ADINA Publications

Page 40

The Theory used in ADINA is richly documented in the following books by K.J. Bathe and co-authors


Finite Element Procedures
 

Finite Element Procedures in Engineering Analysis

Numerical Methods in Finite Element Analysis
 


The Mechanics of Solids and Structures — Hierarchical ...


The Finite Element Analysis of Shells — Fundamentals


Inelastic Analysis of Solids and Structures

 
 
To Enrich Life
(Sample pages here)
 

 

Following are more than 700 publications — that we know of — with reference to the use of ADINA. 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:

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Cracked beam identification by numerically analysing the nonlinear behaviour of the harmonically forced response

U. Andreaus, P. Baragatti

Sapienza Universit di Roma, Dipartimento di Ingegneria strutturale e geotecnica, Via Eudossiana 18, 00184 Roma, Italy

Journal of Sound and Vibration,  330:721–742, 2011

Abstract: Numerical evaluation of the flexural forced vibration of a cantilever beam having a transverse surface crack extending uniformly along the width of the beam was performed to relate the nonlinear resonances to the crack presence, location, and depth. To this end, the qualitative characteristics, namely phase portrait distortions, sub- and super-harmonic components in the Fourier spectrum, and curved shape of the modal line were considered. Furthermore, quantitative parameters, such as the eccentricity and the excursion of the orbit, and the harmonic amplitude in the spectrum were measured. Then, an identification procedure was proposed which was based on the intersection of constructed surfaces which allowed to identify the structural damage. The acceleration record of the beam tip was sufficient to detect the existence of the crack and to identify crack depth and site.

 

FSI Analysis of a Healthy and a Stenotic Human Trachea Under Impedance-Based Boundary Conditions

M. Malvé1,2, A. Pérez Del Palomar1,2, S. Chandra3, J.L. López-Villalobos4, A. Mena1,2, E.A. Finol3, A. Ginel4, and M. Doblaré1,2

1 Group of Structural Mechanics and Materials Modeling, Aragón Institute of Engineering Research (I3A), Universidad de Zaragoza, C/María de Luna s/n, E-50018 Zaragoza, Spain
2 Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina, C/Poeta Mariano Esquillor s/n, 50018 Zaragoza, Spain
3 Institute for Complex Engineered Systems, Carnegie Mellon University, 1205 Hamburg Hall, 5000 Forbes Avenue, Pittsburgh, PA 15213
4 Department of Thoracic Surgery, Hospital Virgen del Rocío, Avenida de Manuel Siurot s/n, 41013 Seville, Spain

Journal of Biomechanical Engineering, 133:02001-1–02001-12, 2011

Abstract: In this work, a fluid-solid interaction (FSI) analysis of a healthy and a stenotic human trachea was studied to evaluate flow patterns, wall stresses, and deformations under physiological and pathological conditions. The two analyzed tracheal geometries, which include the first bifurcation after the carina, were obtained from computed tomography images of healthy and diseased patients, respectively. A finite element-based commercial software code was used to perform the simulations. The tracheal wall was modeled as a fiber reinforced hyperelastic solid material in which the anisotropy due to the orientation of the fibers was introduced. Impedance-based pressure waveforms were computed using a method developed for the cardiovascular system, where the resistance of the respiratory system was calculated taking into account the entire bronchial tree, modeled as binary fractal network. Intratracheal flow patterns and tracheal wall deformation were analyzed under different scenarios. The simulations show the possibility of predicting, with FSI computations, flow and wall behavior for healthy and pathological tracheas. The computational modeling procedure presented herein can be a useful tool capable of evaluating quantities that cannot be assessed in vivo, such as wall stresses, pressure drop, and flow patterns, and to derive parameters that could help clinical decisions and improve surgical outcomes.

