scholarly journals Mechanical Behavior of Blood Vessels: Elastic and Viscoelastic Contributions

Biology ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 831
Author(s):  
David Sánchez-Molina ◽  
Silvia García-Vilana ◽  
Jordi Llumà ◽  
Ignasi Galtés ◽  
Juan Velázquez-Ameijide ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Computational Models ◽  
Viscoelastic Behavior ◽  
Theoretical Explanation ◽  
Uniaxial Tensile ◽  
Strain Rates ◽  
Viscoelastic Effect ◽  
Nonlinear Stress ◽  
Viscoelastic Effects ◽  
Constitutive Parameters

The mechanical properties of the cerebral bridging veins (CBVs) were studied using advanced microtensile equipment. Detailed high-quality curves were obtained at different strain rates, showing a clearly nonlinear stress–strain response. In addition, the tissue of the CBVs exhibits stress relaxation and a preconditioning effect under cyclic loading, unequivocal indications of viscoelastic behavior. Interestingly, most previous literature that conducts uniaxial tensile tests had not found significant viscoelastic effects in CBVs, but the use of more sensitive tests allowed to observe the viscoelastic effects. For that reason, a careful mathematical analysis is presented, clarifying why in uniaxial tests with moderate strain rates, it is difficult to observe any viscoelastic effect. The analysis provides a theoretical explanation as to why many recent studies that investigated mechanical properties did not find a significant viscoelastic effect, even though in other circumstances, the CBV tissue would clearly exhibit viscoelastic behavior. Finally, this study provides reference values for the usual mechanical properties, as well as calculations of constitutive parameters for nonlinear elastic and viscoelastic models that would allow more accurate numerical simulation of CBVs in Finite Element-based computational models in future works.

scholarly journals Viscoelastic Characterization of Parasagittal Bridging Veins and Implications for Traumatic Brain Injury: A Pilot Study

2021 ◽  
Vol 8 (10) ◽  
pp. 145
Author(s):  
Silvia García-Vilana ◽  
David Sánchez-Molina ◽  
Jordi Llumà ◽  
Ignasi Galtés ◽  
Juan Velázquez-Ameijide ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Reference Values ◽  
Computational Models ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Tensile Tests ◽  
Specific Model ◽  
Experimental Point ◽  
Viscoelastic Effects ◽  
Bridging Veins

Many previous studies on the mechanical properties of Parasagittal Bridging Veins (PSBVs) found that strain rate had a significant effect on some mechanical properties, but did not extensively study the viscoelastic effects, which are difficult to detect with uniaxial simple tensile tests. In this study, relaxation tests and tests under cyclic loading were performed, and it was found that PSBVs do indeed exhibit clear viscoelastic effects. In addition, a complete viscoelastic model for the PSBVs is proposed and data from relaxation, cyclic load and load-unload tests for triangular loads are used to find reference values that characterize the viscoelastic behavior of the PSBVs. Although such models have been proposed for other types of blood vessels, this is the first study that clearly demonstrates the existence of viscoelastic effects from an experimental point of view and also proposes a specific model to explain the data obtained. Finally, this study provides reference values for the usual viscoelastic properties, which would allow more accurate numerical simulation of PSBVs by means of computational models.

Mechanical Properties of Human Mitral Valve Chordae Tendineae: Variation with Size and Strain Rate

1975 ◽  
Vol 53 (3) ◽  
pp. 330-339 ◽  
Author(s):  
Koon O. Lim ◽  
Derek R. Boughner
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Collagen Fibers ◽  
Elastic Response ◽  
Uniaxial Tensile ◽  
Prosthetic Heart Valves ◽  
Strain Rates ◽  
Valve Closure ◽  
Chordae Tendineae ◽  
Physiological Strain

