Effect Of Thickness Research Articles

Effects of specimen thickness and fiber length on tensile and cracking behavior of UHPFRC: Uniaxial tensile test and micromechanical modeling

This study aims to investigate the effects of specimen thickness and fiber length on the tensile and cracking behaviors of ultra-high-performance fiber-reinforced concrete (UHPFRC). To this end, a uniaxial tensile test was conducted with three specimen thicknesses (30, 50, and 100 mm) and two fiber lengths (13 and 20 mm), and the fiber orientation, dispersion and specimen void were quantitatively evaluated based on image recognition. The test results indicated that fiber orientation was improved with the decreased specimen thickness and increased fiber length. Meanwhile, the initial cracking and peak stress, capacity to limit cracking were enhanced with the decreased specimen thickness. A modified prediction model considering the wall effect, flattening and squeezing effect was developed to predict the probability density function p(θ) of fiber orientation angle. Additionally, the uniformity factor μ2 was introduced to predict crack number, and the relationship between the μ2 and parameter ψ = (Vf × lf/df)/t was determined. Furthermore, a model was developed to convert the main crack width into uniaxial tensile strain. All models and relationships were validated using test data. A micromechanical model that considered the predicted p(θ) and conversion model was established to predict the uniaxial tensile response of UHPFRC, which was also successfully validated using test data.

Acoustic Waves Coupling with Polydimethylsiloxane in Reconfigurable Acoustofluidic Platform.

Acoustofluidics is a promising technology that leverages acoustic waves for precise manipulation of micro/nano-scale flows and suspended objects within microchannels. Despite many advantages, the practical applicability of conventional acoustofluidic platforms is limited by irreversible bonding between the piezoelectric actuator and the microfluidic chip. Recently, reconfigurable acoustofluidic platforms are enabled by reversible bonding between the reusable actuator and the replaceable polydimethylsiloxane (PDMS) microfluidic chip by incorporating a PDMS membrane for sealing the microchannel and coupling the acoustic waves with the fluid inside. However, a quantitative guideline for selecting a suitable PDMS membrane for various acoustofluidic applications is still missing. Here, a design rule for reconfigurable acoustofluidic platforms is explored based on a thorough investigation of the PDMS thickness effect on acoustofluidic phenomena: acousto-thermal heating (ATH), acoustic radiation force (ARF), and acoustic streaming flow (ASF). These findings suggest that the relative thickness of the PDMS membrane (t) for acoustic wavelength (λPDMS) determines the wave attenuation in the PDMS and the acoustofluidic phenomena. For t/λPDMS≈O(1), the transmission of acoustic waves through the membrane leads to the ARF and ASF phenomena, whereas, for t/λPDMS≈O(10), the acoustic waves are entirely absorbed within the membrane, resulting in the ATH phenomenon.

Investigation of a Hydrophobic Sputtered Cu Electrode to Electrocatalyze CO2 Towards a C2+ Product: The Effect of Substrate and Catalyst Thickness

The overuse of fossil fuels has resulted in massive CO2 emissions, causing global environmental problems. Renewable energy-driven electrocatalysis, which can convert CO2 into fuels and chemicals, is considered an emerging technology for carbon resource recycling. Cu-based catalysts sputtered on hydrophobic carbon paper and a polytetrafluoroethylene (PTFE) membrane were comparatively investigated, while the effect of the thickness of the Cu sputtering layer on the electrocatalytic CO2 reduction performance was investigated. Additionally, the effect of substrate properties on the distribution and morphology of sputtered Cu metal was investigated by SEM and XRD. With carbon paper as the substrate, the highest FEC2+ achieved was 70% at 200 mA/cm2, while the maximum value of FEC2+ on the Cu/PTFE electrode was realized with a Cu thickness of 400 nm (72%). Additionally, the PTFE substrate demonstrated a better inhibiting effect on HER, with a lower FEH2 and high FEC2+ over different applied current densities.

Effect of Blade Thickness on Hemodynamics and Hemolysis: A Case Study of Pediatric Centrifugal Blood Pumps.