Keywords: Cardiovascular system — Computerized tomography — Deformation — Flow patterns — Fractal dimension — Reinforced plastics — Respiratory system

 

Influence of arterial wall-stenosis compliance on the coronary diagnostic parameters

B.C. Konala, A. Das, R.K. Banerjee

Department of Mechanical Engineering, University of Cincinnati, Cincinnati, OH, USA

Journal of Biomechanics, doi:10.1016/j.jbiomech.2010.12.011, 2011

Abstract: Functional diagnostic parameters such as Fractional FlowReserve (FFR), which is calculated from pressure measurements across stenosed arteries, are often used to determine the functional severity of coronary artery stenosis. This study evaluated the effect of arterial wall-stenosis compliance, with limiting scenarios of stenosis severity, on the diagnostic parameters. The diagnostic parameters considered in this study include an established index, FFR and two recently developed parameters: Pressure Drop Coefficient (CDP) and Lesion Flow Coefficient (LFC). The parameters were assessed for rigid artery (RR; signifying high plaque elasticity), compliant artery with calcified plaque (CC; intermediate plaque elasticity) and compliant artery with smooth muscle cell proliferation (CS; low plaque elasticity), with varying degrees of epicardial stenosis. A hyperelastic Mooney–Rivlin model was used to model the arterial wall and plaque materials. Blood wasmodeled as a shear thinning, non-Newtonian fluid using the Carreau model. The arterialwall compliancewas evaluated using the finite element method. The present study found that, with an increase in stenosis severity, FFR decreased whereas CDP and LFC increased. The cutoff value of 0.75 for FFR was observed at 78.7% area stenosis for RR, whereas for CC and CS the cutoff values were obtained at higher stenosis severities of 81.3% and 82.7%, respectively. For a fixed stenosis, CDP value decreased and LFC value increased with a decrease in plaque elasticity (RR to CS). We conclude that the differences in diagnostic parameters with compliance at intermediate stenosis (78.7–82.7% area blockage) could lead to misinterpretation of the stenosis severity.

Keywords: Functional diagnostic parameters — Fractional Flow Reserve — Lesion flow coefficient — Pressure drop coefficient — Fluid-structure interaction — Coronary artery stenosis

 

Numerical simulation of LDL mass transfer in a common carotid artery under pulsatile flows

S. Fazli1, E. Shirani1, M.R. Sadeghi2

1 Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 8415683111, Iran
2 Department of Biomedical Engineering, University of Isfahan, Isfahan, Iran

Journal of Biomechanics, 44:68-76, 2011

Abstract: Symmetrical 30-60% stenosis in carotid artery with a semi-permeable wall under steady/unsteady flows for Newtonian/non-Newtonian fluids is investigated numerically. The results show that the unsteadiness of blood flow, blood pressure rise and LDL component size increase the luminal concentration, LC, of the surface. The maximum LC occurring immediately after the separation point and the non-Newtonian fluid predicts higher LDL accumulation. LC decreased as the recirculation length is increased and reaches maximum at 40% stenosis. This process is used to estimate the time-dependent growth of the arterial wall.

Keywords: Atherosclerosis — Mass transfer — Low density lipoprotein (LDL) — Pulsatile flow — Carotid artery

 

Computational Flow Dynamics of the Severe M1 Stenosis Before and After Stenting

D.C. Suh1, Y.B. Ko3,5, S.-T. Park4, K. Yoon3, O.K. Lim1, J.S. Oh1, Y.G. Jeong1, J.S. Kim2

1 Department of Radiology and Research Institute of Radiology, Asan Medical Center, Seoul, Korea
2 Department of Neurology, Asan Medical Center, Seoul, Korea
3 Department of Mechanical Engreering, Dankook University, Yongin, Korea
4 Department of Radiology, Soonchunhyang University Hospital, Seoul, Korea
5 Molding & Forming Technology Team, KITECH, 7-47, Incheon, Korea

Neurointervention, 6:13-16, 2011

Abstract: Computational flow dynamic (CFD) study has not been widely applied in intracranial artery stenosis due to requirement of high resolution in identifying the small intracranial artery. We described a process in CFD study applied to symptomatic severe intracranial (M1) stenosis before and after stenting. Our study revealed that CFD analysis before and after intracranial stenting was feasible despite of limited vessel wall dimension and could reveal change of WSS as well as flow velocity and wall pressure.

