ADINA Publications

Page 23

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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Parametrical Study of Hydrodynamic Parametrical Study of Hydrodynamic Seal Using a 2D Design Code and Seal Using a 2D Design Code and Comparing with 3D CFD Model Comparing with 3D CFD Model

X. Zheng

Perkin Elmer Centurion Mechanical Seals, Warwick, Rhode Island

NASA/CP—2005-213655/VOL1, 2005

Abstract: Hydrodynamic film-riding gas seal, having been successfully used in industrial pump and compressor applications for decades, is now finding way into aeroengines. Aerospace applications require the seal work robustly under various speeds and constantly changing pressures. Maintaining seal face flatness is also more challenging in aerospace than in industrial applications because of the seal size and the rapid thermal transition in aero-engines. Another difficulty in aerospace application comes from the altitude condition, where air is thin, not enough opening force may be generated to separate the seal faces from touching. Therefore, the hydrodynamic groove design is more critical in aerospace application. In order to maximize the seal performances, the groove shape and depth are optimized for the worst application condition, such as at the altitude, with using a 2D model coupled with a non-linear optimization procedure.

 

Computational simulation of human upper airway collapse using a pressure-/state-dependent model of genioglossal muscle contraction under laminar flow conditions

Y. Huang, A. Malhotra, and D.P. White

Department of Medicine, Division of Sleep Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts

J Appl Physiol, 99: 1138–1148, 2005

Abstract: A three-element, pressure- and state (sleep and wake) -dependent contraction model of the genioglossal muscle was developed based on the microstructure of skeletal muscle and the cross-bridge theory. This model establishes a direct connection between the contractile forces generated in muscle fibers and the measured electromyogram signals during various upper airway conditions. This effectively avoids the difficulty of determining muscle shortening velocity during complex pharyngeal conditions when modeling the muscle’s contractile behaviors. The activation of the genioglossal muscle under different conditions was then simulated. A sensitivity analysis was performed to determine the effects of varying each modeled parameter on the muscle’s contractile behaviors. This muscle contraction model was then incorporated into our anatomically correct, two-dimensional computational model of the pharyngeal airway to perform a finiteelement analysis of air flow, tissue deformation, and airway collapse. The model-predicted muscle deformations are consistent with previous observations regarding upper airway behavior in normal subjects.

Keywords: genioglossus -  muscle activity -  finite element -  pharyngeal airway -  collapsibility

Quantitative Assessment of Coronary Artery Plaque Vulnerability by High-Resolution Magnetic Resonance Imaging and omputational Biomechanics: A Pilot Study ex Vivo

Jie Zheng1, Issam El Naqa2, Faith E. Rowold1, Thomas K. Pilgram1, Pamela K. Woodard1, Jeffrey E. Saffitz3, and Dalin Tang4

1Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri, USA
2Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri, USA
3Department of Pathology, Washington University School of Medicine, St. Louis, Missouri, USA
4Mathematical Sciences Department, Worcester Polytechnic Institute, Worcester, Massachusetts, USA

Magn Reson Med., 54(6): 1360–1368, 2005

Abstract:
The risk of atherosclerotic plaque disruption is thought to be closely related to plaque composition and rupture triggers such as external mechanical forces. The purpose of this study was to integrate MR imaging and computational techniques for the quantification of plaque vulnerability with morphologic data and biomechanical stress/strain distributions that were all based on high-resolution MR images of coronary artery plaque specimens ex vivo. Twenty-two coronary artery plaque specimens were selectively collected from 10 cadavers. Multislice T2-weighted spin echo images were acquired with a resolution of 100 × 100 μm2. Histopathological images were used as the gold standard for the identification of plaque components and vulnerability. Plaque components were classified on MR images, and the stress/strain components were calculated with a two-dimensional computational model with fluid–structure interactions. As expected, vulnerable plaques appeared to result from a large lipid pool, a thin fibrous cap, and some critical stress/strain conditions. An empiric vulnerability marker was derived and was closely related to the vulnerability score that was determined through pathologic examination. Noninvasive quantification of the MR contrast and mechanical properties of plaque may provide a comprehensive biomarker for the assessment of vulnerability of atherosclerotic plaques.

