Strain In Layers Research Articles

Flexural strengthening of RC beams using PGFRP bars embedded in strain-hardening cementitious composites (SHCC)

The application of the near surface mounted (NSM) fiber reinforced polymer (FRP) as an additional reinforcement at tension side of flexural members is efficient to upgrade the flexural strength. However, this technique must be applied to concrete beams having hard concrete cover to avoid premature failure induced by concrete cover deterioration. The current research aims to improve and evaluate the flexural behavior of reinforced concrete (RC) beams strengthened with embedded prestressed glass fiber reinforced polymer (PGFRP) bars, based on replacement of weak concrete cover with a layer of strain hardening cementitious composites (SHCC). For this investigation, one reference beam (without strengthening) and nine flexural strengthened beams were tested under a four-point bending scheme. All beams had the same reinforcement and geometry, 150 mm width, 300 mm total depth, a total length of 3000 mm and the effective span was 2700 mm. The test parameters were: (1) the strengthening technique (conventional NSM-PGFRP bars, NSM-PGFRP bars covered with external SHCC layer and PGFRP bars embedded in SHCC replaced cover), (2) the prestressing levels in the GFRP bars (0, 10 % and 20 % of the ultimate bar strength) and (3) the thickness of the SHCC layer (30, 40 and 50 mm). Compared to the conventional NSM strengthened beams, the conjunction of SHCC with PGFRP bars not only prevented the spalling of the concrete cover but also increased the load carrying capacity up to 26.5 % and the ductility up to 16 %. A model for the prediction of flexural capacity of the strengthened beams having SHCC replaced cover was conducted, the predicted ultimate loads have a good consistency with the test results.

Influence of Biaxial Strain and Interfacial Layer Growth on Ferroelectric Wake-Up and Phase Transition Fields in ZrO2.

Investigations on fluorite-structured ferroelectric HfO2/ZrO2 thin films are aiming to achieve high-performance films required for memory and computing technologies. These films exhibit excellent scalability and compatibility with the complementary metal-oxide semiconductor process used by semiconductor foundries, but stabilizing ferroelectric properties with a low operation voltage in the as-fabricated state of these films is a critical component for technology advancement. After removing the influence of interfacial layers, a linear correlation is observed between the biaxial strain and the electric field for transforming the nonferroelectric tetragonal to the ferroelectric orthorhombic phase in ZrO2 thin films. This observation is supported by applying the principle of energy conservation in combination with ab initio and molecular dynamics simulations. According to the simulations, a rarely reported Pnm21 orthorhombic phase may be stabilized by tuning biaxial strain in the ZrO2 films. This study demonstrates the significant influence of interfacial layers and biaxial strain on the phase transition fields and shows how strain engineering can be used to improve ferroelectric wake-up in ZrO2.

Ultra-sensitive flexible resistive sensor based on modified PEDOT: PSS inspired by earthworm

Flexible resistive sensors currently face challenges such as low sensitivity and poor stability. In this work, inspired by the skin structure of earthworm, a double strain layer with annular cracks aiming to achieve precise construction of conductive pathways in strain materials is proposed. This design strategy enhances the sensitivity, detection range, stability, and consistency of flexible resistive sensor. The sensing materials utilized primarily consist of mechanically and electrically modified PEDOT:PSS. The sensor showcases high sensitivity (with a gauge factor up to 1973.83), a wide detection range (0 ∼ 10 %), rapid response time (60–70 ms), and exceptional repeatability (1000 cycles). The sensor is integrated into finger clips for measurement of pulse wave. By analyzing features extracted from pulse wave, neural networks are employed for the prediction of encompassing coronary heart disease (CHD), atrial septal defect (ASD), atrial fibrillation (AF) and blood pressure levels. The classification accuracy of CHD, ASD and AF surpasses 96 %. The average prediction errors for systolic blood pressure, diastolic blood pressure and mean arterial pressure are found to be −0.3455, −0.2025 and −0.0319, respectively, meeting the standards set by the Association for the Advancement of Medical Instrumentation and the British Hypertension Society Class A criteria.

