Sinusoidal Strain Research Articles

Inactive Mineral Filler as a Stiffness Modulus Regulator in Foamed Bitumen-Modified Recycled Base Layers

The article presents the results of a cold recycled mix test with a foam bitumen including the addition of the inactive mineral filler as a dust of basalt. Basalt dust was derived from dedusting system by extraction of aggregates in the mine. Assessment of the impact of a basalt dust on the properties of a recycled base layer was carried out in terms of the amount of mineral filler (basalt) in the composition of the mineral mixture. This experiment involved a dosing of mineral filler in range from 5 to 20% with steps of 7.5% in the mineral mixture composition. The foamed bitumen was performed at optimum foaming process settings (ie. bitumen temperature, air pressure) and at 2.5% of the water content. The amount of a hydraulic binder as a Portland cement was 2.0%. The evaluation of rheological properties allowed to determine whether the addition of inactive mineral fillers can act as a stiffness modulus controller in the recycled base layer. The analysis of the rheological properties of a recycled base layer in terms of the amount of inactive fillers was performed in accordance with given standard EN 12697-26 Annex D. The study was carried out according to the direct tension-compression test methodology on cylindrical samples. The sample was subjected to the oscillatory sinusoidal strain ε0 < 25με. Studies carried out at a specific temperature set-points: - 7°C, 5°C, 13°C, 25°C and 40°C and at the frequency 0.1 Hz, 0.3 Hz, 1 Hz, 3 Hz, 10 Hz and 20 Hz. The obtained results allow to conclude that the use of an inactive filler can reduce the stiffness of an appropriate designed mixes of the cold recycled foundation. In addition, the analysis of the relation E′-E″ showed a similar behaviour of a recycled base, regardless of the amount of inactive fillers in the mix composition, at high temperatures/high frequency of induced load.

Mechanical energy harvesting using polyurethane/lead zirconate titanate composites

The microelectromechanical systems invade gradually the market with applications in many sectors of activity. Developing these micro-systems allows deploying wireless sensor networks that are useful to collect, process and transmit information from their environments without human intervention. In order to keep these micro-devices energetically autonomous without using batteries because they have a limited lifespan, an energy harvesting from ambient vibrations using electrostrictive polymers can be used. These polymers present best features against inorganic materials, as flexibility and low cost. The aims of this paper are manifold. First of all, we made elaboration of the polyurethane/lead zirconate titanate films of 100 µm thickness using a lead zirconate titanate–volume fraction of [Formula: see text]%. Therefore, we did an observation of the lead zirconate titanate grains dispersion and the electrical characterization of the polyurethane–50 vol% lead zirconate titanate composites. Finally, a detailed study of the electromechanical transduction, for the polyurethane–50 vol% lead zirconate titanate unpolarized and polarized composites sustained to the sinusoidal mechanical strain with amplitude of 1.5% and at very low frequencies ( f = 2 [Hz] and f = 4 [Hz]) and static electric field ( Edc = 10 [ V/µm]) or without it ( Edc = 0 [ V/µm]) has been presented.

Vibration analysis of multi-phase nanocrystalline silicon nanoplates considering the size and surface energies of nanograins/nanovoids

Nanocrystalline nanoplates are composed from three phases which are nano-grains, nano-voids and interface. This paper develops a higher order refined plate model with a sinusoidal shear strain function for vibration analysis of porous nanocrystalline nanoplates based on modified couple stress theory. Nano-voids or porosities inside the material have a stiffness-softening impact on the nanoplate. Modified couple stress theory is employed to capture grains rigid rotations. The governing equations obtained from Hamilton's principle are solved applying Galerkin's method which satisfies various boundary conditions. The reliability of present approach is verified by comparing obtained results with those provided in literature. Finally the influences of couple stress parameter, grain size, porosities and shear deformation on the vibration characteristics of nanocrystalline nanoplates have been explored.

Real time dynamic strain monitoring of optical links using the backreflection of live PSK data.

