scholarly journals Contribution of Collagen Fiber Undulation to Regional Biomechanical Properties Along Porcine Thoracic Aorta

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Shahrokh Zeinali-Davarani ◽  
Yunjie Wang ◽  
Ming-Jay Chow ◽  
Raphaël Turcotte ◽  
Yanhang Zhang
Keyword(s):  
Mechanical Properties ◽  
Mechanical Behavior ◽  
Thoracic Aorta ◽  
Aortic Wall ◽  
Multiphoton Microscopy ◽  
Constitutive Models ◽  
Tensile Tests ◽  
Biomechanical Properties ◽  
Model Parameters ◽  
Extracellular Matrix Components

As major extracellular matrix components, elastin, and collagen play crucial roles in regulating the mechanical properties of the aortic wall and, thus, the normal cardiovascular function. The mechanical properties of aorta, known to vary with age and multitude of diseases as well as the proximity to the heart, have been attributed to the variations in the content and architecture of wall constituents. This study is focused on the role of layer-specific collagen undulation in the variation of mechanical properties along the porcine descending thoracic aorta. Planar biaxial tensile tests are performed to characterize the hyperelastic anisotropic mechanical behavior of tissues dissected from four locations along the thoracic aorta. Multiphoton microscopy is used to image the associated regional microstructure. Exponential-based and recruitment-based constitutive models are used to account for the observed mechanical behavior while considering the aortic wall as a composite of two layers with independent properties. An elevated stiffness is observed in distal regions compared to proximal regions of thoracic aorta, consistent with sharper and earlier collagen recruitment estimated for medial and adventitial layers in the models. Multiphoton images further support our prediction that higher stiffness in distal regions is associated with less undulation in collagen fibers. Recruitment-based models further reveal that regardless of the location, collagen in the media is recruited from the onset of stretching, whereas adventitial collagen starts to engage with a delay. A parameter sensitivity analysis is performed to discriminate between the models in terms of the confidence in the estimated model parameters.

Changes in the biomechanical properties of skin and aorta induced by corticotrophin treatment

1980 ◽  
Vol 94 (1) ◽  
pp. 132-137 ◽  
Author(s):  
H. Oxlund
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Connective Tissue ◽  
Thoracic Aorta ◽  
Aortic Wall ◽  
Biomechanical Properties ◽  
Elastic Stiffness ◽  
Collagen Content ◽  
Dorsal Skin ◽  
Biophysical Properties

Abstract. The work presented here is an investigation of the effect of elevated levels of corticosteroids on the biophysical properties of skin, aorta and muscle tendon. Rats were given corticotrophin injections for 10, 30 and 60 days to elevate the level of plasma endogenous corticosteroids. The corticotrophin treatments did not change the water or collagen content of specimens from dorsal skin, thoracic aorta and peroneal muscle tendons, tested mechanically. Changes became evident after longer treatment times. For both skin and aorta, the tensile strength, elastic stiffness and failure energy were increased after 60 days of treatment. The corticotrophin treatment did not influence the mechanical properties of muscle tendons. Complete reversibility of changes in the mechanical properties induced by 30 days of corticotrophin treatment was found after an additional period of 30 days of saline injections. This study indicates that an increased level of plasma corticosteroids elicited by corticotrophin treatment may increase the stiffness of the connective tissue of the organism. In the aorta this results in loss of capacitive function with increased haemodynamic strain on the aortic wall.

scholarly journals Quantitative Representation of Mechanical Behavior of the Surface Hardening Layer in Shot-Peened Nickel-Based Superalloy

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1437
Author(s):  
Wu Zeng ◽  
Junjie Yang
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Mechanical Behavior ◽  
Surface Hardening ◽  
Indentation Test ◽  
Tensile Tests ◽  
Model Parameters ◽  
Instrumented Indentation ◽  
Stress Strain ◽  
Nickel Based Superalloy

Surface hardening treatment can usually introduce severe grain distortion with a large gradient in the surface layer. It results in mechanical properties being difficult to accurately determine through macroscopic tests due to the non-uniformity of the shot-peened material. In this study, the mechanical behavior of uniformly pre-deformed nickel-based superalloy IN718 was investigated with monotonic tensile tests and instrumented indentation tests. For the shot-peened material, the hardness distribution of the surface hardening layer after shot peening was identified through the instrumented indentation method. According to the stress–strain results of pre-deformed materials, Ramberg–Osgood model parameters could be presented with plastic deformation. Assuming the power-law relationship between hardness and plastic deformation, the plastic deformation distribution along the depth of the surface hardening layer was clarified. Based on the results, a method to identify the stress–strain relationships of hardened material at different depths was established. Finally, the finite-element simulations of the instrumented indentation test considered residual stress and strain hardening were built to verify the method presented herein. The results show that the solution to evaluate the mechanical properties of hardening layer materials in the microscopic zone is feasible, which can provide the foundation for the failure analysis of shot-peened materials.

