An Inverse Method to Measure the Complex Dynamic Moduli of Elastomers

2002 ◽  
Author(s):  
Yves H. Berthelot ◽  
Lei Wu
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Numerical Simulations ◽  
Material Properties ◽  
Inverse Method ◽  
Element Model ◽  
Surface Velocity ◽  
Complex Dynamic ◽  
Dynamic Moduli ◽  
Large Defect

The dynamic moduli of elastomers are estimated from measurements of the surface velocity of a 3D sample. The measured values are matched with predictions from a finite element model in which the material properties are adjustable parameters. The sensitivity of the inversion technique to the locations of the measurements is discussed. Numerical simulations indicate that the method might be used to determine the moduli of two isotropic layers bonded together. Results also indicate the possibility of detecting the presence of a large defect in the sample.

Physical and Numerical Simulations of the Seismic Response of a 1,100 kV Power Transformer Bushing

2018 ◽  
Vol 34 (3) ◽  
pp. 1515-1541 ◽  
Author(s):  
Guo-Liang Ma ◽  
Qiang Xie ◽  
Andrew S. Whittaker
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Numerical Simulations ◽  
Seismic Vulnerability ◽  
Power Transformer ◽  
Element Model ◽  
Ground Shaking ◽  
Earthquake Simulator ◽  
Physical Experiments ◽  
Seismic Tests

Power transformers and bushings are key pieces of substation equipment and are vulnerable to the effects of earthquake shaking. The seismic performance of a 1,100 kV bushing, used in an ultra-high voltage (UHV) power transformer, is studied using a combination of physical and numerical experiments. The physical experiments utilized an earthquake simulator and included system identification and seismic tests. Modal frequencies and shapes are derived from white noise tests. Acceleration, strain, and displacement responses are obtained from the uniaxial horizontal seismic tests. A finite element model of the 1,100 kV bushing is developed and analyzed, and predicted and measured results are compared. There is reasonably good agreement between predicted and measured responses, enabling the finite element model to be used with confidence for seismic vulnerability studies of transformer-bushing systems. A coupling of the experimental and numerical simulations enabled the vertically installed UHV bushing to be seismically qualified for three-component ground shaking with a horizontal zero-period acceleration of 0.53 g.

FEBio finite element model of a pediatric cervical spine

2021 ◽  
pp. 1-7
Author(s):  
Sean M. Finley ◽  
J. Harley Astin ◽  
Evan Joyce ◽  
Andrew T. Dailey ◽  
Douglas L. Brockmeyer ◽  
...  
Keyword(s):  
Finite Element ◽  
Cervical Spine ◽  
Finite Element Model ◽  
Material Properties ◽  
Surgical Simulation ◽  
Element Model ◽  
Axial Stiffness ◽  
Published Data ◽  
Axial Tension ◽  
Flexion Extension

OBJECTIVE The underlying biomechanical differences between the pediatric and adult cervical spine are incompletely understood. Computational spine modeling can address that knowledge gap. Using a computational method known as finite element modeling, the authors describe the creation and evaluation of a complete pediatric cervical spine model. METHODS Using a thin-slice CT scan of the cervical spine from a 5-year-old boy, a 3D model was created for finite element analysis. The material properties and boundary and loading conditions were created and model analysis performed using open-source software. Because the precise material properties of the pediatric cervical spine are not known, a published parametric approach of scaling adult properties by 50%, 25%, and 10% was used. Each scaled finite element model (FEM) underwent two types of simulations for pediatric cadaver testing (axial tension and cardinal ranges of motion [ROMs]) to assess axial stiffness, ROM, and facet joint force (FJF). The authors evaluated the axial stiffness and flexion-extension ROM predicted by the model using previously published experimental measurements obtained from pediatric cadaveric tissues. RESULTS In the axial tension simulation, the model with 50% adult ligamentous and annulus material properties predicted an axial stiffness of 49 N/mm, which corresponded with previously published data from similarly aged cadavers (46.1 ± 9.6 N/mm). In the flexion-extension simulation, the same 50% model predicted an ROM that was within the range of the similarly aged cohort of cadavers. The subaxial FJFs predicted by the model in extension, lateral bending, and axial rotation were in the range of 1–4 N and, as expected, tended to increase as the ligament and disc material properties decreased. CONCLUSIONS A pediatric cervical spine FEM was created that accurately predicts axial tension and flexion-extension ROM when ligamentous and annulus material properties are reduced to 50% of published adult properties. This model shows promise for use in surgical simulation procedures and as a normal comparison for disease-specific FEMs.

A Comparative Study of the Human Body Finite Element Model Under Blast Loadings

2012 ◽  
Author(s):  
X. G. Tan ◽  
R. Kannan ◽  
Andrzej J. Przekwas
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Human Body ◽  
Material Properties ◽  
Complex Geometry ◽  
Blast Loading ◽  
Element Model ◽  
Stress Wave Propagation ◽  
Brain Response ◽  
Time Step

Until today the modeling of human body biomechanics poses many great challenges because of the complex geometry and the substantial heterogeneity of human body. We developed a detailed human body finite element model in which the human body is represented realistically in both the geometry and the material properties. The model includes the detailed head (face, skull, brain, and spinal cord), the skeleton, and air cavities (including the lung). Hence it can be used to accurately acquire the stress wave propagation in the human body under various loading conditions. The blast loading on the human surface was generated from the simulated C4 blast explosions, via a novel combination of 1-D and 3-D numerical formulations. We used the explicit finite element solver in the multi-physics code CoBi for the human body biomechanics. This is capable of solving the resulting large system containing millions of unknowns in an extremely scalable fashion. The meshes generated for these simulations are of good quality. This enables us to employ relatively large time step sizes, without resorting to the artificial time scaling treatment. In order to study the human body dynamic response under the blast loading, we also developed an interface to apply the blast pressure loading on the external human body surface. These newly developed models were used to conduct parametric simulations to find out the brain biomechanical response when the blasts impact the human body. Under the same blast loading we also show the differences of brain response when having different material properties for the skeleton, the existence of other body parts such as torso.

