Flexible Plate Research Articles

Wave scattering by an array of moored floating flexible plates resting on an elastic foundation in the reference of blocking dynamics

Surface gravity wave scattering by an array of floating flexible plates having free/moored edges and resting on a Winkler foundation are studied within the framework of flexural gravity wave blocking. The impact of the floating plates having moored edges compared to that of free edges along with the occurrences of Bragg reflection are analyzed. The study reveals that wave reflection is oscillatory in nature irrespective of the number of plates. Further, the amplitude of wave reflection increases for smaller frequency and decreases for higher frequency in the presence of Winkler foundation. The study depicts the occurrences of removable discontinuities at the blocking frequencies and the existence of a smaller number of extrema in wave reflection outside the blocking limits than within the said limits. Besides, the number of sub-harmonic peaks between two consecutive harmonic peaks in wave reflection depends on the wave frequency, plate length and gap between the consecutive plates. Moreover, the free surface elevations and the floating plate deflections exhibit certain irregularity within the blocking frequencies. The free surface elevation and floating plate deflection in the presence of compressive force wave blocking exhibit the recurrence of scattering of wave pulses in the linear time domain.

A comparative study of wave scattering by non-porous and porous flexible plates in the presence of a submerged porous structure

A comparative study of wave scattering by non-porous and porous flexible plates in the presence of a submerged porous structure

A Damage Identification Method Based on Minimum Mean Square Error Estimation for Wind Tunnel Flexible Plate Condition Monitoring System

In this paper, we propose a damage identification method based on minimum mean square error estimation for a wind tunnel flexible plate condition monitoring system. Critical structural members of important equipment are large in size, and the measurement systems used to monitor their condition are often complex. The proposed damage identification method is based on the minimum mean squared error estimator and the generalized likelihood ratio test. It introduced activation function to generate the standard deviation of the data, which can then simulate the sensor output. A single sensor damage only affects a single dimension of the output data matrix of the measurement system. However, structural damage affects the output of multiple sensors. The damage identification method proposed in this paper can not only distinguish the sensor damage from the structure damage, but also locate the damaged sensor or structure damage location. This method can identify the measurement system output anomalies caused by structural damage and locate the approximate location of the damage. It can be applied to damage identification of important structural members such as flexible wind tunnel plates. The damage identification method proposed in this paper is of great significance for damage identification and localization of key components and sensor systems.

Wave impact on rigid and flexible plates

Wave impact on rigid and flexible plates

Hydrothermal ferromanganese oxides around a petit-spot volcano on old and cold oceanic crust

Areas of old and cold oceanic plate lack conventional volcanism and have been assumed to be devoid of submarine hydrothermal activity. However, petit-spot volcanoes are common in areas of flexure of such oceanic plates. Here, we report hydrothermal ferromanganese oxides dredged from the vicinity of a petit-spot volcano at 5.7 km water depth in an area of oceanic plate flexure east of the Japan Trench. The bulk chemical, lead isotopic and mineralogical compositions of the samples indicate their formation by low-temperature hydrothermal activity, which can be interpreted as being caused by fluid–rock interactions at <200 °C. We propose that interaction of local marine sediments with volatile-rich petit-spot magmas may produce hydrothermal fluids containing not only iron and manganese but also enough amounts of carbon dioxide and methane to have implications for the global carbon cycle. However, contemporary hydrothermal activities at petit-spot volcanoes have not been confirmed yet.

