Page 43

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:

Detection of fatigue microdamage in whole rat femora using contrast-enhanced micro-computed tomography

T.L. Turnbull, J.A. Gargac, G.L. Niebur, R.K. Roeder

Department of Aerospace and Mechanical Engineering, Bioengineering Graduate Program, University of Notre Dame, Notre Dame, IN 46556, USA

Journal of Biomechanics, 44: 2395-2400, 2011

Abstract:  Microdamage in bone tissue is typically studied using destructive, two-dimensional histological techniques. Contrast-enhanced micro-computed tomography (micro-CT) was recently demonstrated to enable non-destructive, three-dimensional (3-D) detection of microdamage in machined cortical and trabecular bone specimens in vitro. However, the accumulation of microdamage in whole bones is influenced by variations in the magnitude and mode of loading due to the complex whole bone morphology. Therefore, the objective of this study was to detect the presence, spatial location, and accumulation of fatigue microdamage in whole rat femora in vitro using micro-CT with a BaSO₄ contrast agent. Microdamage was detected and observed to accumulate at specific spatial locations within the cortex of femora loaded in cyclic three-point bending to a 5% or 10% reduction in secant modulus. The ratio of the segmented BaSO₄ stain volume (SV) to the total volume (TV) of cortical bone was adopted as a measure of damage. The amount of microdamage measured by micro-CT (SV/TV) was significantly greater for both loaded groups compared to the control group (p<0.05), but the difference between loaded groups was not statistically significant. At least one distinct region of microdamage, as indicated by the segmented SV, was observed in 85% of loaded specimens. A specimen-specific finite element model confirmed elevated tensile principal strains localized in regions of tissue corresponding to the accumulated microdamage. These regions were not always located where one might expect a priori based upon Euler-Bernoulli beam theory, demonstrating the utility of contrast-enhanced micro-CT for non-destructive, 3-D detection of fatigue microdamage in whole bones in vitro.

Keywords:Barium sulfate - Contrast agent - Fatigue microdamage - Micro-computed tomography

Non-uniform shrinkage for obtaining computational start shape for in-vivo MRI-based plaque vulnerability assessment

Y. Huang¹, Z. Teng^1,2, U. Sadat^1,3, S. Hilborne¹, V.E. Young¹, M.J. Graves¹, J.H. Gillard¹

¹ University Department of Radiology, University of Cambridge, Cambridge, UK
² Department of Engineering, University of Cambridge, Cambridge, UK
³ Cambridge Vascular Unit, Addenbrooke’s Hospital, Cambridge, Cambridge, UK

Journal of Biomechanics, 44: 2316-2319, 2011

Abstract:
Background: Critical mechanical conditions, such as stress within the structure and shear stress due to blood flow, predicted from in-vivo magnetic resonance image (MRI)-based computational simulations have shown to be potential in assessing carotid plaque vulnerability. Plaque contours obtained from in-vivo MRI are a result of a pressurized configuration due to physiological loading. However, in order to make accurate predictions, the computational model must be based on the loading-free geometry.
A shrinkage procedure can be used to obtain the computational start shape.
Method: In this study, electrocardiograph (ECG)-gated MR-images of carotid plaques were obtained from 28 patients. The contours of each plaque were segmented manually. Additional to a uniform shrinkage procedure, a non-uniform shrinkage refinement procedure was used. This procedure was repeated until the pressurized lumen contour and fibrous cap thickness had the best match with the in-vivo image.
Results: Compared to the uniform shrinkage procedure, the non-uniform shrinkage significantly reduced the difference in lumen shape and in cap thickness at the thinnest site. Results indicate that uniform shrinkage would underestimate the critical stress in the structure by 20.5±10.7%.
Conclusion: For slices with an irregular lumen shape (the ratio of the maximum width to the minimum width is more than 1.05), the non-uniform shrinkage procedure is needed to get an accurate stress profile for mechanics and MRI-based carotid plaque vulnerability assessment.

Keywords: Atherosclerosis – Carotid – Shrinkage – Stress – MRI

Numerical simulation of blood pulsatile flow in a stenosed carotid artery using different rheological models

A. Razavi¹, E. Shirani¹, M.R. Sadeghi^1,2

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: 2021–2030, 2011

Abstract: Symmetrical 30–60% stenosis in a common carotid artery under unsteady flow condition for Newtonian and six non-Newtonian viscosity models are investigated numerically. Results show power-law model produces higher deviations, in terms of velocity and wall shear stress in comparison with other models while generalized power-law and modified-Casson models are more prone to Newtonian state. Comparing separation length of recirculation region at different critical points of cardiac cycle confirms the necessity of considering blood flow in unsteady mode. Increasing stenosis intensity causes flow patterns more disturbed downstream of the stenosis and WSS appear to develop remarkably at the stenosis throat.