Effects of material property variation in composite panels

2017 ◽  
Vol 89 (2) ◽  
pp. 274-279
Author(s):  
Thomas Wright ◽  
Imran Hyder ◽  
Mitchell Daniels ◽  
David Kim ◽  
John P. Parmigiani
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Material Property ◽  
Material Properties ◽  
Damage Model ◽  
Element Model ◽  
Maximum Load ◽  
Content Type ◽  
Property Variation ◽  
Load Carrying

Purpose The purpose of this paper is to determine which of the ten material properties of the Hashin progressive damage model significantly affect the maximum load-carrying ability of center-notched carbon fiber panels under in-plane tension and out-of-plane bending. Design/methodology/approach The approach used is to calculate the maximum load using a finite element model for a range of material property values as specified by a fraction factorial design. The finite element model used has been experimentally validated in prior work. Findings Results showed that for the laminates considered, at most three and as few as one of the ten Hashin material properties significantly affected the magnitude of the maximum load. Practical implications While the results of this paper only specifically apply to the laminates included in the study, the results suggest that, in general, only a small number of the Hashin material properties affect laminate load-carrying ability. Originality/value Knowing which properties are significant is of value in selecting materials to optimize performance and also in determining which properties need to be known to a high accuracy.

scholarly journals Development and initial evaluation of a finite element model of the pediatric craniocervical junction

2016 ◽  
Vol 17 (4) ◽  
pp. 497-503 ◽  
Author(s):  
Rinchen Phuntsok ◽  
Marcus D. Mazur ◽  
Benjamin J. Ellis ◽  
Vijay M. Ravindra ◽  
Douglas L. Brockmeyer
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Material Properties ◽  
Element Model ◽  
Axial Rotation ◽  
Craniocervical Junction ◽  
Lateral Bending ◽  
Fem Method ◽  
Flexion Extension ◽  
Ligament Stiffness

OBJECT There is a significant deficiency in understanding the biomechanics of the pediatric craniocervical junction (CCJ) (occiput–C2), primarily because of a lack of human pediatric cadaveric tissue and the relatively small number of treated patients. To overcome this deficiency, a finite element model (FEM) of the pediatric CCJ was created using pediatric geometry and parameterized adult material properties. The model was evaluated under the physiological range of motion (ROM) for flexion-extension, axial rotation, and lateral bending and under tensile loading. METHODS This research utilizes the FEM method, which is a numerical solution technique for discretizing and analyzing systems. The FEM method has been widely used in the field of biomechanics. A CT scan of a 13-month-old female patient was used to create the 3D geometry and surfaces of the FEM model, and an open-source FEM software suite was used to apply the material properties and boundary and loading conditions and analyze the model. The published adult ligament properties were reduced to 50%, 25%, and 10% of the original stiffness in various iterations of the model, and the resulting ROMs for flexion-extension, axial rotation, and lateral bending were compared. The flexion-extension ROMs and tensile stiffness that were predicted by the model were evaluated using previously published experimental measurements from pediatric cadaveric tissues. RESULTS The model predicted a ROM within 1 standard deviation of the published pediatric ROM data for flexion-extension at 10% of adult ligament stiffness. The model's response in terms of axial tension also coincided well with published experimental tension characterization data. The model behaved relatively stiffer in extension than in flexion. The axial rotation and lateral bending results showed symmetric ROM, but there are currently no published pediatric experimental data available for comparison. The model predicts a relatively stiffer ROM in both axial rotation and lateral bending in comparison with flexion-extension. As expected, the flexion-extension, axial rotation, and lateral bending ROMs increased with the decrease in ligament stiffness. CONCLUSIONS An FEM of the pediatric CCJ was created that accurately predicts flexion-extension ROM and axial force displacement of occiput–C2 when the ligament material properties are reduced to 10% of the published adult ligament properties. This model gives a reasonable prediction of pediatric cervical spine ligament stiffness, the relationship between flexion-extension ROM, and ligament stiffness at the CCJ. The creation of this model using open-source software means that other researchers will be able to use the model as a starting point for research.

Finite Element Modeling of Burr Formation in Metal Cutting with a Backup Material

2007 ◽  
Vol 24-25 ◽  
pp. 71-76 ◽  
Author(s):  
Wen Jun Deng ◽  
Wei Xia ◽  
Long Sheng Lu ◽  
Yong Tang
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Material Properties ◽  
Metal Cutting ◽  
Element Model ◽  
Burr Formation ◽  
Tool Geometry ◽  
Cutting Condition ◽  
Burr Size ◽  
Initiation And Propagation

2D finite element model with the same material for backup to minimize the burr size was developed to investigate mechanism of burr formation and burr minimization. The flowstress of the workpiece and backup material are taken as a function of strain, strain-rate and temperature. Temperature-dependent material properties are also considered. The Cockroft-Latham damage criterion has been adopted to simulate ductile fracture. The crack initiation and propagation is simulated by deleting the mesh element. The result shows putting a backup material behind the edge of the workpiece is an effective way to minimize the burr size. The effects of cutting condition, temperature and different backup material properties on the burr formation and burr size can be investigated using the developed finite element model. This model could be useful in the search for optimal tool geometry and cutting condition for burr minimization and for the modeling of a burr formation mechanism.

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