Following are more than 700 publications — that we know of — with reference to the use of ADINA. Since there are numerous papers published in renowned journals, we can only give here a selection. The pages give the Abstracts of some papers published since 1986 referring to ADINA. The most recent papers are listed first. All these papers may be searched using the box:
Surface coatings and ﬁnite-element analysis of layered fretting contacts
G.K. Nikas and R.S. Sayles
Department ofMechanical Engineering, Tribology Group, Imperial College London, London, UK
Proc. IMechE Vol. 223 Part J: J. Engineering Tribology, 159-181, 2009
Abstract: A fundamental, two-dimensional ﬁnite-element analysis (FEA) of a coated ﬂat surface in a fretting contact with a ﬂat-rounded punch is presented with a detailed listing of all modelling steps. A large number of basic results from a parametric study has been derived, focusing on the stress analysis and the effect of coatings on the life expectancy of the coated solid, without actually getting into the ambiguities of life evaluation. The parameters included in the study are the metallic coating thickness (5, 20, and 50μm) and elastic modulus, the endurance limit of the coated substrate, and the normal and tangential loads applied. A summary of the stress analysis results is presented in a ﬁgure with nine diagrams, which assists the quick selection of the optimum parameter values for maximizing the coating performance and minimizing the risk of fatigue within the design limits used in the study. The model is realistic in that it does not use idealized load distributions in the fretting contact but actual geometrical solids of ﬁnite dimensions in contact under the normal operating conditions, letting the FEA software resolve the loads and stresses, which are subsequently validated.
Keywords: Fretting - contact - coating - layer - ﬁnite-element analysis
The inﬂuence of sea water in oil emulsion on bearing performance
H. Liu1,2, H. Xu1, Y. Zhang1, H. Ji1, Y. Ge1, P. Ellison2, and Z. Jin2
1 Theory of Lubrication and Bearing Institute, Xi’an Jiaotong University, Xi’an, People’s Republic of China
2 Institute of Medical and Biological Engineering, University of Leeds, Leeds, UK
Proc. IMechE Vol. 223 Part J: J. Engineering Tribology, 457-468, 2009
Abstract: The lubricant in the bearings of ships can be easily polluted by sea water.Too much sea water may deteriorate the bearing performance and result in catastrophic failure; therefore, the lubricant should be changed regularly to prevent this. It is important to investigate the effect of adding sea water to mineral oil on the tribological performance of these bearings. In the present study, different amounts of sea water of 1, 2, and 3 per cent (by mass) were mixed with a typical mineral oil with a viscosity of 46mm2/s at 40°C and tested in 12 identical journal bearings under different operation conditions of rotational speed and load. For each case, the temperature within the oil ﬁlm, the loci of the shaft centre, the power consumption, and the viscosity of the emulsion were measured. In parallel to these measurements, a CFD simulation was performed for the test bearings to estimate the friction force and load capacity.The experimental measurements and the computational predictionswerecompared. Amaximum amount of sea water that can be tolerated in the mineral oil was established for the normal working conditions of the journal bearing.
Keywords: sea water in oil emulsion - journal bearing - experimental - CFD computational simulation - tribology
Finite-element analysis of layered rolling contacts
G.K. Nikas and R.S. Sayles
Department ofMechanical Engineering, Tribology Group, Imperial College London, London, UK
Proc. IMechE Vol. 223 Part J: J. Engineering Tribology, 865-886, 2009
Abstract: A fundamental, two-dimensional finite-element analysis (FEA) of coated surfaces in rolling contact is presented with detailed listing of all modelling steps. A large number of basic results from a parametric study has been derived, focusing on the stress analysis and the effect of coatings on the life expectancy of coated surfaces, without actually getting into the ambiguities of fatigue life evaluation. Parameters included in the study are the metallic coating thickness (from zero to 50μm) and elastic modulus (from 180 to 240GPa), the Coulomb friction coefficient (0, 0.05, and 0.10) and the endurance limit of the coated substrate. A generalization involves the application of traction to simulate driving or driven wheels. The effect of that traction on the stress results is thoroughly examined. The set of results, summarized in a figure with nine diagrams, assists the quick selection of the optimum parameter values for maximizing coating performance and minimizing the risk of contact fatigue within the design limits used in the study. The model is realistic in that it does not use idealized load distributions in the rolling contact but actual geometrical solids in contact under normal operating conditions, letting the FEA software resolve the loads and stresses, which are subsequently validated.
Keywords: rolling - contact - coating - layer - finite - element - analysis - finite-element analysis
Assessment of long-term behaviour of Ataturk Dam based on elasto-plastic analysis: comparison of effective and total stress approaches for clay core
M. Wieland1 and S. Malla2
1 Poyry Energy Ltd., Hardturmstrasse 161, Zurich, Switzerland
2 NOK AG, Parkstrasse 23, Baden, Switzerland (formerly with Poyry Energy Ltd.)
Proc. of the Second International Conference on Long Term Behaviour of Dams (LTBD09), Graz, Austria, 2009Abstract: A two-dimensional finite element model of the central section of the Ataturk Dam was developed using the Mohr-Coulomb material model for the various dam zones. Sliding movements were allowed at the core-filter and filter-shell interfaces. Two alternative models of the clay core based on the effective and total stress approaches were considered. For the remaining zones, the effective stress approach was adopted. The geodetically measured dam displacements were fitted with a linear combination, with time-dependent coefficients, of the computed displacements due to the gravity and water loads. The time histories of these coefficients were fitted with asymptotic exponential trends, which were extrapolated to predict the future displacements. A satisfactory fit could be achieved between the measured and computed displacements of benchmarks on the downstream slope and the crest area using both the effective and total stress approaches for the core. The effective stress approach for the core resulted, however, in a relatively large discrepancy between the calculated and measured displacements of the upper part of the upstream slope. The total stress approach for the core substantially reduced this discrepancy and also led to more plausible material properties of the clay core and the interfaces.