Keywords: Carotid artery - Non-Newtonian - Pulsatile blood flow

Identification of geometric parameters influencing the flow-induced vibration of a two-layer self-oscillating computational vocal fold model

B.A. Pickup and S.L. Thomson

Department of Mechanical Engineering, Brigham Young University, Provo, Utah 84602

J. Acoust. Soc. Am., 129(4):2121-2132, 2011

Abstract: Simplified models have been used to simulate and study the flow-induced vibrations of the human vocal folds. While it is clear that the models’ responses are sensitive to geometry, it is not clear how and to what extent specific geometric features influence model motion. In this study geometric features that played significant roles in governing the motion of a two-layer (body-cover), twodimensional, finite element vocal fold model were identified. The model was defined using a flow solver based on the viscous, unsteady, Navier–Stokes equations and a solid solver that allowed for large strain and deformation. A screening-type design-of-experiments approach was used to identify the relative importance of 13 geometric parameters. Five output measures were analyzed to assess the magnitude of each geometric parameter’s effect on the model’s motion. The measures related to frequency, glottal width, flow rate, intraglottal angle, and intraglottal phase delay. The most significant geometric parameters were those associated with the cover—primarily the pre-phonatory intraglottal angle—as well as the body inferior angle. Some models exhibited evidence of improved model motion, including mucosal wave-like motion and alternating convergent-divergent glottal profiles, although further improvements are still needed to more closely mimic human vocal fold motion.

Nonlinear dynamic behavior of saddle-form cable nets under uniform harmonic load

I. Vassilopoulou¹, C.J. Gantes²

¹ Laboratory of Metal Structures, School of Civil Engineering, National Technical University of Athens, 12, Irinis Avenue, GR-15121 Pefki, Greece
² Laboratory of Metal Structures, School of Civil Engineering, National Technical University of Athens, 9 Heroon Polytechniou Street, GR-15780 Zografou, Athens, Greece

Engineering Structures, 33(10): 2762-2771, 2011

Abstract: The dynamic response of saddle-form cable nets is investigated in this paper. Even though they consist of cables, which are well known for their geometric nonlinearity, such systems could be characterized as weakly nonlinear due to the high levels of pretensioning of their cables and to their hyperbolic paraboloid surface, having opposite curvatures at all points and thus increased stiffness. Nevertheless, resonance phenomena that are typical of highly nonlinear systems are detected here, for common geometries and levels of pretension, even for low levels of load amplitude. First, a single-degree-of-freedom (SDOF) cable net is studied analytically and numerically, and nonlinear resonances are confirmed. Then, the response of multi-degree-of-freedom (MDOF) cable nets, subjected to harmonic dynamic excitation, is investigated. Although the static response is proved to be almost linear, the dynamic nonlinearity is intense, as verified by jump phenomena, bending of the response curve, superharmonic resonances, and dependence on the initial conditions.

Keywords: Saddle-form cable net - nonlinear dynamic response - superharmonic resonance - jump phenomena

Effects of seawater–structure–soil interaction on seismic performance of caisson-type quay wall

A. Arablouei¹, A.R.M. Gharabaghi², A. Ghalandarzadeh³, K. Abedi², I. Ishibashi¹

¹ Department of Civil and Environmental Engineering, Old Dominion University, Norfolk, VA, USA
² Department of Civil Engineering, Sahand University of Technology, Tabriz, Iran
³ Department of Civil Engineering, University of Tehran, Tehran, Iran

Computers & Structures, 89:2439-2459, 2011

Abstract: The objective of this paper is to clarify the effects of seawater–structure interaction on the residual displacement of caisson-type quay wall after a real earthquake shock. The dynamic response of quay wall during earthquake, including soil–sea–structure interaction, is calculated using ADINA finite element program. A typical configuration of caisson-type quay wall is used for analysis and seven real earthquake records along with one harmonic excitation are applied as base acceleration. The results demonstrate that the influence of seawater–structure interaction on the permanent displacement of a caisson-type quay wall, constructed on relatively non-liquefiable site, is not significant.

Keywords: Seawater–structure interaction - Caisson-type quay wall - permanent displacement - base acceleration

Page 43