A knowledge of the mechanical properties of valve tissue is a necessary prerequisite for a better understanding of valvular behavior and the design of prosthetic heart valves. Elastic response of chordae tendineae under strain rates of 0.05 cm min−1(6.25% min−1) to 12.7 cm min−1 (1600% min−1) were obtained by the application of an uniaxial tensile stress using an Instron machine. The chordae exhibited viscoelastic properties in that extensibility decreased with increasing strain rates. The approximate maximum physiological strain rate of the chordae was estimated from echocardiographic traces at the instant of valve closure, and a high value of 29 (S.D. = 9) cm s−1 (2000% s−1) was found. The breaking strain and stress were found to have values of 21.4 ± 0.5% and 3.1 ± 0.1 × 108 dyn cm−2 respectively, and were independent of strain rates (1 dyn = 10−5 N). These values are typical of collagen fibers. The final modulus, before the proportional limit, was found to be about 109 dyn cm−2, which is again typical of collagen fibers. In addition, smaller chordae exhibited less extensibility than the larger chordae. This behavior could be due to structural and functional differences and allows the more centrally inserted chordae to maintain an even valve surface during valve closure.

Enhancement of mechanical properties of polypropylene by blending with styrene-(ethylene-butylene)-styrene tri-block copolymer

2014 ◽  
Vol 34 (8) ◽  
pp. 765-774 ◽  
Author(s):  
Aleksey D. Drozdov ◽  
Catalina-Gabriela Sanporean ◽  
Jesper de C. Christiansen
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Block Copolymer ◽  
Impact Resistance ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Strain Rates ◽  
Cyclic Tests ◽  
Data Correlations ◽  
Impact Modifier

Abstract Observations are reported in impact tests, uniaxial tensile tests with various strain rates, relaxation tests with various strains and cyclic tests with a mixed deformation program and various maximum strains per cycle on neat polypropylene (PP) and a blend of PP with styrene-(ethylene-butylene)-styrene copolymer (SEBS). Experimental data demonstrate a pronounced enhancement of impact resistance of PP due to the presence of an impact modifier, accompanied by improvement of its properties under low-speed loading, observed as a decrease in relaxation rate and residual strain under cyclic deformation. Material constants in constitutive equations are determined by matching the experimental data. Correlations are established between changes in the viscoelastoplastic response of PP and evolution of its microstructure induced by the presence of an impact modifier.

Mechanical Properties of 35CrMoA Steel at High Strain Rate Loading

2013 ◽  
Vol 791-793 ◽  
pp. 338-342
Author(s):  
Wen Jun Hu ◽  
Xi Cheng Huang ◽  
Fang Ju Zhang ◽  
Li Ming Wei
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
High Strain ◽  
Strain Rate Range ◽  
Strain Rates ◽  
Experimental Apparatus ◽  
Metallurgical Structure ◽  
Fracture Appearance ◽  
Strain Rate Loading ◽  
Constitutive Parameters

The tensile properties of alloy steel 35CrMoA were measured by dynamic tension experimental apparatus, and the stress-strain curves of the material at strain rate range from 10-2/s to 103/s were obtained. The fracture appearance and metallurgical structure were observed for the recovered specimens. The influence of strain rates on mechanical properties and microstructure of the 35CrMoA steel was analyzed. Based on the experimental data of mechanical properties, the JC constitutive parameters were fitted for 35CrMoA.

scholarly journals Hyperelastic and Viscoelastic Properties of Brain Tissue in Tension

2012 ◽  
Author(s):  
Badar Rashid ◽  
Michel Destrade ◽  
Michael D. Gilchrist
Keyword(s):  
Finite Element ◽  
Brain Tissue ◽  
Brain Injuries ◽  
Diffuse Axonal Injury ◽  
Viscoelastic Behavior ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Strain Rates ◽  
Average Rise