scholarly journals Mimicking the Mechanical Properties of Aortic Tissue with Pattern-Embedded 3D Printing for a Realistic Phantom

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5042
Author(s):  
Jaeyoung Kwon ◽  
Junhyeok Ock ◽  
Namkug Kim
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
3D Printing ◽  
Mechanical Characteristics ◽  
Aortic Wall ◽  
Tensile Tests ◽  
Human Aorta ◽  
Aortic Tissue ◽  
Medical Field ◽  
Base Materials

3D printing technology has been extensively applied in the medical field, but the ability to replicate tissues that experience significant loads and undergo substantial deformation, such as the aorta, remains elusive. Therefore, this study proposed a method to imitate the mechanical characteristics of the aortic wall by 3D printing embedded patterns and combining two materials with different physical properties. First, we determined the mechanical properties of the selected base materials (Agilus and Dragonskin 30) and pattern materials (VeroCyan and TPU 95A) and performed tensile testing. Three patterns were designed and embedded in printed Agilus–VeroCyan and Dragonskin 30–TPU 95A specimens. Tensile tests were then performed on the printed specimens, and the stress-strain curves were evaluated. The samples with one of the two tested orthotropic patterns exceeded the tensile strength and strain properties of a human aorta. Specifically, a tensile strength of 2.15 ± 0.15 MPa and strain at breaking of 3.18 ± 0.05 mm/mm were measured in the study; the human aorta is considered to have tensile strength and strain at breaking of 2.0–3.0 MPa and 2.0–2.3 mm/mm, respectively. These findings indicate the potential for developing more representative aortic phantoms based on the approach in this study.

Evolution of Anand Parameters With Elevated Temperature Aging for SAC Leadfree Alloys

2020 ◽  
Author(s):  
Pradeep Lall ◽  
Vikas Yadav ◽  
Jeff Suhling ◽  
David Locker
Keyword(s):  
Experimental Data ◽  
High Strain ◽  
Constitutive Models ◽  
Tensile Tests ◽  
Model Parameters ◽  
Strain Rates ◽  
Automotive Electronics ◽  
High Strain Rates ◽  
Operating Temperatures ◽  
Electronic Assemblies

Abstract Electronic equipment in automotive, agricultural and avionics applications may be subjected to temperatures in the range of −55 to 200°C during storage, operation and handling in addition to high strain-rates. Strain rates in owing to vibration and shock may range from 1–100 per sec. Temperature in electronic assemblies depends typically on location, energy dissipation and thermal architecture. Some investigators have indicated that the required operating temperature is between −40 to 200°C for automotive electronics located underhood, on engine, on transmission. Prior data indicates the evolution of mechanical properties under extended exposures to high temperatures. However, the constitutive models are often only available for pristine materials only. In this paper, effect of low operating temperatures (−65°C to 0°C) on Anand-model parameters at high strain rates (10–75 per sec) for aged SAC (SAC105 and SAC-Q) solder alloys has been studied. Stress-Strain curves have been obtained at low operating temperatures using tensile tests. The SAC leadfree solder samples were subjected to isothermal-aged up to 4-months at 50°C before testing. Anand Viscoplastic model has been used to describe the material constitutive behavior. Evolution of Anand Model parameters for SAC solder has been investigated. The computed parameters of the experimental data were used to simulate the tensile test and verified the accuracy of the model. A good correlation was found between experimental data and Anand predicted data.

The Precise Determination of the Johnson–Cook Material and Damage Model Parameters and Mechanical Properties of an Aluminum 7068-T651 Alloy

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
B. Bal ◽  
K. K. Karaveli ◽  
B. Cetin ◽  
B. Gumus
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Physical Simulation ◽  
Damage Model ◽  
Rolling Direction ◽  
Stress Triaxiality ◽  
Material Model ◽  
Tensile Tests ◽  
Model Parameters ◽  
Element Analysis

Al 7068-T651 alloy is one of the recently developed materials used mostly in the defense industry due to its high strength, toughness, and low weight compared to steels. The aim of this study is to identify the Johnson–Cook (J–C) material model parameters, the accurate Johnson–Cook (J–C) damage parameters, D1, D2, and D3 of the Al 7068-T651 alloy for finite element analysis-based simulation techniques, together with other damage parameters, D4 and D5. In order to determine D1, D2, and D3, tensile tests were conducted on notched and smooth specimens at medium strain rate, 100 s−1, and tests were repeated seven times to ensure the consistency of the results both in the rolling direction and perpendicular to the rolling direction. To determine D4 and D5 further, tensile tests were conducted on specimens at high strain rate (102 s−1) and temperature (300 °C) by means of the Gleeble thermal–mechanical physical simulation system. The final areas of fractured specimens were calculated through optical microscopy. The effects of stress triaxiality factor, rolling direction, strain rate, and temperature on the mechanical properties of the Al 7068-T651 alloy were also investigated. Damage parameters were calculated via the Levenberg–Marquardt optimization method. From all the aforementioned experimental work, J–C material model parameters were determined. In this article, J–C damage model constants, based on maximum and minimum equivalent strain values, were also reported which can be utilized for the simulation of different applications.