Keywords:  MRI - atherosclerosis - coronary disease - biomechanics - vulnerability

 

Premium & Semi-premium Connections Design Optimization for Varied Drilling-with-Casing Applications

N.J. Santi1, G.E. Carcagno1, R. Toscano2

1 Tenaris
2 Center for Industrial Research, FUDETEC, Av. Córdoba 320, 1054 Buenos Aires, Argentina

Proc. 2005 Offshore Technology Conference, 2005

Abstract: As high resistance to fatigue loading together with high overtorque and compression capacities are at the top of a list of required features for connections to be used in new drilling
and completion techniques such as casing drilling, then special connections with enhanced performance need to be developed. On the other hand, a cost-effective solution should be chosen
to balance the performance when considering low-demanding shallow wells for which sophisticated premium connections could be uneconomical. This paper describes the development and evaluation of premium and semi-premium connections for tubing/casing which were developed to stand cyclic loads and reach an extended number of cycles under such conditions. The development process of an integral connection for casing sizes targetting very demanding applications comprised Finite Element Analysis (FEA) and Full Scale Fatigue Test (FSFT)

showing Stress Concentration Factors (SCF) lower than 2. In addition, during the development of the semi-premium connection to cover less demanding applications, some of these techniques were used to optimize the results until getting SCF lower than 3, good enough when low doglegs are present. The results of the tests are plotted in S-N (Alternating Stress vs Number of cycles to failure) curve with a standard curve as a reference. As per the results, both types of connections achieved the objective set at the beginning of the development process now being suitable alternatives for low and high demanding drilling/completion operations.

 

Parametrical Study of Hydrodynamic Seal Using a 2D Design Code and Comparing with a 3D CFD Model

X. Zheng

Perkin Elmer Centurion Mechanical Seals, Warwick, Rhode Island

Proceedings of the ASME Turbo Expo 2005, 2005

Abstract: Hydrodynamic non-contacting face seals, characterized with small leakage and long life, have been used in almost every sector of industrial pump applications. However, its application to aerospace has been proven challenging mainly owing to the high-speed, large size and vastly varied operating conditions in an engine environment. Design optimization is critical for a successful application in aero-engine. Seals designed with optimized hydrodynamic grooves based on a 2D code have been qualified for production. For certain seal applications, the optimized hydrodynamic grooves can be very different from what is usually used in aerospace applications. In order to verify such extreme design and confirm the optimization procedure, a three-dimensional CFD model was developed. The influences of hydrodynamic features were studied with the 3D CFD model and compared with the solution of the two-dimensional design code. The 3D computation generally supports the 2D result, and the seal design was further validated through rig tests.

Keywords: Computational fluid dynamics — Hydrodynamics — Leakage (fluid) — Mathematical models — Optimization — Parameter estimation — Pumps

 

Three-Dimensional Dynamic Analysis of Flexible Conventional Pavement Foundation

Bassam Saad1; Hani Mitri2; and Hormoz Poorooshasb3

1 McGill Univ., Dept of Mining, Metals and Materials Engineering, 3450 University St., Montreal, Que., Canada H3A 2A7
2 McGill Univ., Dept of Mining, Metals and Materials Engineering, 3450 University St., Montreal, Que., Canada H3A 2A7
3 Dept. of Building, Civil and Environmental Engineering, Concordia, Univ., 1257 Guy St., Montreal, Que., Canada, H3G 1M8.

Journal of Transportation Engineering, 131(6): 460-469, 2005

Abstract: The paper examines the dynamic response of flexible conventional pavement systems to single wheel traffic loads in terms the pavement design criteria, namely the fatigue strain at the bottom of the asphalt concrete layer and rutting strain at the top of
subgrade material. Model setup including geometry, boundary conditions, and load wave characterization are presented. The effect elastoplasticity of the base material and elastoplasticity with strain hardening of the subgrade material on the dynamic response of pavement system are first investigated. A detailed model parametric study then follows to show the effect of the base strength thickness and the subgrade quality on the fatigue and rutting strains and the vertical surface deflection. The study, conducted with program ADINA, employs a three-dimensional, implicit dynamic, finite element method.

Keywords: Finite element method — Dynamic analysis — Flexible pavements —  Elastoplasticity — Foundations

 

Local Maximal Stress Hypothesis and Computational Plaque Vulnerability Index for Atherosclerotic Plaque Assessment

D. Tang1, C. Yang1,2, J. Zheng3, P.K. Woodard3, J.E. Saffitz4, J.D. Petruccelli1, G.A. Sicard5, and C. Yuan6

1 Mathematical Sciences Department, Worcester Polytechnic Institute, Worcester, MA
2 Mathematics Department, Beijing Normal University, Beijing, P. R. China
3 Mallinkcrodt Institute of Radiology, Washington University, St. Louis, MO
4 Department of Pathology, Washington University, St. Louis, MO
5 Department of Surgery, Washington University, St. Louis, MO
6 Deparment of Radiology, University of Washington, Seattle, WA

Annals of Biomedical Engineering, 33(12):1789–1801, 2005

Abstract: It is believed that atherosclerotic plaque rupture may be related tomaximal stress conditions in the plaque.More careful examination of stress distributions in plaques reveals that it may be the local stress/strain behaviors at critical sites such as very thin plaque cap and locations with plaque cap weakness that are more closely related to plaque rupture risk. A “local maximal stress hypothesis” and a stress-based computational plaque vulnerability index (CPVI) are proposed to assess plaque vulnerability. A critical site selection (CSS) method is proposed to identify critical sites in the plaque and critical stress conditions which are be used to determine CPVI values. Our initial results based on 34 2D MRI slices from 14 human coronary plaque samples indicate that CPVI plaque assessment has an 85% agreement rate (91% if the square root of stress values is used) with assessment given by histopathological analysis. Large-scale and long-term patient studies are needed to further validate our findings for more accurate quantitative plaque vulnerability assessment.

