A Parametric Study on Material Properties of Cortical Shell and Trabecular Core in an Osteoporotic, Lumbar Vertebral Bone Model

2004 ◽  
Author(s):  
David R. Sindall ◽  
Noshir A. Langrana ◽  
Alberto Cuitino
Keyword(s):  
Material Properties ◽  
Failure Load ◽  
Compressive Load ◽  
Lumbar Vertebrae ◽  
Failure Strength ◽  
Element Analysis ◽  
Vertebral Bone ◽  
Load Response ◽  
Cortical Shell ◽  
Biomechanical Parameters

This study is about understanding the biomechanical parameters in osteoporosis phenomena. Experimental data are available on intact cadaver normal and osteoporotic lumbar vertebrae. It was observed that there is inconsistency between the clinical DEXA measurements and the mechanical measurements such as failure strength. The vertebral bone parameters include geometry (height, width, curvature, and thickness of the cortical shell) and material properties of cortical and trabecular bone. A non-linear Micromodel Finite Element Analysis (MFEA) program has been developed to include these parameters and obtain the compressive load. Response surface methodology (RSM) was developed to relate BMD to failure strength and is used in this study to see how the mechanical properties of bone influence the failure load. (Sindall, 2003)

scholarly journals The Finite Element Analysis of Osteoporotic Lumbar Vertebral Body by Influence of Trabecular Bone Apparent Density and Thickness of Cortical Shell

2017 ◽  
Vol 11 (4) ◽  
pp. 285-292 ◽  
Author(s):  
Oleg Ardatov ◽  
Algirdas Maknickas ◽  
Vidmantas Alekna ◽  
Marija Tamulaitienė ◽  
Rimantas Kačianauskas
Keyword(s):  
Vertebral Body ◽  
Cancellous Bone ◽  
Apparent Density ◽  
Yield Criterion ◽  
Nonlinear Dynamic Analysis ◽  
Lumbar Vertebrae ◽  
Element Analysis ◽  
Bone Mass Loss ◽  
Lumbar Vertebral Body ◽  
Cortical Shell

AbstractOsteoporosis causes the bone mass loss and increased fracture risk. This paper presents the modelling of osteoporotic human lumbar vertebrae L1 by employing finite elements method (FEM). The isolated inhomogeneous vertebral body is composed by cortical out-er shell and cancellous bone. The level of osteoporotic contribution is characterised by reducing the thickness of cortical shell and elasticity modulus of cancellous bone using power-law dependence with apparent density. The strength parameters are evaluated on the basis of von Mises-Hencky yield criterion. Parametric study of osteoporotic degradation contains the static and nonlinear dynamic analysis of stresses that occur due to physiological load. Results of our investigation are presented in terms of nonlinear interdependence between stress and external load.

Crash Tests of Tension Bolts in Light Safety Collision Devices

2008 ◽  
Vol 385-387 ◽  
pp. 685-688 ◽  
Author(s):  
Jin Sung Kim ◽  
Hoon Huh ◽  
Won Mog Choi ◽  
Tae Soo Kwon
Keyword(s):  
High Speed ◽  
Failure Load ◽  
Compressive Loading ◽  
Crash Test ◽  
Test Results ◽  
Element Analysis ◽  
Load Response ◽  
Collision Safety ◽  
Energy Absorbing ◽  
Crash Tests

This paper demonstrates the jig set for the crash test and the crash test results of the tension bolts with respect to an applied pre-tension. The tension and shear bolts are adopted at Light Collision Safety Devices as a mechanical fuse when tension bolts reach designed failure load. The kinetic energy due to the crash is absorbed by secondary energy absorbing devices after the fracture of tension bolts. One tension bolt was designed to be failed at the load of 375 kN. The jig set was designed to convert a compressive loading to a tensile loading and installed at the high speed crash tester. The strain gauges were attached at the parallel section of the tension bolts to measure the level of the pre-tension acting on the tension bolts. Crash tests were performed with a barrier whose mass was 250 kg and initial speed of the barrier was 9.5 m/sec. The result includes the load response of the tension bolts during both the crash tests and finite element analysis.

