scholarly journals Pore Geometry Optimization of Titanium (Ti6Al4V) Alloy, for Its Application in the Fabrication of Customized Hip Implants

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Sandipan Roy ◽  
Debojyoti Panda ◽  
Niloy Khutia ◽  
Amit Roy Chowdhury
Keyword(s):  
Mechanical Response ◽  
Geometry Optimization ◽  
Combined Loading ◽  
Hip Implants ◽  
Loading Conditions ◽  
Mechanical Responses ◽  
Porous Ti ◽  
Physiological Loading ◽  
Solid Implants

The present study investigates the mechanical response of representative volume elements of porous Ti-6Al-4V alloy, to arrive at a desired range of pore geometries that would optimize the reduction in stiffness necessary for biocompatibility with the stress concentration arising around the pore periphery, under physiological loading conditions with respect to orthopedic hip implants. A comparative study of the two is performed with the aid of a newly defined optimizing parameter called pore efficiency that takes into consideration both the stiffness quantity and the stress localization around pores. To perform a detailed analysis of the response of the porous structure over the entire spectrum of loading conditions that a hip implant is subjected toin vivo, the mechanical responses of 3D finite element models of cubic and rectangular parallelepiped geometries, with porosities varying over a range of 10% to 60%, are simulated under representative compressive, flexural as well as combined loading conditions. The results that are obtained are used to suggest a range of pore diameters that lower the effective stiffness and modulus of the implant to around 60% of the stiffness and modulus of dense solid implants while keeping the stress levels within permissible limits.

Determination of Real Time In-Vivo Cartilage Contact Deformation in the Ankle Joint

2007 ◽  
Author(s):  
Guoan Li ◽  
Lu Wan ◽  
Michal Kozanek
Keyword(s):  
Computational Models ◽  
Ex Vivo ◽  
Loading Conditions ◽  
Contact Deformation ◽  
Normal Cartilage ◽  
Physiological Loading ◽  
Contact Data ◽  
Biomechanical Responses

Knowledge of in-vivo articular cartilage contact deformation is critical for understanding normal cartilage function and the etiology of osteoarthritis (2,8). This knowledge is also instrumental for design of ex-vivo experiment to investigate the chondrocyte mechanotransductions under physiological loading conditions (7). Further, in-vivo cartilage contact data is necessary for validation of 3D computational models used to predict biomechanical responses of the articular joints (1,5). However, due to the complexity of in-vivo joint loading conditions as well as the complicated joint geometry, little information is available on in-vivo cartilage deformation in literature (9). In-vivo cartilage deformation as a function of loading history has not been delineated.

scholarly journals The Role of the Loading Condition in Predictions of Bone Adaptation in a Mouse Tibial Loading Model

2021 ◽  
Vol 9 ◽  
Author(s):  
Vee San Cheong ◽  
Visakan Kadirkamanathan ◽  
Enrico Dall’Ara
Keyword(s):  
Bone Remodeling ◽  
Mechanical Loading ◽  
Axial Load ◽  
Bone Adaptation ◽  
Combined Loading ◽  
Micro Ct ◽  
Loading Conditions ◽  
Physiological Loading ◽  
Physiological Load ◽  
Significant Difference

The in vivo mouse tibial loading model is used to evaluate the effectiveness of mechanical loading treatment against skeletal diseases. Although studies have correlated bone adaptation with the induced mechanical stimulus, predictions of bone remodeling remained poor, and the interaction between external and physiological loading in engendering bone changes have not been determined. The aim of this study was to determine the effect of passive mechanical loading on the strain distribution in the mouse tibia and its predictions of bone adaptation. Longitudinal micro-computed tomography (micro-CT) imaging was performed over 2 weeks of cyclic loading from weeks 18 to 22 of age, to quantify the shape change, remodeling, and changes in densitometric properties. Micro-CT based finite element analysis coupled with an optimization algorithm for bone remodeling was used to predict bone adaptation under physiological loads, nominal 12N axial load and combined nominal 12N axial load superimposed to the physiological load. The results showed that despite large differences in the strain energy density magnitudes and distributions across the tibial length, the overall accuracy of the model and the spatial match were similar for all evaluated loading conditions. Predictions of densitometric properties were most similar to the experimental data for combined loading, followed closely by physiological loading conditions, despite no significant difference between these two predicted groups. However, all predicted densitometric properties were significantly different for the 12N and the combined loading conditions. The results suggest that computational modeling of bone’s adaptive response to passive mechanical loading should include the contribution of daily physiological load.

