Stability Analysis of Arteries Under Torsion

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Nir Emuna ◽  
David Durban
Keyword(s):  
Mechanical Response ◽  
Twist Angle ◽  
Fluid Pressure ◽  
Geometrical Parameters ◽  
Prediction Errors ◽  
Key Factors ◽  
Stability Margins ◽  
Linear Elastic ◽  
Twist Rate ◽  
Experimental Approaches

Abstract Vascular tortuosity may impede blood flow, occlude the lumen, and ultimately lead to ischemia or even infarction. Mechanical loads like blood pressure, axial force, and also torsion are key factors participating in this complex mechanobiological process. The available studies on arterial torsion instability followed computational or experimental approaches, yet single available theoretical study had modeled the artery as isotropic linear elastic. This paper aim is to validate a theoretical model of arterial torsion instability against experimental data. The artery is modeled as a single-layered, nonlinear, hyperelastic, anisotropic solid, with parameters calibrated from experiment. Linear bifurcation analysis is then performed to predict experimentally measured stability margins. Uncertainties in geometrical parameters and in measured mechanical response were considered. Also, the type of rate (incremental) boundary conditions (RBCs) impact on the results was examined (e.g., dead load, fluid pressure). The predicted critical torque and twist angle followed the experimentally measured trends. The closest prediction errors in the critical torque and twist rate were 22% and 67%, respectively. Using the different RBCs incurred differences of up to 50% difference within the model predictions. The present results suggest that the model may require further improvements. However, it offers an approach that can be used to predict allowable twist levels in surgical procedures (like anastomosis and grafting) and in the design of stents for arteries subjected to high torsion levels (like the femoropopliteal arteries). It may also be instructive in understanding biomechanical processes like arterial tortuosity, kinking, and coiling.

scholarly journals The importance of intervertebral disc material model on the prediction of mechanical function of the cervical spine

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Amin Komeili ◽  
Akbar Rasoulian ◽  
Fatemeh Moghaddam ◽  
Marwan El-Rich ◽  
Le Ping Li
Keyword(s):  
Intervertebral Disc ◽  
Mechanical Response ◽  
Fluid Pressure ◽  
Material Model ◽  
Load Sharing ◽  
Disc Height ◽  
Loading Conditions ◽  
Material Models ◽  
Linear Elastic ◽  
Disc Material

Abstract Background Linear elastic, hyperelastic, and multiphasic material constitutive models are frequently used for spinal intervertebral disc simulations. While the characteristics of each model are known, their effect on spine mechanical response requires a careful investigation. The use of advanced material models may not be applicable when material constants are not available, model convergence is unlikely, and computational time is a concern. On the other hand, poor estimations of tissue’s mechanical response are likely if the spine model is oversimplified. In this study, discrepancies in load response introduced by material models will be investigated. Methods Three fiber-reinforced C2-C3 disc models were developed with linear elastic, hyperelastic, and biphasic behaviors. Three different loading modes were investigated: compression, flexion and extension in quasi-static and dynamic conditions. The deformed disc height, disc fluid pressure, range of motion, and stresses were compared. Results Results indicated that the intervertebral disc material model has a strong effect on load-sharing and disc height change when compression and flexion were applied. The predicted mechanical response of three models under extension had less discrepancy than its counterparts under flexion and compression. The fluid-solid interaction showed more relevance in dynamic than quasi-static loading conditions. The fiber-reinforced linear elastic and hyperelastic material models underestimated the load-sharing of the intervertebral disc annular collagen fibers. Conclusion This study confirmed the central role of the disc fluid pressure in spinal load-sharing and highlighted loading conditions where linear elastic and hyperelastic models predicted energy distribution different than that of the biphasic model.

Linear elastic and hyperelastic studies of equine hoof mechanical response at different hydration levels

2021 ◽  
pp. 104622
Author(s):  
Naeim Akbari Shahkhosravi ◽  
Soheil Gohari ◽  
Amin Komeili ◽  
Colin Burvill ◽  
Helen Davies
Keyword(s):  
Mechanical Response ◽  
Linear Elastic ◽  
Equine Hoof

Mechanical response of double-stranded DNA to dynamic excitation

2021 ◽  
pp. 107754632110458
Author(s):  
Hamze Mousavi ◽  
Moein Mirzaei ◽  
Samira Jalilvand
Keyword(s):  
Mechanical Behavior ◽  
Mechanical Response ◽  
Actual Condition ◽  
Dimensional System ◽  
One Dimensional ◽  
Linear Elastic ◽  
Dynamic Excitation ◽  
Double Stranded Dna ◽  
Elastic Forces ◽  
Mass Spring