Keywords: Stroke, Heart attack — Plaque cap rupture — Fluid-structure interaction —  Carotid artery — Coronary — Blood flow — Cardiovascular diseases

 

Project: Shaikh Zayed Bridge, Abu Dhabi, UAE

N. Alca, H.H. Ibrahim, P.G. Buckland

Buckland & Taylor Ltd.

GerwickNews, November 2005

Abstract: This article features highlights of the work of Buckland & Taylor Ltd. in assisting the contractor with the construction of the Shaikh Zayed Bridge.  The bridge was modeled using ADINA.

 

 

Handling refractory glaucoma: Gold microshunt implantation may be an option for lowering IOP

Nancy Groves, (Shlomo Melamed, ed.1)

1Sam Rothberg Glaucoma Center, Goldschleger Eye Institute, Sheba Medical Center, Tel-Hashomer, Israel

Ophthalmology Times, August 1, 2005

Abstract: Implantation of a gold microshunt (SOLX) in the eyes of patients with refractory glaucoma resulted in a mean reduction in IOP of 34% at 18 months. Findings from this study of 60 patients were promising, investigators reported. The device has received the CE mark in Europe, and FDA trials are being planned.

 

3D finite element analysis on functional gradient material piston

Wang, Su (Beihang University); Ni, Chunyang; Zhu, Xinxiong Source: Zhongguo Jixie Gongcheng/China Mechanical Engineering, v 16, n 22, Nov 25, 2005, p 2027-2030 Language: Chinese

ISSN: 1004-132X CODEN: ZJGOE8

Publisher: China Mechanical Engineering Magazine Office

Abstract: Theory of composite performance and finite element analysis software ADINA were used to compute temperature field and stress field of Functional Gradient Material Piston. The results indicate that using gradient aluminum matrix composite layer reinforced by ceramic fibers can change the temperature distribution of piston and relax the stress at interface between the gradient aluminum matrix composite layer reinforced by ceramic fibers and the noumenon of piston which caused by mismatch among different coefficients of thermal expansion. (7 refs.)

 


Modelling of the nanoindentation process of ultrathin films

Zimmerman, J. (Institute of Micromechanics and Photonics); Majewski, T.; Rymuza, Z. Source: Zeitschrift fuer Metallkunde/Materials Research and Advanced Techniques, v 96, n 11, November, 2005, p 1296-1300

ISSN: 0044-3093 CODEN: ZEMTAE

Publisher: Carl Hanser Verlag

Abstract: A model of the nanoindentation process was elaborated using the finite-element method. The ADINA software was used in the computation of the load-displacement curve. The distribution of stresses in the TiN film on a smooth substrate (Si) was found. The influence of mechanical material properties of the film and substrate on the process of indentation and the stress distribution was considered. The effect of yield stress, tip's radius and hardening modulus was discussed. The results were compared with the results of experimental nanoindentation tests performed for ultrathin films. © Carl Hanser Verlag. (17 refs.)

Keywords:  Ultrathin films  -  Indentation  -  Nanotechnology  -  Finite element method  -  Computer software  -  Microelectromechanical devices  -  Stress concentration  -  Elastic moduli

Secondary Keywords:  Nanoindentation  -  MEMS materials  -  Elastic-plastic deformation

 


Bending capacity of girth-welded pipes

Torselletti, Enrico (Snamprogetti); Vitali, Luigino; Bruschi, Roberte Source: Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE, v 3, Proceedings of the 24th International Conference on Offshore Mechanics and Arctic Engineering, 2005 - OMAE2005, 2005, p 619-627

CODEN: PIOSEB

Conference: 24th International Conference on Offshore Mechanics and Arctic Engineering, 2005, Jun 12-17 2005, Halkidiki, Greece Sponsor: ASME Ocean, Offshore, and Arctic Engineering Division

