Magnitude Of Bending Research Articles

Bending classification from interference signals of a fiber optic sensor using shallow learning and convolutional neural networks

Bending monitoring is critical in engineering applications, as it helps determine any structural deformation caused by load action or fatigue effect. While strain gauges and accelerometers were previously used to measure bending magnitude, optical fiber sensors have emerged as a reliable alternative. In this work, a machine-learning-based model is proposed to analyze the interference signal of an interferometric fiber sensor system and characterize the bending magnitude and direction. In particular, shallow learning-based and convolutional neural network-based (CNN) models have been implemented to perform this task. Furthermore, given the repeatability of the interference signals, a synthetic dataset was created to train the models, whereas real interferometric signals were used to evaluate the models’ performance. Experiments were conducted on a flexible rod in fixed–free and fixed–fixed ends configurations for bending monitoring. Although both models achieved mean accuracies above 91%, only the CNN-based model reached a mean accuracy above 98%. This confirms that monitoring bending movements through interference signal analysis by means of a CNN-based model is a viable approach.

Directional bending sensor based on Mach-Zehnder interferometer formed by side-polished multimode fiber

This work proposes a fiber bending sensor based on the Mach-Zehnder interferometer (MZI) constructed using a side-polished multimode fiber (MMF) with bending direction recognition. The sensor is fabricated by directly fusing a section of side-polished MMF sandwiched between two no-core fibers (NCFs) to an input and output single-mode fibers (SMFs). As the applied curvature varies from 0 m−1 to 1.64 m−1, the transmission spectra of the sensor exhibit distinct and linear wavelength shift in opposite directions. The maximum sensitivity observed in 0° and 180° bending is 3.252 nm/m−1 and −1.146 nm/m−1, respectively. The maximum temperature sensitivity is 0.0621 nm/°C and this effect can be compensated by using the sensitivity matrix. The advantages of the proposed sensor include its ability to accurately quantify the direction and magnitude of bending, temperature crosstalk elimination, and cost-effectiveness. These features make the sensor highly desirable for a wide range of practical directional bending applications, such as medical wearable devices for human joint range of motion monitoring.

Ultrastretchable Segmented Sensors for Functional Human-Machine Interfaces.

The key feature that enables soft sensors to shorten the performance gap between robots and biological structures is their deformability, coupled with their capability to measure physical changes. Robots equipped with these sensors can interact safely and proprioceptively with their environments. This has sparked interest in developing novel sensors with high stretchability for application in human-robot interactions. This study presents a novel ultrasoft optoelectronic segmented sensor design capable of measuring strains exceeding 500%. The sensor features an ultrastretchable segment physically joined with an asymmetrically configured soft proprioceptive segment. This configuration enables it to measure high strain and to detect both the magnitude and direction of bending. Although the sensor cannot decouple these types of deformations, it can sense prescribed motions that combine stretching and bending. The proposed sensor was applied to a highly deformable scissor mechanism and a human-robot interface (HRI) device for a robotic arm, capable of quantifying parameters in complex interactions. The results from the experiments also demonstrate the potential of the proposed segmented sensor concept when used in tandem with machine learning, affording new dimensions of proprioception to robots during multilayered interactions with humans.

Impact of Bottom Electrode in HfO2-Based Rram Devices on Switching Characteristics