The Role of Cortical Shell and Trabecular Fabric in Finite Element Analysis of the Human Vertebral Body

2009 ◽  
Vol 131 (11) ◽  
Author(s):  
Yan Chevalier ◽  
Dieter Pahr ◽  
Philippe K. Zysset
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Elastic Strain Energy ◽  
Constant Thickness ◽  
Element Analysis ◽  
Cortical Shell ◽  
Vertebral Bodies ◽  
Ct Density ◽  
Elastic Strain Energy Density ◽  
Vertebral Endplates

Classical finite element (FE) models can estimate vertebral stiffness and strength with much lower computational costs than μFE analyses, but the accuracy of these models rely on calibrated material properties that are not necessarily consistent with experimental results. In general, trabecular bone material properties are scaled with computer tomography (CT) density alone, without accounting for local variations in anisotropy or micro-architecture. Moreover, the cortex is often omitted or assigned with a constant thickness. In this work, voxel FE models, as well as surface-based homogenized FE models with topologically-conformed geometry and assigned with experimentally validated properties for bone, were developed from a series of 12 specimens tested up to failure. The effects of changing from a digital mesh to a smooth mesh, including a cortex of variable thickness and/or including heterogeneous trabecular fabric, were investigated. In each case, FE predictions of vertebral stiffness and strength were compared with the experimental gold-standard, and changes in elastic strain energy density and damage distributions were reported. The results showed that a smooth mesh effectively removed zones of artificial damage locations occurring in the ragged edges of the digital mesh. Adding an explicit cortex stiffened and strengthened the models, unloading the trabecular centrum while increasing the correlations to experimental stiffness and strength. Further addition of heterogeneous fabric improved the correlations to stiffness (R2=0.72) and strength (R2=0.89) and moved the damage locations closer to the vertebral endplates, following the local trabecular orientations. It was furthermore demonstrated that predictions of vertebral stiffness and strength of homogenized FE models with topologically-conformed cortical shell and heterogeneous trabecular fabric correlated well with experimental measurements, after assigning purely experimental data for bone without further calibration of material laws at the macroscale of bone. This study successfully demonstrated the limitations of current classical FE methods and provided valuable insights into the damage mechanisms of vertebral bodies.

Effects of Cortical Shell Concavity on Vertebral Body Compressive Properties

2001 ◽  
Author(s):  
Michael A. K. Liebschner ◽  
Tony M. Keaveny ◽  
William S. Rosenberg
Keyword(s):  
Vertebral Body ◽  
Failure Load ◽  
Compressive Properties ◽  
Vertebral Bone ◽  
Structural Role ◽  
Lateral Plane ◽  
Cortical Shell ◽  
Physical Information ◽  
Vertebral Bodies

Abstract Quantification of the structural role of the vertebral shell and trabecular centrum is essential to determine if the shell should be given equal consideration when predicting the fracture strength. The contribution of the cortical shell and endplate to the stiffness and strength of the vertebral body is not well understood and the literature remains controversial [1–5]. The uncertainty of the mechanistic support of the cortical shell and the role of its geometry is due in part to the difficulty in obtaining physical information about the shell[5]. A study on sheep vertebrae performed by Kasra and Grynpas [6] suggested a negative correlation between failure load and the tangent of the cortical shell curvature measured in the AP and lateral plane. Nevertheless, the structural role of the vertebral shell may be different in human vertebrae due to altered loading situations and different geometry. Another study by Edmonston et al. [7] implied a strong correlation between vertebral bone density and thoracic curvature. No study reported in the literature investigated the effect of the cortical shell concavity of human vertebral bodies on their mechanical properties.

Effects of Endplate Curvature on Stresses in a Vertebral Motion Segment: Finite Element Analysis

2004 ◽  
Author(s):  
Shreedhar P. Kale ◽  
Noshir A. Langrana ◽  
Thomas Edwards
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Distribution ◽  
Lumbar Vertebrae ◽  
Lumbosacral Spine ◽  
Human Cadaver ◽  
Element Analysis ◽  
Linear Elastic ◽  
Motion Segment ◽  
Cortical Shell