Blood pumps have become popular whether for use as an implantable ventricular assist device or as extracorporeal membrane oxygenation. The quality of these pumps is assessed according to their ability to reduce the risk of blood damage thanks to an optimal choice of their geometric and operating properties. Lack of the research focused on the geometrical optimization of impellers has prompted this study. This study evaluated a computational and experimental analysis comparing the hemolytic performance of three centrifugal pumps. For this purpose, methods of Eulerian and Lagrangian are respectively used for hemodynamic and hemocompatibility investigations. Referring to the pediatric demands, these pumps function under clinically applicable pressure-flow conditions: 1 l/min of blood flow and a pressure differential of 60 mm Hg. These three pumps all use the same volute, but their impellers differ in terms of blade thickness. The objective is to examine how surface area affects the generation of hemolysis. In silico simulations were employed for both of the following tasks: first, identifying the distributions of velocities, pressures, and shear stresses; second, applying the Lagrangian approach to estimate the hemolysis index. Results showed the importance of the flow passage and the surface of the clearance on the hemocompatibility of the pumps. However, it was observed that there is not a linear effect of the blade thickness on the shear stress or index of hemolysis. Additionally, this work can provide information to develop an optimal design of a more hemocompatible blood pump.

Investigations on the influence of thickness and preform structure on the mechanical performance of novel textile composites with woven Kevlar® fabric reinforcement and poly methylmethacrylate (Elium®) matrix

Abstract Elium (novel methyl methacrylate (MMA)) resin is a liquid thermoplastic resin curable at room temperature and a possible replacement for epoxies. The main objective of this work is to evaluate the mechanical characteristics of novel Kevlar fabric reinforced Elium composites with different thicknesses. The plain-woven structure Kevlar/Elium laminates were manufactured with 1.5 mm and 2.5 mm thicknesses through vacuum-assisted resin infusion moulding, where 8 and 12 layers of woven fabrics were used, respectively. The effect of laminate thickness was measured in terms of mechanical (tensile, flexural, shear, and dynamic mechanical analysis (DMA)) and physical (density and fibre volume fraction (FVF)) characteristics. The density of the laminates was found in the range of 1.18–1.31 g cm−3. FVF was 50.69 and 52.27% for 1.5 and 2.5 mm thick laminates, respectively. The composite with 1.5 mm thickness exhibited the highest tensile strength (667.9 MPa) and flexural strength of 330.7 MPa. Conversely, the highest interlaminar shear strength measured for 2.5 mm thick laminate is 16.5 MPa. The DMA analysis recorded the highest storage and loss modulus for 2.5 mm thickness laminates. The fractography analysis confirmed the quantified experimental observation of excessive interface debonding and delamination. Elium composites may be suitable for high-end structural applications, including marine and aircraft structures.

Love-type wave characteristics in the heterogeneous hydrogel layer pasted over the functionally graded piezoelectric fiber-reinforced composites semi-infinite substrate

PurposeThis study aims to explore the characteristics of the Love wave propagation through a heterogeneous hydrogel layer bounded to a functionally graded PFRC substrate while determining the displacement and electric potential in a di-electrically faintly conducting, mechanically compliant interface.Design/methodology/approachIn order to calculate the value of response variables, the Wave mode method has been used. The governing modeled equations are non-homogeneous. The analytical solution has been obtained by deploying the boundary conditions.FindingsThe effect of thickness on the field variables for different values of variation parameter, mechanical constant of proportionality, electrical constant of proportionality and volume fraction of the PFRC substrate is examined for both, electrically open and short cases.Originality/valueTo the best of authors' knowledge, no attempt has been made to analyze the propagation characteristics of Love wave through the heterogeneous hydrogel Layer bedded over the functionally graded piezoelectric fiber-reinforced composites substrate.

High-Performance Organic Field-Effect Transistors and Inverters with Good Flexibility and Low Operating Voltage.