A major cause of faults in optical communication links is related to unintentional third party intrusions (normally related to civil/agricultural works) causing fiber breaks or cable damage. These intrusions could be anticipated and avoided by monitoring the dynamic strain recorded along the cable. In this work, a novel technique is proposed to implement real-time distributed strain sensing in parallel with an operating optical communication channel. The technique relies on monitoring the Rayleigh backscattered light from optical communication data transmitted using standard modulation formats. The system is treated as a phase-sensitive OTDR (ΦOTDR) using random and non-periodical non-return-to-zero (NRZ) phase-shift keying (PSK) pulse coding. An I/Q detection unit allows for a full (amplitude, phase and polarization) characterization of the backscattered optical signal, thus achieving a fully linear system in terms of ΦOTDR trace coding/decoding. The technique can be used with different modulation formats, and operation using 4 Gbaud single-polarization dual PSK and 4 Gbaud dual-polarization quadrature PSK is demonstrated. As a proof of concept, distributed sensing of dynamic strain with a sampling of 125 kHz and a spatial resolution of 2.5 cm (set by the bit size) over 500 m is demonstrated for applied sinusoidal strain signals of 500 Hz. The limitations and possibilities for improvement of the technique are also discussed.

The ischemic liver cirrhosis theory and its clinical implications

The canonical pathway theory of cirrhosis addresses inflammation as the main driver of hepatic fibrogenesis in hepatitis, so needing a further hypothesis for etiologies missing inflammation, for which parenchymal extinction is postulated. The present paper reports an alternative hypothesis suggesting a central role of micro-vascular ischemia in fibrogenesis and cirrhosis development, whatever is the aetiology of liver chronic injury. In fact, since chronic liver injury could finally result in endothelial damage and micro-vascular thrombosis, leading to a trigger of inappropriate hepatocyte proliferation and fibrosis, finally cirrhosis development could arise from chronic micro-vascular ischemia. Recently, some important confirmation of this hypothesis has been reported. In fact, in a murine experimental model of congestive hepatopathy, it was found that chronic hepatic congestion leads to sinusoidal thrombosis and strain, which in turn promote hepatic fibrosis. Furthermore, a study on a murine model of cirrhosis reported enoxaparin to reduce hepatic vascular resistance and portal pressure by having a protective role against fibrogenesis.In conclusion, the hypothesis giving a central role of micro-vascular ischemia in fibrogenesis and cirrhosis development could change the clinical scenario of chronic liver disease and have several main implications on management of various liver disease.

Bi-modal polymer networks: Viscoelasticity and mechanics from molecular dynamics simulation

The high strain-rate rheological and mechanical properties of bi-modal epoxy polymer networks were characterized using molecular dynamics simulation. The complex Young's modulus was found by applying a cyclic sinusoidal strain over a wide range of temperatures spanning the glass transition. The non-linear stress response was studied in the glass transition region using uni-axial deformation. We discuss special considerations in computing viscoelastic properties at the high strain-rates available to molecular dynamics. As in experimental studies, the complex modulus is shown to be a function of the network composition and strain rate. However, the high strain-rate simulations performed here predict the existence of broad peaks in the temperature-dependent loss modulus and slow relaxation of the storage modulus. In general, it is observed that network compositions with larger amounts of short, stiff 4,4’-methylenebis(cyclohexylamine) (MCA) cross-linkers lead to an increase in the mechanical glass transition temperature as well as the breadth of the glass transition compared to longer, more flexible poly(oxypropylene) diamine (POP) cross-linkers. When the networks of any composition were deformed beyond the linear region, the stress response displayed a plateau that was associated with the extension of network chains.

2DCOS and I. Three decades of two-dimensional correlation spectroscopy

Historical and personal accounts of the development of two-dimensional correlation spectroscopy (2DCOS) in the last 30 years are presented. 2DCOS originally started as a data sorting technique developed specifically for dynamic IR linear dichroism (DIRLD) spectra of polymers observed under a small amplitude sinusoidal strain. The concept was later generalized to provide a surprisingly versatile analytical tool to study many different types of samples under the influence of not only dynamic but also various static perturbations. Introduction of the efficient computational method based on discrete Hilbert transform and availability of software, as well as the comprehensive textbook in the field, have made the widespread and continuously growing use of 2DCOS technique possible. Evolution of the technique to incorporate new and variant forms of 2DCOS is also noted.

