered. The conditions at the crack-tip are evaluated for a straight stationary crack with a small incipient kink. Remote load is a combined hydrostatic pressure and pure shear applied via a boundary layer. Crack surfaces in contact are assumed to develop homogenous Coulomb friction. The crack opening displacement of an extended kink is examined in a finite element analysis to judge the risk of opening mode failure. It has been found that the direction that maximizes the crack opening displacement of an extended kink tip coincides very well with a prediction of the crack growth direction obtained by using a criterion for continued crack growth direction discussed by the authors elsewhere [Int. J. Fract. 108 (2001) 351]. Moreover, the by the model predicted incipient crack growth directions are qualitatively comparable with reported crack paths obtained in ductile materials in a limited number of experiments performed under a combined load of inplane shear and compression.
|
|
| 4. |
- Isaksson, Per, et al.
(författare)
-
Mechanics of control element during irradiation
- 1997
-
Ingår i: Structural mechanics in reactor technology : transactions of the 14th International Conference on Structural Mechanics in Reactor Technology, Lyon, France, August 17-22, 1997. - [Gif-sur-Yvette] : SMiRT 97.
-
Konferensbidrag (refereegranskat)
|
|
| 5. |
- Isaksson, Per, et al.
(författare)
-
Mode II crack paths under compression in brittle solids : A theory and experimental comparison
- 2002
-
Ingår i: International Journal of Solids and Structures. - 0020-7683 .- 1879-2146. ; 39:8, s. 2281-2297
-
Tidskriftsartikel (refereegranskat)abstract
- A study of crack propagation paths in the situation where the crack is suppressed to open during growth due to high compressive forces has been performed. This problem was analyzed theoretically very recently by the authors and is here extended to involve a limited number of illustrative experimental results reported elsewhere in the literature. By analyzing the experimental crack growth patterns, the conclusion is that the model cannot describe the more realistic microscopic failure in detail. Since shear crack growth on the microscale strongly depend on inhomogenities in the material, like cavities, grains or inclusions; the closed crack growth patterns observed are not smooth or free of kinks. Nevertheless, the model show good agreement with the reported experimental observations of the paths of closed macroscopic mode II cracks on samples in brittle materials, induced under overall compression. Failure patterns experimentally observed supports the theory that the growth of mode II cracks under compression in brittle materials follow a propagation path described by a function y ¼ kxb, where b ¼ 3=2. This is strongly supported by the measured values obtained from various experiments. In all the studied experiments, the exponent b was found in the interval [1.43–1.58]. Further, an investigation of the curvature parameter k has been performed and the conclusion is that k does also agree with the simplified model, even though not as good as the exponent b. However, k differs in general <15% from the theoretical value predicted by the model. The process of crack growth is in the simplified model assumed to be controlled by the mode II stress intensity factor KII of the main crack and the difference between the compressive remote normal stress parallel with the crack plane (r111) and the compressive remote normal stress perpendicular to the crack plane (r122).
|
|
| 6. |
- Isaksson, Per, et al.
(författare)
-
Prediction of shear crack growth direction under compressive loading and plane strain conditions
- 2002
-
Ingår i: International Journal of Fracture. - 0376-9429 .- 1573-2673. ; 113:2, s. 175-194
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract. A directional crack growth prediction in a compressed homogenous elastic isotropic material under plane strain conditions is considered. The conditions at the parent crack tip are evaluated for a straight stationary crack. Remote load is a combined biaxial compressive normal stress and pure shear. Crack surfaces are assumed to be frictionless and to remain closed during the kink formation wherefore the mode I stress intensity factor KI is vanishing. Hence the mode II stress intensity factor KII remains as the single stress intensity variable for the kinked crack. An expression for the local mode II stress intensity factor k2 at the tip of a straight kink has been calculated numerically with an integral equation using the solution scheme proposed by Lo (1978) and refined by He and Hutchinson (1989). The confidence of the solution is strengthened by verifications with a boundary element method and by particular analytical solutions. The expression has been found as a function of the mode II stress intensity factor KII of the parent crack, the direction and length of the kink, and the difference between the remote compressive normal stresses perpendicular to, and parallel with, the plane of the parent crack. Based on the expression, initial crack growth directions have been suggested. At a sufficiently high non-isotropic compressive normal stress, so that the crack remains closed, the crack is predicted to extend along a curved path that maximizes the mode II stress intensity factor k2. Only at an isotropic remote compressive normal stress the crack will continue straight ahead without change of the direction. Further, an analysis of the shape of the crack path has revealed that the propagation path is, according the model, required to be described by a function y = cxγ , where the exponent γ is equal to 3/2. In that case, when γ = 3/2, predicts the analytical model a propagation path that is selfsimilar (i.e. the curvature c is independent of any length of a crack extension), and which can be described by a function of only the mode II stress intensity factor KII at the parent crack tip and the difference between the remote compressive normal stress perpendicular to, and parallel with, the parent crack plane. Comparisons with curved shear cracks in brittle materials reported in literature provide limited support for the model discussed.
