Dependence of Anisotropy of Human Lumbar Vertebral Trabecular Bone on Quantitative Computed Tomography-Based Apparent Density

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
Ameet K. Aiyangar ◽  
Juan Vivanco ◽  
Anthony G. Au ◽  
Paul A. Anderson ◽  
Everett L. Smith ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Mechanical Properties ◽  
Finite Element ◽  
Elastic Modulus ◽  
Yield Strength ◽  
Apparent Density ◽  
Transverse Direction ◽  
Quantitative Computed Tomography ◽  
Axial Direction ◽  
Anisotropy Ratio

Most studies investigating human lumbar vertebral trabecular bone (HVTB) mechanical property–density relationships have presented results for the superior–inferior (SI), or “on-axis” direction. Equivalent, directly measured data from mechanical testing in the transverse (TR) direction are sparse and quantitative computed tomography (QCT) density-dependent variations in the anisotropy ratio of HVTB have not been adequately studied. The current study aimed to investigate the dependence of HVTB mechanical anisotropy ratio on QCT density by quantifying the empirical relationships between QCT-based apparent density of HVTB and its apparent compressive mechanical properties— elastic modulus (Eapp), yield strength (σy), and yield strain (εy)—in the SI and TR directions for future clinical QCT-based continuum finite element modeling of HVTB. A total of 51 cylindrical cores (33 axial and 18 transverse) were extracted from four L1 human lumbar cadaveric vertebrae. Intact vertebrae were scanned in a clinical resolution computed tomography (CT) scanner prior to specimen extraction to obtain QCT density, ρCT. Additionally, physically measured apparent density, computed as ash weight over wet, bulk volume, ρapp, showed significant correlation with ρCT [ρCT = 1.0568 × ρapp, r = 0.86]. Specimens were compression tested at room temperature using the Zetos bone loading and bioreactor system. Apparent elastic modulus (Eapp) and yield strength (σy) were linearly related to the ρCT in the axial direction [ESI = 1493.8 × (ρCT), r = 0.77, p < 0.01; σY,SI = 6.9 × (ρCT) − 0.13, r = 0.76, p < 0.01] while a power-law relation provided the best fit in the transverse direction [ETR = 3349.1 × (ρCT)1.94, r = 0.89, p < 0.01; σY,TR = 18.81 × (ρCT)1.83, r = 0.83, p < 0.01]. No significant correlation was found between εy and ρCT in either direction. Eapp and σy in the axial direction were larger compared to the transverse direction by a factor of 3.2 and 2.3, respectively, on average. Furthermore, the degree of anisotropy decreased with increasing density. Comparatively, εy exhibited only a mild, but statistically significant anisotropy: transverse strains were larger than those in the axial direction by 30%, on average. Ability to map apparent mechanical properties in the transverse direction, in addition to the axial direction, from CT-based densitometric measures allows incorporation of transverse properties in finite element models based on clinical CT data, partially offsetting the inability of continuum models to accurately represent trabecular architectural variations.

Investigation of Pore Structures on Mechanical Properties of Porous Ti by 3D Finite Element Models

2013 ◽  
Vol 647 ◽  
pp. 683-687
Author(s):  
Mi Gong ◽  
Hong Chao Kou ◽  
Yu Song Yang ◽  
Guang Sheng Xu ◽  
Jin Shan Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Elastic Modulus ◽  
Yield Strength ◽  
Finite Element Models ◽  
3D Finite Element ◽  
Pore Model ◽  
Porous Ti ◽  
Pore Structures ◽  
Medium Porosity

The pore structures on mechanical properties of porous Ti were investigated by 3D finite element models. Calculated elastic modulus and yield strength suggested that square-pore models exhibit lower modulus and higher strength compared with another two kinds of shapes (circle and hexagonal). In addition, under the condition of medium porosity (58.96%), integrated property was found in square-pore model which elastic modulus was 26.97GPa, less than 1/3 of hexagonal-pore model; while the yield strength maintained 63.82MPa, doubled the figure of circle-pore model. Thus, models with square-pore structures show potential perspective as hard tissue replacements. Investigation on anisotropy of microstructure implies that the elastic modulus was affected more intensively than the yield strength.