Evaluation of Designer Chicken Eggs Enriched with Vitamin D3 and Zinc

Designer poultry eggs can be produced in various ways. In the present study chicken eggs were enriched with vitamin D3 and zinc by UVB (Ultra Violet Blue) light exposure (3 h/day) and dietary zinc supplementation (75 mg/kg) respectively. The study was conducted in thirty-two crossbred (White Leghorn N strain and Desi) layer birds. The trial was commenced from 29 weeks of age and conducted for 12 weeks. The current research work pointed out the enriching influence of UVB radiation and dietary zinc supplementation on concentration of vitamin D3 and zinc in eggs. Vitamin D3 and zinc concentrations in egg and serum were significantly higher (p<0.01) compared to the control group. UVB exposure and zinc supplementation also had a significant (p<0.01) impact on serum calcium and phosphorus levels. However, Liver enzyme activities of birds were not influenced either by UVB light exposure or by zinc supplementation. The dietary supplementation of hens with zinc is an effective approach to supply consumers with foods from animal sources that are enriched with zinc. Current findings showed that feeding of zinc supplemented diet to chickens offered a promising alternative to fortify egg with zinc. Furthermore, UVB light exposure would be a better choice for enhancing vitamin D3 content of eggs and to produce designer eggs enriched with vitamin D3. It increased the serum vitamin D3 level which was indicative of its transport from skin to ovaries after synthesis. The use of UVB exposure and zinc supplementation as an easy, cheap and safe procedure for producing dual enriched designer eggs with vitamin D3 and zinc is recommended as this would offer additional health benefits to consumers.

High-temperature and continuous wave-operation of all-MOCVD grown InAs/GaAs quantum dot laser diodes with highly strained layer and low temperature p-AlGaAs cladding layer

InAs/GaAs quantum dot laser diodes (QDLDs) on a GaAs substrate grown by utilizing all-metalorganic chemical vapor deposition (MOCVD) technology with a p-AlGaAs cladding layer are systematically investigated to produce 75 °C continuous-wave (CW) operation for the first time. First, the InAs quantum dots (QDs) in a dot-in-a-well (DWELL) structure formed by engineering the strained bottom InGaAs layer are successfully grown without detectable clusters, making it possible to increase the number of DWELL stacks effectively. To avoid degradation of the DWELL active layer during the high-temperature growth of the upper p-AlGaAs cladding layer, a detailed analysis of the p-AlGaAs cladding layer grown at low temperature is then carried out. The results of electron-channeling contrast imaging reveal that dislocations in the p-cladding layer are generated due to the accumulative strain of the DWELL and low-temperature growth. The fabricated InAs/GaAs QDLDs show good electrical and optical characteristics with O-band emission wavelength without high-reflection coating, indicating that the suggested growth technologies and the fabricated devices are promising options for future Si-photonic light source components.

A comprehensive study on production performance in COBB 430 Y strain of broiler and BV 300 strain layer reared in intensive poultry farm of IVSAH, SOA

A comprehensive study on production performance in COBB 430 Y strain of broiler and BV 300 strain layer reared in intensive poultry farm of IVSAH, SOA

Strain modulation effect of superlattice interlayer on InGaN/GaN multiple quantum well