|
|
| 7. |
- Massih, Ali R, et al.
(författare)
-
Modelling the behaviour of a control-element blade during irradiation
- 1997
-
Ingår i: Computers & Structures. ; 64:5-6, s. 1113-1127
-
Konferensbidrag (refereegranskat)abstract
- The control-rod elements in a boiling-water reactor contain natural boron carbide (B4C) powder, used as neutron-absorber material and clad in stainless-steel blades. During in-reactor service, the internal production of helium gas and point defects in neutron-irradiated boron carbide cause swelling which can induce significant contact stresses in the blade causing, eventually, stress-corrosion cracking of the blades. In this work, a finite-element analysis of a control-rod blade consisting of B4C powder and stainless-steel cladding has been performed using ADINA. An algorithm for the finite-element calculation of a porous material such as B4C powder has been developed and which models both swelling and consolidation behaviour of B4C powder. The Drucker-Prager constitutive law has been used to model the consolidation effect. The model has been verified with an analytical solution for a simple geometry. A number of cases with B4C powder in contact with stainless steel and using the actual blade design have been studied for which contact stresses, the displacements and the effective stresses are calculated. Finally, the model has been used to predict the deformation of the blade during irradiation under B4C swelling and irradiation-induced creep of stainless steel.
|
|
| 8. |
- Nilsson, Per, et al.
(författare)
-
Plastic mechanisms during fast brittle fracture
- 1995
-
Ingår i: Current topics in computational mechanics. - New York : American Society of Mechanical Engineers. - 0791813363 ; , s. 69-72
-
Konferensbidrag (refereegranskat)abstract
- Careful studies of cleavage fracture surfaces show that parts of the surface consist of plastically formed ridges, presumably traces of plastically collapsed ligaments. These ligaments are assumed to be formed between the cleavage fractured areas. The collapse process of these ligaments is numerically examined. A finite element method and an asymptotic analysis are employed. The results shows that relatively large amounts of energy are consumed in this process and that the energy consumption is increasing rapidly with increasing crack tip speed. The implications for slow stable crack tip speeds at dynamic fracture are discussed.
|
|
| 9. |
- Ståhle, Per, et al.
(författare)
-
Slack Edges of Paper
- 2006
-
Ingår i: Euromech Colloquium.
-
Konferensbidrag (refereegranskat)
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
- Ahlsson, Anders, 1962-, et al.
(författare)
-
A Swedish consensus on the surgical treatment of concomitant atrial fibrillation
- 2012
-
Ingår i: Scandinavian Cardiovascular Journal. - London, United Kingdom : Informa Healthcare. - 1401-7431 .- 1651-2006. ; 46:4, s. 212-218
-
Forskningsöversikt (refereegranskat)abstract
- Atrial fibrillation (AF) is a common arrhythmia among patients scheduled for open heart surgery and is associated with increased morbidity and mortality. According to international guidelines, symptomatic and selected asymptomatic patients should be offered concomitant surgical AF ablation in conjunction with valvular or coronary surgery. The gold standard in AF surgery is the Cox Maze III ("cut-and-sew") procedure, with surgical incisions in both atria according to a specified pattern, in order to prevent AF reentry circuits from developing. Over 90% of patients treated with the Cox Maze III procedure are free of AF after 1 year. Recent developments in ablation technology have introduced several energy sources capable of creating nonconducting atrial wall lesions. In addition, simplified lesion patterns have been suggested, but results with these techniques have been unsatisfactory. There is a clear need for standardization in AF surgery. The Swedish Arrhythmia Surgery Group, represented by surgeons from all Swedish units for cardiothoracic surgery, has therefore reached a consensus on surgical treatment of concomitant AF. This consensus emphasizes adherence to the lesion pattern in the Cox Maze III procedure and the use of biatrial lesions in nonparoxysmal AF.
|
|
| 13. |
- ALI, ABDALLAH SHOKRY MAHMOUD, et al.