Relationships Between Stiffness of Human Distal Tibia, Distal Radius, Proximal Femur, and Vertebral Body Assessed by HR-pQCT and cQCT Based Finite Element Analyses

2009 ◽  
Author(s):  
X. Sherry Liu ◽  
Adi Cohen ◽  
Perry T. Yin ◽  
Joan M. Lappe ◽  
Robert R. Recker ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Mechanical Properties ◽  
Finite Element ◽  
Lumbar Spine ◽  
Fracture Risk ◽  
Cortical Bone ◽  
Bone Strength ◽  
Distal Radius ◽  
Proximal Femur ◽  
Quantitative Computed Tomography

High-resolution peripheral quantitative computed tomography (HR-pQCT) is a promising clinical tool that permits separate measurements of trabecular and cortical bone compartments at the distal radius and tibia. It has an isotropic voxel size of 82 μm, which is high enough to assess the fine microstructural details of trabecular architecture. HR-pQCT images can also be used for building microstructural finite element (μFE) models to estimate the mechanical competence of whole bone segments. Melton et al. showed that derived bone strength parameters (axial rigidity and fall load to failure load ratio) are additional to BMD and bone geometry and microstructure as determinants of forearm fracture risk prediction [1]. Boutroy et al. found that the proportion of the load carried by trabecular bone versus cortical bone is associated with wrist fracture independently of BMD and microarchitecture [2]. These clinical studies demonstrate that HR-pQCT based μFE analyses can provide measurements of mechanical properties that independently associate with fracture risk. However, microstructure of one skeletal site may be different from that of another site. It is unclear whether and to what extent these peripheral measurements reflect the bone strength of the proximal femur and vertebral bodies, the sites of frequent osteoporotic fractures. Currently, central quantitative computed tomography (cQCT) is the most commonly used clinical imaging modality to quantify the structural and mechanical properties of the proximal femur and lumbar spine. We therefore evaluated relationships between the stiffness of the distal radius and tibia estimated by HR-pQCT-based FEA with that of the proximal femur and lumbar spine which was estimated from cQCT-based FEA in the same human subjects.

Dependence of Human Lumbar Vertebral Trabecular Bone (HVTB) Mechanical Anisotropy Ratio on QCT–Based Apparent Density

2013 ◽  
Author(s):  
Ameet Aiyangar ◽  
Juan Vivanco ◽  
Anthony Au ◽  
Paul Anderson ◽  
Everett Smith ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Trabecular Bone ◽  
Apparent Density ◽  
Quantitative Computed Tomography ◽  
Transversely Isotropic ◽  
Mechanical Anisotropy ◽  
Anisotropy Ratio ◽  
Fabric Tensor ◽  
Clinical Resolution ◽  
Subject Specific

Obtaining bone mechanical properties from clinical resolution quantitative computed tomography (QCT)-derived localized apparent density presents the most attractive, available tool for developing subject-specific finite element (FE) bone models. While QCT density is a good predictor of the mechanical properties of HVTB [1, 2], knowledge of the fabric tensor (anisotropy ratio) can substantially improve prediction [3] and accuracy of CT-based continuum FE models [4]. Unfortunately, resolution of currently available clinical CT scanners is inadequate for mapping the fabric tensor of HVTB, which is known to be at least transversely isotropic [5]. Furthermore, trabecular bone mechanical anisotropy ratio has been shown to vary with density [2].

scholarly journals Determining Equi-Biaxial Residual Stress and Mechanical Properties From the Force-Displacement Curves of Conical Microindentation

2006 ◽  
Vol 129 (2) ◽  
pp. 200-206 ◽  
Author(s):  
J. Yan ◽  
X. Chen ◽  
A. M. Karlsson
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Finite Element ◽  
Elastic Modulus ◽  
Yield Strength ◽  
Evaluation Technique ◽  
Finite Element Analyses ◽  
Simple Test ◽  
Improved Method ◽  
Force Displacement

An alternative, improved method to determine mechanical properties from indentation testing is presented. This method can determine the elastic modulus, yield strength and equi-biaxial residual stress from one simple test. Furthermore, the technique does not require the knowledge of the contact area during indentation, a parameter that is hard to determine for highly elastic material. The evaluation technique is based on finite element analyses, where explicit formulations are established to correlate the parameter groups governing indentation on stressed specimens.

scholarly journals Micro computed tomography based finite element models for elastic and strength properties of 3D printed glass scaffolds