The strong piezoelectric field in InGaN/GaN heterostructure quantum wells severely reduces the light emission efficiency of multiple quantum well (MQW) structures. To address this issue, a strain modulation interlayer is commonly used to mitigate the piezoelectric polarization field and improve the luminescence performance of the devices. To investigate the influence and mechanism of strain modulation in the InGaN/GaN superlattice (SL), epitaxial wafers with an n-type InGaN/GaN SL interlayer sample, and their corresponding control samples are prepared. The measured temperature-dependent photoluminescence (PL) spectra of the epitaxial wafers, show that the introduction of an SL interlayer leads to a shorter-wavelength emission and enhancement of internal quantum efficiency. As the temperature increases, a blue shift of the PL peak is observed. However, for the sample with an SL interlayer, the blue shift of the PL peak with temperature increasing is relatively small. Electroluminescence (EL) experiments indicate that the introduction of an SL interlayer significantly increases the integrated intensity of the EL peak and reduces its full width at half maximum. These phenomena collectively indicate that the incorporation of a superlattice interlayer can partly suppress the quantum-confined Stark effect (QCSE) that affects the light emission efficiency. Theoretical calculations show that the introduction of a superlattice strain layer before growing an active multiple quantum well can weaken the polarization-induced built-in electric field in the active quantum well, reduce the tilt of the energy band in the multiple quantum well active region, increase the overlap of electron and hole wave functions, enhance the emission probability, shorten the radiative recombination lifetime, and promote competition between radiative recombination and non-radiative recombination, thereby achieving higher recombination efficiency and improving light emission intensity. This study provides experimental and theoretical evidence that the strain modulation SL interlayer can effectively improve the device performance and offer guidance for optimizing the structural design of devices.

Spin filtering in Dresselhaus spin-orbit-coupled, layered-semiconductor microstructure

Based on Dresselhaus spin-orbit-coupling effect in a layered semiconductor microstructure, an electron-spin filter is proposed. It is found that an obvious spin polarization effect appears and is related to electron energy and in-plane wave vector. It is also found that both magnitude and sign of spin polarization can be controlled by strain engineering or layer's thickness. This layered-semiconductor microstructure can act as a tunable spin filter.

Structural properties of graded In x GaAs metamorphic buffer layers for quantum dots emitting in the telecom bands

In recent years, there has been a significant increase in interest in tuning the emission wavelength of InAs quantum dots (QDs) to wavelengths compatible with the already existing silica fiber networks. In this work, we develop and explore compositionally graded In x GaAs metamorphic buffer layers (MBLs), with lattice constant carefully tailored to tune the emission wavelengths of InAs QDs towards the telecom O-band. The designed heterostructure is grown by molecular beam epitaxy (MBE), where a single layer of InAs QDs is grown on top of the MBL and is capped with a layer having a fixed indium (In) content. We investigate the structural properties of the grown MBLs by reciprocal space mapping, as well as transmission electron microscopy, and verify the dependence of the absorption edge of the MBL on the In-content by photothermal deflection spectroscopy measurements. This allows us to identify a growth temperature range for which the MBLs achieve a near-equilibrium strain relaxation for In-content up to ∼30. Furthermore, we explore the emission wavelength tunability of QDs grown on top of a residual strained layer with a low density of dislocations. Specifically, we demonstrate a characteristic red-shift of the QD photoluminescence towards the telecom O-band (1300 nm) at low temperature. This study provides insights into the relaxation profiles and dislocation propagation in compositionally graded MBLs grown via MBE thus paving the way for realizing MBE-grown heterostructures containing InAs QDs for advanced nanophotonic devices emitting in the telecom bands.

Fretting Damage Evolution of Copper-Magnesium Alloy in Mixed Fretting Regime

The fretting damage evolution of copper-magnesium alloy in the mixed fretting regime was studied. Based on the characteristics of F t-D-N curves and the morphologies of wear scars, the fretting running condition of the alloy was divided into a partial slip regime (PSR), mixed fretting regime (MFR), and gross slip regime (GSR). Fretting in the MFR not only leads to strong adhesive wear but also promotes the initiation and propagation of fatigue cracks, resulting in serious fatigue wear. The damage evolution of the alloy in the MFR includes four stages, namely, the initial shear deformation stage, adhesion and crack initiation stage, crack growth and fatigue wear stage, and final fatigue damage accumulation stage. The propagation and connection between the fatigue cracks at the stick–slip boundary and the microcracks in the subsurface plastic strain layer are the main reasons for the serious fatigue wear in the MFR.