Organic field-effect transistors (OFETs) with good flexibility and low operating voltage, are of great meaning for the low power stretchable and wearable electronic devices. The operating voltage and flexibility are easily affected by the dielectric layers in the OFETs. Bilayer dielectrics comprising both high- and low-permittivity (k) insulating polymers, have been reported. The flexible bilayer dielectrics can combine the advantages of both insulating polymers, which are high charge carriers from low-k polymers and low operating voltage from high-k polymers. However, the effect of film thicknesses in the bilayer dielectrics on the OFET performance is seldom investigated. Here, bilayer dielectrics comprising high-k polyvinyl alcohol (PVA) and low-k polymethylmethacrylate (PMMA) were fabricated. And PVA/PMMA bilayers with three different PVA film thicknesses are carefully investigated. The 300 nm PVA/100 nm PMMA bilayer dielectric makes the pentacene OFETs show the highest hole mobility of 1.24 cm2V-1s-1 and the corresponding inverters give a high voltage gain of 40 and a noise margin of 2.3 V (77% of 1/2 VDD) at low operating voltage of 6 V. Both the pentacene transistors and the inverters still work properly under bending radium of 5.85 mm, proving the good prospects of the PVA/PMMA bilayer dielectric in practical applications.

Compressive behavior of manufactured sand recycled coarse aggregate concrete-filled steel tubular short columns

To study the mechanical properties of manufactured sand recycled aggregate concrete-filled steel tubular (RACFST) columns, a total of 81 square short RACFST column specimens with different types of manufactured sand and natural sand were created and subjected to axial compression tests. The variables included sand type, core concrete strength, slenderness ratio, and steel tube thickness. The failure mode, axial load-displacement curve, axial compressive capacity, and deformation capacity of the specimens were analyzed in detail. The results indicate that the failure mode of the specimen is generally waist drum-type failure and shear-type failure, and both of them are local buckling. The load-displacement curve of the manufactured sand specimen is similar to that of the natural sand specimen, but the steel tube of the manufactured sand specimen yields later than that of the natural sand specimen. Generally, the limestone manufactured sand specimen has the highest axial compressive capacity and the best ductility ratio, while the pebble manufactured sand specimen has an axial compressive capacity similar to the natural sand specimen but a lower ductility ratio. The effects of concrete compressive strength, slenderness ratio, and steel tube thickness on specimens with manufactured sand are similar to those with natural sand. Based on the results of this experimental study, a formula for calculating the axial compressive capacity of square RACFST columns is provided.

Effect of Occlusal and Axial Thickness on the Fracture Load of Implant-Supported Monolithic Zirconia Crowns.

To evaluate the fracture load of monolithic zirconia crowns with implant screw holes, focusing on variations in occlusal and axial thicknesses, and to assess the interaction between these variables. Six different prostheses were designed using CAD software, varying in occlusal thickness (0.5 mm, 1.0 mm) and axial thickness (0.4 mm, 0.8 mm, 1.2 mm) based on the height and thickness differences of the titanium implant abutment. Twelve specimens per design were created by milling zirconia blocks and titanium abutments. These specimens were cemented with resin and subjected to thermomechanical aging (50 N, 200,000 cycles, 5°C-55°C, 30 seconds dwell time) using a chewing simulator. Static loading was applied using a universal testing machine at a rate of 0.5 mm/min until fracture occurred, and the load value (N) at the moment of the initial fracture was recorded. Fracture pattern and surface analyses were performed. Statistical analyses included two-way analysis of variance, Tukey HSD test, multiple regression analysis, and Fisher's exact test. Both occlusal and axial thicknesses significantly influenced the fracture load (P < .05), with a significant interaction between them (P < .05). An occlusal thickness of 1.0 mm exhibited a significantly higher fracture load compared to 0.5 mm (P < .05). An axial thickness of 1.2 mm showed a significantly higher fracture load compared to 0.4 mm and 0.8 mm (P < .05). The difference in axial thickness between 0.8 mm and 1.2 mm had a more substantial impact on fracture load than the difference in occlusal thickness between 0.5 mm and 1.0 mm (P < .05). Fractographic analysis showed that the thin axial wall exhibited twist hackles without involvement of the crown margin, whereas the thick axial wall exhibited no hackles and a more catastrophic failure involving the crown margin. For monolithic zirconia crowns with implant screw holes, when sufficient occlusal thickness cannot be achieved, an axial thickness of at least 1.2 mm is recommended to ensure higher fracture resistance.