Study On Unloading Rock Mass Constitutive Relationship
J. Liu1, J.-L. Li2, X.-H. Wang3, J.-J. Qu4, Ti. Zhu4
1 College of Civil & Hydropower Engineering, Three Gorges University, China2
2 Key Laboratory of Geological Hazards on Three Gorges Reservoir Area, Ministry of Education, Three Gorges University, China
3 Hubei Qingjiang Hydropower Development Co., Ltd. , China
4 Three Gorges University, China.
Proc. of Int. Symp. on Geoenvironmental Eng., ISGE2009, 480-486, 2009
Abstract: The model experiment is applied to the geology material models, plaster cast models and sand syrup models. With analysis and fitting of the results got from model experiments, an initiatory increment constitutive relationship of jointed unloading rock masses is put forward. Fully considering the deficiency of the constitutive relationship, a new one is established with change on parameter choosing and physical meaning. Afterwards the constitutive relationship is put into ADINA, and an analysis is made for the high slope model of Geheyan hydropower station. By comparing the calculation results with those which were got by loading method, the rationality of the constitutive relationship is proved.
Keywords: model experiments - constitutive relationship - jointed unloading rock masses
Fluid-structure interactions of physiological flow in stenosed artery
B. Buriev1, T. Kim2 and T. Seo1
1 School of Mechanical Engineering, Andong National University, Andong, 760-749, Korea
2 Department of Environmental Engineering, Andong National University, Andong, 760-749, Korea
Korea-Australia Rheology Journal, 21(1):39-46, 2009
Atherosclerosis is a disease that narrows, thickens, hardens, and restructures a blood vessel due to substantial plaque deposit. The geometric models of the considered stenotic blood flow are three different types of constriction of cross-sectional area of blood vessel; 25%, 50%, and 75% of constriction. The computational model with the fluid-structure interaction is introduced to investigate the wall shear stresses, blood flow field and recirculation zone in the stenotic vessels. The velocity profile in a compliant stenotic artery with various constrictions is subjected to prescribed physiologic waveform. The computational simulations were performed, in which the physiological flow through a compliant axisymmetric stenotic blood vessel was solved using commercial software ADINA 8.4 developed by finite element method. We demonstrated comparisons of the wall shear stress with or without the fluid-structure interaction and their velocity profiles under the physiological flow condition in the compliant stenotic artery. The present results enhance our understanding of the hemodynamic characteristics in a compliant stenotic artery.
Keywords: stenosis – atherosclerosis - recirculation zone - fluid-structure interaction - physiological flow
Theoretical And Experimental Analysis Of The Sheet-Titanium Forming Process
Czestochowa University Of Technology, Institute Of Metal Forming, Quality Engineering And Bioengineering, 42-200 Czestochowa, 21 Armii Krajowej Av., Poland
Archives Of Metallurgy and Materials, 54(3):705-709, 2009
Abstract: In the paper sheet-metal forming process, the essential part of modern industry, which enable us to produce the applied drawpiece e.g. in the aircraft, car or building industry, was discussed. Advantages and disadvantages of application of titanium and its alloys in the drawpieces were presented. The numerical simulation results of the stamping process of CP 2 titanium cylindrical cup were given. Material data needed for the numerical simulation, such as: Re, Rm, r-value, hardening coeffcient n, forming limit diagram (FLD), were determined experimentally. A special attention was paid to the impact of such parameters as: friction coefficient, tool geometry (corner radius of the die and punch) and holding-down force on the strain distribution in the drawpiece. The simulation results were compared with the experimental ones. The numerical simulation was carried out with the ADINA System based on the finite element methods (MES).
Keywords: sheet-metal forming process – titanium - numerical simulation
Impact Of Wide-Base Single Tires On Pavement Damage
J. Greene, U. Toros, S. Kim, T. Byron, B. Choubane
State of Florida Research Report FL/DOT/SMO/09-528, 2009
Abstract: Dual tires have traditionally been used to limit pavement damage by efficiently distributing axle loads over a larger contact area than single tires. However, in recent years the trucking industry has promoted the use of wide-base single tires stating economical and safety benefits. The Super Single tire, an early type of wide-base tire, proved inadequate and induced excessive pavement damage. In contrast, the new generation wide-base tires have contact areas that approach those of dual tires and offer the potential for improved performance. The Florida Department of Transportation (FDOT) investigated the pavement damage potential of four tire types including a conventional dual tire (11R22.5), a Super Single (425/65R22.5), and two newly-designed wide-base single tires (445/50R22.5 and 455/55R22.5, respectively). A controlled accelerated pavement testing program in addition to theoretical modeling was performed to determine critical pavement response parameters. Pavement damage was measured in terms of rutting and fatigue cracking (bottom-up or top-down), the predominant distresses in Florida. The investigation revealed the 455-mm wide-base tire performed as well as the dual tire. In comparison, the 445-mm wide-base tire was shown to create more rut damage on a dense-graded pavement surface and was also predicted to create more bottom-up cracking than a dual tire. As expected, the Super Single induced the most damage to the pavement. This paper presents a description of the test program, the data collection efforts, and the subsequent analysis and findings.
Mitigation of Railway Traffic Induced Vibrations: The Influence of Barriers in Elastic Half-Space
M. Buonsanti,1 Fr. Cirianni,2 G. Leonardi,2 A. Santini,1 and F. Scopelliti2
1 Department of Mechanics and Materials (MECMAT), Mediterranean University of Reggio Calabria, Via Graziella, Feo di Vito, 89100 Reggio Calabria, Italy
2 Department of Information Science, Mathematics, Electronics, and Transportations (DIMET), Mediterranean University of Reggio Calabria, Via Graziella, Feo di Vito, 89100 Reggio Calabria, Italy
Advances in Acoustics and Vibration, Volume 2009
Abstract: In this paper, the problem of vibrations induced by trains and their propagation through the soil is studied. Particular attention is focused on the vibration induced by trains in motion and on the effects of such vibrations on the foundations of buildings in proximity of the tracks. The interaction between propagating waves induced by trains in motion and buildings foundations is a problem which does not admit a straightforward analytical solution; thus a solution is given by the use of a model based on the finite elements method. Firstly, we analyze the theoretical aspects of the problem by considering constant or harmonic loads moving along a straight railway track; then, we define a transfer function soil-railway and the response function of the entire system. The study aims to address the wave propagation in an elastic semi-space and the presence in the ground of a discontinuity element, such as a barrier of a given depth is considered. The efficiency variation of barriers is analyzed in function of the different materials used, and different numerical simulations are analyzed in order to study how the wave propagation and the track-soil interaction are influenced by the membrane, seen as damping barrier.