Strain-Balanced Organic Semiconductor Film for Improving the Stability of Organic Field-Effect Transistors.

Strain-induced aggregate state instability in organic semiconductor (OSC) films is a critical and bottleneck issue in the practicalization process of organic field-effect transistors (OFETs), but this issue lacks deep insight and effective solutions for a long time. Herein, we developed a novel and general strain balance strategy for stabilizing the aggregate state of OSC films and enhancing the robustness of OFETs. The charge transport zone in OSC films located at the OSC/dielectric interface always suffers from the intrinsic tensile strain induced by substrates and tends to dewet. By introducing a compressive strain layer, the tensile strain can be well balanced and OSC films attain a highly stable aggregate state. Consequently, the OFETs based on strain-balanced OSC heterojunction films exhibit excellent operational and storage stability. This work provides an effective and general strategy to stabilize OSC films and gives guidance in constructing highly stable organic heterojunction devices.

Effects of shear deformation and rotary inertia on elastically constrained beam resting on pasternak foundation

This study investigates the free vibrations of elastically constrained shear and Rayleigh beams placed on the Pasternak foundation. Of particular interest, it is aimed to analyze the influence of shear strain, rotational inertia, elastic stiffness, and shear layer on the natural frequencies and eigenmodes of beam vibrations. For this purpose, the eigenfrequencies and eigenmodes are determined using analytical and numerical techniques. A finite element scheme is developed employing quadratic and cubic polynomials for slope and transverse displacement, respectively. The efficiency and accuracy of the finite element method are illustrated by comparing it with the analytical results for generalized and special cases. The underlying model analysis justifies that the natural frequencies of the beam vibration depend only on the geometry of the Rayleigh beam, while these frequencies depend on the physical and geometric properties of the shear beam. However, the natural frequencies of the Euler-Bernoulli depend solely on the geometric conditions of the beam.

Effect of Surface Strain to Hydroxide Layer Formation on High-Pressure Die Casting Magnesium Alloy

Magnesium hydroxide layer improve corrosion resistance of magnesium alloys. Nonuniform strain on magnesium alloys surface was reported that affected to layer formation and corrosion resistance properties. Hydroxide layer formed to high pressure die cast ASTM AZ91D magnesium alloy, then investigated to correlation between hydroxide layer formation and residual stress and strain distribution on alloy surface which were measured by X-ray. Strain distribution was evaluated by full width half maximum (FWHM) value. Formed hydroxide layer was well compatible with FWHM distribution in as cast specimen. Heat treated for homogenization was carried out to inspection for correlation FWHM. FWHM was significantly lowering by heat treatment. Hydroxide layer tends to thin where FWHM value was low, therefore correlation between nonuniform strain and hydroxide layer formation was found out.

An Ultra‐Sensitive Flexible Resistive Sensor with Double Strain Layer and Crack Inspired by the Physical Structure of Human Epidermis: Design, Fabrication, and Cuffless Blood Pressure Monitoring Application

AbstractThe cuffless blood pressure (BP) monitoring device has attracted much attention because of its comfortable and real‐time monitoring. Inspired by the physical structure of the human epidermis, an ultra‐sensitive flexible resistive sensor with a double strain layer and crack structure is prepared by screen printing in this study. The strain material of the sensor is mainly prepared by blending Poly(3,4‐ethylenedioxythiophene) :poly(styrenesulfonate) (PEDOT:PSS) with waterborne polyurethane and reduced graphene oxide. The sensor exhibits a high gauge factor (GF, ≈1682), fast response (≈48 ms), and long‐term stability (> 2000 cycles) at low strain (≈0–5%). The sensor is placed on the human radial artery and can accurately measure the pulse wave. The features of the pulse wave are automatically extracted using a convolutional neural network. Then the features are corrected using a long short‐term memory neural network, and the current BP value is predicted using a fully connected network layer. The BP result meets the A‐level standards of the Association for the Advancement of Medical Instrumentation and the British Hypertension Society. This study provides an efficient device and method for continuous and non‐invasive BP monitoring.