Optimization and performance assessment of Ag@SiO2 core–shell nanofluids for spectral splitting PV/T system: Theoretical and experiment analysis

Ag@SiO2 nanofluid is widely used in spectral splitting PV/T system. Its core–shell structure has great influence on the optical properties. In this work, we focus on the comprehensive analysis and structure optimization of Ag@SiO2 nanofluid to achieve its optimal spectral performance. DDA method is used to predict the optical properties of Ag@SiO2 nanofluid and an optimization model based on filter efficiency is proposed. The effect of the SiO2 shell thickness and Ag core mass concentration is analyzed. It indicates that the spectral performance of Ag@SiO2 nanofluid can be improved with SiO2 shell thickness of 15–40 nm and Ag core mass concentration of 81–135 mg/L. To achieve the same theoretical merit function of 1.46, the usage of Ag mass can be reduced by 25/33/44/62 % with SiO2 coating of 10/20/40/70 nm. The optimal structure to achieve the highest filter efficiency η of 37.8 % is with a shell thickness of 20 nm and a mass concentration of 113.9 mg/L. An indoor PV/T operation testing is conducted to verify the optimization results. The merit function of Ag-based nanofluids increases from 1.58 to 1.598 and a reduction in Ag usage of 17 % is achieved with a SiO2 coating shell of 17.8 nm. Operation stability is also enhanced with no aggregation observed during the working cycle and 7-day static experiment.

Design and damping characterization of sandwich composite made of particle-filled hollow spheres and steel sheets

Sandwich composites made of particle-filled hollow sphere structures (PHSS) and steel sheets offer excellent lightweight and damping properties, ideal for high-speed machine tool components under dynamic loads. Previous research has focused on single particle-filled hollow sphere (PHS) and small PHSS, leaving a gap understanding of PHSS/steel sandwich composites. In this study a test rig was developed, and Design of Experiments and Response Surface Analysis were used to investigate the effects of sheet and core thickness (design parameters), filling ratio, and particle size (particle parameters) on the damping performance of PHSS/steel sandwiches. The results indicate that the design parameters have a significant influence on damping performance. The interaction between design and particle parameters also substantially affects damping. Minimizing particle size, increasing filling ratio, thinning the face layer, and thickening the core layer significantly improve structural damping. To address manufacturing tolerances, a finite element (FE) model-based optimization was developed to accurately determine PHSS material parameters. These parameters were used in an FE model of the PHSS-steel composite, with identified contact parameters minimizing measurement and simulation differences. The homogenized material model and the linear model using global damping parameters accurately reproduce the dynamic properties of the PHSS-steel sandwich composite in low vibration modes.

The Effect of the Wall Thickness of the Material Loaded Cavity On the RCS Reduction

In this paper, the effect of a parallel plate waveguide's wall thickness on radar cross-section reduction (RCS) is rigorously analyzed for H-polarization by using the Wiener-Hopf Technique, when the waveguide region is loaded with dielectric material and terminated with a perfect electric conductor (PEC) plate. Transfer matrices are incorporated into the analysis to account for the effect of different material layers through continuity relations. The Fourier transforms of the diffracted field and the boundary conditions yield a modified scalar Wiener-Hopf equation of the second kind (MWHE-2). The classical procedure to solve the MWHE-2 is applied and the approximate expression of the diffracted far field is obtained. Numerical results are given by comparing with the results available in the literature for the case of the wall thickness of the cavity not being considered.

Investigation of Low Velocity Impact Behavior of Aluminum Honeycomb Sandwich Structures with GFRP Face Sheets by Finite Element Method

The aim of this study is to examine the low velocity impact behavior of aluminum honeycomb sandwich structures with glass fiber reinforced plastic (GFRP) face sheets with the help of finite element method. In the study, low velocity impact tests were carried out in the LS DYNA finite element program to examine the effects of face sheets thickness, core number, wall thickness, impact location and impact velocity on maximum contact force, absorbed energy efficiency and damage mode. Progressive damage analysis based on the Hashin damage criterion and the combination of Cohesive Zone Model (CZM) and the bilinear traction-separation law was performed using the MAT-54 material model. At the end of the study, it was determined that the face sheets thickness in sandwich structures had a significant effect on the impact resistance up to a certain impact energy. It has been observed that as the impact velocity gradually increases, there is a decrease in the contact force after a certain threshold value. As the impactor velocity increases, the energy absorption efficiency also increases. It has been determined that the location of the impact is very effective on peak force and energy absorption efficiency. The effect of the number of core layers depends on the face sheets thickness. When the face sheets thickness was not damaged at first contact, the peak force value increased in parallel with the number of layers. It was determined that the dominant damage mode after impact was matrix damage. It has been observed that as the energy level of the impactor increases, damage also occurs on the back surfaces.

