A Transmural Path Model Improves The Definition of The Orthotropic Tissue Structure in Heart Simulations

2021 ◽  
Author(s):  
David Holz ◽  
Minh Tuan Duong ◽  
Denisa Martonova ◽  
Muhannad Alkassar ◽  
Sigrid Leyendecker
Keyword(s):  
Finite Element ◽  
Diffusion Tensor ◽  
Element Model ◽  
Path Model ◽  
Tissue Structure ◽  
Patient Specific ◽  
Mechanical And Electrical Properties ◽  
Local Material ◽  
Accurate Definition ◽  
Definition Of

Abstract In the past decades, the structure of the heart, human as well as other species, has been explored in a detailed way e.g. via histological studies or diffusion tensor magnetic resonance imaging. Nevertheless, the assignment of the characteristic orthotropic structure of the material in a patient-specific finite element model remains a challenging task. Various types of rule-based models, which define the local fibre and sheet orientation depending on the transmural depth, have been developed. However, the correct assessment of the transmural depth is not trivial. Its accuracy has a substantial influence on the overall mechanical and electrical properties of the model. The main purpose of this study is the developement of a finite-element-based approach to accurately determine the transmural depth. We propose a finite-element-based discontinuous Galerkin approach to determine the transmural path, thickness and depth. Based on the accurate transmural depth, we assign the local material orientation of the orthotropic tissue structure in a usual fashion. We show that this approach leads to a more accurate definition of the transmural depth. Furthermore, for the left ventricle, we propose rules for the transmural fibre and sheet orientation by fitting them to literature based data. The proposed functions show a distinct improvement compared to existing rules.

Perforation mechanics of UHMWPE soft ballistic sub-laminate and soft ballistic armor pack: A finite element study

2021 ◽  
pp. 089270572110420
Author(s):  
Bazle Z (Gama) Haque ◽  
John W Gillespie
Keyword(s):  
Finite Element ◽  
Single Layer ◽  
Areal Density ◽  
Element Model ◽  
Transverse Impact ◽  
Free Standing ◽  
Uhmwpe Fibers ◽  
Ballistic Limit Velocity ◽  
Definition Of ◽  
First Time

Soft-ballistic sub-laminate (SBSL) made from ultra-high molecular weight polyethylene (UHMWPE) fibers in [0/90] stacking sequence are the building block of a multi-layer soft-ballistic armor pack (SBAP, aka Soft Armor). A systematic study of the perforation dynamics of a single layer SBSL and several multi-layer SBAPs (2, 3, 4, 8, 16, 24, 32 layers) is presented for the first time in the literature. A previously validated finite element model of transverse impact on a single layer is used to study the perforation mechanics of multi-layer SBAPs with friction between individual layers. Following the classical definition of ballistic limit velocity, a minimum perforation velocity has been determined for free-standing single layer SBSL and multi-layer SBAPs. For the multi-layer SBAPs, complete perforations have been identified as progressive perforation of individual layers through the thickness. The minimum perforation velocities of multi-layer SBAPS is linear with the areal density for the eight (8) layer target and thicker. Large deformation behavior and perforation mechanics of the SBAPs is discussed in detail.

scholarly journals Derivation of a finite-element model of lingual deformation during swallowing from the mechanics of mesoscale myofiber tracts obtained by MRI

2010 ◽  
Vol 109 (5) ◽  
pp. 1500-1514 ◽  
Author(s):  
Srboljub M. Mijailovich ◽  
Boban Stojanovic ◽  
Milos Kojic ◽  
Alvin Liang ◽  
Van J. Wedeen ◽  
...  
Keyword(s):  
Finite Element ◽  
Connective Tissue ◽  
Diffusion Tensor ◽  
Element Model ◽  
Out Of Plane ◽  
Posterior Direction ◽  
Elastic Constraints ◽  
The Relationship ◽  
Passive Muscle ◽  
Anterior Posterior

To demonstrate the relationship between lingual myoarchitecture and mechanics during swallowing, we performed a finite-element (FE) simulation of lingual deformation employing mesh aligned with the vector coordinates of myofiber tracts obtained by diffusion tensor imaging with tractography in humans. Material properties of individual elements were depicted in terms of Hill's three-component phenomenological model, assuming that the FE mesh was composed of anisotropic muscle and isotropic connective tissue. Moreover, the mechanical model accounted for elastic constraints by passive and active elements from the superior and inferior directions and the effect of out-of-plane muscles and connective tissue. Passive bolus effects were negligible. Myofiber tract activation was simulated over 500 ms in 1-ms steps following lingual tip association with the hard palate and incorporated specifically the accommodative and propulsive phases of the swallow. Examining the displacement field, active and passive muscle stress, elemental stretch, and strain rate relative to changes of global shape, we demonstrate that lingual reconfiguration during these swallow phases is characterized by (in sequence) the following: 1) lingual tip elevation and shortening in the anterior-posterior direction; 2) inferior displacement related to hyoglossus contraction at its inferior-most position; and 3) dominant clockwise rotation related to regional contraction of the genioglossus and contraction of the hyoglossus following anterior displacement. These simulations demonstrate that lingual deformation during the indicated phases of swallowing requires temporally patterned activation of intrinsic and extrinsic muscles and delineate a method to ascertain the mechanics of normal and pathological swallowing.