Publisher: American Society of Mechanical Engineers

Abstract: In the last ten years, several studies were completed with the aim to define a design format for the local buckling of pipes subjected to differential pressure, axial load and bending moment Experimental tests were carried out and simplified analytical solutions were developed in order to predict the pipe bending moment capacity and the associated level of deformation. Standard finite element (FE) structural codes, such as ABAQUS, ADINA, ANSYS, etc., were and are used as a "numerical testing laboratory", where the model is suitably calibrated to few experimental tests. The outcomes of these research efforts were, implemented in the design equations enclosed in international design rules, as DNV OS-F101. The local buckling design formats, included in these rules, give the limit bending moment and associated longitudinal strain as a function of the relevant parameters. The effect of the girth weld is introduced with a reduction factor only for what regards the strain at limit bending moment. This paper addresses the effects of the presence of the girth weld on both limit bending moment and corresponding compressive longitudinal strain. A 3-dimensionaI (3D) FE model developed in ABAQUS has been developed to perform a parametric analysis. The FE model results are shown to compare reasonably well with full scale experiments performed for on-shore pipelines. The limit bending moment is reduced by the weld misalignment and this reduction is also dependent on both internal pressure load and linepipe material mechanical strength. The FE results are compared with the limit bending moment calculated with DNV OS-F101. Copyright © 2005 by ASME. (5 refs.)

Keywords:  Pipe  -  Bending (deformation)  -  Buckling  -  Bending moments  -  Finite element method  -  Mathematical models  -  Parameter estimation

Secondary Keywords:  Girth-welded pipes  -  Bending capacity  -  Axial load  -  Design equations

 


Numerical modeling of plain concrete beams strengthened with externally bonded CFRP

Issa, Camille A. (Department of Civil Engineering, School of Engineering and Architecture, Lebanese American University); Awwad, Rita; Sfeir, Anthony Source: Proceedings of the 2005 ASCE International Conference on Computing in Civil Engineering, Computing in Civil Engineering - Proceedings of the 2005 International Conference, 2005, p 1267-1276

ISBN-10: 0784407940

Conference: 2005 ASCE International Conference on Computing in Civil Engineering, Jul 12-15 2005, Cancun, Mexico Sponsor: ASCE, Technical Council on Computing and Information Technology

Publisher: American Society of Civil Engineers

Abstract: A detailed finite element model for plain concrete beams strengthened with externally bonded CFRP sheets was developed using ADINA a commercially available code and specific materials behavior models. The beams are modeled in full length in two-dimensions and all the thicknesses are included in the FEM input data. 2D-solid, plane stress eight noded quadrilaterals are used to model the concrete and CFRP warps elements, and the reinforcement bars and CFRP sheets are modeled as three node truss elements. Comparisons are made for load-deflection plots at mid span; loads at failure and crack patterns at failure. Modeling simplifications and assumptions developed during this research are presented. Conclusions from current research efforts and recommendations for further studies are included. (2 refs.)

Keywords:  Concrete beams and girders  -  Codes (standards)  -  Data acquisition  -  Trusses  -  Cracks  -  Carbon fiber reinforced plastics  -  Finite element method  -  Mathematical models

Secondary  Keywords:  Plain Concrete  -  Reinforcement bars  -  Load-deflection plots  -  Specific materials

 


Computational simulation of flow over stepped spillways

Tabbara, Mazen (Department of Civil Engineering, School of Engineering and Architecture, Lebanese American University-LAU); Chatila, Jean; Awwad, Rita Source: Computers and Structures, v 83, n 27, October, 2005, p 2215-2224

ISSN: 0045-7949 CODEN: CMSTCJ

Publisher: Elsevier Ltd

Abstract: Numerical simulations of water flow over stepped spillways with different step configurations are presented. The finite element computational fluid dynamics module of the ADINA software was used to predict the main characteristics of the flow. This included the determination of the water surface, the development of skimming flow over corner vortices, and the determination of energy dissipation. Since the actual flow is turbulent, the k-ε flow model was used. A two-phase solution process was adopted in order to optimize the overall simulation efficiency. In the first phase, a simple yet reasonable water surface consisting of three straight lines was used as an initial guess and was treated as a fixed wall. In the second phase, the results from the first phase were used as initial conditions and the water surface was treated as a free surface that evolved to attain a steady state configuration. For all the cases considered, the predicted water surface profile over the entire length of the spillway was in close agreement with the experimentally measured water surface profile. The predicted energy dissipation was also comparable to the experimentally attained values. © 2005 Elsevier Ltd. All rights reserved. (24 refs.)