Viscoelastic Analysis of Flexible Pavements and Its Effects on Top-Down Cracking
J. Kim1, R. Roque2, and T. Byron3
1 National Center for Asphalt Technology, 277 Technology Parkway, Auburn, AL 36830
2 Dept. of Civil and Costal Engineering, Univ. of Florida, 265N Weil Hall, Gainesville, FL 32611
3 Florida Dept. of Transportation, 5007 N.E. 39th Ave., Gainesville, FL 32609
Journal Of Materials In Civil Engineering, July 2009
Abstract: When employing linear elastic layer analysis, which is widely used for the structural analysis of flexible pavements, it is commonly observed that most critical tensile strains occur at the bottom of an asphalt layer. It is well known that an asphalt mixture is a viscoelastic material, so its response is time and rate dependent; therefore, the results from the elastic assumption may not be borne out in the response of the asphalt layer. This study utilized viscoelastic analysis to identify critical tensile strains and their time-dependent responses. It was found that tensile strains occurred at the bottom and at the top of an asphalt layer and grew because of the rheological behavior of an asphalt mixture. As load repetitions continued, the strain at the top showed a higher strain value than the strain value at the bottom. A sensitivity analysis performed on various design parameters indicated that the development of strains at the top and at the bottom is a function of the structural characteristics of pavement structures. Expected trends were observed and findings compared favorably to results of field-calibrated top-down cracking model predictions.Keywords: Viscoelasticity - Finite element method - Tensile strain - Cracking - Flexible pavements
Modeling of Interfacial Debonding Analysis for Reinforced Concrete Based on ADINA
Qing-Jie Zhu1, Shi-Lin Lu2
1 College of Civil Engineering and Architecture, Hebei Polytechnic University, Tangshan 063009, China
2 Jinzhou Oil Production Plant, Liaohe Oil Field Company of PetroChina, Linghai 121209, China
icic, vol. 4, pp.292-295, 2009 Second International Conference on Information and Computing Science, 2009
Abstract: Reinforced concrete (RC) can work normally in actual engineering, which depends on well interfacial bond strength between reinforcing steel bar and concrete. Interfacial debonding is one of the main damage forms for RC and its structure. Relative sliding or interfacial debonding may occur under external loading, especially cyclic loading. Cyclic loading exists in many projects, for example, ocean platform and crane girder. Finite element model for interfacial debonding investigation of RC under cyclic loading is designed as basis of ADINA. The friction between reinforcing steel bar and concrete is defined, and bond stress-slippage relationship between concrete and reinforcing steel bar is established. According to the calculating result, effects of reinforcing steel bar type and anchor depth on interfacial fatigue are analyzed. It can provide effective numerical ideal and method for investigation of RC lasting quality.
Keywords: interfacial debonding - slippage - finite element method (FEM) – modeling – ADINA
Compressive strength of concrete cylinders with variable widths CFRP wraps: Experimental study and numerical modeling
Camille A. Issa, Pedro Chami, George Saad
Department of Civil Engineering, Lebanese American University, Byblos, Lebanon
Construction and Building Materials, 23:2306–2318, 2009
Abstract: There is an urgent need for models that can accurately predict performance of fiber-wrapped concrete columns. Axial compression tests on a total of 30 carbon-wrapped concrete cylinders of normal concrete and different number of wraps and height of confinement were used to verify the finite model. A nonlinear finite element model with a non-associative Drucker–Prager plasticity was used. The model compared favorably with test results. It was concluded that the adhesive bond between concrete and the wrap would not significantly affect the confinement behavior. From tests results, one can conclude that the wider the wrap, the higher the strength, also the thicker the wrap the higher the strength. However, it was impossible to reach a clear conclusion on the effect of the combination of variation of number of CFRP wraps and height of confinement. In a couple of cases, the same amount of material resulted in the same increase in the strength of the cylinders.
Keywords: Experimental - FEM - CFRP – Concrete
Numerical modelling of tracer tests and estimation of hydro-geological properties of a shear zone at the Grimsel Test Site
Alexandra Pudewills, Florian Huber and Thorsten Schäfer
Forschungszentrum Karlsruhe GmbH, Institut für Nukleare Entsorgung, Karlsruhe, Germany
Proc. TRePro II – Workshop on Modelling Transport Reaction Processes, Karlsruhe, 2009
Crystalline rocks such as granite have been extensively investigated as a potential host rock for nuclear waste disposal. The crystalline rock matrix is nearly impermeable and the groundwater flows predominantly through discrete features as fractures or shear zones filled with porous material. Such features provide the primary pathway for the migration of radionuclides from an underground repository to the biosphere. In order to predict the movement of radionuclides, the processes involved must be understood and quantified. For this purpose, laboratory tests, field experiments and adequate numerical models are needed.
The Colloid Formation and Migration (CFM) project aims to investigate and quantify the impact of colloids on the transport of waste-derived radionuclides in a waterconducting fracture under near-natural hydrogeochemical conditions. The in situ experiment is located in the Grimsel Test Site (GTS) in Switzerland (Blechschmidt 2006). In the first phase of this project, different tracer tests with uranine as conservative tracer were performed. Prior to the tracer tests, the experimental tunnel was equipped with a 3m-diameter surface packer system. The scope of this packer was to avoid uncontrolled flow rates towards the tunnel wall, to reduce the hydraulic gradient in the shear zone and to achieve longer tracer travel times.