Key Words : Cerebral artery — Atherosclerosis — Magnetic resonance imaging (MRI) — Plaque rupture — Fluid structure interaction

 

High-resolution Magnetic Resonance Imaging-based Biomechanical Stress Analysis of Carotid Atheroma: A Comparison of Single Transient Ischaemic Attack, Recurrent Transient Ischaemic Attacks, Nondisabling Stroke and Asymptomatic Patient Groups

U. Sadat1,2, Z. Teng1, V.E. Young1 , M.J. Graves1, M.E. Gaunt2, J.H. Gillard1

1 University Department of Radiology, University of Cambridge, Cambridge, UK
2 Cambridge Vascular Unit, Addenbrooke’s Hospital, Cambridge, UK

Eur J Vasc Endovasc Surg, 41:83-90, 2011

Abstract: Vulnerable carotid plaques are associated with cerebrovascular ischaemic events. High-resolution magnetic resonance (MR) imaging not only allows the morphological assessment of such plaques, but also provides geometrical data, which can be used for biomechanical stress analysis. We assess its utility to assess the plaque stress profiles of symptomatic (transient ischaemic attack (TIA) and non-disabling stroke) and asymptomatic patients.

Keywords: Carotid plaque — Atherosclerosis — Magnetic resonance imaging — Biomechanical stresses — Stroke — Transient ischaemic attack

 

A Mechanical Model for CCK-Induced Acalculous Gallbladder Pain

W.G. Li,1 X.Y. Luo,1 N.A. Hill,1 R.W. Ogden,1 A. Smythe,2 A. Majeed,22 and N. Bird2

1 School of Mathematics and Statistics, University of Glasgow, Glasgow G12 8QW, UK
2 Academic Surgical Unit, Royal Hallamshire Hospital, Sheffield S10 2JF, UK

Annals of Biomedical Engineering, 39(2):786-800, 2011

Abstract: This study investigates the potential correlation between acalculous biliary pain and mechanical stress during the bile-emptying phase. This study is built on the previously developed mathematical model used to estimate stress in the gallbladder wall during emptying [Li, W. G., X. Y. Luo, et al. Comput. Math. Methods Med. 9(1):27-45, 2008]. Although the total stress was correctly predicted using the previous model, the contribution from patient-specific active stress induced by the cholecystokinin (CCK) test was overlooked. In this article, we evaluate both the active and passive components of pressure in a gallbladder, which undergoes isotonic refilling, isometric contraction and emptying during the infusion of CCK. The pressure is estimated from in vivo ultrasonographical scan measurements of gallbladder emptying during CCK tests, assuming that the gallbladder is a thin ellipsoidal membrane. The passive stress is caused by the volume and shape changes during refilling at the gallbladder basal pressure, whereas the active stress arises from the pressure rise during the isometric gallbladder contraction after the CCK infusion. The effect on the stress estimates of the gallbladder to the liver is evaluated to be small by comparing numerical simulations of a gallbladder model with and without a rigid 'flat top' boundary.

Keywords: Gallbladder — Active stress — Passive stress — Acalculous biliary pain — Emptying — Refilling — Isometric contraction — Isotonic refilling — CCK

 

Preconsolidation, structural strength of soil, and its effect on subsoil upper structure interaction

P. Kuklík

Czech Technical University in Prague, Faculty of Civil Engineering, 166 29 Prague, Prague 6, Czech Republic

Engineering Structures, 33: 1195-1204, 2011

Abstract: When constructing a building, manufactured materials are used. That is the reason for their excellent material properties. In the case of the foundation, the natural condition of the soils must mostly always be respected. The geostatical stress plays a significant role on the subsoil behavior because it is the de facto natural form of the soil compaction. The soil has a memory of the highest stress that has ever been loaded on it. The soil can be considered incompressible if the magnitude of a surcharge is lower. In engineering practice the construction of higher buildings is founded in a deeper hole so that the depth of the influence zone achieves an acceptable value for the future surcharge of the upper structure. For very tall buildings, the deep hole foundation must be prolonged by piles. In particular, this article deals with laboratory testing that provides the preconsolidation. In Czech, we term it the structural strength of soil. The test provides the initial void ratio as well as the initial coefficient of fully saturated hydraulic conductivity. The isotropic consolidation test with the triaxial test apparatus and consequent knowledge of the pore pressure course was chosen to determine the initial soil properties, including the preconsolidation level. Derived theory together with the genetic algorithms provide an efficient tool for the determining parameters. Good knowledge of the influence zone is crucial when solving soil structure interaction. The progress of the influence zone was considered from the extensive research carried out at the University of Brasília, Brazil. Thus, using the measurements, the econsolidation and its effect were verified in situ. The derived formulas and presented graphs for influence zone depth estimation have considerable importance for civil engineering practice. The Kantorovich method together with the strategy of convolution was used to reach dimensional reduction when deriving analytical formulas. Recommended results and formulas were verified against FEM code ADINA.