Resistive random-access memory (RRAM) devices with hydrogen plasma treated HfO2 have shown low power switching (1) and good conductance quantization with programing pulsed operation (2) that qualify them to be used for in-memory computing. Engineering the distribution of defects or oxygen vacancies near the top and bottom electrodes has a significant impact on reducing the switching power and improving the multi-level cell (MLC) characteristics of the device. A graded distribution with higher concentration of oxygen vacancies closer to the top electrode (TE) due to hydrogen plasma treatment and lower concentration near the bottom electrode (BE) reduces switching energy (power) (1). However, the impact of the bottom electrode is not well understood. In this work we investigated three RRAM stacks as shown in Figure 1 that have the same top electrode metal (50nm PVD TiN/5nm ALD TiN) and dielectric (HfO2 with hydrogen plasma treatment at the mid-point) but with different BE for each stack: TiN (device A (control)), TiN plus Mo with thermal anneal (device B), and TiN plus Mo with plasma nitridation (device C). Choosing a more inert metal as the BE provides a lower oxygen vacancy concentration at the interface between the BE and the dielectric (3) which in turn reduces the switching power as noted with device C (TiN plus Mo with plasma nitridation) which switches at a minimum compliance current (Icc) of 500pA. It is possible that the presence of nitrogen prevents the increase in oxygen vacancy concentration near the BE. On the other hand, a higher concentration of oxygen vacancies at the BE and the dielectric interface leads to a larger magnitude of band bending and increases the height of Schottky barrier. This possibly leads to an increase in the switching power in device A and device B as compared to device C (3-4). Note that device A (TiN) switched at Icc=30µA and device B (TiN plus Mo with thermal anneal) switched at Icc=8µA, which is superior compared to device A in switching power. This suggests that the alloy of TiN with Mo is reducing the oxygen vacancies near the BE. To study the MLC characteristics of the devices, we performed a train of 36 RESET pulses with fixed amplitude Vp= -1V and pulse width starting at 4µs and increasing by 20µs every 3 pulses, while we applied Vr=0.1V and tr=10µs after each pulse to measure the conductance. Figure 2 shows that device B (TiN plus Mo with thermal anneal) has good MLC with no overlap between the states while device A shows unstable MLC behavior due to time constant variation. Figure 3a shows the results of device C for the same RESET pulse train that was applied to devices A and B. Since device C switches at very low current and voltage, the conductance quantization was unstable after 15 pulses due to overstress of the conductive filament. Figure 3b shows the results after selecting the proper pulse set Vp= -0.5V and pulse width starting at tp=100ns and increasing by 100ns every 3 pulses, while we applied Vr=0.05V and tr=100ns after each pulse, resulting in a better conductance quantization compared to the previous setup. Appropriate engineering of the BE and managing of the oxygen vacancy distribution by hydrogen plasma treatment can significantly reduce the switching power.

Crystal structure of selenium-substituted acetylacetonates of boron difluoride

The molecular and crystal structure of boron difluoride acetylacetonates containing selenophenyl (1), diselenide (2) and selenocyanate groups (3) at the central carbon atom (γ) has been determined. As a result of comparing the structure of selenium- and sulfur-substituted complexes, it is shown that the replacement of a sulfur atom with a selenium atom practically does not change the relative position of substituents and chelate cycles, as well as the values of the main angles. The packing of complexes 2 and 3 in crystals repeats the packing of sulfur-containing analogues. For phenyl-substituted selenide and sulfide, the crystals are not isostructural. In the diselenide complex 2 molecules crystallize in pairs with one chelate cycle of each molecule participating in pair formation. The pairs are linked by an interaction similar to the stacking interaction. The second chelate cycle of each molecule in the pair does not participate in intermolecular interactions. In the acetylacetonate complexes studied, the chelate rings are not planar. These cycles have a “boat” conformation. The magnitude of bending of the cycle is determined by intermolecular interactions.

Substrate Effect on Band Bending of MoSe2 Monolayer Near Mirror‐Twin Domain Boundaries

AbstractBand bending near mirror twin domain boundaries (MTBs) in a MoSe2 monolayer grown on different substrates, i.e., highly oriented pyrolytic graphite (HOPG), graphene‐on‐SiC, and crystalline Au(110), is investigated by low temperature scanning tunneling microscopy/spectroscopy. Upshift bending of the valence band edge near MTB is observed on both graphene and HOPG substrates, whereas a downshift bending is found on Au(110). For the former, the magnitudes of bending are different. This is explained based on the static charge model, where an accumulative charge exists at MTBs due to both the electrical dipole discontinuity across the MTB as well as charge transfer between the substrate and MoSe2 epilayer. The relevance of the static electric model is further affirmed by noting a geometric effect on the band bending, where it is asymmetric across the vertex of an MTB loop.

Dynamic Construction and Maintenance of Confined Nanoregions via Hydrogen-Bond Networks between Acetylene Reactants and a Polyoxometalate-Based Metal-Organic Framework.

The nanoconfinement effect in catalysis has attracted much attention because it provides a novel means of regulating the molecular properties and related reactions. Confined nanoregions composed of both reactants and catalysts through weak interactions are expected to improve the catalytic performance and promote the mass transport of relevant molecules simultaneously. However, at reaction temperatures, the structural variation of such confined spaces constructed via weak interactions remains unclear. Herein, through density functional theory calculations combined with ab initio molecular dynamics simulations, we have systematically investigated the dynamic structural evolution of the confined space constructed by acetylene reactants and a polyoxometalate-based metal-organic framework (POMOF) via hydrogen-bond networks. It is found that, at the reaction temperature of acetylene semihydrogenation, the hydrogen-bond networks and generated confined nanoregions are not rigid but are constantly changing and dynamically maintained. The steering role played by the O atoms at the surfaces of the polyoxometalate clusters is essential for generation of the hydrogen-bond networks and maintenance of the nanoregions. Upon confinement, the acetylene reactants can be better activated than those in an unconstrained atmosphere, which is reflected by the different dynamic distributions of the ∠CHC bending magnitude. Moreover, from a comparison of the distinct interaction characteristics between acetylene/ethylene and POMOF, the different manifestations in the adsorption energy variations of the confined molecules can be interpreted. This work helps to elucidate the underlying mechanisms of confined catalysis and may promote its application in practical catalytic processes.