In this contribution the tracer tests performed in two different dipoles were analyzed numerically. The objectives of these numerical analyses are to calibrate the model and determine its parameters from a series of conservative tracer tests and to test the model with respect to its ability to simulate the migration of bentonite colloids. It was assumed that the groundwater flow and the solute transport take place in fractures filled with fault gouges, and the shear zone at the test location is plane which allows a two dimensional approach for the model geometry. The mathematical model is based on the Darcy’s law for groundwater flow and the advection-dispersion equations for solute transport with a linear sorption in the fracture material. However, the model represents a planar confined porous media with a constant porosity and an anisotropic permeability. The analyses were performed with the ADINA-F finite element code (ADINA, Report ARD 01-9 2006). The calculation starts with the modelling of the steady-state groundwater flow field in each dipole experiment. After these conditions were established, the injection of the uranine solution was simulated. A comparison of the numerical results and test data is presented as breakthrough curves at the extraction holes where the uranine concentration is plotted versus time. The overall agreement of model results and experiment data is reasonable. Regarding the all hydraulic and transport properties obtained from this calibration work on tracer tests, it can be concluded that the area below the tunnel (dipole #2) is less permeable than the investigated region around the first dipole. However, these results confirm the earlier model proposed in Ref. (Meier et al., 2001).
Application Study of Polypropylene Fiber Reinforced Concrete Railway Tunnel Lining Structure within Hard Rock Mass Using Wet-Sprayed Technique
Taiquan Zhou, Yuan Hua
College of Environmental and Civil Engineering, Jiangnan University, Jiangsu, China, 214122
Materials Science Forum, Vols. 610-613, pp 76-80, 2009.
Abstract: The wet sprayed concrete technique has good virtue of improving the working condition within the tunnel, fewer reflective concrete loss and higher sprayed concrete quality. The concrete mixed with polypropylene fiber could improve the concrete inner structure, the flexural strength, tensile strength and anti-penetrating ability. The application of the wet sprayed polypropylene fiber reinforced concrete in the construction of tunnel lining structure could improve the stability of tunnel rock mass. The nonlinear finite element analysis is performed on rock mass stability of the railway tunnel lining structure and the rock mass stability is analyzed both for the un-lining tunnel and the lining tunnel. The computation result shows that the rock mass plasticity zone distribution with the lining structure is fewer than that without lining structure. To measure the deformation behavior, tunnel deformation measurement sensors are installed in the railway tunnel transverse section. The measured railway tunnel deformation result also shows that the lining structure deforms little and the rockmass is in stable state.
Key Words: Hard rock mass - Tailway tunnel - Wet sprayed concrete technique - Polypropylene fiber-reinforced concrete - Stability analysis - Nonlinear finite element analysis
Prevention of vascular graft occlusion and thrombus-associated thrombin generation by inhibition of factor XI
Erik I. Tucker,1 Ulla M. Marzec,1 Tara C. White,1 Sawan Hurst,1 Sandra Rugonyi,1 Owen J. T. McCarty,1,2 David Gailani,3 Andra´s Gruber,1,4,5 and Stephen R. Hanson1,5
1 Department of Biomedical Engineering and
2 Department of Cell and Developmental Biology, Oregon Health & Science University School of Medicine, Portland;
3 Departments of Pathology and Medicine, Vanderbilt University School of Medicine, Nashville, TN;
4 Department of Medicine, Oregon Health & Science University School of Medicine, Portland;
5 Oregon National Primate Research Center, Beaverton
Blood, 113:936-944, 2009Abstract: The protease thrombin is required for normal hemostasis and pathologic thrombogenesis. Since the mechanism of coagulation factor XI (FXI)–dependent thrombus growth remains unclear, we investigated the contribution of FXI to thrombus formation in a primate thrombosis model. Pretreatment of baboons with a novel anti–human FXI monoclonal antibody (aXIMab; 2 mg/kg) inhibited plasma FXI by at least 99% for 10 days, and suppressed thrombin-antithrombin (TAT) complex and b-thromboglobulin (bTG) formation measured immediately downstream from thrombi forming within collagen-coated vascular grafts. FXI inhibition with aXIMab limited platelet and fibrin deposition in 4-mm diameter grafts without an apparent increase in D-dimer release from thrombi, and prevented the occlusion of 2-mm diameter grafts without affecting template bleeding times. In comparison, pretreatment with aspirin (32 mg/kg) prolonged bleeding times but failed to prevent graft occlusion, supporting the concept that FXI blockade may offer therapeutic advantages over other antithrombotic agents in terms of bleeding complications. In whole blood, aXIMab prevented fibrin formation in a collagencoated flow chamber, independent of factor XII and factor VII. These data suggest that endogenous FXI contributes to arterial thrombus propagation through a striking amplification of thrombin generation at the thrombus luminal surface.
A mechanical study of patient-specific cerebral aneurysm models: The correlations between stress and displacement with geometrical indices
Alvaro Valenciaa, Pedro Torrensa, Rodrigo Riverab, Marcelo Galvezb, Eduardo Bravob
aDepartment of Mechanical Engineering, Universidad de Chile, Beauchef 850, Santiago, Chile
bNeuroradiology Department, Instituto de Neurocirugía Asenjo, Jose Manuel Infante 553, Santiago, Chile
Mechanics Research Communications 36 (2009) 642–651
Abstract: Solid mechanics plays an important role in the progression and rupture of cerebral aneurysms. The hypothesis is that the mechanism that control aneurysm enlargement is the wall remodeling under the effect of time dependent arterial pressure. When the aneurysm enlarges, the characteristics of the collagen fibers change, increasing the risk of rupture. The current work describes the solid dynamics in 30 patient-specific models of cerebral aneurysms. An area based index shows important difference between unruptured and ruptured aneurysms. The effective wall stress and displacement showed large variations depending on aneurysm size and form. The effects of hypertension were reported and correlations between the maximal effective stress and displacement with geometrical indices were found.