(författare)
-
A Superposition Procedure for Calculation of Effective Diffusion and Elastic Parameters of Sparsely Porous Materials
- 2017
-
Ingår i: Transport in Porous Media. - : Springer Science and Business Media LLC. - 0169-3913 .- 1573-1634. ; 118:3, s. 473-494
-
Tidskriftsartikel (refereegranskat)abstract
- Effective material parameters for diffusion and elastic deformation are calculatedfor porous materials using a continuum theory-based superposition procedure. The theory that is limited to two-dimensional cases, requires that the pores are sufficiently sparse. The methodleads to simple manual calculations that can be performed by, e.g. hospital staff at clinicaldiagnoses of bone deceases that involve increasing levels of porosity. An advantage is that theresult relates to the bone material permeability and stiffness instead of merely pore densities.The procedure uses precalculated pore shape factors and exact size scaling. The remainingcalculations do not require any knowledge of the underlying field methods that are used tocompute the shape factors. The paper establishes the upper limit for the pore densities that aresufficiently sparse. A cross section of bovine bone is taken as an example. The superpositionprocedure is evaluated against a full scale finite element calculation. The study compares thepore induced change of the diffusion coefficient and elastic modulus. The predictions differbetween superposition and full scale calculations with 0.3% points when pore contributionto the diffusion constant is 3–7%, and 0.7% points when the pore contribution to the modulusof elasticity is 4.5–5%. It is uncertain if the error is in the superposition method, which isexact for small pore densities, while the full scale finite model is not.
|
|
| 14. |
- Andersson, P., et al.
(författare)
-
Shielding effects and dislocation repositioning at cleavage crack growth
- 1996
-
Ingår i: Mechanisms and mechanics of damage and failure. - : EMAS. - 0947817905 ; , s. 419-424
-
Konferensbidrag (refereegranskat)abstract
- The motion of pre-existing edge dislocations in an infinite linear elastic body is studied. Motion, is due to a quasi-statically steady-state growing crack. In the model, the dislocations glide if the force on the dislocation exceeds a critical value. Obtained results are changes in dislocation density, the shielding effect on the crack tip and residual stresses. The model is applied to an isotropic material. The residual stress far behind the crack tip is tensile near the crack, decreasing to zero at a certain distance above the crack plane. The indication is that the shielding effect may be considerable
|
|
| 15. |
- Andersson, P., et al.
(författare)
-
Shielding effects and residual stresses at cleavage due to pre-existing dislocations
- 1997
-
Ingår i: International Journal of Fracture. - 0376-9429 .- 1573-2673. ; 85:4, s. 365-380
-
Tidskriftsartikel (refereegranskat)abstract
- The motion of pre-existing edge dislocations in an infinite linear elastic body is studied at initiation of crack growth and at quasi-static steady-state crack growth. Dislocation nucleation is assumed not to occur. Thus, the study concerns only dislocations that are present in the virgin material. A dislocation is assumed to glide if its driving force exceeds a critical value. Changes in dislocation density, crack tip shielding and residual stresses are obtained. The shielding of a stationary crack tip is found to be small compared with the shielding of a growing crack tip. At steady-state the residual stresses far behind the crack tip are tensile near the crack, decreasing to zero at a certain distance from the crack plane. It is shown that the shielding due to pre-existing dislocations, e.g., for cleavage in α-iron crystals may be considerable.
|
|
| 16. |
- Andreasson, Eskil, et al.
(författare)
-
Micro-mechanisms of a laminated packaging material during fracture
- 2014
-
Ingår i: Engineering Fracture Mechanics. - : Elsevier BV. - 1873-7315 .- 0013-7944. ; 127, s. 313-326
-
Tidskriftsartikel (refereegranskat)abstract
- The micro-mechanisms of fracture in a laminate composed of an aluminium foil and a polymer film are considered in this study. The laminates as well as the individual layers, with and without premade centre-cracks, were tensile tested. Visual inspection of the broken cross-sections shows that failure occurs through localised plasticity. This leads to a decreasing and eventually vanishing cross-section ahead of the crack tip for both the laminate and their single constituent layers. Experimental results are examined and analysed using a slip-line theory to derive the work of failure. An accurate prediction was made for the aluminium foil and for the laminate but not for the freestanding polymer film. The reason seems to be that the polymer material switches to non-localised plastic deformation with significant strain-hardening. (C) 2014 Elsevier Ltd. All rights reserved.
|
|
| 17. |
- Banks-Sills, Leslie, et al.