Keywords: Influence zone — Preconsolidation — Structural strength — FEM — Triaxial test — In situ testing — Deep foundation — Layered subsoil — Modified Cam clay model — Kantorovich method — Theory of convolution

 

Dynamic characteristic of ice-shedding on UHV overhead transmission lines

X. Meng1, L. Wang1, L.Hou2, G. Fu1, B. Sun1, M. MacAlpine1, W. Hu3, Y. Chen3

1 Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, Guangdong Province, China
2 State Grid Corporation of China, AC Project Construction Branch, Beijing 100140, China
3 State Grid Electric Power Research Institute, Wuhan 430074, Hubei Province, China

Cold Regions Science and Technology, 66: 44-52, 2011

Abstract: The dynamic effect of ice-shedding can cause mechanical damage and electrical faults due to the clashing of conductors. The ice-shedding problem is more serious on UHV lines as the quantity of bundled conductors and the cross-sectional areas of the conductors are larger. Consideration of the ice-shedding problems is very important in determining the alignment of the conductors, the type of towers and the configurations of spans. In this paper, the actual dynamic responses of the conductor displacement and tension are acquired through physical testing, in which the natural ice formed on conductors is simulated by lumped loads hanging on the conductors, using full-size multi-span configurations. Various ice- shedding modes are considered. Furthermore, a multiple degrees of freedom dynamic model of the multi-span lines, suitable for analyzing ice-shedding, has been developed and gives good agreement between the computation and test results, which demonstrates the validity of both the use of lumped-loads in the tests and of the numerical simulation program, which may therefore be applied to both existing UHV transmission lines and the design of new lines.

Keywords: Simulation test — UHV — Overhead transmission line — Ice shedding — Multi-span configurations — Numerical computation

 

Multi-physics MRI-based two-layer fluid–structure interaction anisotropic models of human right and left ventricles with different patch materials: Cardiac function assessment and mechanical stress analysis

D. Tang1, C. Yang1,2, T. Geva3,4, G. Gaudette5, P.J. del Nido6,7

1 Mathematical Sciences Department, Worcester Polytechnic Institute, Worcester, MA 01609, USA
2 School of Mathematics, Beijing Normal University, Beijing, China
3 Department of Cardiology, Children’s Hospital Boston, Boston, MA 02115, USA
4 Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA
5 Department of Biomedical Engineering, Worcester Polytechnic Institute, MA 01609, USA
6 Department of Cardiac Surgery, Children’s Hospital Boston, Boston, MA 02115, USA
7 Department of Surgery, Harvard Medical School, Boston, MA 02115, USA

Computers and Structures, In press 2011

Abstract: Multi-physics right and left ventricle (RV/LV) fluid–structure interaction (FSI) models were introduced to perform mechanical stress analysis and evaluate the effect of patch materials on RV function. The FSI models included three different patch materials (Dacron scaffold, treated pericardium, and contracting myocardium), two-layer construction, fiber orientation, and active anisotropic material properties. The models were constructed based on cardiac magnetic resonance (CMR) images acquired from a patient with severe RV dilatation and solved by ADINA. Our results indicate that the patch model with contracting myocardium leads to decreased stress level in the patch area, improved RV function and patch area contractility.

Keywords: Right ventricle — Congenital heart disease — Heart model — Dacron scaffold patch — Fluid–structural interaction

 

Numerical simulation of the electron beam welding process

P. Lacki1, K. Adamus2

1 Faculty of Civil Engineering, Czestochowa University of Technology, Akademicka 3, Czestochowa 42-218, Poland
2 Faculty of Mechanical Engineering and Computer Science, Armii Krajowej 21, Czestochowa 42-201, Poland