Strain Engineering in Si Split-Gate Trench Power MOSFETs by Partial Oxidation of Polysilicon Electrodes

Performance improvement of Si split-gate trench power MOSFETs due to conventional scaling is approaching a physical and economical limit. Strain engineering, however, enables enhanced device characteristics without the need for further shrinkage as a result of an increased charge carrier mobility in monocrystalline Si. In this work, thermally grown SiO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathbf {2}}$ </tex-math></inline-formula> functional strain layers are introduced into a state-of-the-art Si trench power MOSFET by partial oxidation of the source and gate electrode. The influence of the additional SiO2 layers on the strain distribution in monocrystalline Si is described by the thermomechanical (TM) strain simulation and the resulting device properties are assessed by means of detailed electrical analysis. For the strain-modified devices, the simulation shows higher longitudinal tensile strains in the direction of current flow and stronger out-of-plane compressive strains perpendicular to it, which have a beneficial effect on the electron mobility. The electrical characterization revealed improved ON-state resistances at gate voltages of 4.5 V ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{ON}4.5$ </tex-math></inline-formula> ) and 10 V ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{ON}10$ </tex-math></inline-formula> ) of up to 16.8% and 13.8%, respectively, while the breakdown voltage did not change. In the presence of the SiO2 layer in the gate electrode, the threshold voltage was reduced, which also contributed to the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{ON}$ </tex-math></inline-formula> improvement. The functional strain layer in the gate electrode mainly influences the mobility in the channel, while it primarily alters the mobility in the drift region when introduced into the source electrode. However, the modification of mechanical strain in the channel area shows less impact on the overall device performance compared to the drift region.

Characterization of hyperelastic materials for manufacturing soft bending actuators

Unlike rigid link robots, the geometry and material properties of soft-bending actuators play an important role in preprogramming their bending behavior. The material properties of low-shore hardness silicones can be approximated through mathematical models of hyperelastic materials and can be determined experimentally using uniaxial and planer biaxial testings. This article investigates the bending behavior of soft actuators of similar geometry made of Elastosil M4601 and Smoothsil 950. Yeoh and NeoHookean mathematical models were selected to investigate the designed actuators in Abaqus simulation software. The effect of change in internal pneumatic pressures on the bending angles of actuators is investigated through simulations. Further, the bending behavior has also been investigated to verify the impact of strain-limiting layers. The results indicate that Elastosil M4601 is more sensitive to internal pressure and is suitable for low-pressure applications compared to Smoothsil 950. Comparisons between pneunets with and without strain layers indicate that there is a minimum or no effect of strain layer on the bending performance of the actuator with open wall configuration.

A Novel Carbide-Free Bainitic Heavy-Haul Wheel Steel with an Excellent Wear-Resistance under Rolling-Sliding Condition

With the rapid development of railways towards high speed and larger carrying capacity, the problem of wear and fatigue damage between wheel/rail is gradually becoming serious. However, traditional pearlite wheel/rail has reached the limit, which leads to more attention to developing a novel wheel/rail material. This study aims to report a novel carbide-free bainite wheel steel. The wear-resistance of novel steel was tested by a rolling-sliding wear experiment under heavy-haul condition and investigated the impacts of the running speeds on the damage mechanism of wear and fatigue. The results show that the yield strength of the bainite wheel was as high as 950 MPa and the hardness was 415 HV, which was superior to most of the reported typical wheel steel. During the process of wear, the surface damage of the wheel was mainly adhesive wear and fatigue damage, and the gradient strain layer (GS layer) was formed on the wheel surface. As the running speed increased, fatigue damage gradually became more serious than adhesive wear, and the shear stress and strain of the GS layer were enhanced. The higher thickness and hardening were produced on the GS layer, which is the main reason for the higher wear-resistance of the bainitic wheel under higher running speeds. In addition, the wear-resistance of the novel wheel steel was better than that of the reported wheel steel. This novel bainitic wheel is a promising wheel for heavy-haul condition applications, which could provide a guide in choosing bainitic wheel steel for the railway.