(författare)
-
Strain Driven Transport for Bone Modeling at the Periosteal Surface
- 2011
-
Ingår i: Mathematical Biosciences. - : Elsevier. - 0025-5564 .- 1879-3134. ; 230:1, s. 37-44
-
Tidskriftsartikel (refereegranskat)abstract
- Bone modeling and remodeling has been the subject of extensive experimental studies. There have been several mathematical models proposed to explain the observed behavior, as well. A different approach is taken here in which the bone is treated from a macroscopic view point. In this investigation, a one-dimensional analytical model is used to shed light on the factors which play the greatest role in modeling or growth of cortical bone at the periosteal surface. It is presumed that bone growth is promoted when increased amounts of bone nutrients, such as nitric oxide synthase (NOS) or messenger molecules, such as prostaglandin E2 (PGE2), seep out to the periosteal surface of cortical bone and are absorbed by osteoblasts. The transport of the bone nutrients is assumed to be a strain controlled process. Equations for the flux of these nutrients are written for a one-dimensional model of a long bone. The obtained partial differential equation is linearized and solved analytically. Based upon the seepage of nutrients out of the bone, the effect of loading frequency, number of cycles and strain level is examined for several experiments that were found in the literature. It is seen that bone nutrient seepage is greatest on the tensile side of the bone; this location coincides with the greatest amount of bone modeling
|
|
| 18. |
- Bind, A. K., et al.
(författare)
-
Influence of loading rate and hydrogen content on fracture toughness of Zr-2.5Nb pressure tube material
- 2015
-
Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115. ; 465, s. 177-188
-
Tidskriftsartikel (refereegranskat)abstract
- For the safety assessment of PHWR, it is required to study the flaw tolerance capacity of the pressure tubes as a function of the loading rate. In this work, the effect of loading rate and hydrogen content on the fracture behaviour of a Zr-2.5Nb alloy pressure tube was investigated between 25 and 300 degrees C. For the as received material, the pulling rate only had an effect on fracture toughness at 25 degrees C whereas for. hydrided material the pulling rate affected fracture toughness in the transition regime. For all pulling rates, hydrided materials showed typical S curve behavior with an increase in lower shelf, upper shelf and transition temperature with pulling rate. The number of axial splits on fracture surfaces increased with an increase in the pulling rate and a decrease in temperature and fracture toughness was found to decrease with an increase in the number of axial splits. The reduction in fracture toughness is attributed to a localised deformation between axial splits. (C) 2015 Elsevier B.V. All rights reserved.
|
|
| 19. |
- Bjerkén, Christina, et al.
(författare)
-
Branching of growing corrosion fatigue cracks
- 2005
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Strain-driven corrosion of branching cracks, initiated from a virtually plane surface, has been studied using a moving boundary technique. The material is assumed linear elastic and is subjected to fatigue loading under plain strain conditions. The surface of the material is covered by a protective film. During loading this film can be damaged if it is strained above a threshold value, thus revealing an unprotected surface. Corrosion advances by material dissolution, eventually evolving into cracks. The rate of surface evolution is a function of the degree of protective film damage. During unloading the protective film is assumed to develop and heal the surface. A low frequency cyclic loading is applied to ensure that total healing is assumed. The moving boundary technique, simulating corrosion, results in arc-shaped crack tips, rather than singular crack tip points, thus no crack growth criterion is needed in the analysis. For each load step, the strain distribution is found using the finite element method, followed by required the movement the boundary and then remeshing. The crack growth has been investigated for at least 2000 cycles. A more or less pronounced branching of the cracks is found to develop. The crack branches can be classified in three groups; main cracks that grows with maximum rate and branches further, branch cracks that initially retards and then find a steady state growth rate that is a fraction of maximum speed, and finally, arresting cracks that after a period of retardation stop growing. The crack patterns are realistic, showing a sort of self-similarity with tree-like structure, cf. the picture below that shows a typical finite element result. The width of a crack branch together with the shielding from the applied stresses, caused by the other branches and main cracks, seem to govern the evolution of the crack branch. A steady-state growth rate is achieved during parts of the evolution as the crack width and the strain field surrounding the crack tip is in balance, i.e. the crack widens while the crack grows longer. As the bluntness of the tip reaches an upper limit, branching results.
|
|
| 20. |
- Bjerkén, Christina, et al.