Keywords:  Spillways  -  Computational fluid dynamics  -  Finite element method  -  Energy dissipation  -  Turbulent flow  -  Optimization  -  Computer simulation

Secondary Keywords:  Stepped spillways  -  Experimental  -  Free surface  -  Water surface

 


Three-dimensional dynamic analysis of flexible conventional pavement foundation

Saad, Bassam (McGill Univ., Dept. of Mining Metals and Materials Engineering); Mitri, Hani; Poorooshasb, Hormoz Source: Journal of Transportation Engineering, v 131, n 6, June, 2005, p 460-469

ISSN: 0733-947X

Publisher: American Society of Civil Engineers

Abstract: The paper examines the dynamic response of flexible conventional pavement systems to single wheel traffic loads in terms of the pavement design criteria, namely the fatigue strain at the bottom of the asphalt concrete layer and rutting strain at the top of the subgrade material. Model setup including geometry, boundary conditions, and load wave characterization are presented. The effect of elastoplasticity of the base material and elastoplasticity with strain hardening of the subgrade material on the dynamic response of the pavement system are first investigated. A detailed model parametric study then follows to show the effect of the base strength and thickness and the subgrade quality on the fatigue and rutting strains and the vertical surface deflection. The study, conducted with program ADINA, employs a three-dimensional, implicit dynamic, finite element method. Journal of Transportation Engineering © ASCE. (29 refs.)

Keywords:  Pavements  -  Three dimensional computer graphics  -  Dynamic response  -  Traffic control  -  Structural design  -  Cracks  -  Strain measurement  -  Elastoplasticity  -  Strength of materials  -  Computational geometry  -  Finite element method  -  Boundary conditions  -  Mathematical models

Secondary  Keywords:  Flexible conventional pavement systems  -  Wheel traffic loads  -  Fatigue strains

 


Analysis of the nonlinear dynamic response of a 600 MW turbogenerator shafting

Jiao, Ying-Hou (Coll. of Mech. and Elec. Eng., Harbin Inst. of Technol.); Chen, Zhao-Bo; Jing, Jian-Ping; Qu, Xiu-Quan Source: Reneng Dongli Gongcheng/Journal of Engineering for Thermal Energy and Power, v 20, n 2, March, 2005, p 178-181 Language: Chinese

ISSN: 1001-2060 CODEN: RDGOEE

Publisher: Harbin Research Institute

Abstract: By employing a finite element method with equal-parameter elements a nonlinear dynamics model was set up for the shafting of a Chinese-made 600 MW Turbogenerator. With the use of a finite element analysis program ADINA an analysis and a calculation were conducted of the nonlinear dynamics response of the 600 MW turbogenerator shafting. During the calculation, by way of the user interface provided by the program ADINA the nonlinear oil-film force of the journal bearing has been taken into account and compared with the nonlinear dynamics analysis and calculation results. The results of the calculation indicate that the use of the program ADINA in conjunction with a nonlinear dynamics theory is essential and feasible for the nonlinear dynamics analysis and calculation of the shafting of large-sized turbogenerators, thus providing a solid basis for the nonlinear dynamics stability analysis and optimal design of the shafting of specific large-sized units. (6 refs.)

 

Computational analysis of the three-dimensional hemodynamics of the blood sac in the twin-pulse life-support system

Gi Seok Jeong1,6, Eun Bo Shim2, Hyun Jong Ko1, Chan Hyun Youn3, Kyung Sun4,6, Byoung Goo Min5

1Department of Mechanical Engineering, Kumoh National Institute of Technology, Kumi, Korea
2Department of Mechanical Engineering, Kangwon National University, Hyoja-dong, Chuncheon, Kangwon-do 200-701, Korea
3Information and Communications University, Taejeon, Korea
4Department of Thoracic and Cardiovascular Surgery, Medical College of Korea University, Seoul, Korea
5Department of Biomedical Engineering, Seoul National University Medical School, Seoul, Korea
6 Korea Artificial Organ Center, Korea University, Seoul, Korea

J Artif Organs (2004) 7:174–180

Abstract: Blood flow in the twin-pulse life-support system (T-PLS) pulsatile blood pump was simulated using a threedimensional rigid body–fluid–solid interaction model. This model can delineate the blood flow in the T-PLS resulting from operation of a moving actuator. The numerical method used in this study was a commercial finite element package called ADINA. We used a contact and fluid–solid interaction model to compute the blood hemodynamics in the sac. Blood flow is generated by the motion of the actuator, which strongly interacts with the solid material surrounding the blood. To obtain basic bioengineering data on the optimum operation of the T-PLS, we simulated four models in which the actuator moved at different speeds and investigated both the flow pattern and the distribution of
shear stress. During the contraction phase, a strong axial flow is observed around the outlet, whereas there is stagnant flow around the inlet. The maximum shear stress in each model depends on the operation mode; however, all four models have similar flow rates. The sinusoidal mode exhibited the lowest maximum shear stress and is thus considered the most efficient of the four operating modes.