The present work investigates the vibrational properties of a DNA-like structure by means of a harmonic Hamiltonian and the Green’s function formalism. The DNA sequence is considered as a quasi one-dimensional system in which the mass-spring pairs are randomly distributed inside each crystalline unit. The sizes of the units inside the system are increased, in a step-by-step approach, so that the actual condition of the DNA could be modeled more accurately. The linear-elastic forces mimicking the bonds between the pairs are initially considered constant along the entire length of the system. In the next step, these forces are randomly shuffled so as to take into account the inherent randomness of the DNA. The results reveal that increasing the number of mass-spring pairs in the crystalline structure decreases the influence of randomness on the mechanical behavior of the structure. This also holds true for systems with larger crystalline units. The obtained results can be used to investigate the mechanical behavior of similar macro-systems.

The role of geomechanical modeling in the measurement and understanding of geophysical data collected during carbon sequestration

2021 ◽  
Vol 40 (6) ◽  
pp. 413-417
Author(s):  
Chunfang Meng ◽  
Michael Fehler
Keyword(s):  
Pore Pressure ◽  
Fault Location ◽  
Mechanical Response ◽  
Fluid Pressure ◽  
Geophysical Data ◽  
Fluid Injection ◽  
Coupled Flow ◽  
Cap Rock ◽  
Stress And Deformation ◽  
Pressure Changes

As fluids are injected into a reservoir, the pore fluid pressure changes in space and time. These changes induce a mechanical response to the reservoir fractures, which in turn induces changes in stress and deformation to the surrounding rock. The changes in stress and associated deformation comprise the geomechanical response of the reservoir to the injection. This response can result in slip along faults and potentially the loss of fluid containment within a reservoir as a result of cap-rock failure. It is important to recognize that the slip along faults does not occur only due to the changes in pore pressure at the fault location; it can also be a response to poroelastic changes in stress located away from the region where pore pressure itself changes. Our goal here is to briefly describe some of the concepts of geomechanics and the coupled flow-geomechanical response of the reservoir to fluid injection. We will illustrate some of the concepts with modeling examples that help build our intuition for understanding and predicting possible responses of reservoirs to injection. It is essential to understand and apply these concepts to properly use geomechanical modeling to design geophysical acquisition geometries and to properly interpret the geophysical data acquired during fluid injection.

scholarly journals Anisotropic mechanical behaviour of calendered nonwoven fabrics: Strain-rate dependency

2020 ◽  
pp. 002199832097679
Author(s):  
V Cucumazzo ◽  
E Demirci ◽  
B Pourdeyhimi ◽  
VV Silberschmidt
Keyword(s):  
Strain Rate ◽  
Mechanical Behaviour ◽  
Mechanical Response ◽  
Tensile Tests ◽  
Elastic Response ◽  
Uniaxial Tensile ◽  
Rate Dependency ◽  
Fibrous Matrix ◽  
Nonwoven Fabrics ◽  
Linear Elastic

Calendered nonwovens, formed by polymeric fibres, are three-phase heterogeneous materials, comprising a fibrous matrix, bond-areas and interface regions. As a result, two main factors of anisotropy can be identified. The first one is ascribable to a random fibrous microstructure, with the second one related to orientation of a bond pattern. This paper focuses on the first type of anisotropy in thin and thick nonwovens under uniaxial tensile loading. Individual and combined effects of anisotropy and strain rate were studied by conducting uniaxial tensile tests in various loading directions (0°, 30°, 45°, 60° and 90° with regard to the main fabric’s direction) and strain rate (0.01, 0.1 and 0.5 s−1). Fabrics exhibited an initial linear elastic response, followed by nonlinear strain hardening up to necking and final softening. The studied allowed assessment of the extent the effects of loading direction (anisotropy), planar density and strain rate on the mechanical response of the calendered fabrics. The evidence supported the conclusion that anisotropy is the most crucial factor, also delineating the balance between the fabric’s load-bearing capacity and extension level along various directions. The strain rate produced a marked effect on the fibre’s response, with increased stress at higher strain rate while this effect in the fabric was small. The results demonstrated the differences of the mechanical behaviour of fabrics from that of their constituent fibres.