(författare)
-
Fracture Mechanisms of a Thin Elastic Plastic Laminate
- 2006
-
Konferensbidrag (refereegranskat)abstract
- The fracture toughness of a polymer-metal laminate composite is obtained by mechanical testing of a specimen containing a pre-crack. The laminate is a material used for packaging. It consists of a thin aluminium foil and a polymer coating. A centre cracked panel test geometry is used. Each of the layers forming the laminate is also tested separately. The result is compared with the measured fracture strength of the individual layers. It is observed that the load carrying capacity increases dramatically for the laminate. At the strain when peak load is reached for the laminate only aluminium is expected to carry any substantial load because of the low stiffness of the LDPE. However, the strength of the laminate is almost twice the strength of the aluminium foil. The reason seems to be that the aluminium forces the polymer to absorb large quantities of energy at small nominal strain. The toughness compares well with the accumulated toughness of all involved layers. Possible fracture of the interface between the layers is discussed.
|
|
| 21. |
|
|
| 22. |
- Bjerkén, Christina, et al.
(författare)
-
Simulation of corrosion fatigue crack growth under mixed-mode loading
- 2008
-
Ingår i: Engineering Fracture Mechanics. - : Elsevier BV. - 1873-7315 .- 0013-7944. ; 75:3-4, s. 440-451
-
Tidskriftsartikel (refereegranskat)abstract
- The kinking of a corrosion crack due to mixed-mode fatigue loading is studied using an adaptive finite element procedure. The rate of material dissolution is assumed to be proportional to the stretching of the corroding surface. The dissolution of material is governed by a corrosion law, where no criterion is needed for neither crack growth nor growth direction. The problem is treated as a general moving boundary problem. The kink angles are found to be in very good agreement with results for sharp cracks using criteria reported in the literature.
|
|
| 23. |
- Bjerkén, Christina, et al.
(författare)
-
The path of a growing crack - A simulation of the fracture process
- 2006
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The growth of a crack subjected to corrosion fatigue is studied using adaptive finite elements. The crack is the image of a deep corrosion pit, and the growth is the result of a repeated cycle of dissolution of the material, formation of a protective oxide film and break-down of the oxide film. The break-down of the film is governed by the strain at the surface and the dissolution rate is assumed to be proportional to this stretching. A threshold strain is assumed to exist below which the oxide film remains intact. With this model, no criterion is needed, neither for crack growth, nor for prediction of the growth direction. The reason is that both are immediate results of the evolution of the body shape. The growth of a semi-infinite crack lying in an infinite strip subjected to different degrees of mixed-mode loading is studied and the results are compared to crack path criteria for sharp cracks. Additionally, the path of a corrosion fatigue crack starting at the surface of an elastic layer attached to a stiff substrate is simulated. The result showed some agreement with experimental results found in the literature.
|
|
| 24. |
|
|
| 25. |
|
|
| 26. |
- Djureinovic, Dijana, et al.
(författare)
-
Multiplex plasma protein profiling identifies novel markers to discriminate patients with adenocarcinoma of the lung
- 2019
-
Ingår i: BMC Cancer. - : Springer Science and Business Media LLC. - 1471-2407. ; 19
-
Tidskriftsartikel (refereegranskat)abstract
- Background:The overall prognosis of non-small cell lung cancer (NSCLC) is poor, and currently only patients with localized disease are potentially curable. Therefore, preferably non-invasively determined biomarkers that detect NSCLC patients at early stages of the disease are of high clinical relevance. The aim of this study was to identify and validate novel protein markers in plasma using the highly sensitive DNA-assisted multiplex proximity extension assay (PEA) to discriminate NSCLC from other lung diseases. Methods:Plasma samples were collected from a total of 343 patients who underwent surgical resection for different lung diseases, including 144 patients with lung adenocarcinoma (LAC),68 patients with non-malignant lung disease, 83 with lung metastasis of colorectal cancers and 48 patients with typical carcinoid. One microliter of plasma was analyzed using PEA, allowing detection and quantification of 92 established cancer related proteins. The concentrations of the plasma proteins were compared between disease groups.Results:The comparison between LAC and benign samples revealed significantly different plasma levels for four proteins; CXL17, CEACAM5, VEGFR2 and ERBB3 (adjusted p-value < 0.05). A multi-parameter classifier was developed to discriminate between samples from LAC patients and from patients with non-malignant lung conditions. With a bootstrap aggregated decision tree algorithm (TreeBagger) a sensitivity of 93% and specificity of 64% was achieved to detect LAC in this risk population. Conclusion:By applying the highly sensitive PEA, reliable protein profiles could be determined in microliter amounts of plasma. We further identified proteins that demonstrated different plasma concentration in defined disease groups and developed a signature that holds potential to be included in a screening assay for early lung cancer detection.
