| 1. |
- Banks-Sills, Leslie, et al.
(författare)
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Interface fracture toughness of a multi-directional woven composite
- 2013
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Ingår i: International Journal of Fracture. - : Springer Science and Business Media LLC. - 0376-9429 .- 1573-2673. ; 182:2, s. 187-207
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this investigation is to measure the interface fracture toughness of a woven composite. For this purpose, double cantilever beam (DCB) specimens are tested to measure the load as the delamination grows. The specimen is composed of 15 layers of a carbon-epoxy, balanced weave with alternate layers containing fibers in the directions and the directions. A thin piece of Teflon is placed between two layers of differing directions. The specimens are analyzed by means of the finite element method and an interaction energy or -integral to determine the stress intensity factors, interface energy release rate and phase angles. The first term of the asymptotic solution for the stress and displacement fields obtained by means of the Stroh and Lekhnitskii formalisms is used to define auxiliary solutions for the -integral. The critical interface energy release rate is found and exhibits a slowly increasing resistance curve. Comparisons are made to a simple expression from the literature.
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| 2. |
- Banks-Sills, Leslie, et al.
(författare)
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Strain Driven Transport for Bone Modeling at the Periosteal Surface
- 2011
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Ingår i: Mathematical Biosciences. - : Elsevier. - 0025-5564 .- 1879-3134. ; 230:1, s. 37-44
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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
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| 3. |
- Ben David, O., et al.
(författare)
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Evaluation of the Mechanical Properties of PMMA Reinforced with Carbon Nanotubes - Experiments and Modeling
- 2014
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Ingår i: Experimental Mechanics. - : Springer Science and Business Media LLC. - 1741-2765 .- 0014-4851. ; 54:2, s. 175-186
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Tidskriftsartikel (refereegranskat)abstract
- The effective mechanical properties of polymethyl-methacrylate (PMMA) reinforced with carbon nanotubes (CNTs) were evaluated by means of two approaches: experiments and a micromechanical model. With various concentrations of CNTs, two specimen fabrication processes were examined: hot pressing (HP) and injection molding (IM). Experiments included a series of uniaxial tensile tests guided by an ASTM standard. Using displacement control, tests were carried out while images were taken of the gage area. The in-plane displacement fields were evaluated by means of Digital Image Correlation (DIC). A MATLAB program was then used to calculate strains, create stress-strain and strain-force curves and determine Young's modulus E, Poisson's ratio , the ultimate tensile stress and the strain to failure . In addition, simulations were carried out using a micromechanical model (High-Fidelity Generalized Method of Cells or HFGMC). A Repeating Unit Cell (RUC) consisting of one CNT and PMMA surrounding it was modeled and analyzed in order to determine the effective mechanical properties of the composite. This method allows for imperfect bonding between the phases which is controlled by two parameters. These damage parameters decrease the stress-strain response of the material. However, the increase of the volume fraction increases the composite response. These two conflicting effects appear to provide the observed decrease in Young's modulus for low volume fractions as discussed. The effects of CNT concentration, geometry and orientation, as well as the interface between the phases, were examined. It was seen from the experimental results, for HP specimens, that for low concentrations of CNTs, E initially decreases and then increases significantly as the weight fraction increases. This behavior of E was quantitatively predicted by the HFGMC model. For IM specimens, Young's modulus is nearly constant for low weight fractions of CNTs and then increases with weight fraction.
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| 4. |
- Hallberg, Håkan, et al.
(författare)
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Crack tip transformation zones in austenitic stainless steel
- 2012
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Ingår i: Engineering Fracture Mechanics. - : Elsevier BV. - 1873-7315 .- 0013-7944. ; 79, s. 266-280
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Tidskriftsartikel (refereegranskat)abstract
- Crack tip conditions in SUS 304 austenitic stainless steel are studied using a constitutive model in which the martensitic phase transformation is an integral part. The phase transformation occurring in the crack tip region gives rise to fracture toughening of the material whereby the resistance against crack initiation, as well as the macroscopic material response are strongly altered by the presence of a martensitic phase. The constitutive model employed herein permits studying the transformation zones under different isothermal conditions. Local crack tip conditions and related plastic deformation is confirmed to depend strongly on the varying extent of the martensitic phase transformation at different temperatures. The shape and size of the plastic and transformation zones in the neighborhood of the crack tip are obtained from numerical simulations, as well as derived analytically.