動的粘弾性 OCSA を用いた軟骨変性力学診断法の基礎的検討

Many of the elderly are predisposed to develop osteoarthritis (OA), although it is quite difficult to diagnose the earlygrade OA even by latest imaging modalities. In this study, we have proposed Dynamic Mechanical Analyzing Optical Coherence Straingraphy, namely DMA-OCSA, which is a tomographically micro-visualizing method of visco-elastic properties estimated from continuous OCT images. This is based on the speckle tracking algorithm having high sensitivity and S/N under micrometer resolution, thus can provide temporal and spatial distribution of not only deformation velocity but also strain rate during a dynamic visco-elasticity test. This was experimentally applied to comparatively both normal cartilages and cartilages degenerated by the collagenase enzyme treatment. Consequently, the sinusoidal time-varying strain rate was locally observed to have phase difference between the superficial tangential zone and middle zone, which could cause degradation of visco-elasticity.

Development of a Test Protocol to Measure Uniaxial Fatigue Damage and Healing

Various laboratory testing methods have been developed to characterize the fatigue response of asphalt concrete mixtures. These test methods attempt to simulate in-service conditions or formulate constitutive models. Experiments such as the four-point beam fatigue test have attempted to simulate in-service conditions. The prediction accuracy of such experiments depends on their effectiveness in simulating actual field conditions such as loading, support, stress state, and environment. Constitutive modeling experiments have aimed at measuring fundamental stress–strain relationships so that rigorous constitutive models can be formulated. The results from these experiments are used as input for field performance prediction algorithms. The uniaxial fatigue test is a promising method in this category because of the constant stress state across the specimen section. A few documents have focused on standard test methods for the uniaxial fatigue test; however, there are no AASHTO or ASTM protocols available that include the healing of asphalt concrete mixtures. The main objective of this study was to report on the development of a uniaxial fatigue test protocol that measures fatigue damage and healing of asphalt concrete mixtures. The documented work includes surrogate studies to identify appropriate sample fabrication procedures, gluing materials and procedures, alignment, machine compliance, type of strain wave shape, and strain-control mode of loading. It was found that the use of a gluing jig and 180-mm compaction height was essential to achieve successful mid-specimen failures. In addition, the sinusoidal strain wave shape and on-specimen strain-controlled mode of loading are appropriate test conditions for fatigue damage and healing characterization of asphalt concrete mixtures.

Dynamic and stress relaxation properties of the whole porcine temporomandibular joint disc under compression

In this study, the dynamic and static compressive properties of the whole porcine temporomandibular joint (TMJ) disc were investigated. The aim of the study was to develop a new simple method for the evaluation of joint viscoelasticity, enabling examination of the load-bearing capacity and joint flexibility of the entire disc. For the experiments, a novel testing fixture that reproduces the condylar and fossa surfaces of the TMJ was developed to replicate TMJ disc geometry. Ten porcine discs were used in the experiments. Each disc was dissected from the TMJ and sinusoidal compressive strain was applied to obtain the storage and loss moduli. Static strain control tests were carried out to obtain the relaxation modulus. The result of static and dynamic tests indicated that the whole disc presented viscoelastic behavior under compression. Storage and loss moduli increased with frequency and the relaxation modulus decreased over time. The loss tangent showed less frequency dependence, with values ranging from 0.2 to 0.3, suggesting that the viscous properties of the disc cannot be neglected. These results provide a better understanding of whole disc mechanical compression behavior under realistic TMJ working conditions.

In situ analysis of texture development from sinusoidal stress at high pressure and temperature.

Here, we present a new experimental protocol to investigate the relationship between texture, plastic strain, and the mechanisms of plastic deformation at high pressure and temperature. The method utilizes synchrotron X-ray radiation as the probing tool, coupled with a large-volume high pressure deformation device (D-DIA). The intensity of X-ray diffraction peaks within the spectrum of the sample is used for sampling texture development in situ. The unique feature of this study is given by the sinusoidal variation of the intensity when a sinusoidal strain is applied to the sample. For a sample of magnesium oxide at elevated pressure and temperature, we demonstrate observations that are consistent with elasto-plastic models for texture development and for diffraction-peak measurements of apparent stress. The sinusoidal strain magnitude was 3%.