|
|
| 27. |
|
|
| 28. |
- Grann, Martin, et al.
(författare)
-
Methodological development : structured outcome assessment and community risk monitoring (SORM)
- 2005
-
Ingår i: International Journal of Law and Psychiatry. - : Elsevier BV. - 0160-2527 .- 1873-6386. ; 28:4, s. 442-456
-
Tidskriftsartikel (refereegranskat)abstract
- This paper describes an effort to develop a clinical tool for the continuous monitoring of risk for violence in forensic mental health clients who have left their institutions and who are dwelling in the community on a conditional release basis. The model is called Structured Outcome Assessment and Community Risk Monitoring (SORM). The SORM consists of 30 dynamic factors and each factor in SORM is assessed in two ways: The current absence, presence or partial och intermittent presence of the factors, which is an actuarial (systematized and 'objective') assessment. Secondly, the risk effect, i.e. whether the presence/absence of factors currently increases, decreases or is perceived as unrelated to violence risk, is a clinical (or impressionistic) assessment. Thus, the factors considered via the SORM can be coded as risk factors or protective factors (or as factors unimportant to risk of violence) depending on circumstances that apply in the individual case. Further, the SORM has a built-in module for gathering idiographical information about risk-affecting contextual factors. The use of the SORM and its potential as a risk monitoring instrument is illustrated via preliminary data and case vignettes from an ongoing multicenter project. In this research project, patients leaving any of the 9 participating forensic hospitals in Sweden is assessed at release on a variety of static background factors, and the SORM is then administered every 30 days for 2 years.
|
|
| 29. |
- Hejman, Ulf, et al.
(författare)
-
Experiment and simulation of a crack growing by material dissolution
- 2007
-
Ingår i: Abstracts 1st Bertram Broberg symposium on mechanics of materials;1.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Crack growth and crack path under a fracture mechanical experiment in polycarbonate is studied. The material, a polycarbonate, is photo elastic witch makes it possible to do an optical stress field analysis. The crack path and crack branching is also predicted by an adaptive finite element analysis. The crack growth is a result of stress induced, chemically activated material dissolution that completely determines the geometry of the specimen, including the shape and length of the crack. In this case, the mechanisms and processes leading to crack growth are assumed to be incorporated in a general material dissolution process. As a consequence of this assumption there is no need for a crack criterion or crack path hypothesis. The lack of crack path criterion imposes an arbitrary length scale where the crack width scales with the square of the applied load but the crack growth rate is independent of the load. Numerical calculations suggest that the crack is capable of branching and that the branches will continue to grow at the same rate as the original crack. The numerical results are verified by the photo elastic experiments and a reasonable agreement is established.
|
|
| 30. |
- Hejman, Ulf, et al.
(författare)
-
Experiment och simulering av materialupplösningsspricka
- 2007
-
Ingår i: Abstracts Svenska mekanikdagarna, Luleå, Sweden. - : Luleå tekniska universitet.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Sprickväg och sprickgrening studeras under brottmekaniska experiment i polykarbonat. Detta material är spänningsoptiskt och fotoelastiska analyser utförs. Sprickväg och sprickgrening beräknas också med hjälp av en adaptiv finit element-metod. Spricktillväxten är ett resultat av spänningsunderstödd, kemiskt eller biologiskt aktiverad, materialupplösning, som helt bestämmer provkroppens geometri inklusive sprickans form och längd. På så sätt är de processer som leder till sprickpropagering inkluderade i en allmän materialupplösningsprocess. Som en konsekvens av detta behövs varken brottkriterium eller sprickvägshypotes. Den fotoelastiska undersökningen jämförs med de numeriska resultaten. Avsaknaden av brottkriterium gör att sprickpropageringsprocessen saknar längdskala. Därmed följer att sprickans bredd skalar med kvadraten på den pålagda lasten medan spricktillväxthastigheten blir oberoende av pålagd last. Förhållandet gör vidare att sprickan förgrenas och att alla grenar fortsätter att växa utan att förlora fart.
|
|
| 31. |
|
|
| 32. |
|
|
| 33. |
|
|
| 34. |
- Hellgren, Laila, et al.