Computers and Structures, In press 2011

Abstract: Electron beam welding is a highly efficient and precise welding method that is being increasingly used in industrial manufacturing and is of growing importance in industry. Compared to other welding processes it offers the advantage of very low heat input to the weld, resulting in low distortion in components. Modeling and simulation of the laser beam welding process has proven to be highly efficient for research, design development and production engineering. In comparison with experimental studies, a modeling study can give detailed information concerning the characteristics of weld pool and their relationship with the welding process parameters (welding speed, electron beam power, workpiece thickness, etc.) and can be used to reduce the costs of experiments. A simulation of the electron beam welding process enables estimation of weld pool geometry, transient temperature, stresses, residual stresses and distortion. However this simulation is not an easy task since it involves the interaction of thermal, mechanical and metallurgical phenomena. Understanding the heat process of welding is important for the analysis of welding structure, mechanics, microstructure and controlling weld quality. In this paper the results of numerical simulation of electron beam welding of tubes were presented. The tubes were made of 30HGSA steel. The numerical calculation takes into consideration thermomechanical coupling (TMC). The simulation aims at: analysis of the thermal field, which is generated in welding process, determination of the heat-affected zone and residual stresses in the joint. The obtained results allow for determination both the material properties, and stress and strain state in the joint. Furthermore, numerical simulation allows for optimization of the process parameters (welding speed, power of the heat source) and shape of the joint before welding. The numerical simulation of electron beam welding process was carried out with the ADINA System v. 8.6. using finite element method.

Keywords: Electron beam welding (EBW) — Heat-affected zone — Numerical simulation — 3D conical heat source — Thermomechanical coupling analysis

 

Static behavior and bifurcation of a monosymmetric open cross-section thinwalled beam: Numerical and experimental analysis

A. Di Egidio1 and F. Vestroni2

1 Department of Structural, Hydraulic and Geotechnical Engineering, University of L'Aquila, L'Aquila, Italy
2 Department of Structural and Geotechnical Engineering, University of Rome “La Sapienza”, Rome, Italy

International Journal of Solids and Structures, In press 2011

Abstract: The aim of the paper is the numerical and experimental validation of a previously developed nonlinear one-dimensional model of inextensional, shear undeformable, thin-walled beam with an open cross-section. Nonlinear in-plane and out-of-plane warping and torsional elongation effects are included in the model. To better understand the role of these new contributions a beam with a section with one symmetry axis, undergoing moderately large flexural curvatures and large torsional curvature is taken into account. To obtain a section of a cantilever beam for which the torsional curvature is expected to prevail with respect to the flexural ones, a preliminary study is performed. The attention is focused on the response to static forces and on the stability of the equilibrium branches. Analytical results are compared with results of two different nonlinear finite element models and mainly with experimental results to confirm the validity of the analytical model. Interesting results are obtained for the critical values of the flexural-torsional instability loads.

Keywords: Open cross section beam — Nonlinear warping — Torsional elongation — Experimental investigation — Finite element model — Flexural-torsional instability

 

Investigation of hemodynamics in the development of dissecting aneurysm within patient-specific dissecting aneurismal aortas using computational fluid dynamics (CFD) simulations

K.M. Tse1, P. Chiu2,3, H.P. Lee1, P. Ho2,3

1 Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576, Singapore
2 Department of Cardiac, Thoracic and Vascular Surgery, Yong Loo Lin School of Medicine, National University of Singapore, c/o National University Hospital Service Block, Basement 1, 5 Lower Kent Ridge Road, Singapore 119074, Singapore
3 Department of Surgery, Yong Loo Lin School of Medicine, National University of Singapore, c/o National University Hospital Service Block, Basement 1, 5 Lower Kent Ridge Road, Singapore 119074, Singapore

Journal of Biomechanics, In press 2011.

Abstract: Aortic dissecting aneurysm is one of the most catastrophic cardiovascular emergencies that carries high mortality. It was pointed out from clinical observations that the aneurysm development is likely to be related to the hemodynamics condition of the dissected aorta. In order to gain more insight on the formation and progression of dissecting aneurysm, hemodynamic parameters including flow pattern, velocity distribution, aortic wall pressure and shear stress, which are difficult to measure in vivo, are evaluated using numerical simulations. Pulsatile blood flow in patient-specific dissecting aneurismal aortas before and after the formation of lumenal aneurysm (pre-aneurysm and post-aneurysm) is investigated by computational fluid dynamics (CFD) simulations. Realistic time-dependent boundary conditions are prescribed at various arteries of the complete aorta models. This study suggests the helical development of false lumen around true lumen may be related to the helical nature of hemodynamic flow in aorta. Narrowing of the aorta is responsible for the massive recirculation in the poststenosis region in the lumenal aneurysm development. High pressure difference of 0.21 kPa between true and false lumens in the pre-aneurismal aorta infers the possible lumenal aneurysm site in the descending aorta. It is also found that relatively high time-averaged wall shear stress (in the range of 4–8 kPa) may be associated with tear initiation and propagation. CFD modeling assists in medical planning by providing blood flow patterns, wall pressure and wall shear stress. This helps to understand various phenomena in the development of dissecting aneurysm.