Directional enhancement of underwater impact and bubble loads in neighbor two-phase fluid domains charge

The loading characteristics of underwater explosions and the dynamic behavior of bubbles are directly related to the charge structure. This study proposes a unique charge structure in a gas–liquid two-phase fluid domain. Numerical methods are used to investigate the effects of fluid layer thickness and gas–liquid ratio on underwater explosion shock wave load, bubble dynamics, and bubble pulsation load. The results show that the two-phase fluid layer significantly enhances the directional release of shock wave energy and bubble pulsation load. During the shock wave phase, a lagging wave effect appears in the liquid layer direction, causing a secondary high-energy shock, significantly increasing the specific impulse. The gas layer direction may form a pressure relief channel effect, enhancing the shock wave peak pressure. For the bubble motion phase, differences in the physical properties of the fluid layer medium lead to irregular bubble boundary movements, promoting bubble tearing and rupture. The gaseous medium converts the accumulated shock wave energy into the internal energy of the bubble, increasing its volume potential. Although this characteristic reduces the pulsation frequency, it significantly increases the specific impulse. Altering the fluid layer medium can control explosion loads and bubble movement, offering new insights for ocean engineering applications.

Anomalous wavefront control of Lamb wave with metasurfaces via superposed prism resonance

As a special branch of metamaterials characterized by phase discontinuity, elastic metasurfaces have presented extraordinary capacity for elastic wave manipulation. This class of metamaterials has received extensive attention in recent years. In this paper, a subwavelength elastic metasurface with locally resonant prisms is employed to steer the propagation of the A0 Lamb wave. Based on the dispersion curve and transmission ratio, we establish that the resonant feature of prisms is influenced by the diagonal ratio of cross section. By gradually tuning the diagonal ratio of prism cross section, the pattern of resonance modes and the mechanism of resonance superposition are clarified. In this regard, two different resonant modes can be superimposed at a certain frequency. A complete 2 π phase shift that is crucial for redirecting wave propagation can therefore be realized. To have a broader working frequency range, the influence of prism height on the resonance superposed frequency and the effect of plate thickness on the incident flexural wave are explored. Based on the generalized Snell’s law, negative refraction is verified numerically through a metasurface assembled from unit cells with constant phase change. In addition, other wavefront modulations such as eccentric focusing, nonparaxial propagation are also demonstrated. This novel design introduces new degrees of freedom in many engineering applications such as seismic wave protection, structural health monitoring and energy harvesting.

Ni/n-Si Schottky junction: Self-biased infrared photodetection via hot carrier photoemission

Internal photoemission-based hot electron generation at metal-semiconductor junctions holds significant potential for silicon-based sub-bandgap NIR photodetectors. In this work, we designed a simple nickel-silicon Schottky junction using the pulsed laser deposition technique and performed both experimental and theoretical analyses. To reduce the complexity of fabrication and lower costs, we used a planar nickel thin film on top of n-type silicon. The thickness of the nickel thin film was optimized to improve absorption and hot electron generation near the Ni/Si interface. We measured and calculated reflectance using the transfer matrix approach to quantify the effect of thickness on EQE. We also calculated the thickness-dependent absorption profile to estimate hot electron production near the junction. The current-voltage characterization of Ni/n-Si Schottky photodetector was investigated under the dark conditions as well under 1200 nm and 1300 nm light illumination. Under self-bias conditions, a photodiode with a 12 nm Ni thickness exhibits responsivity of 0.124 mA/W and 0.069 mA/W under illumination from 1200 nm and 1300 nm LED light, respectively. Furthermore, we used a comprehensive theoretical model to quantify the planar Ni/Si hot carrier generation and emission efficiency. and experimentally validated the calculated EQEs with the fabricated device. We believe the proposed complementary metal-oxide-semiconductor-compatible and simply structured Ni/Si Schottky photodetector will have potential applications in the silicon-based optoelectronics market.

