Repeated Loading Behavior of Pediatric Porcine Common Carotid Arteries

Rapid flexion and extension of the neck may occur during scenarios associated with traumatic brain injury (TBI), and understanding the mechanical response of the common carotid artery (CCA) to longitudinal stretch may enhance understanding of contributing factors that may influence CCA vasospasm and exacerbate ischemic injury associated with TBI. Immature (4-week-old) porcine CCAs were tested under subcatastrophic (1.5 peak stretch ratio) cyclic loading at 3 Hz for 30 s. Under subcatastrophic cyclic longitudinal extension, the immature porcine CCA displays softening behavior. This softening can be represented by decreasing peak stress and increasing corner stretch values with an increasing number of loading cycles. This investigation is an important first step in the exploration of fatiguelike behavior in arterial tissue that may be subjected to repeated longitudinal loads.

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Understanding the Strain Path Effect on the Deformed Microstructure of Single Crystal Pure Aluminum

Metals ◽

10.3390/met11081189 ◽

2021 ◽

Vol 11 (8) ◽

pp. 1189

Author(s):

Yingjue Xiong ◽

Qinmeng Luan ◽

Kailun Zheng ◽

Wei Wang ◽

Jun Jiang

Keyword(s):

Strain Rate ◽

Single Crystal ◽

Strain Path ◽

Mechanical Response ◽

Pure Aluminum ◽

Lattice Rotation ◽

Softening Behavior ◽

Theoretical Support ◽

Commercial Applications ◽

Electron Back Scattered Diffraction

During plastic deformation, the change of structural states is known to be complicated and indeterminate, even in single crystals. This contributes to some enduring problems like the prediction of deformed texture and the commercial applications of such material. In this work, plane strain compression (PSC) tests were designed and implemented on single crystal pure aluminum to reveal the deformation mechanism. PSC tests were performed at different strain rates under strain control in either one-directional or two-directional compression. The deformed microstructures were analyzed according to the flow curve and the electron back-scattered diffraction (EBSD) mappings. The effects of grain orientation, strain rate, and strain path on the deformation and mechanical response were analyzed. Experimental results revealed that the degree of lattice rotation of one-dimensional compression mildly dependents on cube orientation, but it is profoundly sensitive to the strain rate. For two-dimensional compression, the softening behavior is found to be more pronounced in the case that provides greater dislocations gliding freeness in the first loading. Results presented in this work give new insights into aluminum deformation, which provides theoretical support for forming and manufacturing of aluminum.

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Simulation of Cyclic Loading on Pipe Elbows Using Advanced Plane-Stress Elastoplasticity Models1

Journal of Pressure Vessel Technology ◽

10.1115/1.4047876 ◽

2020 ◽

Vol 143 (2) ◽

Author(s):

Konstantinos Chatziioannou ◽

Yuner Huang ◽

Spyros A. Karamanos

Keyword(s):

Cyclic Loading ◽

Large Scale ◽

Mechanical Response ◽

Low Cycle Fatigue ◽

Constitutive Relations ◽

Cyclic Plasticity ◽

Integration Scheme ◽

Repeated Loading ◽

Finite Element Software ◽

Hardening Models

Abstract This work investigates the response of industrial steel pipe elbows subjected to severe cyclic loading (e.g., seismic or shutdown/startup conditions), associated with the development of significant inelastic strain amplitudes of alternate sign, which may lead to low-cycle fatigue. To model this response, three cyclic-plasticity hardening models are employed for the numerical analysis of large-scale experiments on elbows reported elsewhere. The constitutive relations of the material model follow the context of von Mises cyclic elasto-plasticity, and the hardening models are implemented in a user subroutine, developed by the authors, which employs a robust numerical integration scheme, and is inserted in a general-purpose finite element software. The three hardening models are evaluated in terms of their ability to predict the strain range at critical locations, and in particular, strain accumulation over the load cycles, a phenomenon called “ratcheting.” The overall good comparison between numerical and experimental results demonstrates that the proposed numerical methodology can be used for simulating accurately the mechanical response of pipe elbows under severe inelastic repeated loading. Finally, this paper highlights some limitations of conventional hardening rules in simulating multi-axial material ratcheting.