A flexible bearing plate based on steel plate and rubber mat

The bearing plates used in plate load test for highway engineering are typically rigid. However, due to limitations in obtaining the accurate distribution of compressive stress at the bottom of the bearing plate, there is often a significant deviation between the measured subgrade resilient modulus and the actual condition. To address this issue, a flexible bearing plate can be used to test the subgrade and obtain a more accurate resilient modulus. In this study, we use variance and degree of mean deviation to quantitatively evaluate the distribution uniformity of compressive stress. To create a rigid-flexible bearing plate that is similar to a flexible bearing plate, we explore the combinatorial design of steel plates and rubber mats. We examine factors such as the thickness (10, 20, and 30 mm) of the steel plate, elastic modulus (5, 10, and 20 MPa) and thickness (10, 20, and 30 mm) of the rubber mat, friction coefficient (μ:0, 0,2, 0.4, 0.6, 0.8, ∞) between the bearing plate and subgrade, and the combined shape characteristics of the rubber mat and steel plate. To reduce friction between the rubber mat and subgrade, we use lubricant, and through our design process, we develop a flexible bearing plate with relatively uniform compressive stress. Our computations show that when μ = 0.05, the variance is 0.0001, and the degree of mean deviation is 0.0780. These results indicate that the distribution uniformity of the compressive stress is very close to the uniform distribution load, which meets the necessary accuracy requirements for engineering applications.

Modeling of Advanced Helmholtz Resonator Liners with a Flexible Wall

Acoustic liners are an effective way to dampen aircraft noise. Conventional single-degree-of-freedom liners consist of a perforated facesheet backed with a honeycomb structure and a rigid end plate. Their damping excels near their resonance frequency, which is antiproportional to the cavity depth (-resonator) or the cavity volume (Helmholtz resonator). However, this is a challenge for low-frequency noise with long wavelengths due to the limited installation space. We therefore propose a resonator in which the back cavity is divided into two cavities by a flexible plate. The aim is to combine the damping mechanisms of the Helmholtz resonator with the material damping of the flexible plate. With carefully chosen parameters, this flexible plate resonates well below the Helmholtz frequency. We derived an analytic model based on waveguide theory to predict the impedance of the resonator concept. The Helmholtz equation was solved to (numerically) determine the scattering coefficients of a channel section in which one wall is lined with the predicted resonator impedance. The predicted dissipation agreed well with experimental data from measurements at the aeroacoustic wind tunnel DUCT-R.

A new higher-order plate/shell element for dynamic analysis of flexible plate and shell with variable thickness

A new higher-order plate/shell element for dynamic analysis of flexible plate and shell with variable thickness

Heat transfer enhancement in channels with roughened and elastic walls

In this research, a combination of passive and active heat transfer enhancements are used synergistically to assist in the increase of absorbed heat from a channel by roughened and fluctuating walls. To this end, the upper wall is artificially roughened and a fluctuating segment is added to the lower wall. Flow regime is considered to be laminar and Reynolds number is 1000 at the entrance of the channel. Combinations of various roughness geometries and fluctuations are studied. It was found that due the increase of the fluid kinetic energy and its interaction with roughened surface and elastic segment, heat transfer rate is amplified. To investigate the overall efficiency of the system, Nusselt number and friction factor are calculated and a maximum value of 37.5% increase in average Nusselt number of the midsection where elastic wall is placed has been reached by flexible plate displacement. A maximum Nusselt number increase of 167% has been observed when the elastic plate reaches its peak value.

Performance of two vertically submerged piezoelectric plate wave energy converters in presence of a non-flat flexible barrier

Wave energy converters together with flexible breakwaters not only provide shelter to the energy devices against wave attacks but also offer improved performance, longer survivability and lower costs. Thus, in the present work we are interested to investigate the interaction of linear water waves with an array of three thin vertical plates, comprising of two plate wave energy converters and one flexible breakwater, submerged in water of finite depth in a two dimensional space. The plate in the middle of the setup is a flexible plate of variable thickness, and on either side of it are piezoelectric plate wave energy converters with constant thickness. The problem is solved by converting the associated boundary value problem into a system of coupled integral equations. A modified form of the energy balance equation is derived, which results due to the presence of the two piezoelectric plates. We investigate how the structural properties of the piezoelectric plates like their submergence depths, plate lengths, distance from the breakwater and different edge conditions can affect the wave attenuation and wave power absorption efficiency. Further, it is also examined how the presence of the non-uniform flexible plate with different flexibility and lengths can improve the performance of the system. It is analysed that shorter sized piezoelectric plate wave energy converters in the presence of non-flat flexible plate offer higher wave power absorption efficiency at lower frequencies.