Evaluation of the Low-Cycle Fatigue Life in Seven Steel Bar Types

AbstractThe low-cycle fatigue (LCF) behavior of steel in energy-dissipating seismic connections is an important consideration, especially in light of the interest in performance-based seismic design. In this study, the LCF performance of seven steel bar types (AISI 8620, 1018, 1045, 1117, 1215, 4140 and ASTM A36 steel) was experimentally examined and compared. The bar specimens were subjected to sinusoidal strains of constant amplitude from zero to peak strains of 4%, 6%, or 8%. Equations that relate the applied strain amplitudes with the number of cycles to failure were developed and compared. In addition, relationships for calculating the total dissipated energy corresponding to the applied strain amplitude were proposed based on the experimental results. This study demonstrated that, in general, the LCF resistance of AISI 1045 steel type outperformed the other steel materials at a strain amplitude of ±2%. However, at ±3 and ±4% strain amplitudes, the LCF lives of ASTM A36 and AISI 1117 bars outperforme...

The energy dissipation behaviors of magneto-sensitive polymer gel under cyclic shear loading

The energy dissipation behaviors of a typical magneto-sensitive polymer gel, named as magnetorheological plastomer (MRP), under two types (linear and sinusoidal strains) of cyclic loading was studied. The energy dissipation capability is evaluated by the dissipated energy density which is calculated from the stable stress–strain curve within a cycle. It was found that the dissipated energy changes with the variation of magnetic field and particle content, the anisotropic MRP dissipates more energy than the isotropic one. The type of actuating strain can also decide the value of dissipated energy density, but the energy dissipation mechanism of MRP cannot be changed by it. These results give valuable guidance to the potential application of MRP on dampers or absorbers, as well as to further understand its energy dissipation mechanism.

Modeling and experimental investigation on dielectric electro-active polymer generator

Dielectric electro-active polymers (DEAP) have been attracted for the energy harvesting application due to its low cost, lightweight and flexible deformation capability. This paper presents a validated model and experimental investigation on energy conversion of a typical DEAP generator. Firstly, a dynamics model based on Mooney-Rivlin proposition is developed to describe the strain–force relationship of DEAP material. Then, the effect of charging voltages and energy conversion are also taken into account. In addition, identification processes are done separately for stretching and relaxing strokes using an adaptive PSO scheme to find best material parameters for the model. This makes the model be available to describe the sinusoidal strain forms in practical conditions. The validated model is then employed in investigating input mechanical energy, return energy and conversion energy for the DEAP generator. Experimental evaluations show that the developed model can describe the behavior of DEAP material accurately. Finally, analyses based on the energy conversion demonstrate the abilities of DEAP material as wave energy converter.

The Measurement of the Fatigue Crack-Tip Displacement and Strain Fields under High Frequency Resonant Loading Applying DIC Method

In order to measure the displacement and strain field in the fatigue crack tip area of CT specimens under high frequency resonant loading condition in the fatigue crack propagation test, a method based on the digital image correlation (DIC) and digital high-speed photography technology are proposed in this paper. First, a series of digital speckle images of CT specimen under sinusoidal alternating load were collected by digital high-speed photography equipment, the displacement and strain fields within the region of crack tip in each image were calculated by DIC. The sinusoidal changing strain curve has been obtained by the least square sine wave fitting method, and the characteristic parameters of sinusoidal strain are calculated, such as the amplitude, frequency, phase, mean load . The images of characteristic position in one stress cycle were obtained by comparing the fitted sine curve of strain with the corresponding speckle images. Finally, the dynamic strain gauge was used to measure the strain at crack tip point during one stress cycle, and the accuracy and feasibility of DIC method were verified by the experimental results. The study result presented in this paper will supply a foundation for exploring the crack propagation law and measuring the fatigue crack growth parameters under high frequency resonant loading condition further.

Chronic passive venous congestion drives hepatic fibrogenesis via sinusoidal thrombosis and mechanical forces.

Chronic passive hepatic congestion (congestive hepatopathy) leads to hepatic fibrosis; however, the mechanisms involved in this process are not well understood. We developed a murine experimental model of congestive hepatopathy through partial ligation of the inferior vena cava (pIVCL). C57BL/6 and transgenic mice overexpressing tissue factor pathway inhibitor (SM22α-TFPI) were subjected to pIVCL or sham. Liver and blood samples were collected and analyzed in immunohistochemical, morphometric, real-time polymerase chain reaction, and western blot assays. Hepatic fibrosis and portal pressure were significantly increased after pIVCL concurrent with hepatic stellate cell (HSC) activation. Liver stiffness, as assessed by magnetic resonance elastography, correlated with portal pressure and preceded fibrosis in our model. Hepatic sinusoidal thrombosis as evidenced by fibrin deposition was demonstrated both in mice after pIVCL as well as in humans with congestive hepatopathy. Warfarin treatment and TFPI overexpression both had a protective effect on fibrosis development and HSC activation after pIVCL. In vitro studies show that congestion stimulates HSC fibronectin (FN) fibril assembly through direct effects of thrombi as well as by virtue of mechanical strain. Pretreatment with either Mab13 or Cytochalasin-D, to inhibit β-integrin or actin polymerization, respectively, significantly reduced fibrin and stretch-induced FN fibril assembly. Chronic hepatic congestion leads to sinusoidal thrombosis and strain, which in turn promote hepatic fibrosis. These studies mechanistically link congestive hepatopathy to hepatic fibrosis.