Structural performance of reinforced concrete beams with self-healing cover zone

In the current study, experiments were carried out to investigate the structural performance of reinforced concrete (RC) beams with a self-healing cover zone. The cover zone consists of a 1.5-cm-thick layer of bacteria-embedded strain hardening cementitious composite (SHCC) for a combination of crack width control and crack healing. The aim is to bring together two emerging technologies (i.e., self-healing and strain-hardening) that show great potential for realizing highly efficient concrete structures. RC beam without the self-healing cover was also prepared as the control specimen for comparison purposes. The experimental program includes loading the beams to failure in four-point bending configuration and sawing the beams to segments for crack pattern analysis and crack healing. Results show that the beams with selfhealing cover exhibited a 45-60% improvement in structural capacity. The crack patterns of the hybrid beams were also largely modified. While the reference beam formed only a few major cracks, the hybrid beams formed around 40 fine cracks in the constant bending moment region with an average crack width smaller than 0.2 mm even at maximum load. By having an improved cracking behavior and an enhanced self-healing capacity, it is expected that the beams with a self-healing cover will possess an extended service life at the expense of minimal additional cost.

Surface Microstructure Refinement and Mechanical Properties of GCr15 Steels Improved During Ultrasonic Surface Rolling Processing

In this paper, ultrasonic surface rolling processing (USRP) was used to strengthen GCr15-bearing steel. A finite element three-dimensional model of USRP was established to analyze the residual compressive stress and equivalent plastic strain distribution on the bearing steel surface. The microstructure, hardness, surface roughness, and corrosion resistance before and after USRP treatment were characterized by SEM, EBSD, X-ray diffraction (XRD), and electrochemical techniques. Results indicated that USRP treatment can significantly improve the material's surface microstructure and residual compressive stress distribution and obtain a plastic strain layer of about 60μm. After USRP treatment, the Kernel Average Misorientation (KAM) increased, and the dislocation activity was more intensive, resulting in aggregation near grain boundaries, and the percentage of LAGBs increased to 38.8%. Under the combined effect of surface grain refinement, residual compressive stress, and high glossy surface, the self-corrosion current density is reduced by two orders of magnitude, and the corrosion resistance is significantly improved. This investigation suggests a solution to the bearing failure problem and has implications for understanding the deformation mechanism of ultrasonic surface rolling processing.

Band Alignment in Black Phosphorus/Transition Metal Dichalcogenide Heterolayers: Impact of Charge Redistribution, Electric Field, Strain, and Layer Engineering

The objective of this work is to study the effects of charge redistribution, applied layer-normal electric fields, applied strain, and layer engineering on the band alignment of Black Phosphorus (BP)/Molybdenum disulphide (MoS2) heterostructure through Density Functional Theory (DFT) simulations. Black phosphorus works as a p-type material with high mobility, mechanical flexibility, and sensitivity to number of layers. Combining it with the more electronegative material, MoS2 results in strong carrier confinement and a Type II heterostructure. Charge redistribution among the layers shifts the band alignment expected from the Electron Affinity Rule. Applied external fields, strain and multiple BP layers provide band-alignment tunability within the Type II range and/or, transition to Type I and Type III heterostructures. The tunability in BP/MoS2 heterostructure may be useful as tunnel field effect transistors, rectifier diodes with tunable barrier height, reconfigurable FETs, and electro-optical modulators. Furthermore, considering heterostructures of monolayer BP with other monolayer Transitional Metal Dichalcogenides (TMD) suggests the ability to achieve different band alignment types. In our simulations, a Type I alignment is found with Tungsten diselenide (WSe2), Molybdenum diselenide (MoSe2), and Tungsten disulphide (WS2), and a Type III for Hafnium disulphide (HfS2) and Hafnium diselenide (HfSe2).