Keywords: Aortic dissecting aneurysm — Lumenal aneursym — Computational fluid dynamics (CFD) — Simulation — Hemodynamics — Pre- and post-aneurismal patient-specific models

 

Timing of tensor and levator veli palatini force application determines Eustachian tube resistance patterns during the forced-response test

S.N. Ghadiali1,2, E.D. Bell3, J.D. Swarts4

1 Department of Biomedical Engineering, The Ohio State University, Columbus, OH 43210, United States
2 Department of Internal Medicine, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Ohio State University Medical Center, Columbus, OH 43210, United States
3 Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, PA 18015, United States
4 Department of Pediatric Otolaryngology, Children’s Hospital of Pittsburgh, Pittsburgh, PA 15213, United States

Auris Nasus Larynx, 37:720-729, 2010

Abstract: The forced-response test (FRT) is used to assess eustachian tube (ET) function in patients with middle ear disease (otitis media). This test often documents a dynamic pattern of luminal dilation and constriction during swallowing which can be quantified as a function relating active tubal resistance with time. The goal of this study is to use a generalized finite element model (FEM) to test the hypothesis that the relative timing of muscle force application by the tensor veli palatini muscle (mTVP) and levator veli palatini muscle (mLVP) on the ET determines the form of active resistance functions.

Keywords: Muscle timing — Finite element method — Tissue mechanics — Otitis media —  Eustachian tube function

 

Intraplaque hemorrhage is associated with higher structural stresses in human atherosclerotic plaques: an in vivo MRI-based 3d fluid-structure interaction study

X. Huang1,2, Z. Teng2,3, G. Canton4, M. Ferguson4, C. Yuan4, D. Tang2

1 School of Mathematical Sciences, Xiamen University, Xiamen, Fujian 361005, PR China.
2 Mathematical Sciences Department, Worcester Polytechnic Institute, MA 01609, USA.
3 University Department of Radiology, University of Cambridge, Cambridge, UK.
4 Deparment of Radiology, University of Washington, Seattle, WA 98195, USA.

BioMedical Engineering OnLine, 9:86, 2010

Abstract:
Background: Studies using medical images have shown that intraplaque hemorrhage may accelerate plaque progression and may produce a stimulus for atherosclerosis development by increasing lipid core and plaque volume and creating new destabilizing factors. Image-based 3D computational models with fluid-structure interactions (FSI) will be used to perform plaque mechanical analysis and investigate possible associations between intraplaque hemorrhage and both plaque wall stress (PWS) and flow shear stress (FSS).
Methods: In vivo MRI data of carotid plaques from 5 patients with intraplaque hemorrhage confirmed by histology were acquired. 3D multi-component FSI models were constructed for each plaque to obtain mechanical stresses. Plaque Wall Stress (PWS) and Flow Shear Stress (FSS) were extracted from all nodal points on the lumen surface of each plaque for analysis.
Results: The mean PWS value from all hemorrhage nodes of the 5 plaques combined was higher than that from non-hemorrhage nodes (75.6 versus 68.1 kPa, P = 0.0003). The mean PWS values from hemorrhage nodes for each of the 5 plaques were all significantly higher (5 out of 5) than those from non-hemorrhage nodes (P < 0.05). The mean FSS value from all hemorrhage nodes of the 5 plaques combined was 30.4% higher than that from all non-hemorrhage nodes (15.0 versus 11.5 dyn/cm2, P = 0.0002). However, the mean flow shear stress values from individual cases showed mixed results: only one out of five plaques showed mean FSS value from hemorrhage nodes was higher than that from non-hemorrhage nodes; three out of five plaques showed that their mean FSS values from hemorrhage nodes were lower than those from non-hemorrhage nodes; and one plaque showed that the difference had no statistical significance.
Conclusion: The results of this study suggested that intraplaque hemorrhage nodes were associated with higher plaque wall stresses. Compared to flow shear stress, plaque wall stress has a better correlation with plaque component feature (hemorrhage) linked to plaque progression and vulnerability. With further validation, plaque stress analysis may provide additional stress indicators for image-based vulnerability assessment.