Local Non-Affine Deformations and Fiber Kinematics of Elastomeric Electrospun Scaffolds

2007 ◽  
Author(s):  
Todd D. Courtney ◽  
Jun Liao ◽  
William R. Wagner ◽  
Michael S. Sacks
Keyword(s):  
Mechanical Response ◽  
De Novo ◽  
Mechanical Load ◽  
Strain Analysis ◽  
Fiber Network ◽  
Mechanical Responses ◽  
Electrospun Scaffolds ◽  
Global Strain

For most tissue engineering applications that seek to generate tissue de novo, the scaffold is the first step in a series of important developmental considerations. Whether synthetic or natural, scaffolds developed for immediate in vivo use must have mechanical properties comparable to the native tissue for at least the minimum time necessary for the accompanying seeded cells, and eventual cells that migrate in, to lay down an equivalent supporting matrix. Scaffolds developed for the purpose of growing a tissue in vitro, with eventual in vivo use, need not necessarily meet these mechanical requirements. However, to better develop new tissues in bioreactors or in vivo, it is pertinent to understand how the fiber network changes under some regimen of mechanical load, in essence to understand what the cell witnesses within the scaffold. Extending our previous work, which focused on measuring and modeling the mechanical response of electrospun poly ester urethane urea (es-PEUU) scaffolds [1], we investigated the intricate and detailed es-PEUU fiber networks that are created during scaffold synthesis and how these networks change under various levels of strain. Specifically, we focused on several scaffold responses to strain: 1) Characteristics of fiber tortuosity, which when increased can yield delayed onset of scaffold stiffness as well as other varying mechanical responses. 2) Fiber splay, which determines the orientation of the all fibers within the scaffold. 3) Local vs global strain analysis to determine whether the scaffolds follow affine or non-affine deformations. 4) Fiber strain, to investigate how increasing levels of scaffold strain are transmitted to local fibers. 5) Changes in fiber tortuosity and overall fiber directions under strain.

The critical size of a defect in the glenoid causing anterior instability of the shoulder after a Bankart repair, under physiological joint loading

2019 ◽  
Vol 101-B (1) ◽  
pp. 68-74 ◽  
Author(s):  
C. Klemt ◽  
D. Toderita ◽  
D. Nolte ◽  
E. Di Federico ◽  
P. Reilly ◽  
...  
Keyword(s):  
Bone Grafting ◽  
Critical Size ◽  
Computational Study ◽  
Bankart Repair ◽  
Anterior Dislocation ◽  
Loading Conditions ◽  
Anterior Instability ◽  
Physiological Loading ◽  
Osseous Defect

Aims Patients with recurrent anterior dislocation of the shoulder commonly have an anterior osseous defect of the glenoid. Once the defect reaches a critical size, stability may be restored by bone grafting. The critical size of this defect under non-physiological loading conditions has previously been identified as 20% of the length of the glenoid. As the stability of the shoulder is load-dependent, with higher joint forces leading to a loss of stability, the aim of this study was to determine the critical size of an osseous defect that leads to further anterior instability of the shoulder under physiological loading despite a Bankart repair. Patients and Methods Two finite element (FE) models were used to determine the risk of dislocation of the shoulder during 30 activities of daily living (ADLs) for the intact glenoid and after creating anterior osseous defects of increasing magnitudes. A Bankart repair was simulated for each size of defect, and the shoulder was tested under loading conditions that replicate in vivo forces during these ADLs. The critical size of a defect was defined as the smallest osseous defect that leads to dislocation. Results The FE models showed a high risk of dislocation during ADLs after a Bankart repair for anterior defects corresponding to 16% of the length of the glenoid. Conclusion This computational study suggests that bone grafting should be undertaken for an anterior osseous defect in the glenoid of more than 16% of its length rather than a solely soft-tissue procedure, in order to optimize stability by restoring the concavity of the glenoid.

scholarly journals An Elaborate Data Set Characterizing the Mechanical Response of the Foot