scholarly journals Predicting calvarial morphology in sagittal craniosynostosis

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Oyvind Malde ◽  
Connor Cross ◽  
Chien L. Lim ◽  
Arsalan Marghoub ◽  
Michael L. Cunningham ◽  
...  
Keyword(s):  
Finite Element ◽  
Input Parameter ◽  
Surgical Techniques ◽  
Element Model ◽  
Specific Model ◽  
Patient Specific ◽  
Sagittal Craniosynostosis ◽  
Sensitivity Tests ◽  
Ct Data

AbstractEarly fusion of the sagittal suture is a clinical condition called, sagittal craniosynostosis. Calvarial reconstruction is the most common treatment option for this condition with a range of techniques being developed by different groups. Computer simulations have a huge potential to predict the calvarial growth and optimise the management of this condition. However, these models need to be validated. The aim of this study was to develop a validated patient-specific finite element model of a sagittal craniosynostosis. Here, the finite element method was used to predict the calvarial morphology of a patient based on its preoperative morphology and the planned surgical techniques. A series of sensitivity tests and hypothetical models were carried out and developed to understand the effect of various input parameters on the result. Sensitivity tests highlighted that the models are sensitive to the choice of input parameter. The hypothetical models highlighted the potential of the approach in testing different reconstruction techniques. The patient-specific model highlighted that a comparable pattern of calvarial morphology to the follow up CT data could be obtained. This study forms the foundation for further studies to use the approach described here to optimise the management of sagittal craniosynostosis.

Shock environment design for space equipment testing

2016 ◽  
Vol 231 (6) ◽  
pp. 1154-1167 ◽  
Author(s):  
OMF Morais ◽  
CMA Vasques
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Test System ◽  
Test Apparatus ◽  
Shock Test ◽  
Shock Testing ◽  
Test Parameters ◽  
Shock Environment ◽  
Definition Of

The main specification in the verification by testing of space hardware vulnerability to shock excitations is the shock response spectrum. Although it compiles the most relevant information needed to describe the overall shock environment characteristics, shock testing still poses various difficulties and uncertainties concerning the suitability and operation of the shock test system used, and the adequate definition of the underlying test parameters. The approach followed from the interpretation of typical shock testing specifications to the development, validation, and characterization of the developed shock test system, including the definition and design of the relevant parameters influencing the attained shock environment, is described in this paper. The shock testing method here presented consists of a pendular in-plane resonant mono-plate shock test apparatus where the structural response of the ringing plate depends upon well-defined controllable parameters (e.g. impact velocity, striker shape, mass, and contact stiffness), which are parametrically determined to achieve the target shock environment specification. The concept and analytical model of two impacting bodies are used in a preliminary analysis to perform a rigid body motion analysis and contact assessment. A detailed finite element model is developed for the definition of the ringing plate dimensions, analysis of the plate dynamics and virtual shock testing. The assembled experimental apparatus is described and a test campaign is undertaken in order to properly characterize and assess the design and test parameters of the system. The developed shock test apparatus and corresponding finite element model are experimentally verified and validated. As a result of this study, a reliable finite element modeling methodology available for future shock test simulation and prediction of the experimental results was created, being an important tool for the adjustment of the shock test input parameters for future works. The developed shock test system was well characterized and is readily available to be used for shock testing of space equipment with varying specifications.

scholarly journals Physical validation of a patient-specific contact finite element model of the ankle

2007 ◽  
Vol 40 (8) ◽  
pp. 1662-1669 ◽  
Author(s):  
Donald D. Anderson ◽  
Jane K. Goldsworthy ◽  
Wendy Li ◽  
M. James Rudert ◽  
Yuki Tochigi ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Patient Specific ◽  
Specific Contact

Predicting the effects of knee focal articular surface injury with a patient-specific finite element model

The Knee ◽  
2010 ◽  
Vol 17 (1) ◽  
pp. 61-68 ◽  
Author(s):  
George Papaioannou ◽  
Constantine K. Demetropoulos ◽  
Yang H. King
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Articular Surface ◽  
Element Model ◽  
Patient Specific

scholarly journals Seismic Strengthening of the Bagh Durbar Heritage Building in Kathmandu Following the Gorkha Earthquake Sequence

Buildings ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 128 ◽  
Author(s):  
Rabindra Adhikari ◽  
Pratyush Jha ◽  
Dipendra Gautam ◽  
Giovanni Fabbrocino
Keyword(s):  
Finite Element ◽  
Element Model ◽  
Gorkha Earthquake ◽  
Seismic Safety ◽  
Early 19Th Century ◽  
Heritage Sites ◽  
Greco Roman ◽  
Heritage Building ◽  
Definition Of

The so-called Greco-Roman monuments, also known as neoclassical monuments, in Nepal represent unique construction systems. Although they are not native to Nepal, they are icons of the early 19th century in the Kathmandu valley. As such structures are located within the heritage sites and historical centers, preservation of Greco-Roman monuments is necessary. Since many buildings are in operation and accommodate public and critical functions, their seismic safety has gained attention in recent times, especially after the Gorkha earthquake. This paper first presents the background of the Bagh Durbar monument, reports the damage observations, and depicts some repair and retrofitting solutions. Attention is paid to the implementation of the different phases of the structural characterization of the building, the definition of reference material parameters, and finally, the structural analysis made by using finite element models. The aim of the contribution consists of comparison of the adequacy of the finite element model with the field observations and design of retrofitting solutions to assure adequate seismic safety for typical Greco-Roman buildings in Nepal. Thus, this paper sets out to provide rational strengthening solutions compatible with the existing guidelines rather than complex numerical analyses.

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