Subject-Specific Finite Element Model of the Pelvis: Development, Validation and Sensitivity Studies

2005 ◽  
Vol 127 (3) ◽  
pp. 364-373 ◽  
Author(s):  
Andrew E. Anderson ◽  
Christopher L. Peters ◽  
Benjamin D. Tuttle ◽  
Jeffrey A. Weiss
Keyword(s):  
Finite Element ◽  
Elastic Modulus ◽  
Cortical Bone ◽  
Material Properties ◽  
Experimental Results ◽  
Patient Specific ◽  
Fe Model ◽  
Bone Thickness ◽  
Subject Specific ◽  
Bone Strains

A better understanding of the three-dimensional mechanics of the pelvis, at the patient-specific level, may lead to improved treatment modalities. Although finite element (FE) models of the pelvis have been developed, validation by direct comparison with subject-specific strains has not been performed, and previous models used simplifying assumptions regarding geometry and material properties. The objectives of this study were to develop and validate a realistic FE model of the pelvis using subject-specific estimates of bone geometry, location-dependent cortical thickness and trabecular bone elastic modulus, and to assess the sensitivity of FE strain predictions to assumptions regarding cortical bone thickness as well as bone and cartilage material properties. A FE model of a cadaveric pelvis was created using subject-specific computed tomography image data. Acetabular loading was applied to the same pelvis using a prosthetic femoral stem in a fashion that could be easily duplicated in the computational model. Cortical bone strains were monitored with rosette strain gauges in ten locations on the left hemipelvis. FE strain predictions were compared directly with experimental results for validation. Overall, baseline FE predictions were strongly correlated with experimental results (r2=0.824), with a best-fit line that was not statistically different than the line y=x(experimental strains=FEpredicted strains). Changes to cortical bone thickness and elastic modulus had the largest effect on cortical bone strains. The FE model was less sensitive to changes in all other parameters. The methods developed and validated in this study will be useful for creating and analyzing patient-specific FE models to better understand the biomechanics of the pelvis.

Development of a customized density—modulus relationship for use in subject-specific finite element models of the ulna

2009 ◽  
Vol 223 (6) ◽  
pp. 787-794 ◽  
Author(s):  
R L Austman ◽  
J S Milner ◽  
D W Holdsworth ◽  
C E Dunning
Keyword(s):  
Finite Element ◽  
Cortical Bone ◽  
Material Properties ◽  
Beam Theory ◽  
Average Density ◽  
Experimental Results ◽  
Finite Element Models ◽  
Theory Analysis ◽  
Distal Ulna ◽  
Subject Specific

Assigning an appropriate density—modulus relationship is an important factor when applying inhomogeneous material properties to finite element models of bone. The purpose of this study was to develop a customized density—modulus equation for the distal ulna, using beam theory combined with experimental results. Five custom equations of the form E = aρb were used to apply material properties to models of eight ulnae. All equations passed through a point (1.85, Ec), where ρ = 1.85 g/cm3 represents the average density of cortical bone. For custom equations (1) to (3), Ec was predicted using beam theory, and the value of b was varied within the range reported in the literature. Custom equations (4) and (5) used other values of Ec from the literature, while keeping b constant. Results obtained from the custom equations were compared with those from other equations in the literature, and with experimental results. The beam theory analysis predicted Ec = 21 ± 1.6 GPa, and the three custom equations using this value tended to have the lowest errors. The power of the equations did not affect the results as much as the value used for Ec. Overall, a customized density—modulus relationship for the ulna was generated, which provided improved results over using previously reported density—modulus equations.