Keywords: Cerebral aneurysm - Effective stress - Displacement - Geometrical indices
A Simulation of Vessel–Clamp Interaction: Transient Closure Dynamics
Henry Y. Chen,1,2 Jose A. Navia,3 and Ghassan S. Kassab1,2,4,5
1 Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA;
2 Department of Cellular and Integrative Physiology, Indiana University Purdue University Indianapolis, Indianapolis, IN 46202, USA;
3 Department of Cardiovascular Surgery, School of Medicine, Austral University, Buenos Aires 1011, Argentina;
4 Department of Biomedical Engineering, Indiana University Purdue University Indianapolis, Indianapolis, IN 46202, USA; and
5 Department of Surgery, Indiana University Purdue University Indianapolis, Indianapolis, IN 46202, USA
Annals of Biomedical Engineering, Vol. 37, No. 9, September 2009, pp. 1772–1780
Abstract—Cross-clamping of aorta is routinely performed in cardiac surgery. The objective of this study was to simulate cross-clamping of the aorta to elucidate the perturbation of stresses in the wall (solid mechanics) and lumen of the vessel (fluid mechanics). Models of the aorta and clamp were created in Computer Assisted Design and Finite Element Analysis packages. The vessel wall was considered as a nonlinear anisotropic material while the fluid was simulated as Newtonian with pulsatile flow. The clamp was applied to produce total occlusion in approximately 1 s. A cylindrical and rectangular geometry for the clamp were considered. High jet speed and flow reversal were demonstrated during clamping. It was found that the clamp design and vessel wall anisotropy affected both the fluid wall shear stress (WSS) and solid stresses in vessel wall. The maximum wall stresses increased by about 170 and 220% during closure in the cases of plate and cylindrical clamps, respectively. The plate clamp design was superior for reduction of both solid stresses as well as fluid shear stresses. The cylindrical clamp causes much larger stresses than the plate clamp in each of the stress components; e.g., radial compression of -180 vs.-50 kPa. Vibrations, flow and WSS oscillations were detected immediately before total vessel occlusion. The present findings provide valuable insights into the mode of tissue injury during clamping and may also be useful for improving surgical clamp designs.
Keywords: Fluid–solid interaction - Endothelium - Intramural wall stress - Wall shear stress - Surgical clamps
Sensitivity of unsteady collapsible channel flows to modelling assumptions
H. F. Liu1, X. Y. Luo1, Z. X. Cai2 and T. J. Pedley3
1 Department of Mathematics, University of Glasgow, Glasgow G12 8QW, U.K.
2 Department of Mechanics, Tianjin University, Tianjin, China
3 DAMTP, University of Cambridge, Cambridge CB3 0WA, U.K.
Commun. Numer. Meth. Engng 2009; 25:483–504
We investigate the influences of modelling assumptions on the dynamic behaviour of collapsible channel flows. The elastic wall is modelled in various different ways: as a large strain Bernoulli–Euler beam, as a small strain Timoshenko beam, and as a 2D-solid model derived from a general virtual work approach, using small strain or large strain assumptions. Different inlet boundary conditions are also considered. The in-house finite element codes and the commercial finite element package ADINA 8.4 are used. The steady results agree very well when using the different models/approaches. The unsteady results, on the other hand, can be quite different. The dynamic behaviour of the system is analysed for a set of chosen parameters, using the full numerical solvers, the linear stability analysis, and the Fourier transform. It is found that the system stability is highly sensitive to the solid modelling assumptions used, numerical solvers adopted, or the boundary conditions imposed. Accuracy of the numerical schemes also has an impact on the system’s unsteady behaviour. However, despite the high sensitivity of the unsteady solutions to the modelling assumptions, a cascade stability structure previously revealed by the authors seems to exist when different numerical approaches are used.
Keywords: collapsible channel flow - self-excited oscillations - cascade structure - fluid–structure interactions - linear stability analysis - finite element methods
Experimental and analytical behavior of haunched thin-walled RC girders and box girders
Khaled Galal, Qing Yang
Department of Building, Civil and Environmental Engineering, Concordia University, Montreal, Quebec, Canada H3G 1M8
Thin-Walled Structures 47 (2009) 202– 218
Abstract: This paper presents an experimental and analytical investigation on the behavior of haunched thinwalled reinforced concrete (RC) girders and box girders subjected to centric and eccentric loads. Five tests were conducted on medium-scale RC girders and box girders to study the effect of load eccentricity and the influence of bottom slabs on their ultimate load-carrying capacities, failure mechanisms and
load–deformation relationships. Accordingly, the tested girders were modeled using ADINA, and a nonlinear finite element analysis was conducted. The investigation showed that load eccentricities considerably reduced the ultimate loads and the ductility of the girders with open sections. However, when the open section was converted to a full-span box section, the behaviors of the girders were significantly improved.
Keywords: Reinforced concrete - Bridges - Haunched girder - Torsion - Eccentric load - Box section - Open section - ADINA
Behavior of a flat internal delamination within a fiber reinforced cross-ply composite
Leslie Banks-Sills, Yuval Freed, Arkady Alperovitch
The Dreszer Fracture Mechanics Laboratory, School of Mechanical Engineering, The Fleischman Faculty of Engineering, Tel Aviv University, 69978 Ramat Aviv, Tel Aviv, Israel
Int J Fract (2009) 155:127–142
Abstract: A penny-shaped delamination is modeled as a flat octahedral shaped crack between layers of a cross-ply laminate. The fibers of the laminate intersect the edges of the delamination at angles of 0 deg/90 deg, +45 deg /-45 deg, 90 deg /0 deg and -45 deg /+45 deg as one proceeds along the delamination edge. Two lay-ups are considered, a cross-ply consisting of two layers, and a symmetric composite, consisting of three layers. The delamination is always between two of the layers. Both tension and shear are applied to the outer boundary of the body. Stress intensity factors about the delamination edge are calculated by means of a conservative M-integral. These are employed to calculate the interface energy release rate and corresponding phase angles. Use is made of existing experimental results to predict the location of propagation along the edge of the delamination. It was found that the most dangerous regions along the delamination front occurred for the 0 deg /90 deg or 90 deg /0 deg interfaces.