Fiber-optic amplitude bend direction and magnitude sensor

A variant of the implementation of a fiber-optic sensor for the direction and magnitude of the bend is proposed. Unlike existing spectral measuring systems, the solution under consideration involves the use of an amplitude polling technique which makes it possible to increase the speed of the sensor when using simpler and more affordable components. A sensitive element based on special diffraction structures consisting of pairs of chirped fiber Bragg gratings has been studied. The sensing elements are mounted on a tooling — a steel rod subjected to bending. The ability of the sensor to determine the magnitude and direction of bending in the deviation range from 0 to 30 mm was demonstrated with a standard deviation of the measured values from the real values of 0.536 mm. This measurement result is achieved by processing data obtained from three measuring devices and by the neural network with a hidden layer of 10 neurons and the sigmoid as the activation function. The research results are essential for modern monitoring systems. The implementation of the direction and magnitude of the bend sensor in the format of a fiber-optic device allows you to overcome the limitations of piezoelectric sensors, due to high noise immunity and resistance to environmental influences. The proposed technological solution makes it possible to avoid the spectral measurement technique that has become widely used in fiber-optic sensor systems. The use of an amplitude sensor for the magnitude and direction of bending will allow its use in devices where there is a need for precise positioning of control elements or structural components subjected to bending. Also, due to the measurement of the desired bending effect by estimating the optical power of the signal, the design of the sensor does not require the presence of a complex measuring device, and the sensor’s performance can be ensured using a cascade of inexpensive, but at the same time high-speed and durable photodetectors.

Machining sound analysis for the effects of fiber bending on cutting mechanisms during carbon fiber reinforced plastic composite milling

Fiber bending during carbon fiber reinforced plastic (CFRP) milling is an important factor on the machined surface quality. During milling, the fiber first contacts the rake face instead of the tool edge at a certain cutting angle, and then the fiber is bent instead of being cut by the tool, causing the matrix and the fiber to fall out. The fiber is then broken from inside the machined surface and subsequently pulled out as the tool rotates, which are known as pull-out fibers. The machining defect is the main cause of deteriorating the surface quality. To reduce such machining defects, it is important to predict the fiber bending during CFRP milling. However, it is difficult to determine where fiber bending occurs because the fiber cutting angle changes every moment as the tool rotates. This study analyzed the fiber cutting mechanism considering bent fibers during CFRP milling and proposed a method to identify the type of machining mechanism through machining sound analysis. Moreover, CFRP milling simulation was performed to numerically analyze the machining parameters such as fiber cutting angle, fiber length, and the magnitude of fiber bending at different milling conditions. Through experiments, it was verified that fiber bending or defects can be identified through sound analysis of machining in the high-frequency range between 7500 and 14,800 Hz. The effect of chip thickness in up-milling and down-milling on fiber bending was investigated by analyzing simulation and sound signal, and their effects on cutting force and machining quality was experimentally verified.

Numerical and experimental investigation of the ballistic performance of the armor structure with in-layer deflector against bullets

This is a study to investigate ballistics performance of armor structures with in-layer deflector against projectiles. For this purpose, the armor structure, which consists of a v-cross section sheet metal array covered with aluminum and steel plates, has been designed and optimized. Firstly, numerical simulations were studied using the finite-element method (FEM). The ANSYS LS-DYNA FE software is used for the ballistic analysis. The Johnson-Cook constitutive equation and damage model were used to model the behavior of metal armors under impact in the ballistic simulations. In the next step, experimental studies were carried out. Penetration depths were measured; including the magnitude of plate bending in front of the target plate and bulging behind it. Comparisons between the results of the finite element analysis (FEA) and the tests reveal that a bullet with a velocity of 868 m/s penetrated the target, but the target could not be penetrated at a firing speed of 631 m/s Furthermore the experimental and numerical results were in good agreement.

Multicore optical fibre embedded Fabry–Perot sensing element of a bend sensor

We propose a new type of a sensing element of a sensor for measuring the bending direction and magnitude, based on fibre Fabry–Perot interferometers embedded in the cores of multicore optical fibre. The measured sensitivity to the bend radius is 81 pm/m−1. It is found that this sensitivity can be increased by varying the diameters of the optical fibres forming the sensing element.