Nonlinear Dynamic Viscoelastic Model for Osteoarthritic Cartilage Indentation Force

2011 ◽  
Author(s):  
A. Vidal-Lesso ◽  
E. Ledesma-Orozco ◽  
R. Lesso-Arroyo ◽  
L. Daza-Benitez
Keyword(s):  
Mechanical Properties ◽  
Soft Tissues ◽  
Mechanical Response ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Indentation Test ◽  
Maxwell Model ◽  
Relaxation Curve ◽  
Geometrical Parameters ◽  
Osteoarthritic Cartilage

Biomechanical properties and dynamic response of soft tissues as articular cartilage remains issues for attention. Currently, linear isotropic models are still used for cartilage analysis in spite of its viscoelastic nature. Therefore, the aim of this study was to propose a nonlinear viscoelastic model for cartilage indentation that combines the geometrical parameters and velocity of the indentation test with the thickness of the sample as well as the mechanical properties of the tissue changing over time due to its viscoelastic behavior. Parameters of the indentation test and mechanical properties as a function of time were performed in Laplace space where the constitutive equation for viscoelasticity and the convolution theorem was applied in addition with the Maxwell model and Hayes et al. model for instantaneous elastic modulus. Results of the models were compared with experimental data of indentation tests on osteoarthritic cartilage of a unicompartmental osteoarthritis cases. The models showed a strong fit for the axial indentation nonlinear force in the loading curve (R2 = 0.992) and a good fit for unloading (R2 = 0.987), while an acceptable fit was observed in the relaxation curve (R2 = 0.967). These models may be used to study the mechanical response of osteoarthritic cartilage to several dynamical and geometrical test conditions.

Simulation and Optimization on Dynamic Hydraulic Drawing for Spiral Bottom Shell Parts

2014 ◽  
Vol 496-500 ◽  
pp. 935-938
Author(s):  
Wen Chao Zhou ◽  
Wei Zhou ◽  
Cun Ping Liu ◽  
Shan Hua Xiao
Keyword(s):  
Wall Thickness ◽  
Deep Drawing ◽  
Fluid Pressure ◽  
Processing Parameters ◽  
Key Factors ◽  
Forming Process ◽  
Simulation And Optimization ◽  
Simulation Process ◽  
Optimal Processing ◽  
Blank Shape

The dynamic hydraulic drawing simulation is a valid method that reduces costs, increases quality and discovers hydraulic forming process problems.The simulation process of hydraulic drawing for spiral bottom brake shell parts with space surface feature was investigated and the optimal processing parameters were acquired by using Dynaform software. The results showed that model approaches, model methods, meshing and parameters setting were the foundation of hydraulic drawing simulation and the optimized control of holder force and fluid pressure were the key factors for preventing defects during hydraulic deep drawing. Meanwhile, the suitable blank shape was found good for reducing the defects of Wall Thickness Unevenness and oral flange earing, etc.

Mechanical Response of Asphalt Pavement under Overloading

2013 ◽  
Vol 361-363 ◽  
pp. 1869-1872 ◽  
Author(s):  
Sheng Jie Liu ◽  
Qing Long You
Keyword(s):  
Tensile Stress ◽  
Mechanical Response ◽  
Asphalt Pavement ◽  
Compressive Strain ◽  
Flexible Pavement ◽  
Load Application ◽  
Rigid Base ◽  
Linear Elastic ◽  
Application Procedure ◽  
Surface Increase

This paper examines theoretically the possible mechanical response changes on both bituminous pavement structure using linear elastic method, the change regulation of deflection,stress on the bottom of base and subbase and compress strain on the top of subgrades between semi-rigid base and flexible pavement pavement. In the load application procedure, a dual wheel with the a series of pressure was chosen.The results have shown that the deflection tensile stress and subgrade compressive strain on the surface increase with the increase of axle load and they would result in serious effect of overloading on the earlier damage of asphalt pavement.

Simulation Research of a Type of Pressure Vessel under Complex Loading Part 1 Component Load of the Numerical Analysis

2013 ◽  
Vol 756-759 ◽  
pp. 4656-4661
Author(s):  
Yu Fu Zhang ◽  
Hui Xia Guo ◽  
Jun Chen Li ◽  
Gui Rong Yang ◽  
Ying Ma ◽  
...  
Keyword(s):  
Finite Element ◽  
Pressure Vessel ◽  
Geometric Modeling ◽  
Mechanical Response ◽  
Complex Loading ◽  
Strain Response ◽  
The Finite Element Method ◽  
Key Factors ◽  
Dead Weight ◽  
Simulation Research

Macroscopic mechanical response is one of the key factors in designing pressure vessel. A geometric modeling of pressure vessel was established and the mesh of this modeling then generated by using the finite element simulating methods in software ABAQUS. Loading and boundary conditions of dead weight, hydraulic and uniform internal pressure which often suffered pressure vessel were set and calculated by the finite element method. Stress/strain response of pressure vessel in all kinds of alone loading ways were obtained. The results of finite element simulating were in accordance with those of theoretical calculation which provided useful data for research on mechanical response of pressure vessel under complex loading conditions.

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