(författare)
-
Optimal timing of aortic valve replacement for aortic stenosis : are we operating late?
- 2003
-
Ingår i: Scandinavian Cardiovascular Journal. - : Informa UK Limited. - 1401-7431 .- 1651-2006. ; 37:5, s. 266-269
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To evaluate the adherence to current guidelines for surgery in patients with aortic valve stenosis.DESIGN: From 1 January 1997 to 31 May 1999, 99 patients were accepted for aortic valve surgery with preserved left ventricular function and normal coronary angiogram. On admission for operation, 20 patients were evaluated regarding symptoms, exercise capacity, and left ventricular morphology and function.RESULTS: There were 14 men and 6 women, mean age 64.3 years. Years from symptom onset varied from 2.1 to 3.2. Dyspnoea was the most common limiting symptom. Thirty per cent of the patients were classified as NYHA IIIB. Physical capacity was reduced to 79% of the expected. Left ventricular hypertrophy was present in 14/20 patients. Left ventricular systolic function was reduced with mean ejection fraction of 0.46. Diastolic dysfunction (E/A ratio <1) was present in 12 patients.CONCLUSION: Many patients accepted for aortic valve replacement due to aortic stenosis show advanced disease and are referred for surgery later in the disease process than is recommended in the current guidelines.
|
|
| 35. |
- Hellgren, Laila, et al.
(författare)
-
Severe mitral regurgitation : relations between magnetic resonance imaging, echocardiography and natriuretic peptides
- 2008
-
Ingår i: Scandinavian Cardiovascular Journal. - : Informa UK Limited. - 1401-7431 .- 1651-2006. ; 42:1, s. 48-55
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND:Assessment of the severity of mitral regurgitation by echocardiography can be technically demanding in certain patients and supplementary methods are therefore desirable. This study addressed the agreement between magnetic resonance imaging (MRI) and echocardiography, and their relations to natriuretic peptides (NT-proANP and NT-proBNP), in quantifying severe mitral regurgitation.METHODS:Eighteen patients with severe mitral regurgitation scheduled for surgery underwent MRI, echocardiography and assay of natriuretic peptides preoperatively for clinical assessment.RESULTS:MRI and echocardiography were comparable in measuring severity of regurgitation qualitatively but not quantitatively, mitral regurgitant fraction (mean difference 27.5 (11) ml). There was a correlation between increasing regurgitant fraction on MRI and increased levels of plasma NT-proANP and NT-proBNP. In echocardiography, increasing vena contracta width and increasing PISA correlated to increased levels of plasma NT-proANP and NT-proBNP. No other correlation was found between measures on MRI and echocardiography and natriuretic peptides.CONCLUSIONS:MRI and echocardiography were comparable grading the severity of mitral regurgitation with qualitative measures but not with quantitative measures. MRI might be a complement to echocardiography when a more distinct measure of the regurgitant volume is needed, as in paravalvular leakage.
|
|
| 36. |
|
|
| 37. |
- Holmberg, Kenneth, et al.
(författare)
-
Residual stresses in TiN, DLC and MoS2 coated surfaces with regard to their tribological fracture behaviour
- 2009
-
Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 267:12, s. 2142-2156
-
Tidskriftsartikel (refereegranskat)abstract
- Thin hard coatings on components and tools are used increasingly due to the rapid development in deposition techniques, tribological performance and application skills. The residual stresses in a coated surface are crucial for its tribological performance. Compressive residual stresses in PVD deposited TiN and DLC coatings were measured to be in the range of 0.03-4 GPa on steel substrate and 0.1-1.3 GPa on silicon. MoS2 coatings had tensional stresses in the range of 0.8-1.3 on steel and 0.16 GPa compressive stresses on silicon. The fracture pattern of coatings deposited on steel substrate were analysed both in bend testing and scratch testing. A micro-scale finite element method (FEM) modelling and stress simulation of a 2 m TiN-coated steel surface was carried out and showed a reduction of the generated tensile buckling stresses in front of the sliding tip when compressive residual stresses of 1 GPa were included in the model. However, this reduction is not similarly observed in the scratch groove behind the tip, possibly due to sliding contact-induced stress relaxation. Scratch and bending tests allowed calculation of the fracture toughness of the three coated surfaces, based on both empirical crack pattern observations and FEM stress calculation, which resulted in highest values for TiN coating followed by MoS2 and DLC coatings, being KC = 4-11, about 2, and 1-2 MPa m1/2, respectively. Higher compressive residual stresses in the coating and higher elastic modulus of the coating correlated to increased fracture toughness of the coated surface.