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Compressive Test Characteristics and Constitutive Relationship of Wet Polypropylene Macrofiber-Reinforced Shotcrete

Shock and Vibration ◽

10.1155/2021/6649283 ◽

2021 ◽

Vol 2021 ◽

pp. 1-9

Author(s):

Fenghui Li ◽

Yunhai Cheng ◽

Fei Wu ◽

Chang Su ◽

Gangwei Li

Keyword(s):

Mechanical Response ◽

Average Energy ◽

Strain Curve ◽

Peak Stress ◽

Constitutive Relationship ◽

Compression Tests ◽

Response Characteristics ◽

Test Characteristics ◽

High Crack ◽

Relationship Of

Shotcrete is often subject to poor ductility and cracking problems, particularly under high stresses. In order to deal with these issues, the feasibility of adding polypropylene macrofibers to shotcrete was verified. To ascertain the supporting effect, dry shotcrete, wet shotcrete, and wet polypropylene macrofiber-reinforced shotcrete (WPMS) were used as samples. Furthermore, the mechanical response characteristics thereof in uniaxial compression tests were compared and analyzed by acoustic emission (AE) monitoring. The results showed that the three materials were brittle, but the ductility, residual strength, and bearing capacity of polypropylene macrofiber-reinforced shotcrete were significantly enhanced. The energy absorption value of plain shotcrete was higher in the cracking stage, while that of polypropylene macrofiber-reinforced shotcrete was greater in the postpeak stage, which showed that the polypropylene macrofiber-reinforced shotcrete had the characteristics of a high crack-initiation strength and toughness. Besides, the energy release from fiber shotcrete occurred after the peak stress rather than near the peak stress. The average energy absorbed by polypropylene macrofiber-reinforced shotcrete was significantly higher than that in dry shotcrete and wet shotcrete, which implied that polypropylene macrofiber-reinforced shotcrete could mitigate the brittle instability of a shotcrete layer. A constitutive model of damage statistics was established based on the test data. The comparison between the experimental data and the fitting results can reflect the characteristics of the total stress-strain curve of such shotcrete. The results provide a basis for the optimization of polypropylene macrofiber-reinforced shotcrete layers.

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Flexural Behavior of a Layer-to-Layer Orthogonal Interlocked Three-Dimensional Textile Composite

Journal of Engineering Materials and Technology ◽

10.1115/1.4006501 ◽

2012 ◽

Vol 134 (3) ◽

Cited By ~ 10

Author(s):

D. Zhang ◽

A. M. Waas ◽

M. Pankow ◽

C. F. Yen ◽

S. Ghiorse

Keyword(s):

Mechanical Response ◽

Peak Load ◽

Three Dimensional ◽

Peak Stress ◽

Surface Strain ◽

Image Correlation ◽

Flexural Behavior ◽

Fe Model ◽

Textile Composite ◽

The Matrix

The flexural response of a three-dimensional (3D) layer-to-layer orthogonal interlocked textile composite has been investigated under quasi-static three-point bending. Fiber tow kinking on the compressive side of the flexed specimens has been found to be a strength limiting mechanism for both warp and weft panels. The digital image correlation (DIC) technique has been utilized to map the deformation and identify the matrix microcracking on the tensile side prior to the peak load in the warp direction loaded panels. It has been shown that the geometrical characteristics of textile reinforcement play a key role in the mechanical response of this class of material. A 3D local–global finite element (FE) model that reflects the textile architectures has been proposed to successfully capture the surface strain localizations in the predamage region. To analyze the kink banding event, the fiber tow is modeled as an inelastic degrading homogenized orthotropic solid in a state of plane stress based on Schapery Theory (ST). The predicted peak stress is in agreement with the tow kinking stress obtained from the 3D FE model.

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The Effect of Flash Freezing on Variability in Spinal Cord Compression Behavior

Journal of Biomechanical Engineering ◽

10.1115/1.4000079 ◽

2009 ◽

Vol 131 (11) ◽

Cited By ~ 5

Author(s):

Carolyn J. Sparrey ◽

Tony M. Keaveny

Keyword(s):

Spinal Cord ◽

Mechanical Behavior ◽

Mechanical Response ◽

Peak Stress ◽

Specimen Geometry ◽

Specimen Preparation ◽

Spinal Cord Tissue ◽

Compression Behavior ◽

Interface Friction ◽

Cord Injury

The compression behavior of spinal cord tissue is important for understanding spinal cord injury mechanics but has not yet been established. Characterizing compression behavior assumes precise specimen geometry; however, preparing test specimens of spinal cord tissue is complicated by the extreme compliance of the tissue. The objectives of this study were to determine the effect of flash freezing on both specimen preparation and mechanical response and to quantify the effect of small deviations in specimen geometry on mechanical behavior. Specimens of porcine spinal cord white matter were harvested immediately following sacrifice. The tissue was divided into two groups: partially frozen specimens were flash frozen (60 s at −80°C) prior to cutting, while fresh specimens were kept at room temperature. Specimens were tested in unconfined compression at strain rates of 0.05 s−1 and 5.0 s−1 to 40% strain. Parametric finite element analyses were used to investigate the effect of specimen face angle, cross section, and interface friction on the mechanical response. Flash freezing did not affect the mean mechanical behavior of the tissue but did reduce the variability in the response across specimens (p<0.05). Freezing also reduced variability in the specimen geometry. Variations in specimen face angle (0–10 deg) resulted in a 34% coefficient of variation and a 60% underestimation of peak stress. The effect of geometry on variation and error was greater than that of interface friction. Taken together, these findings demonstrate the advantages of flash freezing in biomechanical studies of spine cord tissue.