2021 ◽  
Author(s):  
Erica Farina ◽  
Dario Gastaldi ◽  
Francesco Baino ◽  
Enrica Vernè ◽  
Jonathan Massera ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Mechanical Properties ◽  
Finite Element ◽  
Elastic Modulus ◽  
Strength Properties ◽  
Design Parameters ◽  
Finite Element Models ◽  
Micro Ct ◽  
Micro Computed Tomography ◽  
3D Printed

Abstract In this study, the mechanical properties of glass scaffolds manufactured by robocasting are investigated through micro computed tomography ($$\mu -CT$$ μ - C T ) based finite element modeling. The scaffolds are obtained by printing fibers along two perpendicular directions on parallel layers with a $$90^\circ $$ 90 ∘ tilting between two adjacent layers. A parametric study is first presented with the purpose to assess the effect of the major design parameters on the elastic and strength properties of the scaffold; the mechanical properties of the 3D printed scaffolds are eventually estimated by using the $$\mu -CT$$ μ - C T data with the aim of assessing the effect of defects on the final geometry which are intrinsic in the manufacturing process. The macroscopic elastic modulus and strength of the scaffold are determined by simulating a uniaxial compressive test along the direction which is perpendicular to the layers of the printed fibers. An iterative approach has been used in order to determine the scaffold strength. A partial validation of the computational model has been obtained through comparison of the computed results with experimental values presented in [10] on a ceramic scaffold having the same geometry. All the results have been presented as non-dimensional values. The finite element analyses have shown which of the selected design parameters have the major effect on the stiffness and strength, being the porosity and fiber shifting between adjacent layers the most important ones. The analyses carried out on the basis of the $$\mu -CT$$ μ - C T data have shown elastic modulus and strength which are consistent with that found on ideal geometry at similar macroscopic porosity. Graphic Abstract In this work, elastic and strength properties of glass-ceramic Bone Tissue Engineering scaffolds manufactured by robocasting are investigated through micro-CT based finite element models. An incremental simulation using a multi-grid finite element solver has been implemented to perform a parametric study on the effect of the major geometrical parameters of the scaffold design as well as the effect. Eventually, the effect of the geometrical imperfections deriving from the 3D printing process has been investigated by means of micro-CT image-based models. The porosity and the shifting between adjacent layers play the dominant role in determing elasticity and strength of the scaffolds. The elastic and strength properties of 3D-printed real scaffold were assessed to be consistent those obtained from the idealized geometric models, at least for the subdomain used in this study.

The equivalent method of double V-wing honeycombs on the in-plane dynamic impact

2021 ◽  
pp. 073168442199086
Author(s):  
Yunfei Qu ◽  
Dian Wang ◽  
Hongye Zhang
Keyword(s):  
Mechanical Properties ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Elastic Modulus ◽  
Energy Absorption ◽  
Width Ratio ◽  
Size Factor ◽  
Dynamic Impact ◽  
Element Analysis ◽  
Equivalent Method

The double V-wing honeycomb can be applied in many fields because of its lower mass and higher performance. In this study, the volume, in-plane elastic modulus and unit cell area of the double V-wing honeycomb were analytically derived, which became parts of the theoretical basis of the novel equivalent method. Based on mass, plateau load, in-plane elastic modulus, compression strain and energy absorption of the double V-wing honeycomb, a novel equivalent method mapping relationship between the thickness–width ratio and the basic parameters was established. The various size factor of the equivalent honeycomb model was denoted as n and constructed by the explicit finite element analysis method. The mechanical properties and energy absorption performance for equivalent honeycombs were investigated and compared with hexagonal honeycombs under dynamic impact. Numerical results showed a well coincidence for each honeycomb under dynamic impact before 0.009 s. Honeycombs with the same thickness–width ratio had similar mechanical properties and energy absorption characteristics. The equivalent method was verified by theoretical analysis, finite element analysis and experimental testing. Equivalent honeycombs exceeded the initial honeycomb in performance efficiency. Improvement of performance and weight loss reached 173.9% and 13.3% to the initial honeycomb. The double V-wing honeycomb possessed stronger impact resistance and better load-bearing capacity than the hexagonal honeycomb under impact in this study. The equivalent method could be applied to select the optimum honeycomb based on requirements and improve the efficiency of the double V-wing honeycomb.

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