S0520202 大振幅せん断振動におけるひも状ミセル水溶液のシアバンド形成過程

The formation process of Shear-bands in a wormlike micellar solution of cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal) in the large amplitude oscillatory shear (LAOS) is examined experimentally. A transient response of shear stress after applying a large amplitude sinusoidal strain is measured by rheometer with concentric cylinder. In order to observe the spatial distribution of the optical anisotropy in the flow field, a new visualization technique recently developed by the authors, which can evaluate distribution of both the birefringence and the orientation angle from a photograph taken by the crossed-Nicols method, was applied. The highly-birefringent layer was formed near the moving wall when the strain exceeds 2.3 in the LAOS flow. In the oscillation with the higher strain, the shear-bands are formed but the bands disappeared at when the strain turns to zero. Therefore, the formation and dissipation of the shear-bands are repeated in each cycle of the LAOS flow.

Pulsating fluid induced dynamic instability of visco-double-walled carbon nano-tubes based on sinusoidal strain gradient theory using DQM and Bolotin method

This research deals with the dynamic instability analysis of double-walled carbon nanotubes (DWCNTs) conveying pulsating fluid under 2D magnetic fields based on the sinusoidal shear deformation beam theory (SSDBT). In order to present a realistic model, the material properties of DWCNTs are assumed viscoelastic using Kelvin–Voigt model. Considering the strain gradient theory for small scale effects, a new formulation of the SSDBT is developed through the Gurtin–Murdoch elasticity theory in which the effects of surface stress are incorporated. The surrounding elastic medium is described by a visco-Pasternak foundation model, which accounts for normal, transverse shear and damping loads. The van der Waals interactions between the adjacent walls of the nanotubes are taken into account. The size dependent motion equations and corresponding boundary conditions are derived based on the Hamilton’s principle. The differential quadrature method in conjunction with Bolotin method is applied for obtaining the dynamic instability region. The detailed parametric study is conducted, focusing on the combined effects of the nonlocal parameter, magnetic field, visco-Pasternak foundation, Knudsen number, surface stress and fluid velocity on the dynamic instability of DWCNTs. The results depict that the surface stress effects on the dynamic instability of visco-DWCNTs are very significant. Numerical results of the present study are compared with available exact solutions in the literature. The results presented in this paper would be helpful in design and manufacturing of nano/micro mechanical systems in advanced biomechanics applications with magnetic field as a parametric controller.

Modelling advanced composite plates resting on elastic foundation by using a quasi-3D hybrid type HSDT

This paper presents a free vibration analysis of functionally graded plates (FGPs) resting on elastic foundation by using a generalized quasi-3D hybrid type higher-order shear deformation theory (HSDT). The significant feature of this formulation is that it deals with only 5 unknowns as the first order shear deformation theory (FSDT), instead of 6 as in for example the well-known trigonometric plate theory (TPT). The displacement field is modeled combining hyperbolic and sinusoidal shear strain shape functions in which the stretching effect is included. The elastic foundation follows the Pasternak (two-parameter) mathematical model. The governing equations are obtained through the Hamilton’s principle. These equations are then solved via Navier-type, closed form solutions. The fundamental frequencies are found by solving the eigenvalue problem. The accuracy of the current solutions can be visualized by comparing it with the 3D and other closed form solutions available in the literature.

Does cardiac resynchronization therapy benefit patients with right bundle branch block: cardiac resynchronization therapy has a role in patients with right bundle branch block.

Does cardiac resynchronization therapy benefit patients with right bundle branch block: cardiac resynchronization therapy has a role in patients with right bundle branch block.