Vector bending sensor based on an edge-core cladding-type fiber Bragg grating.

A two-dimensional vector bending sensor that is both compact and simple is proposed and demonstrated, based on an edge-core cladding-type fiber Bragg grating (ECLFBG) inscribed in an edge-core. The ECLFBG is written parallel to the edge-core using a femtosecond laser point-by-point technique. The reflection spectrum of this ECLFBG varies significantly depending on the magnitude and direction of the fiber's bend. Combining the trend and sensitivity of the wavelength shift and reflection intensity variations of the ECLFBG, the bending magnitude and direction can be measured simultaneously.

Burst capacity analysis of thin-walled pipe elbows under combined internal pressure and bending moment

Structural integrity analysis of pipe elbows is of critical significance because they not only withstand the internal or external pressure but also absorb the bending moment in a pipeline system. While the burst capacity of pipe elbows under internal pressure only have been extensively investigated in the literature, the study on the burst capacity of pipe elbows under combined internal pressure and bending moment is still limited. In this paper, the effect of bending on the burst capacity of thin-walled defect-free and local wall-thinning (LWT) elbows subjected to combined internal pressure and bending moment is systematically investigated. A correction factor is defined to quantify the bending effect on the burst capacity; extensive parametric finite element analysis (FEA) is carried out to analyze the dependence of the correction factor on the bending mode and magnitude, elbow size and steel grade, and LWT size and location. The results indicate that as the magnitude of the bending increases, the burst capacity of both the defect-free and LWT elbows generally deceases. For the defect-free elbows, the elbow steel grade has a significant influence on the correction factor while the influence of the elbow geometry is marginal. For the LWT elbows, the correction factor depends markedly on the LWT location and bending mode.

Schottky contact formation by an insulator: Lithium fluoride on silicon

The low work function material lithium fluoride (LiF) facilitates electron-selective contacts to n-type silicon and is frequently used in dopant-free heterocontacts for silicon solar cells. Our photoelectron spectroscopy (PES) data show that LiF deposition on n-Si leads, indeed, to Fermi-level crossing of the conduction band minimum. Furthermore, PES reveals intrinsic surface band bending on hydrogen-terminated p-Si(100). LiF deposition on p-Si leads to a rigid shift of the Si core-levels and the vacuum-level pointing to ideal Schottky contact formation. This is further supported by the open-circuit voltage of Al/LiF/p-Si/Al solar cells, which corresponds to the photoelectron spectroscopy (PES)-measured band bending magnitude.

Tuning oxygen vacancies and resistive switching properties in ultra-thin HfO2 RRAM via TiN bottom electrode and interface engineering

Resistive random access memory (RRAM) technologies based on non-volatile resistive filament redox switching oxides have the potential of drastically improving the performance of future mass-storage solutions. However, the physico-chemical properties of the TiN bottom metal electrode (BME) can significantly alter the resistive switching (RS) behavior of the oxygen-vacancy RRAM devices, yet the correlation between RS and the physico-chemical properties of TiN and HfOx/TiN interface remains unclear. Here, we establish this particular correlation via detailed material and electrical characterization for the purpose of achieving further performance enhancement of the stack integration. Two types of RRAM stacks were fabricated where the TiN BME was fabricated by physical vapor deposition (PVD) and atomic layer deposition (ALD), respectively. The HfOx layer in HfOx/PVD-TiN is more oxygen deficient than that of the HfOx/ALD-TiN because of more defective PVD-TiN and probably because pristine ALD-TiN has a thicker TiO2 overlayer. Higher concentration of oxygen vacancies induces a larger magnitude of band bending at the HfOx/PVD-TiN interface and leads to the formation of a higher Schottky barrier. Pulsed endurance measurements of up to 106 switches, with 10 μA ± 1.0 V pulses, demonstrate the potentialof the studied ultra-thin-HfOx/TiN device stack for dense, large scale, and low-power memory integration.

Critical bending and shape memory effect in magnetoactive elastomers

The results of a study of magnetoactive elastomers (MAEs) consisting of an elastomer matrix with embedded ferromagnetic particles are presented. A continuous critical bending induced by the magnetic field, characterized by a critical exponent for the bending magnitude, and the derivative of which has a singularity in the critical region is reported for the first time. The mechanical stability loss and the symmetry reduction of the magnetic state, which are interrelated with each other, take place at the critical point. The magnetization in the high-symmetric state (below the critical point) is directed along the magnetic field and the torque is absent. Above the critical point, the magnetization and the magnetic field are noncollinear and there arises a torque, which is self-consistent with the bending. The magnetic field dependence of the MAE bending was found to have a hysteresis, which is associated with the magneto-rheological effect. The shape memory effect was also obtained for the MAE bending in a cycle consisting of magnetization, cooling (at H ≠ 0), and heating (at H = 0). The influence of the critical glass transition temperature of the matrix, as well as its melting/solidification temperature, on the magnetic shape memory effect was studied.