Crack Growth and Fatigue Strength of Deck‐Rib Welded Joints in Orthotropic Steel Decks Integrating Mean Stress Effect

ABSTRACTFatigue tests were conducted to investigate the effects of mean stress, stress range, and deck thickness on crack growth and fatigue failure of the deck‐rib welded joint. According to the experimental results, a fatigue failure criterion and a fatigue evaluation method for deck‐rib welded joints, which consider mean stress effect, was proposed. The results indicated that the stress range remains the dominating factor, but the influence of mean stress cannot be ignored. It was proposed that the crack length reaching approximately 150 mm and the depth reaching around 70% deck thickness can be taken as the fatigue failure criterion, while increase in mean stress would reduce the critical crack length but increase the critical crack depth. Besides, multiple cracks will weaken the fatigue strength. It is recommended to use Walker method and the FAT 71 curve with enhancement factor to evaluate the fatigue strength under symmetrical stress cycle.

Experimental and numerical investigation on composite beam–column joint connection behavior using different types of connection schemes

Abstract Over the past few decades, composite joints have been regarded as one of the most promising approaches. After reviewing the research articles dealing with composite beam-column joints, it can be withdrawn that few researchers studied and developed different types of composite beam-column joints. The objectives of this paper to study the effect and behavior of different connection types on the composite beam – column joint under repeated loading as well as to investigate new forms of slab connection with column flange in composite connection joints, aiming to enhance the behaviors of the joints and make the slab endure a part of the load in a more efficient way. Five specimens with various connection types were tested to failure; the composite model number two (CM2) was considered the control specimen. Regarding the ultimate moment, the result found that CM5 has moment 50.47% more than control specimen, the lowest rotation value was in CM5. The general behaviours of the FEM were in good accordance with the experiment results. According to the parametric a higher yield strength is more rigid stiffer, the effect of web thickness on the load is too small and increase in load resistance with an increase in beam flange thickness.

Time-resolved x-ray imaging of nanoscale spin-wave dynamics at multi-GHz frequencies using low-alpha synchrotron operation

Time-resolved x-ray microscopy is used in a low-alpha synchrotron operation mode to image spin dynamics at an unprecedented combination of temporal and spatial resolution. Thereby, nanoscale spin waves with wavelengths down to 70 nm and frequencies up to 30 GHz are directly observed in ferromagnetic thin film microelements with spin vortex ground states. In an antiparallel ferromagnetic bilayer system, we detect the propagation of both optic and acoustic modes, the latter exhibiting even a strong non-reciprocity. In single-layer systems, quasi-uniform spin waves are observed together with modes of higher order (up to the 4th order), bearing precessional nodes over the thickness of the film. Furthermore, the effects of magnetic material properties, film thickness, and magnetic fields on the spin-wave spectrum are determined experimentally. Our experimental results are consistent with numerical calculations from a micromagnetic theory even on these so-far unexplored time- and length scales.

Research on Air Cushion Flow Field and Bearing Characteristics of Single Row Hole Air Cushion Belt Conveyor

In order to obtain information regarding changes in the air cushion flow field and load-bearing characteristics of a single row hole air cushion belt conveyor, a structural model of the air cushion of the belt conveyor was established, with the single row hole air cushion belt conveyor as the research object. Firstly, according to the theory of fluid lubrication, a mathematical model of the air cushion was established. Then, the effects of air cushion thickness, pore velocity, and belt velocity on the pressure and bearing characteristics of the air cushion flow field were studied using FLUENT software. In addition, the equivalent stress, displacement, and pressure curves between the air cushion flow field and the conveyor belt and the material were analyzed using the two-way fluid–solid coupling method. Finally, the experimental platform of a single row hole air cushion belt conveyor was built, and the flow field and bearing characteristics of the belt were verified through experiments. The results show that reducing the thickness of the air cushion and increasing the pore flow rate can improve the pressure and bearing characteristics of the air cushion, while speed has little effect at lower belt speeds.