Key words: Pulsatile blood pump - Three-dimensional blood flow - Rigid body–fluid–solid interaction - Maximum shear stress distribution

 

A preliminary theoretical investigation for developing an artificial meniscus

Singh, A. (Department of Mechanical, Industrial and Manufacturing Engineering, Northeastern University); Vaziri, A.; Nayeb-Hashemi, H. Source: Advances in Bioengineering, BED, Advances in Bioengineering - 2004, 2004, p 341-342

ISSN: 0360-9960 CODEN: ADBIDL

Conference: 2004 ASME International Mechanical Engineering Congress and Exposition, IMECE, Nov 13-19 2004, Anaheim, CA, United States Sponsor: ASME, Bioengineering Division

Publisher: American Society of Mechanical Engineers

Abstract: The effect of meniscectomy on the shear stress distributions through the joint knee cartilages was studied by modeling the cartilage as three layers. For this purpose, an axisymmetric finite element model of the knee joint was developed using finite element code, Adina. The model included the femoral and tibial cartilages, meniscus, and tibia. For the artificial meniscus, the material was considered as isotropic elastic with Young's modulus of elasticity varying from 10 MPa to 1600 Mpa. It was observed that meniscectomy causes the maximum shear stresses at the cartilage to increase substantially, with the maximum increase of nearly 450% at the cartilage interfaces. (5 refs.)

Keywords:  Cartilage  -  Joints (anatomy)  -  Stress concentration  -  Biomechanics  -  Pathology  -  Bone  -  Biomedical engineering  -  Finite element method  -  Shear stress  -  Elastic moduli

Secondary  Keywords:  Meniscus  -  Tibia  -  Isotropic materials  -  Human knee joint

 


3D computational mechanical analysis for human atherosclerotic plaques using MRI-based models with fluid-structure interactions

Tang, Dalin (Mathematical Sciences Department, Worcester Polytechnic Institute); Yang, Chun; Zheng, Jie; Woodard, Pamela K.; Sicard, Gregorio A.; Saffitz, Jeffrey E.; Kobayashi, Shunichi; Pilgram, Thomas K.; Yuan, Chun Source: Lecture Notes in Computer Science, v 3217, n 1 PART 2, Medical Image Computing and Computer-Assisted Intervention, MICCAI 2004 - 7th International Conference, Proceedings, 2004, p 328-336

ISSN: 0302-9743

Conference: Medical Image Computing and Computer-Assisted Intervention, MICCAI 2004 - 7th International Conference, Proceedings, Sep 26-29 2004, Saint-Malo, France

Publisher: Springer Verlag

Abstract: Atherosclerotic plaques may rupture without warning and cause acute cardiovascular syndromes such as heart attack and stroke. It is believed that mechanical forces play an important role in plaque progression and rupture. A three-dimensional (3D) MRI-based finite-element model with multi-component plaque structure and fluid-structure interactions (FSI) is introduced to perform mechanical analysis for human atherosclerotic plaques and identify critical flow and stress/strain conditions which may be related to plaque rupture. The coupled fluid and structure models are solved by ADINA, a well-tested finite-element package. Our results indicate that pressure conditions, plaque structure, component size and location, material properties, and model assumptions all have considerable effects on flow and plaque stress/strain behaviors. Large-scale patient studies are needed to validate the computational findings. This FSI model provides more complete stress/strain analysis and better interpretation of information from MR images and may lead to more accurate plaque vulnerability assessment and rupture predictions. © Springer-Verlag Berlin Heidelberg 2004. (9 refs.)

Keywords:  Cardiovascular system  -  Magnetic resonance imaging  -  Patient treatment  -  Stress analysis  -  Three dimensional  -  Computational methods  -  Finite element method

Secondary  Keywords:  Cardiovascular diseases  -  Computational mechanical analysis  -  Atherosclerotic plaques  -  Fluid-structure interactions (FSI)

 


One-way and two-way directional heavy-vehicle simulator loading effects on rutting in hot-mix asphalt pavements

Novak, Marc (365 Weil Hall, Dept. of Civ. and Coast. Engineering, University of Florida); Birgisson, Bjorn; Roque, Reynaldo; Choubane, Bouzid Source: Transportation Research Record, n 1896, 2004, p 208-214

ISSN: 0361-1981 CODEN: TRREDM

Publisher: National Research Council

Abstract: Instability rutting generally occurs within the top 5 cm (2 in.) of the asphalt layer when the structural properties of the asphalt concrete are inadequate to resist the stresses imposed on it. It is generally believed that near-surface transverse shear stresses perpetuate instability rutting. Field observations of heavy-vehicle simulator testing noted greater rutting in one-way directional loading than with two-way directional loading, even at lower temperatures and with longer rest periods between load applications. An analysis of stress states in the asphalt pavement layer using the three-dimensional finite element commercial code ADINA showed that longitudinal stress path patterns varied between the different directional loadings. A hypothesis was developed that the differences in longitudinal plane stress path patterns between one-way and two-way directional loading could be attributed to the different levels of rutting. A viscoelastic model with load applications simulating the different directional loadings was constructed and used to test this hypothesis. The viscoelastic model results indicated qualitatively that even with greater relaxation times, one-way directional loading produces greater strains. (18 refs.)