Development and Validation of Patient-Specific Finite Element Models of the Hemipelvis Generated From a Sparse CT Data Set

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
Vickie B. Shim ◽  
Rocco P. Pitto ◽  
Robert M. Streicher ◽  
Peter J. Hunter ◽  
Iain A. Anderson
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Patient Data ◽  
Ct Scans ◽  
Patient Specific ◽  
Data Sets ◽  
Fe Model ◽  
Data Set ◽  
Spatially Varying ◽  
Ct Slices

To produce a patient-specific finite element (FE) model of a bone such as the pelvis, a complete computer tomographic (CT) or magnetic resonance imaging (MRI) geometric data set is desirable. However, most patient data are limited to a specific region of interest such as the acetabulum. We have overcome this problem by providing a hybrid method that is capable of generating accurate FE models from sparse patient data sets. In this paper, we have validated our technique with mechanical experiments. Three cadaveric embalmed pelves were strain gauged and used in mechanical experiments. FE models were generated from the CT scans of the pelves. Material properties for cancellous bone were obtained from the CT scans and assigned to the FE mesh using a spatially varying field embedded inside the mesh while other materials used in the model were obtained from the literature. Although our FE meshes have large elements, the spatially varying field allowed them to have location dependent inhomogeneous material properties. For each pelvis, five different FE meshes with a varying number of patient CT slices (8–12) were generated to determine how many patient CT slices are needed for good accuracy. All five mesh types showed good agreement between the model and experimental strains. Meshes generated with incomplete data sets showed very similar stress distributions to those obtained from the FE mesh generated with complete data sets. Our modeling approach provides an important step in advancing the application of FE models from the research environment to the clinical setting.

scholarly journals Subject-Specific Finite Element Modelling of the Human Hand Complex: Muscle-Driven Simulations and Experimental Validation

2019 ◽  
Vol 48 (4) ◽  
pp. 1181-1195 ◽  
Author(s):  
Yuyang Wei ◽  
Zhenmin Zou ◽  
Guowu Wei ◽  
Lei Ren ◽  
Zhihui Qian
Keyword(s):  
Finite Element ◽  
Contact Pressure ◽  
Material Properties ◽  
Finite Element Modelling ◽  
Human Hand ◽  
Fe Model ◽  
Muscle Forces ◽  
Element Modelling ◽  
Subject Specific

AbstractThis paper aims to develop and validate a subject-specific framework for modelling the human hand. This was achieved by combining medical image-based finite element modelling, individualized muscle force and kinematic measurements. Firstly, a subject-specific human hand finite element (FE) model was developed. The geometries of the phalanges, carpal bones, wrist bones, ligaments, tendons, subcutaneous tissue and skin were all included. The material properties were derived from in-vivo and in-vitro experiment results available in the literature. The boundary and loading conditions were defined based on the kinematic data and muscle forces of a specific subject captured from the in-vivo grasping tests. The predicted contact pressure and contact area were in good agreement with the in-vivo test results of the same subject, with the relative errors for the contact pressures all being below 20%. Finally, sensitivity analysis was performed to investigate the effects of important modelling parameters on the predictions. The results showed that contact pressure and area were sensitive to the material properties and muscle forces. This FE human hand model can be used to make a detailed and quantitative evaluation into biomechanical and neurophysiological aspects of human hand contact during daily perception and manipulation. The findings can be applied to the design of the bionic hands or neuro-prosthetics in the future.

scholarly journals Development and Validation of a Finite Element Model of the Pelvis

2003 ◽  
Author(s):  
Andrew E. Anderson ◽  
Christopher L. Peters ◽  
Benjamin D. Tuttle ◽  
Jeffrey A. Weiss
Keyword(s):  
Finite Element ◽  
Cortical Thickness ◽  
Hip Joint ◽  
Material Properties ◽  
Hip Osteoarthritis ◽  
Bone Geometry ◽  
Diagnostic Methods ◽  
Fe Model ◽  
Joint Mechanics ◽  
Subject Specific

An improved understanding of the stress distribution in and around the hip joint may provide important information regarding the relationship between altered pelvic and acetabular geometry and development of hip osteoarthritis, as well as point to improved diagnostic methods and analysis of surgical treatment. It is very difficult to accurately assess how changes in pelvic geometry affect the stress and strain distribution of the joint in an experimental setting. The finite element (FE) method provides an alternative approach for study of hip joint mechanics. Although FE models of the pelvis have been developed, validation by direct comparison with subject-specific experimental measurements has not been performed. In addition, previous models have utilized over-simplified bone geometry and homogeneous material properties. The objectives of this study were to 1) develop and validate a FE model of the pelvis using subject-specific measurements of bone geometry as well as location-dependent cortical thickness and trabecular bone elastic modulus, and 2) assess the sensitivity of the subject-specific FE model to changes in material properties and cortical thickness.