Mechanical characterization of brain tissue at high loading velocities is particularly important for modelling Traumatic Brain Injury (TBI). During severe impact conditions, brain tissue experiences a mixture of compression, tension and shear. Diffuse axonal injury (DAI) occurs in animals and humans when the strains and strain rates exceed 10% and 10/s, respectively. Knowing the mechanical properties of brain tissue at these strains and strain rates is thus of particular importance, as they can be used in finite element simulations to predict the occurrence of brain injuries under different impact conditions. In this research, uniaxial tensile tests at strain rates of 30, 60 and 90/s up to 30% strain and stress relaxation tests in tension at various strain magnitudes (10%–60%) with an average rise time of 24 ms were performed. The brain tissue showed a stiffer response with increasing strain rates, showing that hyperelastic models are not adequate and that viscoelastic models are required. Specifically, the tensile engineering stress at 30% strain was 3.1 ± 0.49 kPa, 4.3 ± 0.86 kPa, 6.5 ± 0.76 kPa (mean ± SD) at strain rates of 30, 60 and 90/s, respectively. The Prony parameters were estimated from the relaxation data. Numerical simulations were performed using a one-term Ogden model to analyze hyperelastic and viscoelastic behavior of brain tissue up to 30% strain. The material parameters obtained in this study will help to develop biofidelic human brain finite element models, which subsequently can be used to predict brain injuries under impact conditions.

scholarly journals The Influence of Microstructure on the Mechanical Properties and Fracture Behavior of Medium Mn Steels at Different Strain Rates

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4228 ◽  
Author(s):  
Zheng Wang ◽  
Juanping Xu ◽  
Yu Yan ◽  
Jinxu Li
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Strain Rate ◽  
Fracture Behavior ◽  
Total Elongation ◽  
Uniaxial Tensile ◽  
Strain Rates ◽  
Car Crash ◽  
Δ Ferrite

The primary task of automotive industry materials is to guarantee passengers’ safety during a car crash. To simulate a car crash, the influence of strain rates on mechanical properties and fracture behavior of medium Mn steels with different Si content (0Si without δ-ferrite and 0.6Si with about 20% δ-ferrite) was conducted using the uniaxial tensile test. The results show that ultimate tensile strength is higher, whereas total elongation is lower in 0Si than in 0.6Si. As the strain rate increases, ultimate tensile strength and total elongation decrease in both 0Si and 0.6Si; nonetheless, total elongation of 0.6Si decreases faster. Meanwhile, the area reduction of 0.6Si increases as the strain rate increases. The microcrack′s number on a rolling direction (RD)-transverse direction (TD) surface is considerably increased; nonetheless, the microcrack′s size is restrained in 0.6Si compared with 0Si. Microcracks start at γ(α′)/α-ferrite interfaces in both 0Si and 0.6Si, whereas little nucleation sites have also been found at (γ(α′)+α-ferrite)/δ-ferrite boundaries in 0.6Si. Meanwhile, δ-ferrite reveals a higher capacity for microcrack arrest. As the strain rate decreases, increased lower crack growth results in fine and even dimples on fractographs with abundant second cracks on fractographs; meanwhile, the small microcrack′s number increases, while the large microcrack′s number decreases on an RD-TD surface.

Viscoelastic Properties of Macaque Neural Tissue at Low Strain Rates

2010 ◽  
Author(s):  
Sarah A. Bentil ◽  
Sean MacLean ◽  
Rebecca B. Dupaix
Keyword(s):  
Mechanical Properties ◽  
Surgical Simulation ◽  
Tissue Sample ◽  
Surgical Techniques ◽  
Viscoelastic Behavior ◽  
Neural Tissue ◽  
Physiological Saline ◽  
Strain Rates ◽  
Unconfined Compression ◽  
Unconfined Compression Test