Keywords: Internal delamination - Interface fracture toughness - Fiber-reinforced composite material - Cross-ply - Three-dimensional conservative integrals - Finite elements
On the finite element modeling of fatigue crack growth in pressurized cylindrical shells
C.H. Furukawa, M.L. Bucalem, I.J.G. Mazella
Department of Structural and Geotechnics Engineering, University of São Paulo, Avenida Jorge Zarur, 330 ap 93, Sao Paulo Sao Jose dos Campos, Sao Paulo, Brazil
International Journal of Fatigue 31 (2009) 629–635
Abstract: A methodology for the computational modeling of the fatigue crack growth in pressurized shell structures, based on the finite element method and concepts of Linear Elastic Fracture Mechanics, is presented. This methodology is based on that developed by Potyondy [Potyondy D, Wawrzynek PA, Ingraffea, AR. Discrete crack growth analysis methodology for through crack in pressurized fuselage structures. Int J Numer Methods Eng 1995;38:1633–1644], which consists of using four stress intensity factors, computed from the modified crack integral method, to predict the fatigue propagation life as well as the crack trajectory, which is computed as part of the numerical simulation. Some issues not presented in the study of Potyondy are investigated herein such as the influence of the crack increment size and the number of nodes per element (4 or 9 nodes) on the simulation results by means of a fatigue crack propagation simulation of a Boeing 737 airplane fuselage. The results of this simulation are compared with experimental results and those obtained by Potyondy .
Keywords: Aircraft engineering - Bulging - Fatigue crack growth - Life prediction - Shells
Thermo-mechanical and diffusion modelling in the process of ceramic–metal friction welding
Jolanta Zimmermanb, Wladyslaw Wlosinskia, Zdzislaw R. Lindemannb
aWelding Department of I.T.B., Faculty of Production Engineering, Warsaw University of Technology, Polish Academy of Science, Poland
bInstitute of Mechanics and Design, Faculty of Production Engineering, Warsaw University of Technology, 85 Narbutta Str., 02-524 Warsaw, Poland
Journal of Materials Processing Technology 209 (2009) 1644–1653
Abstract: In this paper a modelling of friction welding of elastic materials with elastic–plastic metals is presented. This model has been practically verified in the process of friction welding of corundum ceramic of 97.5% Al2O3 content and aluminium alloy 6061-T6 as well as in the same ceramic and electrolytic copper of 99.9% Cu content. Mechanical strength of the acquired welded joints was around 30MPa. A simulation of the process was performed by means of the finite element method using two FEM systems, namely ADINA-T and ADINA. The simulations made it possible to observe the temperature distribution and thermo-mechanical fields that take place during the process. The obtained results show that the temperature, pressure and the deformation distribution near the contact surface are non-homogeneous. It causes not even conditions to create the bond and internal stresses generation. The agreement between the numerical geometry prediction and the experimental data proves the validity of the proposed model. The performed calculations and preliminary studies on the in.uence of the diffusion phenomena on the welding process showed that the diffusion depth is approximately 4mm
and the calculated diffusion coefficient of Al into Al2O3 is 1.8×10-13m2/s.
Numerical simulation of the friction welding process allows better understanding of the whole process, final products shape prediction and can be helpful during design of the process using other materials.
Keywords: Friction welding - Ceramic–metal bonding - Thermo-mechanical phenomena - FEM - Diffusion effects
Microstructure and temperature monitoring during the hot rolling of AZ31
E. Essadiqa, M.T. Shehataa, A. Javaida, C. Galvania, G. Shena, S. Yueb, and R. Vermac
aMaterials Technology Laboratory–CANMET, Ottawa, Ontario K1A 0G1, Canada;
bDepartment of Metals and Materials Engineering, McGill University, 3610 University, Montreal, Quebec H3A 2B2, Canada;
cGeneral Motors R&D, Materials & Processes Laboratory, Warren, MI 48090.
JOM, Vol. 61 No. 8 (August 2009)
Abstract: This study details the microstructural evolution during hot rolling of AZ31 alloy sheet using a pilot-scale rolling mill. The aim is to understand the deformation mechanisms leading to grain refinement under industrial processing conditions and to design and optimize the hot rolling schedule for AZ31 in order to produce sheet with a fine and homogeneous microstructure. The study examined three different hot rolling temperatures, 350, 400, and 450 deg C, and two rolling speeds, 20 and 50 rpm. A total thickness reduction of 67% was obtained using multiple passes, with reductions of either 15% or 30% per pass. It was found that the microstructure of the AZ31 alloy was sensitive to the rolling temperature, the reduction (i.e., strain) per pass and the rolling speed (i.e., strain rate). The results show that the large cast grain structure is broken down by segmentation of the cast grain through localized deformation in twin bands, where dynamic recrystallization occurs in these bands as well as at the grain boundaries (necklacing).