 

Mechanical behavior of the erythrocyte in microvessel stenosis

Z. Zhang1,2 & X. Zhang2

1 State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian 116024, China
2 School of Aerospace, Tsinghua University, Beijing 100084, China

Sci China Life Sci, doi: 10.1007/s11427-011-4152-3, 2010

Abstract: The passage of red blood cells (RBCs) through capillaries is essential for human blood microcirculation. This study used a moving mesh technology that incorporated leader-follower pairs to simulate the fluid-structure and structure-structure interactions between the RBC and a microvessel stenosis. The numerical model consisted of plasma, cytoplasm, the erythrocyte membrane, and the microvessel stenosis. Computational results showed that the rheology of the RBC is affected by the Reynolds number of the plasma flow as well as the surface-to-volume ratio of the erythrocyte. At a constant inlet flow rate, an increased plasma viscosity will improve the transit of the RBC through the microvessel stenosis. For the above reasons, we consider that the decreased hemorheology in microvessels in a pathological state may primarily be attributed to an increase in the number of white blood cells. This leads to the aggregation of RBCs and a change in the blood flow structure. The present fundamental study of hemorheology aimed at providing theoretical guidelines for clinical hemorheology.

Keywords: Red blood cell — Moving mesh — Leader-follower pair — Rheology — Fluid-structure interaction

 

 

Volume integral equation method for multiple isotropic inclusion problems in an infinite solid under tension or in-plane shear

J. Lee

Department of Mechanical and Design Engineering, Hongik University, Jochiwon-Eup, Yeonki-Gun, Chungnam, 339-701, Korea

Journal of Mechanical Science and Technology, 24(12):2529-2537, 2010

Abstract: A volume integral equation method (VIEM) is introduced for the solution of elastostatic problems in an unbounded isotropic elastic solid containing interacting multiple isotropic inclusions subject to uniform remote tension or in-plane shear. This method is applied to two-dimensional problems involving long parallel cylindrical inclusions. A detailed analysis of the stress field at the interface between the matrix, and the central inclusion is carried out for square and hexagonal packing of the inclusions. The effects of the number of isotropic inclusions and various fiber volume fractions on the stress field at the interface between the matrix and the central inclusion are also investigated in detail. The accuracy and efficiency of the method are examined in comparison with results obtained from analytical and finite element methods.

Keywords: Composite materials — Inclusions — Integral equations — Stresses — Titration —  Volume fraction

 

Seismic Design Recommendations for Steel Girder Bridges with Integral Abutments

G. Pekcan, A.M. Itani, and E. Monzon

Department of Civil and Environmental Engineering, University of Nevada, Reno, Reno, NV 89557

Proc. TRB 2010 Annual Meeting, 2010

Abstract: This paper discusses the results of the longitudinal seismic behavior of straight bridges with integral abutments. Detailed nonlinear finite element (FE) models were utilized to establish the flexibility (translational and rotational) of the steel plate girders and the abutment connections. These connection springs were incorporated in a three dimensional global model of an integral abutment bridge to study the structural dynamics characteristics, as well as the seismic load path and distribution to piles, soil, girder elements. A procedure was demonstrated to determine embedment length of steel girders in the abutment to ensure the connection rigidity and more importantly to ensure that the piles will develop their ultimate flexural capacity.

 

Development of Design Parameters for Mass Concrete Using Finite Element Analysis

M. Tia, C. Ferraro, A. Lawrence, S. Smith, F. Ochiai

Dept. of Civil and Coastal Eng., 365 Weil Hall – P.O. Box 116580, University of Florida, Gainesville, FL 32399.

Florida Department of Transportation Report No. 000548 63, 2010

Abstract: A finite element model for analysis od mass concrete was developed in this study. To validate the developed model, large concrete blocks made with four different types of concrete, typical of use in mass concrete applications in Florida, were made and monitored for their temperature and strain developments, and compared with the computed temperature and stress distributions from the finite element model. A parametric analysis was also conducted to determine the effects of various factors on the temperature distribution, induced stresses and the cracking risk. Investigation was also made on testing methods to measure the thermal and mechanical properties of mass concrete needed as input parameters for the finite element model.