Increased knowledge of the mechanical properties of soft tissue subjected to low strain rates is beneficial to biomedical applications, such as designing bio-compatible implants, developing minimally invasive surgical techniques and surgical simulation devices for training surgeons. Unconfined compression and indentation experiments were conducted to extract macro- and micro-level mechanical properties of Macaque neural tissue. The tissues were placed in physiological saline solution and tested at room temperature within one hour post-sacrifice and three weeks post sacrifice using unconfined compression and indentation experiments. For each test, the temporal lobe was sectioned into 26 mm diameter disks that were subjected to 1%, 2%, 5%, and 10% strain at a loading rate of 5 mm per minute. The impermeable platen used in the unconfined compression test had a diameter equivalent to the tissue sample. The diameter of the flat tip used in the indentation experiment was 5 mm. Both test configurations utilized a ramp-and-hold strain input to capture the features of the tissue attributed to the stress-strain relationship (ramp) and stress-relaxation (hold). Viscoelastic theory was applied to the experimental data for the calculation of the secant and relaxation modulus, which correspond to the ramp and hold portion of the strain input, respectively. The resulting viscoelastic behavior of the Macaque brain at the macro- and micro-scale were compared with (i) bovine and porcine neural tissue, commonly found in the literature and (ii) viscoelastic models for neural tissue, which in the literature are generally applicable only to large deformations.

scholarly journals Experimental and Numerical Evaluation of Mechanical Properties of 3D-Printed Stainless Steel 316L Lattice Structures

2021 ◽  
Author(s):  
M. Carraturo ◽  
G. Alaimo ◽  
S. Marconi ◽  
E. Negrello ◽  
E. Sgambitterra ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Mechanical Behavior ◽  
Numerical Simulations ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Lattice Structures ◽  
Stainless Steel 316L ◽  
Research Attention ◽  
Octet Truss

AbstractAdditive manufacturing (AM), and in particular selective laser melting (SLM) technology, allows to produce structural components made of lattice structures. These kinds of structures have received a lot of research attention over recent years due to their capacity to generate easy-to-manufacture and lightweight components with enhanced mechanical properties. Despite a large amount of work available in the literature, the prediction of the mechanical behavior of lattice structures is still an open issue for researchers. Numerical simulations can help to better understand the mechanical behavior of such a kind of structure without undergoing long and expensive experimental campaigns. In this work, we compare numerical and experimental results of a uniaxial tensile test for stainless steel 316L octet-truss lattice specimen. Numerical simulations are based on both the nominal as-designed geometry and the as-build geometry obtained through the analysis of µ-CT images. We find that the use of the as-build geometry is fundamental for an accurate prediction of the mechanical behavior of lattice structures.

Experimental investigation of the mechanical behavior of glass fiber/high fluidity polyamide-based composites for automotive market

2021 ◽  
pp. 073168442110140
Author(s):  
Hossein Ramezani-Dana ◽  
Moussa Gomina ◽  
Joël Bréard ◽  
Gilles Orange
Keyword(s):  
Mechanical Properties ◽  
Glass Fiber ◽  
Mechanical Performance ◽  
Physical And Mechanical Properties ◽  
Ultimate Strain ◽  
Uniaxial Tensile ◽  
Compression Tests ◽  
Automotive Market ◽  
Glass Fiber Reinforced ◽  
Glass Fiber Reinforcement

In this work, we examine the relationships between the microstructure and the mechanical properties of glass fiber–reinforced polyamide 6,6 composite materials ( V f = 54%). These materials made by thermocompression incorporate different grades of high fluidity polyamide-based polymers and two types of quasi-UD glass fiber reinforcement. One is a classic commercial fabric, while the other specially designed and manufactured incorporates weaker tex glass yarns (the spacer) to increase the planar permeability of the preform. The effects of the viscosity of the polymers and their composition on the wettability of the reinforcements were analyzed by scanning electron microscopy observations of the microstructure. The respective influences of the polymers and the spacer on the mechanical performance were determined by uniaxial tensile and compression tests in the directions parallel and transverse to the warp yarns. Not only does the spacer enhance permeability but it also improves physical and mechanical properties: tensile longitudinal Young’s modulus increased from 38.2 GPa to 42.9 GPa (13% growth), tensile strength increased from 618.9 MPa to 697 MPa (3% growth), and decrease in ultimate strain from 1.8% to 1.7% (5% reduction). The correlation of these results with the damage observed post mortem confirms those acquired from analyses of the microstructure of composites and the rheological behaviors of polymers.

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