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Compressive Mechanical Properties of Porcine Brain: Experimentation and Modeling of the Tissue Hydration Effects

Bioengineering ◽

10.3390/bioengineering6020040 ◽

2019 ◽

Vol 6 (2) ◽

pp. 40 ◽

Cited By ~ 1

Author(s):

Raj K. Prabhu ◽

Mark T. Begonia ◽

Wilburn R. Whittington ◽

Michael A. Murphy ◽

Yuxiong Mao ◽

...

Keyword(s):

High Strain Rate ◽

Strain Rate ◽

Water Content ◽

Mechanical Response ◽

High Strain ◽

Peak Stress ◽

Human Head ◽

Element Analysis ◽

Porcine Brain ◽

Strain Behavior

Designing protective systems for the human head—and, hence, the brain—requires understanding the brain’s microstructural response to mechanical insults. We present the behavior of wet and dry porcine brain undergoing quasi-static and high strain rate mechanical deformations to unravel the effect of hydration on the brain’s biomechanics. Here, native ‘wet’ brain samples contained ~80% (mass/mass) water content and ‘dry’ brain samples contained ~0% (mass/mass) water content. First, the wet brain incurred a large initial peak stress that was not exhibited by the dry brain. Second, stress levels for the dry brain were greater than the wet brain. Third, the dry brain stress–strain behavior was characteristic of ductile materials with a yield point and work hardening; however, the wet brain showed a typical concave inflection that is often manifested by polymers. Finally, finite element analysis (FEA) of the brain’s high strain rate response for samples with various proportions of water and dry brain showed that water played a major role in the initial hardening trend. Therefore, hydration level plays a key role in brain tissue micromechanics, and the incorporation of this hydration effect on the brain’s mechanical response in simulated injury scenarios or virtual human-centric protective headgear design is essential.

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Geometry Governs Mechanics of Cardiovascular Stents

Volume 2: Biomedical and Biotechnology Engineering ◽

10.1115/imece2009-12924 ◽

2009 ◽

Author(s):

Graeham R. Douglas ◽

Tho Wei Tan ◽

Tim Bond ◽

A. Srikantha Phani

Keyword(s):

Arterial Wall ◽

Mechanical Response ◽

Neointimal Hyperplasia ◽

Stent Migration ◽

Contributing Factors ◽

Poisson Effect ◽

Element Analysis ◽

Cardiovascular Stents ◽

Stent Restenosis ◽

Longitudinal Strains

Cardiovascular stents are tubular lattice structures implanted into a stenosed artery to provide adequate lumen support and promote circulation. Commonly encountered complications are stent migration, NeoIntimal Hyperplasia (NIH), and damage to the arterial wall. Central to all these problems is the mechanical response of a stent to forces operating in situ including stent-artery interaction. The influence of geometry or repetitive pattern of the stent upon its mechanical response is the subject of this study. We focus on damage to the arterial wall caused by the stent which can lead to eventual in-stent restenosis. Stent-artery compliance mismatch and longitudinal strain due to Poisson effect are hypothesized as the main contributing factors to restenosis. Finite Element Analysis (FEA) is employed to compare radial compliance and longitudinal strains of different stent geometries. Existing geometrical calculations in the literature [1] are applied to stents of different geometries to compute a non-dimensional NIH index. The main finding is that hybrid lattice stent designs exhibit negligible longitudinal strains (Poisson effect) as the stent expands/contracts during each Cardiac cycle. Wall stresses can be minimized though a careful tailoring of stent geometry.