Keywords: Mass Concrete — Finite Element Model — Isothermal Calorimetry — Heat of Hydration — Insulation — Temperature Differential — Cracking Risk — Micro-cracks — Parametric Study — Tensile Strength

 

On The Kinematics Of Solar Mirrors Using Massively Parallel Binary Actuation

S.J. Lee1, A.M. Bilton1, S. Dubowsky2

1 Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, MA 02139
2 Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139

Proceedings of the ASME 2010 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference IDETC/CIE 2010, 2010

Abstract: Precision mirrors are required for effective solar energy collectors. Manufacturing such mirrors and making them robust to disturbances such as thermal gradients is expensive. In this paper, the use of parallel binary actuation to control the shape of mirrors for solar concentrators is explored. The approach embeds binary actuators in a compliant mirror substructure. Actuators are deployed in a specified pattern to correct the mirror shape. The analysis for binary-actuated compliant mirror structures is presented. Analytical models are developed for one-dimensional and two-dimensional compliant structures with embedded binary actuators. These analytical models are validated using finite element analysis and experimental studies. The models and experiments demonstrate the capabilities of binary actuated mirrors. System workspace is explored, the principle of superposition required for their control is demonstrated, as is the mirror ability to correct its figure.

 

 

Relative contributions of strain-dependent permeability and fixed charged density of proteoglycans in predicting cervical disc biomechanics: A poroelastic C5–C6 finite element model study

M. Hussain1, R.N. Natarajan2,3, G. Chaudhary4, H.S. An2, G.B.J. Andersson2

1 Division of Research, Logan University, 1851 Schoettler Rd, Chesterfield, MO 63017, USA
2 Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL 60612, USA
3 Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
4 Medical Residency Applicant, St. Louis, MO 63108, USA

Medical Engineering & Physics, In press 2010

Abstract: Disc swelling pressure (P(swell)) facilitated by fixed charged density (FCD) of proteoglycans (P(fcd)) and strain-dependent permeability (P(strain)) are of critical significance in the physiological functioning of discs. FCD of proteoglycans prevents any excessive matrix deformation by tissue stiffening, whereas strain-dependent permeability limits the rate of stress transfer from fluid to solid skeleton. To date, studies involving the modeling of FCD of proteoglycans and strain-dependent permeability have not been reported for the cervical discs. The current study objective is to compare the relative contributions of strain-dependent permeability and FCD of proteoglycans in predicting cervical disc biomechanics. Three-dimensional finite element models of a C5-C6 segment with three different disc compositions were analyzed: an SPFP model (strain-dependent permeability and FCD of proteoglycans), an SP model (strain-dependent permeability alone), and an FP model (FCD of proteoglycans alone). The outcomes of the current study suggest that the relative contributions of strain-dependent permeability and FCD of proteoglycans were almost comparable in predicting the physiological behavior of the cervical discs under moment loads. However, under compression, strain-dependent permeability better predicted the in vivo disc response than that of the FCD of proteoglycans.

Keywords: Fixed charged density of proteoglycans — Strain-dependent permeability and porosity — Cervical disc biomechanics — Tissue swelling — Poroelastic finite element

 

Fracture Mechanics Prevention: Comprehensive Approach-based Modelling?

M. Kuffová1, P. Nečas2

1 Mechanical Engineering Department, Armed Forces Academy of General Milan Rastislav Stefanik, Demanova 393, 031 06 Liptovsky Mikulas 6, Slovakia
2 Armed Forces Academy of General Milan Rastislav Stefanik, Vice-Rector for Science, Demanova 393, 031 06 Liptovsky Mikulas 6, Slovakia

Acta Polytechnica Hungarica, 7(5):5-17, 2010

Abstract: The paper presented focuses on fatigue crack growth observation in the microstructure of magnesium alloy AZ 91D using finite element software ADINA. ADINA offers a wide range of capabilities based on reliable and efficient finite element procedures. For this reason, ADINA is often chosen for applications where reliability and safety is of critical importance in different industries such as biomedical, automotive, nuclear, forming, civil engineering, hi-tech and others, e.g., in the dynamic analysis of bridge structures – earthquake analysis ,in biomedical applications, in the design of nuclear reactors or in studies on safety. This work shows efficiency and good correlation between experimental and numerical results and verifies this program for its utilization in the field of fatigue endurance determination and evaluation.

Keywords: Microstructure — Modelling and simulation — Material fatigue — Experiments — Cracks and defects — Reliability and personnel security

 



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