A Structural Continuum Constitutive Model for a Two-Phase Soft Tissue

2010 ◽  
Author(s):  
Silvia Wognum ◽  
Michael S. Sacks
Keyword(s):  
Mechanical Behavior ◽  
Soft Tissues ◽  
Bladder Wall ◽  
Constitutive Models ◽  
Tissue Level ◽  
Model Parameters ◽  
Two Phase ◽  
Tissue Properties ◽  
Highly Nonlinear ◽  
Cord Injury

Due to the complexity in determining multi-constituent tissue properties, most structural constitutive models for soft tissues focus on a single constituent. However, many tissues contain multiple load-bearing constituents, such as collagen fibers and smooth muscle (SM) cells. Moreover, to elucidate how observed changes in tissue components are related to altered net mechanical behavior at the tissue level, structural constitutive models require physiological relevant model parameters and formulations for changes in referential configuration when one component is physically removed. As an excellent example application that underscores these issues, we have examined the urinary bladder wall (UBW), which undergoes large deformations and exhibits highly nonlinear and anisotropic mechanical behavior [1,2]. Moreover, it undergoes profound remodeling in response to different pathologies such as spinal cord injury (SCI) [1,2].

scholarly journals A Contemporary Look at Biomechanical Models of Myocardium

2019 ◽  
Vol 21 (1) ◽  
pp. 417-442 ◽  
Author(s):  
Reza Avazmohammadi ◽  
João S. Soares ◽  
David S. Li ◽  
Samarth S. Raut ◽  
Robert C. Gorman ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Constitutive Models ◽  
Underlying Structure ◽  
Model Parameters ◽  
Specific Test ◽  
Future Directions ◽  
Passive Components ◽  
Biomechanical Models ◽  
The Past ◽  
And Function

Understanding and predicting the mechanical behavior of myocardium under healthy and pathophysiological conditions are vital to developing novel cardiac therapies and promoting personalized interventions. Within the past 30 years, various constitutive models have been proposed for the passive mechanical behavior of myocardium. These models cover a broad range of mathematical forms, microstructural observations, and specific test conditions to which they are fitted. We present a critical review of these models, covering both phenomenological and structural approaches, and their relations to the underlying structure and function of myocardium. We further explore the experimental and numerical techniques used to identify the model parameters. Next, we provide a brief overview of continuum-level electromechanical models of myocardium, with a focus on the methods used to integrate the active and passive components of myocardial behavior. We conclude by pointing to future directions in the areas of optimal form as well as new approaches for constitutive modeling of myocardium.

Mechanical Properties and Modeling of Subcutaneous Adipose Tissue: a Comprehensive Review

2021 ◽  
Author(s):  
Zhaonan Sun ◽  
Bronislaw Gepner ◽  
Patrick S. Cottler ◽  
Sang-hyun Lee ◽  
Jason Kerrigan
Keyword(s):  
Mechanical Properties ◽  
Adipose Tissue ◽  
Constitutive Models ◽  
Rate Sensitivity ◽  
Material Behavior ◽  
Failure Behavior ◽  
Model Parameters ◽  
Comprehensive Review ◽  
Nonlinear Stress ◽  
Human Body Models

Abstract Mechanical models of adipose tissue are important for various medical applications including cosmetics, injuries, implantable drug delivery systems, and plastic surgeries, and biomechanical applications such as computational human body models for surgery simulation, and blunt impact trauma. This article presents a comprehensive review of experimental approaches that aimed to characterize the mechanical properties of adipose tissue, and the resulting constitutive models and model parameters identified. In particular, this study examines the material behavior of adipose tissue, including its nonlinear stress-strain relationship, viscoelasticity, strain hardening and softening, rate-sensitivity, anisotropy, preconditioning, failure behavior, and temperature dependency.

Constitutive Models of Vascular Tissue

2008 ◽  
Vol 144 ◽  
pp. 100-105
Author(s):  
Kryspin Mirota
Keyword(s):  
Mechanical Properties ◽  
Mechanical Behavior ◽  
Vascular Tissue ◽  
Constitutive Models ◽  
Wall Material ◽  
Flow State ◽  
Local Flow ◽  
Geometry Factor ◽  
Arterial Tissue ◽  
Hemodynamic Function

Knowledge of mechanical properties of vascular tissue - especially arterial tissue - is fundamental to understanding of vascular hemodynamic function. This work takes into consideration problems connected with description of mechanical behavior of main constitutes of the tissue and overall wall material in relation with local flow state and geometry factor.

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