Diurnal photoperiods and rhythmicity of the phototropic bending response in hypocotyls of sunflower, Helianthus annuus L. seedlings

Research on phototropic (PT) bending in sunflower (Helianthus annuus L. cv. Kondi (Syngenta)) seedling hypocotyls presented herein focused on a comparison of diurnal and free-running photoperiods with the aim of explaining the development of diurnal rhythmicity. PT bending magnitudes and lag phase duration exhibited strong daily rhythmicity in all diurnal photoperiods, contrasting with the uniform PT bending response to constant light (CL) conditions. Plants had a daytime maximum for PT bending magnitudes in experiments starting around midday and a minimum in the dark period in those starting 4 h after dusk. Plants could compensate for large differences in the daytime duration of diurnal photoperiods. They required the first 4 h of darkness to recover and synchronize the PT bending and to start increasing the magnitudes of PT bending. The daily pattern of lag phase duration changes was similar but inverted, showing that synchronization also occurred during nighttime. Darkness was not required for PT bending under CL conditions, however, during diurnal photoperiods it enabled the establishment of diurnal rhythmicity and synchronized changes in PT bending capacity to occur when needed, providing maximal values at midday and minimal during the nighttime. Under prolonged duration of daytime corresponding to the start of CL condition, plantlets rapidly abandoned circadian regulation, their PT bending response becoming arrhythmic.

Physical modelling of bending moments in single piles under combined loads in layered soil

Pile foundations are very important elements in the design of railways and bridges. In many projects, piles are under the combination of vertical and horizontal loads. In this regard, the maximum moment which is applied to the piles is a key factor for designers. Therefore, in this study, experimental investigations on loaded single piles in sandy soils with different energies in various conditions of loading and relative densities were performed. Nine physical modeling tests were created to evaluate the load-deflection response, bending moment and strain along with the driven aluminum model pile. The single piles were subjected under both horizontal and combination of horizontal and vertical loads. The dimensions of soil tank and model pile were designed by considering chamber size effects and internal scale effects. The results showed a significant difference in magnitude and shapes of bending when the mole pile was subjected to combined loads with a relative density of 30% (loose) and 75% (dense). Additionally, the combined load test results demonstrated that the bending moments and lateral deflection of the pile head increase substantially in the presence of vertical loads. Finally, two computational models were proposed to estimate the maximum moment on the piles.

Deciphering Morphological Changes in a Sinuous River System by Higher-Order Velocity Moments

Bank erosion in a sinuous alluvial channel is a continuous phenomenon resulting in bank instability and migration of sediment. In this study, flume experiments were conducted in a sinuous channel to investigate its morphological changes and hydrodynamics. High-order velocity fluctuation moments are analyzed at outer and inner banks to explain the morphological variation in a sinuous river channel. The variance of streamwise velocity fluctuations on both banks of the sinuous channel follows a logarithmic law from a particular depth. In the outer bend region, the magnitude of velocity fluctuation moment is significant, indicating erosion. The trend of velocity fluctuation at higher even-order moments is similar to the variance of streamwise velocity fluctuations where the outer bend magnitude is greater than the inner bend. The premultiplied probability density functions (PDFs) and the flatness factor show greater magnitude in the outer bend of the channel as compared to the inner bend.

Design and benchmarking of a robust strain-based 3D shape sensing system

Shape sensing can provide insight into the structural health and operating conditions of slender engineered lifting and control surfaces in aerospace and maritime applications. Shape sensing often relies upon digital image correlation, inertial measurement, or inverse finite element methods, which can be impractical in applications involving real-time reconstructions, static and dynamic deformations, or dynamic mode shape identification, especially outside of controlled laboratory environments. This work describes ongoing efforts to design, build, and validate a low-cost and robust tool for real-time shape sensing. The sensor consists of a simple aluminum spar, instrumented with strategically placed strain gauges. A kinematic model is used to reconstruct bi-axial bending and torsional displacements along the spar. The model is validated against FEM simulations and canonical analytical solutions. A prototype of the spar is benchmarked using a motion capture system. The pre-calibrated errors are correlated with the direction of bending, permitting a directionally compensative calibration scheme. After calibration of the spar and kinematic model, validation errors are 2.18% in bending magnitude and 0.97° in bending direction. This work addresses the emerging need for new low-cost sensors for structural health monitoring in environments where other sensing methods do not perform well.