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| 5. |
- Iacoviello, Francesco, et al.
(författare)
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Preface: 1st Virtual European Conference on Fracture
- 2020
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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
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 6. |
- Lindberg, Gustav, et al.
(författare)
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A two-dimensional model for stress driven diffusion in bone tissue.
- 2015
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Ingår i: Computer Methods in Biomechanics and Biomedical Engineering. - : Informa UK Limited. - 1025-5842 .- 1476-8259. ; 18:5, s. 457-467
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Tidskriftsartikel (refereegranskat)abstract
- The growth and resorption of bone are governed by interaction between several cells such as bone-forming osteoblasts, osteocytes, lining cells and bone-resorbing osteoclasts. The cells considered in this study reside in the periosteum. Furthermore, they are believed to be activated by certain substances to initiate bone growth. This study focuses on the role that stress driven diffusion plays in the transport of these substances from the medullary cavity to the periosteum. Calculations of stress driven diffusion are performed under steady state conditions using a finite element method with the concentration of nutrients in the cambium layer of the periosteum obtained for different choices of load frequencies. The results are compared with experimental findings, suggesting that increased bone growth occurs in the neighbourhood of relatively high nutrient concentration.
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| 7. |
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| 8. |
- Singh, R. N., et al.
(författare)
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Modeling of temperature dependence of stress-reorientation of hydrides in CWSR Zr-alloys
- 2008
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Ingår i: Defect and Diffusion Forum. ; :279, s. 105-110
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen in excess of solid solubility precipitates as hydride phase of plate shaped morphology in hcp α-Zr with the broad face of the hydride plate coinciding with certain crystallographic plane of α-Zr crystal called habit plane. The objective of the present investigation is to predict the habit plane of δ-hydride precipitating in α-Zr at 298 K using strain energy minimization technique. The δ-hydride phase is modeled to undergo isotropic elasto-plastic deformation. The α-Zr phase was modeled to undergo transverse isotropic elastic deformation but isotropic plastic deformation. Accommodation strain energy of δ-hydride forming in α-Zr crystal was computed using initial strain method as a function of hydride nuclei orientation. Hydride was modeled as disk with round edge. Contrary to several habit planes reported in literature for δ- hydrides precipitating in α-Zr crystal, the total accommodation energy minima at 298 K suggests only basal plane i.e. (0001) as the habit plane.
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| 9. |
- Singh, Ram N, et al.
(författare)
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δ-hydride habit plane determination in α-Zirconium at 298 K by strain energy minimization technique
- 2008
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Ingår i: Diffusion and defect data, solid state data. Part A, Defect and diffusion forum. - 1012-0386 .- 1662-9507. ; 279, s. 105-110
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen in excess of solid solubility precipitates as hydride phase of plate shaped morphology in hcp α-Zr with the broad face of the hydride plate coinciding with certain crystallographic plane of α-Zr crystal called habit plane. The objective of the present investigation is to predict the habit plane of δ-hydride precipitating in α-Zr at 298 K using strain energy minimization technique. The δ-hydride phase is modeled to undergo isotropic elasto-plastic deformation. The α-Zr phase was modeled to undergo transverse isotropic elastic deformation but isotropic plastic deformation. Accommodation strain energy of δ-hydride forming in α-Zr crystal was computed using initial strain method as a function of hydride nuclei orientation. Hydride was modeled as disk with round edge. Contrary to several habit planes reported in literature for δ- hydrides precipitating in α-Zr crystal, the total accommodation energy minima at 298 K suggests only basal plane i.e. (0001) as the habit plane.
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| 10. |
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