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Microstructural Modelling of P91 Martensitic Steel Under Uniaxial Loading Conditions

Volume 5: High-Pressure Technology; ASME NDE Division; Rudy Scavuzzo Student Paper Symposium ◽

10.1115/pvp2013-97514 ◽

2013 ◽

Author(s):

Brian Golden ◽

Dongfeng Li ◽

Noel O’Dowd

Keyword(s):

Power Plant ◽

Mechanical Response ◽

Electron Backscatter Diffraction ◽

Voronoi Tessellation ◽

Peak Stress ◽

Grain Structure ◽

Plant Materials ◽

Deformation And Failure ◽

Rate Dependent ◽

Modelling Studies

The changing face of power generation requires an improved understanding of the deformation and failure response of power plant materials. Important insights can be obtained through microstructurally motivated modelling studies. This paper deals with the comparisons of predictions of the mechanical response of a power plant steel (P91), obtained from a model with a measured microstructure with those obtained from a numerically simulated microstructure. Electron backscatter diffraction (EBSD) is employed to obtain the orientation of the martensitic grain structure of the steel. This information is incorporated within a representative volume element (RVE) to represent the material microstructure. A non-linear, rate dependent, finite strain crystal plasticity model is used to represent the deformation of the material, with the orientation of each finite-element integration point determined from the EBSD analysis. The deformation under uniaxial tension is analysed. Due to the inhomogeneous microstructure strong strain gradients are generated within the RVE even under remote homogenous strain states. It is seen that peak stress/strain states are associated with particular features of the microstructure. The results taken from the model are compared with those obtained with an equiaxed microstructure generated using the Voronoi tessellation method.

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Enhancing Damage-Sensing Capacity of Strain-Hardening Macro-Steel Fiber-Reinforced Concrete by Adding Low Amount of Discrete Carbons

Materials ◽

10.3390/ma12060938 ◽

2019 ◽

Vol 12 (6) ◽

pp. 938 ◽

Cited By ~ 5

Author(s):

Duy-Liem Nguyen ◽

Dong-Joo Kim ◽

Duc-Kien Thai

Keyword(s):

Strain Hardening ◽

Carbon Fibers ◽

Mechanical Response ◽

Steel Fiber ◽

Fiber Reinforced Concrete ◽

Fiber Reinforced ◽

Steel Fiber Reinforced Concrete ◽

Damage Sensing ◽

Softening Behavior ◽

Multi Walled Carbon Nanotubes

The effects of adding micro-carbon fibers on the electro-mechanical response of macro-steel fiber-reinforced concretes (MSFRCs) under tension were investigated. Two MSFRCs were investigated and they had identical mortar matrix but different fiber contents: MSFRC1 and MSFRC2 contained 1.0 and 1.5 vol.% fibers, respectively. The volume contents of added micro-carbon fibers were 0 to 1.5 vol.% in MSFRC1 and 0 to 0.75 vol.% in MSFRC2, respectively. The addition of 0.5 vol.% micro-carbon fibers, in both MSFRC1 and MSFRC2, produced significantly enhanced damage-sensing capability and still retained their strain-hardening performance together with multiple micro cracks. However, when the content of carbon fibers was more than 0.5 vol.%, the MSFRCs generated tensile strain-softening behavior and reduced damage-sensing capability. Furthermore, the effects of temperature and humidity on the electrical resistivity of MSFRCs were investigated, as were the effects of adding multi-walled carbon nanotubes on the damage-sensing capability of MSFRCs.

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Dynamic Behavior and Fatigue Damage Evolution of Sandstone under Uniaxial Cyclic Loading

Shock and Vibration ◽

10.1155/2020/1452159 ◽

2020 ◽

Vol 2020 ◽

pp. 1-9 ◽

Cited By ~ 1

Author(s):

Yidan Sun ◽

Yu Yang ◽

Min Li

Keyword(s):

Cyclic Loading ◽

Fatigue Damage ◽

Mechanical Response ◽

Compressive Strain ◽

Damage Model ◽

Testing Machine ◽

Strain Curve ◽

Peak Stress ◽

Creep Theory ◽

Cycle Number

The mechanical response characteristics of sandstone specimens under different stress amplitudes and loading frequencies were tested by a TAW-2000 rock triaxial testing machine. The characteristics of the stress-strain curve and the evolution process of strain damage under cyclic loading are analyzed. Based on creep theory and the disturbance state concept, a theoretical model between the axial compressive strain, axial compressive stress, and cycle number is established. The results show that there exists an upper threshold value of stress in cyclic loading above which the specimen will be damaged. As peak stress increases, the energy loss and irreversible deformation caused by damage gradually increase. When loading to an unstable peak stress under cyclic loading, the fatigue damage of sandstone under cyclic loading undergoes three characteristic stages: the initial stage; the stable stage; and the accelerated failure stage. The parameters of the strain damage model based on the disturbance state concept of sandstone are identified by test data, and the rationality of the model is validated by comparing theoretical values with experimental measurements.

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