|
|
| 38. |
- Iacoviello, Francesco, et al.
(författare)
-
Preface: 1st Virtual European Conference on Fracture
- 2020
-
Ingår i: Procedia Structural Integrity : Part of special issue: 1st Virtual European Conference on Fracture - VECF1 - Part of special issue: 1st Virtual European Conference on Fracture - VECF1. - : Elsevier BV. - 2452-3216. ; 28, s. 2181-2186
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 39. |
|
|
| 40. |
-
IUTAM Symposium on Field Analyses for Determination of Material Parameters : Experimental and Numerical Aspects
- 2003
-
Proceedings (redaktörskap) (refereegranskat)abstract
- The need for modelling of materials behaviour under various mechanical conditions is driven by the evolution of computer capacity and the ability of scientists to address complex mechanical problems. Reliable models for materials behaviour, including accurate numerical values of parameters, are necessary for a continued beneficial development of the computational side of solid mechanics. High rate plasticity, thermally assisted creep and phase transformations are only a few examples of areas where more accurate models are needed. Experiments are necessary for the establishment of models and parameters, and modified versions of conventional test methods can make important contributions. Also modern optical methods offer a high potential for future experimental development. Numerical simulations of experiments and so-called inverse modelling are also frequently used techniques. In this book researchers with an interest in the area of experimental and computational aspects of materials modelling present modern advance methods and results.
|
|
| 41. |
|
|
| 42. |
|
|
| 43. |
|
|
| 44. |
- Jivkov, Andrey, et al.
(författare)
-
A model for graded materials with application to cracks
- 2003
-
Ingår i: International Journal of Fracture. - 0376-9429 .- 1573-2673. ; 124:1-2, s. 93-105
-
Tidskriftsartikel (refereegranskat)abstract
- Stress intensity factors are calculated for long plane cracks with one tip interacting with a region of graded material characteristics. The material outside the region is considered to be homogeneous. The analysis is based on assumed small differences in stiffness in the entire body. The linear extent of the body is assumed to be large compared with that of the graded region. The crack tip, including the graded region, is assumed embedded in a square-root singular stress field. The stress intensity factor is given by a singular integral. Solutions are presented for rectangular regions with elastic gradient parallel to the crack plane. The limiting case of infinite strip is solved analytically, leading to a very simple expression. Further, a fundamental case is considered, allowing the solution for arbitrary variation of the material properties to be represented by Fourier's series expansion. The solution is compared with numerical results for finite changes of modulus of elasticity and is shown to have a surprisingly large range of validity. If an error of 5% is tolerated, modulus of elasticity may drop by around 40% or increase with around 60%.
|
|
| 45. |
|
|
| 46. |
|
|
| 47. |
- Jivkov, Andrey, et al.
(författare)
-
Corrosion crack growth in a bi-material system
- 2003
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Bi-materials composed of thin layers ideally bonded to large substrates are considered. Cracks emerging from an almost flat surface and propagating through the bi-materials are studied. The cracks acquire realistic geometrical shapes, where the tips are integral parts of the crack surfaces. Crack propagation is related to surface evolution resulting from material loss due to corrosion. Controlling mechanism for the evolution is the rupture of a brittle passive film, which is frequently building-up along the surface. The evolution rate is a function of the degree of film damage caused by the surface straining. The model leads to a moving boundary formulation, for which a numerical solution is used. The mismatch of the material plastic properties is being varied in the study. The results show how cracks pass the interface. The growth rate variation close to the interface is studied. Typical surface evolution for a crack passing through a soft-hard material interface is presented. The resulting crack morphology of the model resembles what has been observed in reality. It is shown how the results can be used in designing bi-material systems to inhibit corrosion crack growth.
|
|
| 48. |
|
|
| 49. |
|
|
| 50. |
|
|