Keywords:  Automobile simulators  -  Asphalt pavements  -  Asphalt  -  Viscoelasticity  -  Tires  -  Shear stress  -  Finite element method  -  Mathematical models

Secondary  Keywords:  Hot-mix asphalt (HMA)  -  Florida Department of Transportation (FDOT)  -  Rutting  -  Stress path patterns

 


Deformability of WC-Co sinters and 17-4 PH steel brazed joints

Nowacki, J. (Institute of Materials Engineering, Technical University of Szczecin); Kawiak, M. Source: Journal of Materials Processing Technology, v 157-158, n SPEC. ISS., Dec 20, 2004, p 584-589

ISSN: 0924-0136 CODEN: JMPTEF

Publisher: Elsevier Ltd

Abstract: Tests of the vacuum brazing joints of WC-Co sinters and age-hardened steels of the 17-4 PH using the Cu solder were carried out. Stresses and strains of the joints have been analysed. The joints have been used in large dimension spinning nozzles of a die for polyethylene granulation, in that considerable strength and ductility of the joints are required. Shearing tests of the joints have been executed on specimens done in the spinning nozzle brazed joint model. The results of mechanical properties of the joint tests were a base for the fooling them numerical investigations. Numerical calculation of tensions and deformations of the joints have been made by means of the finite element method of the ADINA system. Influence of the geometrical parameters of the joints like the connection thickness as well as a fixed load on stresses and displacements of the joints have been analysed. Results of the experimental test were the base for identification and verification of the theoretical model parameters. The thickness of the joints has an essential influence on the values of the local stress and the significant influence on the joint rigidity. In a case of the considered joints the values of the local stress differences have been considerable (a few hundred percent) in dependence of a fixed load manner. © 2004 Elsevier B.V. All rights reserved. (12 refs.)

Keywords:  Soldered joints  -  Steel  -  Vacuum brazing  -  Tungsten alloys  -  Cobalt  -  Copper  -  Sintering  -  Age hardening  -  Polyethylenes  -  Mechanical properties  -  Strain  -  Stress analysis  -  Numerical analysis  -  Finite element method

Secondary  Keywords:  Vacuum brazed joints  -  Mechanical properties of joints

 


Back analysis on macromechanics parameters of rock masses of the slope of Geheyan hydraulic power station

Zhou, Jifang (Coll. of Civil and Hydropower Eng., China Three Gorges Univ.); Li, Jianlin; Liu, Jie; Yang, Xuetang Source: Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering, v 23, n SUPPL. 1, July, 2004, p 4506-4508 Language: Chinese

ISSN: 1000-6915 CODEN: YLGXF5

Publisher: Academia Sinica

Abstract: Based on the characteristics of the slope of Geheyan hydraulic power station, the simulation models are constructed for the rock masses in the zone of decisive influence. The mechanical parameters of unloaded rock masses are adopted in the back analysis with the large-scale FEA software, ADINA. The macromechanics parameters and the degradation law of these parameters are obtained. (6 refs.)

Keywords:  Landslides  -  Finite element method  -  Mechanical properties  -  Hydroelectric power plants  -  Rock mechanics  -  Slope stability

Secondary  Keywords:  Macromechanics parameter  -  Back analysis  -  Geheyan hydraulic power station

 

Simulating and predicting welding solidification cracks

Wei, Yanhong (Lab. of Adv. Welding Technol., Harbin Inst. of Technol.); Dong, Zhibo; Liu, Renpei; Dong, Zujue Source: Jixie Gongcheng Xuebao/Chinese Journal of Mechanical Engineering, v 40, n 7, July, 2004, p 93-98 Language: Chinese

ISSN: 0577-6686 CODEN: CHHKA2

Publisher: Editorial Office of Chinese Journal of Mechanical Engineering

Abstract: A computer system is developed which can predict the weld solidification cracks for weldment in two dimensions. Firstly, the pre-data-treatment subsystem helped users to discretize the workpiece, calculate heat generation and the time to add or remove the nodes of the welding molten pool, input the physical properties of materials and generate a calculated card for final FEM calculation. Secondly, the system transferred the calculated cards to software package of Adina and t to complete the calculation of thermal, strain and stress distributions. Next, the post-data treatment section could deal with the calculated data and display the results in featured curves, contours and 3D figures. Lastly, the system regressed the experimental data of trans-varestraint test to obtain the resistance curve of weld solidification cracks and had it compared with the driving force in the same figures and thus predicted the possibility of weld solidification cracks. The system is completed with computer languages Visual Basic 6.0 by combining with the matrix calculating and graphic functions of Matlab 5.3 and Matrix VB to realize the display the graphs. (6 refs.)