The vertebral endplates of the lumbosacral spine have various degrees of concavity and/or convexity. Several investigators including Seenivasan G., Goel, V. K., 1994, Liebschner et al, 2003, etc have performed finite element analysis on the vertebral bones, but the endplate curvatures are not included. Therefore, the effect of morphological details of the endplate curvatures on the stress distribution is unknown. Differences in these curvatures will increase stress in some regions and decrease stress elsewhere as the spine is compressed. In our previous study [Kale et al, 2003], lumbar vertebral endplate curvatures in the anterior-posterior and medial-lateral directions on human cadaver lumbar vertebrae were measured. The measurements were carried out using a reverse engineering instrument, built at Rutgers University [Hsieh et al, 2002]. Six sets of measurements (on human male-female L4 lower to S1 upper endplates) were performed. The data was later used in a linear elastic cylindrical model containing cortical shell and trabecular core. The model then was modified to a more accurate model, with more realistic, characteristic kidney shaped cross section (obtained from equation by Mizrahi et al, 1993) and linearly varying height. The endplates were assigned curvatures extracted from our human cadaver data. FEA, done on both the models, showed that the endplate curvatures and their location had significant effect on the stress distribution in the vertebral bone. In the current study we have extended our bone model into a motion segment and have investigated the effects of the curvatures on the stresses in the motion segment.

scholarly journals Impact of residual stress evoked by pyramidal embossing on the magnetic material properties of non-oriented electrical steel

2021 ◽  
Author(s):  
Ines Gilch ◽  
Tobias Neuwirth ◽  
Benedikt Schauerte ◽  
Nora Leuning ◽  
Simon Sebold ◽  
...  
Keyword(s):  
Magnetic Material ◽  
Residual Stress ◽  
Magnetic Flux ◽  
Material Properties ◽  
Electrical Steel ◽  
Maximum Energy ◽  
Material Behavior ◽  
Electrical Machine ◽  
Element Analysis ◽  
Steel Sheets

AbstractTargeted magnetic flux guidance in the rotor cross section of rotational electrical machines is crucial for the machine’s efficiency. Cutouts in the electrical steel sheets are integrated in the rotor sheets for magnetic flux guidance. These cutouts create thin structures in the rotor sheets which limit the maximum achievable rotational speed under centrifugal forces and the maximum energy density of the rotating electrical machine. In this paper, embossing-induced residual stress, employing the magneto-mechanical Villari effect, is studied as an innovative and alternative flux barrier design with negligible mechanical material deterioration. The overall objective is to replace cutouts by embossings, increasing the mechanical strength of the rotor. The identification of suitable embossing geometries, distributions and methodologies for the local introduction of residual stress is a major challenge. This paper examines finely distributed pyramidal embossings and their effect on the magnetic material behavior. The study is based on simulation and measurements of specimen with a single line of twenty embossing points performed with different punch forces. The magnetic material behavior is analyzed using neutron grating interferometry and a single sheet tester. Numerical examinations using finite element analysis and microhardness measurements provide a more detailed understanding of the interaction of residual stress distribution and magnetic material properties. The results reveal that residual stress induced by embossing affects magnetic material properties. Process parameters can be applied to adjust the magnetic material deterioration and the effect of magnetic flux guidance.

scholarly journals Strength and Failure Mechanism of Composite-Steel Adhesive Bond Single Lap Joints

2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Kai Wei ◽  
Yiwei Chen ◽  
Maojun Li ◽  
Xujing Yang
Keyword(s):  
Failure Mechanism ◽  
Shear Failure ◽  
Failure Load ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Adhesive Failure ◽  
Interface Failure ◽  
Element Analysis ◽  
Single Lap Joints ◽  
Structural Adhesive

Carbon fiber-reinforced plastics- (CFRP-) steel single lap joints with regard to tensile loading with two levels of adhesives and four levels of overlap lengths were experimentally analyzed and numerically simulated. Both joint strength and failure mechanism were found to be highly dependent on adhesive type and overlap length. Joints with 7779 structural adhesive were more ductile and produced about 2-3 kN higher failure load than MA830 structural adhesive. Failure load with the two adhesives increased about 147 N and 176 N, respectively, with increasing 1 mm of the overlap length. Cohesion failure was observed in both types of adhesive joints. As the overlap length increased, interface failure appeared solely on the edge of the overlap in 7779 adhesive joints. Finite element analysis (FEA) results revealed that peel and shear stress distributions were nonuniform, which were less severe as overlap length increased. Severe stress concentration was observed on the overlap edge, and shear failure of the adhesive was the main reason for the adhesive failure.

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