Fluid–structure interaction of turbulent pulsatile flow within a flexible wall axisymmetric aortic aneurysm model
Khalil M. Khanafera, Joseph L. Bulla, Ramon Berguera,b
aVascular Mechanics Laboratory, Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
bSection of Vascular Surgery, University of Michigan, Ann Arbor, MI 48109, USA
European Journal of Mechanics B/Fluids 28 (2009) 88–102
Abstract: Pulsatile turbulent flow characteristics in an axisymmetric aortic aneurysm (AA) model were analyzed numerically using a simulated physiological waveform. The transport equations were solved using the finite element formulation based on the Galerkin method of weighted residuals. A fully-coupled fluid–structure interaction (FSI) analysis was utilized in this work. We investigated the effects of turbulent flow characteristics on the distribution of wall stress and flow patterns in AAmodels.Wall stress distributions were calculated by computational solid stress (CSS) model, which ignores the effect of the blood flow, and the FSI model that takes into account flow and solid mechanics. Our results showed that peak wall stress and peak deformation were found to occur shortly after peak systolic flow in the FSI model and at the peak luminal pressure condition in the CSS model. Further, CSS model underestimated wall stress calculations when compared to the FSI model. There were also significant differences in the structure of flow fields between the flexible and rigid wall aneurysm models. Contour plots of kinetic energy dissipation and the application of the Kolmogorov microscale suggest that the conditions that result in red blood cell damage and platelet activation most likely occur in the near-wall region of AA during turbulent flow.
Keywords: Aneurysm - Finite element - Flexible wall - Rigid wall - Turbulent
Quantitative analysis of epithelial morphogenesis in Drosophila oogenesis: New insights based on morphometric analysis and mechanical modeling
K.S. Kolahia, P.F. Whitea, D.M. Shretera, A.-K. Classenb, D. Bilderb, M.R.K. Mofrada
aMolecular Cell Biomechanics Laboratory, Department of Bioengineering, University of California, Berkeley, 208A Stanley Hall #1762, Berkeley, CA 94720-1762, USA
bDepartment of Molecular and Cellular Biology, University of California, 142 LSA #3200, Berkeley, CA 94720-3200, USA
Developmental Biology 331 (2009) 129–139
Abstract: The process of epithelial morphogenesis is ubiquitous in animal development, but much remains to be learned about the mechanisms that shape epithelial tissues. The follicle cell (FC) epithelium encapsulating the growing germline of Drosophila is an excellent system to study fundamental elements of epithelial development. During stages 8 to 10 of oogenesis, the FC epithelium transitions between simple geometries–cuboidal, columnar and squamous–and redistributes cell populations in processes described as posterior migration, squamous cell flattening andmain body cell columnarization. Here we have carried out a quantitative morphometric analysis of these poorly understood events in order to establish the parameters of and delimit the potential processes that regulate the transitions. Our results compel a striking revision of accepted views of these phenomena, by showing that posterior migration does not involve FC movements, that there is no role for columnar cell apical constriction in FC morphogenesis, and that squamous cell flattening may be a compliant response to germline growth. We utilize mechanical modeling involving finite element computational technologies to demonstrate that time varying viscoelastic properties and growth are sufficient to account for the bulk of the FC morphogenetic changes.
Keywords: Epithelial morphogenesis - Drosophila melanogaster oogenesis - Mechanics - Morphometric analysis - Computational modeling
Screw angulation affects bone-screw stresses and bone graft load sharing in anterior cervical corpectomy fusion with a rigid screw-plate construct: a finite element model study
Mozammil Hussaina, Raghu N. Natarajanb,c, Amir H. Fayyazid, Brian R. Braaksmab, Gunnar B.J. Anderssonb, Howard S. Anb
aDivision of Research, Logan University, Chesterfield, MO 63017, USA
bDepartment of Orthopedic Surgery, Rush University Medical Center, Chicago, IL 60612, USA
cDepartment of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
dDepartment of Orthopaedics and Rehabilitation, Penn State College of Medicine, Allentown, PA 18103, USA
The Spine Journal (2009) (in press)
BACKGROUND CONTEXT: Anterior corpectomy and reconstruction with bone graft and a rigid screw-plate construct is an established procedure for treatment of cervical neural compression. Despite its reliability in relieving symptoms, there is a high rate of construct failure, especially inmultilevel cases.
PURPOSE: There has been no study evaluating the biomechanical effects of screw angulation on construct stability; this study investigates the C4–C7 construct stability and load-sharing properties among varying screw angulations in a rigid plate-screw construct.
STUDY DESIGN: A finite element model of a two-level cervical corpectomy with static anterior cervical plate.
METHODS: A three-dimensional finite element (FE) model of an intact C3–T1 segment was developed and validated. From this intact model, a fusion model (two-level [C5, C6] anterior corpectomy) was developed and validated. After corpectomy, allograft interbody fusion with a rigid anterior screw-plate construct was created from C4 to C7. Five additional FE models were developed from the fusion model corresponding to five different combinations of screw angulations within the vertebral bodies (C4, C7): (0 deg, 0 deg), (5 deg, 5 deg), (10 deg, 10 deg), (15 deg, 15 deg), and (15 deg, 0 deg). The fifth fusion model was termed as a hybrid fusion model.
RESULTS: The stability of a two-level corpectomy reconstruction is not dependent on the position of the screws. Despite the locked screw-plate interface, some degree of load sharing is transmitted to the graft. The load seen by the graft and the shear stress at the bone-screw junction is dependent on the angle of the screws with respect to the end plate. Higher stresses are seen at more divergent angles, particularly at the lower level of the construct.
CONCLUSION: This study suggests that screw divergence from the end plates not only increases load transmission to the graft but also predisposes the screws to higher shear forces after corpectomy reconstruction. In particular, the inferior screw demonstrated larger stress than the upper-level screws. In the proposed hybrid fusion model, lower stresses on the bone graft, end plates, and bonescrew interface were recorded, inferring lower construct failure (end-plate fractures and screw pullout) potential at the inferior construct end.