Keywords:  Welding  -  Solidification  -  Cracks  -  Computer simulation  -  Strain  -  Stresses  -  Physical properties  -  Finite element method  -  Welds

Secondary  Keywords:  Welding solidification cracks  -  Post data treatment


3D MRI-based multicomponent FSI models for atherosclerotic plaques

Tang, Dalin (Mathematical Sciences Department, Worcester Polytechnic Institute); Yang, Chun; Zheng, Jie; Woodard, Pamela K.; Sicard, Gregorio A.; Saffitz, Jeffrey E.; Yuan, Chun Source: Annals of Biomedical Engineering, v 32, n 7, July, 2004, p 947-960

ISSN: 0090-6964 CODEN: ABMECF

Publisher: American Institute of Physics Inc.

Abstract: A three-dimensional (3D) MRI-based computational model with multicomponent plaque structure and fluid-structure interactions (FSI) is introduced to perform mechanical analysis for human atherosclerotic plaques and identify critical flow and stress/strain conditions which may be related to plaque rupture. Three-dimensional geometry of a human carotid plaque was reconstructed from 3D MR images and computational mesh was generated using Visualization Toolkit. Both the artery wall and the plaque components were assumed to be hyperelastic, isotropic, incompressible, and homogeneous. The flow was assumed to be laminar, Newtonian, viscous, and incompressible. The fully coupled fluid and structure models were solved by ADINA, a well-tested finite element package. Results from two-dimensional (2D) and 3D models, based on ex vivo MRI and histological images (HI), with different component sizes and plaque cap thickness, under different pressure and axial stretch conditions, were obtained and compared. Our results indicate that large lipid pools and thin plaque caps are associated with both extreme maximum (stretch) and minimum (compression when negative) stress/strain levels. Large cyclic stress/strain variations in the plaque under pulsating pressure were observed which may lead to artery fatigue and possible plaque rupture. Large-scale patient studies are needed to validate the computational findings for possible plaque vulnerability assessment and rupture predictions. (56 refs.)

Keywords:  Magnetic resonance imaging  -  Fluid structure interaction  -  Diseases  -  Blood vessels  -  Three dimensional computer graphics  -  Computational methods  -  Incompressible flow  -  Newtonian flow  -  Viscous flow  -  Finite element method  -  Thickness measurement  -  Lipids  -  Stresses  -  Pulsatile flow

Secondary Keywords:  Stroke  -  Heart attack  -  Plaque cap rupture  -  Stenosis  -  Cartoid artery  -  Blood flow  -  Cariovascular diseases

 

Finite element analysis of active Eustachian tube function

S.N. Ghadiali1,2,3, J. Banks3, and J.D. Swarts2,3

1Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, PA 18015

2Department of Otolaryngology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260

3Department of Pediatric Otolaryngology, Children's Hospital of Pittsburgh, Pittsburgh, PA 15213

J. Appl. Physiol. 97:648-654, 2004.

Abstract: The inability to open the collapsible Eustachian tube (ET) has been related to the development of chronic otitis media. Although ET dysfunction may be due to anatomic and/or mechanical abnormalities, the precise mechanisms by which these structural properties alter ET opening phenomena have not been investigated. Previous investigations could only speculate on how these structural properties influence the tissue deformation processes responsible for ET opening. We have, therefore, developed a computational technique that can quantify these structure-function relationships. Cross-sectional histological images were obtained from eight normal adult human subjects, who had no history of middle ear disease. A midcartilaginous image from each subject was used to create two-dimensional finite element models of the soft tissue structures of the ET. ET opening phenomena were simulated by applying muscle forces on soft tissue surfaces in the appropriate direction and were quantified by calculating the resistance to flow (Rv) in the opened lumen. A sensitivity analysis was conducted to determine the relative importance of muscle forces and soft-tissue elastic properties. Muscle contraction resulted in a medial-superior rotation of the medial lamina, stretching deformation in the Ostmann's fatty tissue, and lumen dilation. Variability in baseline Rv values correlated with tissue size, whereas the functional relationship between Rv and a given mechanical parameter was consistent in all subjects. ET opening was found to be highly sensitive to the applied muscle forces and relatively insensitive to cartilage elastic properties. These computational models have, therefore, identified how different tissue elements alter ET opening phenomena, which elements should be targeted for treatment, and the optimal mechanical properties of these tissue constructs.

Keywords: Young's modulus - biomechanics - elasticity - respiratory airway - compliance - fluid-structure interactions - mathematical modeling




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