Determination of Charge Coefficient of Piezoelectric Films Using a Combined Finite Element Model and Dynamic Loading Technique

2020 ◽  
Vol 835 ◽  
pp. 229-242
Author(s):  
Oboso P. Bernard ◽  
Nagih M. Shaalan ◽  
Mohab Hossam ◽  
Mohsen A. Hassan
Keyword(s):  
Finite Element ◽  
Dynamic Loading ◽  
Material Properties ◽  
Accurate Determination ◽  
Substrate Material ◽  
Experimental Results ◽  
Piezoelectric Composite ◽  
Piezoelectric Film ◽  
Piezoelectric Charge

Accurate determination of piezoelectric properties such as piezoelectric charge coefficients (d33) is an essential step in the design process of sensors and actuators using piezoelectric effect. In this study, a cost-effective and accurate method based on dynamic loading technique was proposed to determine the piezoelectric charge coefficient d33. Finite element analysis (FEA) model was developed in order to estimate d33 and validate the obtained values with experimental results. The experiment was conducted on a piezoelectric disc with a known d33 value. The effect of measuring boundary conditions, substrate material properties and specimen geometry on measured d33 value were conducted. The experimental results reveal that the determined d33 coefficient by this technique is accurate as it falls within the manufactures tolerance specifications of PZT-5A piezoelectric film d33. Further, obtained simulation results on fibre reinforced and particle reinforced piezoelectric composite were found to be similar to those that have been obtained using more advanced techniques. FE-results showed that the measured d33 coefficients depend on measuring boundary condition, piezoelectric film thickness, and substrate material properties. This method was proved to be suitable for determination of d33 coefficient effectively for piezoelectric samples of any arbitrary geometry without compromising on the accuracy of measured d33.

Finite Element Study of the Cutting Mechanics of the Three Dimensional Rock Turning Process

2015 ◽  
Author(s):  
Demeng Che ◽  
Jacob Smith ◽  
Kornel F. Ehmann
Keyword(s):  
Finite Element ◽  
Oil And Gas ◽  
Three Dimensional ◽  
Polycrystalline Diamond ◽  
Close Correlation ◽  
Experimental Results ◽  
Failure Behavior ◽  
Fe Model ◽  
Gas Drilling ◽  
Cutting Mechanics

The unceasing improvements of polycrystalline diamond compact (PDC) cutters have pushed the limits of tool life and cutting efficiency in the oil and gas drilling industry. However, the still limited understanding of the cutting mechanics involved in rock cutting/drilling processes leads to unsatisfactory performance in the drilling of hard/abrasive rock formations. The Finite Element Method (FEM) holds the promise to advance the in-depth understanding of the interactions between rock and cutters. This paper presents a finite element (FE) model of three-dimensional face turning of rock representing one of the most frequent testing methods in the PDC cutter industry. The pressure-dependent Drucker-Prager plastic model with a plastic damage law was utilized to describe the elastic-plastic failure behavior of rock. A newly developed face turning testbed was introduced and utilized to provide experimental results for the calibration and validation of the formulated FE model. Force responses were compared between simulations and experiments. The relationship between process parameters and force responses and the mechanics of the process were discussed and a close correlation between numerical and experimental results was shown.