Keywords: Finite element model - Cervical corpectomy - Stiffness - Screw pullout - Locked anterior cervical plate
On quasi-steady laminar flow separation in the upper airways
A. Van Hirtum, J. Cisonni and X. Pelorson
Gipsa-lab, Grenoble, France
Commun. Numer. Meth. Engng, 25:447–461, 2009
Abstract: Accurate prediction of the position of flow separation along a constriction is important to model fluid–structure interaction phenomena in the upper airways such as phonation and obstructive sleep apnea. Flow assumptions underlying common flow descriptions along the upper airways are formulated. Flow separation positions obtained from theories with different degrees of complexity are qualitatively and
quantitatively discussed. In particular, geometrical and flow features determining the influence of viscosity are varied. Increasing the constriction degree and the constriction length is shown to affect the position of flow separation. Boundary layer solutions and simulations with the two-dimensional Navier Stokes equations result in an accurate quantitative prediction of flow separation. Furthermore, Jeffery–Hamel flow solutions qualitatively predict the effect of both constriction height and length on the position of flow separation. The ad hoc assumption applied in quasi-one-dimensional flow descriptions does not accurately predict flow separation.
Keywords: two dimensional - laminar flow - phonation - obstructive sleep apnea - experimental validation
Vertical hydrodynamic focusing in glass microchannels
Tony A. Lin,1,2 A. E. Hosoi,2 and Daniel J. Ehrlich1
1 Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge,Massachusetts 02142, USA
2 Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02142, USA
Biomicrofluidics, 3:014101 (2009)
Abstract: Vertical hydrodynamic focusing in microfluidic devices is investigated through simulation and through direct experimental verification using a confocal microscope and a novel form of stroboscopic imaging. Optimization for microfluidic
cytometry of biological cells is examined. By combining multiple crossing junctions,
it is possible to confine cells to a single analytic layer of interest. Subtractive
flows are investigated as a means to move the analysis layer vertically in the
channel and to correct the flatness of this layer. The simulation software (ADINA
and Coventor) is shown to accurately capture the complex dependencies of the layer interfaces, which vary strongly with channel geometry and relative flow rates.
Effects of altered corneal stiffness on native and postoperative LASIK corneal biomechanical behavior: A whole-eye finite element analysis
Abhijit Sinha Roy1, William J. Dupps, Jr.1,2
1 Cole Eye Institute, Cleveland Clinic, Cleveland,Ohio.
2 Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland,Ohio.
J Refract Surg., 25:875-887, 2009
Purpose: To investigate the impact of corneal elasticity on corneal shape changes before and after simulated LASIK with and without consideration of whole-eye biomechanics.
Methods: A finite element whole-eye model of a human eye was constructed. The cornea was modeled as hyperelastic and incompressible using experimental data representing a range of corneal stiffness. The corneal response to intraocular pressure loading and LASIK for 2.00, 4.00, and 6.00 diopters of spherical myopia was analyzed as a function of corneal stiffness and limbal boundary conditions.
Results: Myopic LASIK produced different degrees of central flattening and postoperative ametropia in low-stiffness and high-stiffness corneas. Although a cornea-only model demonstrated maximum stresses and displacements in the central cornea and predicted residual myopia, a whole-eye model with equivalent corneal stiffness predicted greater paracentral displacements and less myopic undercorrection. In a whole-eye model with a stiffer cornea, maximum displacements shifted further toward the limbus, favoring additional mechanically mediated central flattening and refractive overcorrection (hyperopia). In postoperative LASIK models thinned by high myopic corrections, corneal stiffening caused central cornea flattening.
Conclusions: Differences in the corneoscleral stiffness relationship affect simulated refractive outcomes after LASIK and may be a source of individual variation in refractive surgery outcomes. A whole-eye model allowing limbal motion illustrates a stiffness-dependent biomechanical balance between central corneal flattening and pre-ectatic weakening of the corneal apex not demonstrated in previous computational models and provides insight into under- and overcorrection in myopic LASIK and the previously unexplained phenomenon of corneal flattening after therapeutic collagen cross-linking for keratoconus.
Patient-specific artery shrinkage and 3D zero-stress state in multi-component 3D FSI models for carotid atherosclerotic plaques based on in vivo MRI data
Xueying Huang1, Chun Yang2, Chun Yuan3, Fei Liu3, Gador Canton3, Jie Zheng4, Pamela K. Woodard4, Gregorio A. Sicard5, and Dalin Tang1
1 Mathematical Sciences Department, Worcester Polytechnic Institute, Worcester, MA 01609
2 Mathematics Department, Beijing Normal University, Beijing, China
3 Deparment of Radiology, University of Washington, Seattle, WA 98195
4 Mallinkcrodt Institute of Radiology, Washington University, St. Louis, MO. 63110
5 Department of Surgery, Washington University, St. Louis, MO, USA
Mol Cell Biomech. 2009 ; 6(2): 121–134.
Abstract: Image-based computational models for atherosclerotic plaques have been developed to perform mechanical analysis to quantify critical flow and stress/strain conditions related to plaque rupture which often leads directly to heart attack or stroke. An important modeling issue is how to determine zero stress state from in vivo plaque geometries. This paper presents a method to quantify human carotid artery axial and inner circumferential shrinkages by using patient-specific ex vivo and in vivo MRI images. A shrink-stretch process based on patient-specific in vivo plaque morphology and shrinkage data was introduced to shrink the in vivo geometry first to find the zero-stress state (opening angle was ignored to reduce the complexity), and then stretch and pressurize to recover the in vivo plaque geometry with computed initial stress, strain, flow pressure and velocity conditions. Effects of the shrink-stretch process on plaque stress/strain distributions were demonstrated based on patient-specific data using 3D models with fluid-structure interactions (FSI). The average artery axial and inner circumferential shrinkages were 25% and 7.9%, respectively, based on a data set obtained from 10 patients. Maximum values of maximum principal stress and strain increased 349.8% and 249% respectively with 33% axial stretch. Influence of inner circumferential shrinkage (7.9%) was not very noticeable under 33% axial stretch, but became more noticeable under smaller axial stretch. Our results indicated that accurate knowledge of artery shrinkages and the shrink-stretch process will considerably improve the accuracy of computational predictions made based on results from those in vivo MRI-based FSI models.
Keywords: Atherosclerosis - vulnerable plaques - carotid artery - blood flow - artery shrinkage - fluid-structure interactions