2009 ◽  
Vol 131 (9) ◽  
Author(s):  
Ahmet Erdemir ◽  
Pavana A. Sirimamilla ◽  
Jason P. Halloran ◽  
Antonie J. van den Bogert
Keyword(s):  
Mechanical Properties ◽  
Computational Models ◽  
Mechanical Response ◽  
Three Dimensional ◽  
Normal Function ◽  
Combined Loading ◽  
Anatomical Reconstruction ◽  
Imaging Data ◽  
Data Set ◽  
Mechanical Responses

Mechanical properties of the foot are responsible for its normal function and play a role in various clinical problems. Specifically, we are interested in quantification of foot mechanical properties to assist the development of computational models for movement analysis and detailed simulations of tissue deformation. Current available data are specific to a foot region and the loading scenarios are limited to a single direction. A data set that incorporates regional response, to quantify individual function of foot components, as well as the overall response, to illustrate their combined operation, does not exist. Furthermore, the combined three-dimensional loading scenarios while measuring the complete three-dimensional deformation response are lacking. When combined with an anatomical image data set, development of anatomically realistic and mechanically validated models becomes possible. Therefore, the goal of this study was to record and disseminate the mechanical response of a foot specimen, supported by imaging data. Robotic testing was conducted at the rear foot, forefoot, metatarsal heads, and the foot as a whole. Complex foot deformations were induced by single mode loading, e.g., compression, and combined loading, e.g., compression and shear. Small and large indenters were used for heel and metatarsal head loading, an elevated platform was utilized to isolate the rear foot and forefoot, and a full platform compressed the whole foot. Three-dimensional tool movements and reaction loads were recorded simultaneously. Computed tomography scans of the same specimen were collected for anatomical reconstruction a priori. The three-dimensional mechanical response of the specimen was nonlinear and viscoelastic. A low stiffness region was observed starting with contact between the tool and foot regions, increasing with loading. Loading and unloading responses portrayed hysteresis. Loading range ensured capturing the toe and linear regions of the load deformation curves for the dominant loading direction, with the rates approximating those of walking. A large data set was successfully obtained to characterize the overall and the regional mechanical responses of an intact foot specimen under single and combined loads. Medical imaging complemented the mechanical testing data to establish the potential relationship between the anatomical architecture and mechanical responses and to further develop foot models that are mechanically realistic and anatomically consistent. This combined data set has been documented and disseminated in the public domain to promote future development in foot biomechanics.

Design of Pipeline Composite Repairs: From Lab Scale Tests to FEA and Full Scale Testing

2014 ◽  
Author(s):  
Remy Her ◽  
Jacques Renard ◽  
Vincent Gaffard ◽  
Yves Favry ◽  
Paul Wiet
Keyword(s):  
Finite Element ◽  
Full Scale ◽  
Combined Loading ◽  
Material Strength ◽  
Repair System ◽  
Loading Conditions ◽  
Original Design ◽  
Composite Repair ◽  
Repair Systems ◽  
Composite Properties

Composite repair systems are used for many years to restore locally the pipe strength where it has been affected by damage such as wall thickness reduction due to corrosion, dent, lamination or cracks. Composite repair systems are commonly qualified, designed and installed according to ASME PCC2 code or ISO 24817 standard requirements. In both of these codes, the Maximum Allowable Working Pressure (MAWP) of the damaged section must be determined to design the composite repair. To do so, codes such as ASME B31G for example for corrosion, are used. The composite repair systems is designed to “bridge the gap” between the MAWP of the damaged pipe and the original design pressure. The main weakness of available approaches is their applicability to combined loading conditions and various types of defects. The objective of this work is to set-up a “universal” methodology to design the composite repair by finite element calculations with directly taking into consideration the loading conditions and the influence of the defect on pipe strength (whatever its geometry and type). First a program of mechanical tests is defined to allow determining all the composite properties necessary to run the finite elements calculations. It consists in compression and tensile tests in various directions to account for the composite anisotropy and of Arcan tests to determine steel to composite interface behaviors in tension and shear. In parallel, a full scale burst test is performed on a repaired pipe section where a local wall thinning is previously machined. For this test, the composite repair was designed according to ISO 24817. Then, a finite element model integrating damaged pipe and composite repair system is built. It allowed simulating the test, comparing the results with experiments and validating damage models implemented to capture the various possible types of failures. In addition, sensitivity analysis considering composite properties variations evidenced by experiments are run. The composite behavior considered in this study is not time dependent. No degradation of the composite material strength due to ageing is taking into account. The roadmap for the next steps of this work is to clearly identify the ageing mechanisms, to perform tests in relevant conditions and to introduce ageing effects in the design process (and in particular in the composite constitutive laws).