Age Dependent and Anisotropic Material Properties of Immature Porcine Sclera

2013 ◽  
Author(s):  
Jami M. Saffioti ◽  
Brittany Coats
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Anisotropic Material ◽  
Computational Models ◽  
Fe Model ◽  
Ocular Tissues ◽  
Load Bearing ◽  
Anisotropic Properties ◽  
Age Dependent ◽  
Testing Protocols

Current finite element (FE) models of the pediatric eye are based on adult material properties [2,3]. To date, there are no data characterizing the age dependent material properties of ocular tissues. The sclera is a major load bearing tissue and an essential component to most computational models of the eye. In preparation for the development of a pediatric FE model, age-dependent and anisotropic properties of sclera were evaluated in newborn (3–5 days) and toddler (4 weeks) pigs. Data from this study will guide future testing protocols for human pediatric specimens.

Effect of Ramp Angle on the Anti-Loosening Ability of Wedge Self-Locking Nuts Under Vibration

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Jianhua Liu ◽  
Hao Gong ◽  
Xiaoyu Ding
Keyword(s):  
Finite Element ◽  
Numerical Simulations ◽  
Production Technology ◽  
Material Properties ◽  
Threshold Value ◽  
Commercial Production ◽  
Experimental Results ◽  
Fe Method ◽  
Transversal Vibration

Recently, the wedge self-locking nut, a special anti-loosening product, is receiving more attention because of its excellent reliability in preventing loosening failure under vibration conditions. The key characteristic of a wedge self-locking nut is the special wedge ramp at the root of the thread. In this work, the effect of ramp angle on the anti-loosening ability of wedge self-locking nuts was studied systematically based on numerical simulations and experiments. Wedge self-locking nuts with nine ramp angles (10 deg, 15 deg, 20 deg, 25 deg, 30 deg, 35 deg, 40 deg, 45 deg, and 50 deg) were modeled using a finite element (FE) method, and manufactured using commercial production technology. Their anti-loosening abilities under transversal vibration conditions were analyzed based on numerical and experimental results. It was found that there is a threshold value of the initial preload below which the wedge self-locking nuts would lose their anti-loosening ability. This threshold value of initial preload was then proposed for use as a criterion to evaluate the anti-loosening ability of wedge self-locking nuts quantitatively and to determine the optimal ramp angle. Based on this criterion, it was demonstrated, numerically and experimentally, that a 30 deg wedge ramp resulted in the best anti-loosening ability among nine ramp angles studied. The significance of this study is that it provides an effective method to evaluate the anti-loosening ability of wedge self-locking nuts quantitatively, and determined the optimal ramp angle in terms of anti-loosening ability. The proposed method can also be used to optimize other parameters, such as the material properties and other dimensions, to guarantee the best anti-loosening ability of wedge self-locking nuts.

Altered Load Transfer in the Pelvis in the Presence of Periprosthetic Osteolysis

2014 ◽  
Vol 136 (11) ◽  
Author(s):  
Jacob T. Munro ◽  
Justin W. Fernandez ◽  
James S. Millar ◽  
Cameron G. Walker ◽  
Donald W. Howie ◽  
...  
Keyword(s):  
Cortical Bone ◽  
Load Transfer ◽  
Von Mises Stress ◽  
Patient Specific ◽  
Fe Model ◽  
Stress Concentrations ◽  
Periprosthetic Osteolysis ◽  
Total Hip ◽  
Long Term Follow Up ◽  
Von Mises

Periprosthetic osteolysis in the retroacetabular region with cancellous bone loss is a recognized phenomenon in the long-term follow-up of total hip replacement. The effects on load transfer in the presence of defects are less well known. A validated, patient-specific, 3D finite element (FE) model of the pelvis was used to assess changes in load transfer associated with periprosthetic osteolysis adjacent to a cementless total hip arthroplasty (THA) component. The presence of a cancellous defect significantly increased (p < 0.05) von Mises stress in the cortical bone of the pelvis during walking and a fall onto the side. At loads consistent with single leg stance, this was still less than the predicted yield stress for cortical bone. During higher loads associated with a fall onto the side, highest stress concentrations occurred in the superior and inferior pubic rami and in the anterior column of the acetabulum with larger cancellous defects.

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