Split beam method for determining mode shapes of cantilever beams under multiple loading conditions

2021 ◽  
pp. 107754632110276
Author(s):  
Jun-Jie Li ◽  
Shuo-Feng Chiu ◽  
Sheng D Chao
Keyword(s):  
Operation Mode ◽  
Point Contact ◽  
Mode Shapes ◽  
Cantilever Beams ◽  
Loading Conditions ◽  
Mechanical Responses ◽  
Relative Contribution ◽  
Resonance Frequencies ◽  
Beam Method ◽  
Multiple Loading

We have developed a general method, dubbed the split beam method, to solve Euler–Bernoulli equations for cantilever beams under multiple loading conditions. This kind of problem is, in general, a difficult inhomogeneous eigenvalue problem. The new idea is to split the original beam into two (or more) effective beams, each of which corresponds to one specific load and bears its own Young’s modulus. The mode shape of the original beam can be obtained by linearly superposing those of the effective beams. We apply the split beam method to simulating mechanical responses of an atomic force microscope probe in the “dynamical” operation mode, under which there are a stabilizing force at the positioner and a point-contact force at the tip. Compared with traditional analytical or numerical methods, the split beam method uses only a few number of basis functions from each effective beam, so a very fast convergence rate is observed in solving both the resonance frequencies and the mode shapes at the same time. Moreover, by examining the superposition coefficients, the split beam method provides a physical insight into the relative contribution of an individual load on the beam.

The Role of Mechanical Tension in Neurons

2010 ◽  
Vol 1274 ◽  
Author(s):  
Taher Saif ◽  
Jagannathan Rajagopalan ◽  
Alireza Tofangchi
Keyword(s):  
Mechanical Response ◽  
Mechanical Forces ◽  
Active Tension ◽  
Mechanical Tension ◽  
Deformation Response ◽  
Linear Force ◽  
Tension Regulation ◽  
Over Time

AbstractWe used high resolution micromechanical force sensors to study the in vivo mechanical response of embryonic Drosophila neurons. Our experiments show that Drosophila axons have a rest tension of a few nN and respond to mechanical forces in a manner characteristic of viscoelastic solids. In response to fast externally applied stretch they show a linear force-deformation response and when the applied stretch is held constant the force in the axons relaxes to a steady state value over time. More importantly, when the tension in the axons is suddenly reduced by releasing the external force the neurons actively restore the tension, sometimes close to their resting value. Along with the recent findings of Siechen et al (Proc. Natl. Acad. Sci. USA 106, 12611 (2009)) showing a link between mechanical tension and synaptic plasticity, our observation of active tension regulation in neurons suggest an important role for mechanical forces in the functioning of neurons in vivo.

scholarly journals Discrete element analysis of the punching behaviour of a secured drapery system: from laboratory characterization to idealized in situ conditions

2021 ◽  
Author(s):  
Antonio Pol ◽  
Fabio Gabrieli ◽  
Lorenzo Brezzi
Keyword(s):  
Mechanical Response ◽  
Steel Wire ◽  
Discrete Element ◽  
Wire Mesh ◽  
Steel Plates ◽  
Loading Conditions ◽  
Element Analysis ◽  
In Situ Conditions ◽  
Wire Meshes

AbstractIn this work, the mechanical response of a steel wire mesh panel against a punching load is studied starting from laboratory test conditions and extending the results to field applications. Wire meshes anchored with bolts and steel plates are extensively used in rockfall protection and slope stabilization. Their performances are evaluated through laboratory tests, but the mechanical constraints, the geometry and the loading conditions may strongly differ from the in situ conditions leading to incorrect estimations of the strength of the mesh. In this work, the discrete element method is used to simulate a wire mesh. After validation of the numerical mesh model against experimental data, the punching behaviour of an anchored mesh panel is investigated in order to obtain a more realistic characterization of the mesh mechanical response in field conditions. The dimension of the punching element, its position, the anchor plate size and the anchor spacing are varied, providing analytical relationships able to predict the panel response in different loading conditions. Furthermore, the mesh panel aspect ratio is analysed showing the existence of an optimal value. The results of this study can provide useful information to practitioners for designing secured drapery systems, as well as for the assessment of their safety conditions.

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