Numerical Analysis of Vibration Attenuation and Bandgaps in Radially Periodic Plates

ObjectivePeriodic configuration of mechanical and civil structures has shown great potential for noise and vibration reduction. However, the use of Cartesian coordinates in studying periodicity effects in elastic structures overlooks the benefits of radially periodic configurations when dealing with wave propagation in large flexible plates disturbed by a small source area. This paper presents an easy-to-use numerical approach to predicting bandgap characteristics in polar coordinates.MethodologyTo demonstrate the vibration-attenuation effect, we consider a circular radially periodic plate model. We use an adapted Wave Finite-Element method in numerical experiments to demonstrate the existence of the attenuation effect. To verify the numerical results, we apply an adapted Floquet theory to polar coordinates.Results and ConclusionsOur findings indicate that theoretical and numerical results are in excellent agreement considering a new parameter that introduces the distance from the origin. The adapted Wave Finite-Element approach and Floquet theory presented here demonstrate their potential to model more complex structures in polar coordinates.

The effects of elongation strain on choroid plexus endothelial cells as a model of mild traumatic brain injury

Traumatic Brain Injuries (TBIs) account for a significant portion of morbidity and mortality accounting for approximately 2.5 million reported cases per year. However, there has been little research regarding the blood-cerebrospinal fluid barrier (BCSFB), the choroid plexus, in TBI pathophysiology. Choroid plexus endothelial cells (CPECs) play a critical role in maintaining CSF homeostasis and regulating neuroinflammation. These endothelial cells, once exposed to the shearing force associated with TBI, release proinflammatory cytokines and become leaky via the breakdown of gap junctions leading to an influx of immune cells. Identifying key cytokines involved in this process and critical timepoints post-injury will allow researchers to better understand key TBI pathophysiology. The aim of this study was to elucidate the cytokine response of CPECs post-mild shearing strain to mimic mild TBI (mTBI). We hypothesized that pro-inflammatory cytokines like IL-6 &amp; TNFα would be elevated post mTBI. Using primary human choroid plexus endothelial cells (HCPECs) purchased from ScienCell (Cat# 1300) and the FlexCell Tension system, HCPECs were subjected to a 12% mild mechanical strain (“one hit”), supernatant was collected, and 36 different cytokines and chemokines were measured at multiple time points post-injury using a membrane-based array (R&amp;D Systems, Cat# ARY005B). This was repeated in a “two hit” model where the cells were subjected to a second 12% strain, 24 hours after the first to examine two subsequent mild head injuries. The multiple time points of supernatant collection allowed for longitudinal measurement of cell behavior and cytokine profiles. Experimental controls included HCPECs plated on the FlexCell flexible membrane 6-well plates without being subjected to mechanical strain. Consistent with the literature and clinical TBI presentation, cytokines were elevated 48-hours post-injury. There were changes in cytokine production between 24- to 48- hours post-injury, most notably CCL2, MIP1α/MIP1β, G-CSF, IL-10 and CCL5 (RANTES), to name a few. Interestingly, while some cytokines increased after injury, such as the 2-fold and 4-fold increase in CCL2 between 24- and 48-hours post one and two hit, respectively, others decreased. There was a 3-fold decrease in RANTES between 24- and 48- hours post one hit, and a 2-fold decrease in G-CSF. Contrary to our hypothesis, cytokine responses post-injury were related to regulatory and anti-inflammatory responses as opposed to pro-inflammatory responses. As both RANTES and G-CSF are implicated in chronic inflammation, the results indicate that there was a decrease in pro-inflammatory responses in favor of more regulatory and anti-inflammatory responses post mTBI. Overall, this pilot project helped identify key cytokines involved in HCPEC signaling after mild mechanical strain and demonstrated a critical window between 24- and 48- hours post-injury for the treatment of mTBI. Indiana Academy of Sciences; Marian University This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Fluid-structure interaction of a thin flexible heater inside a lid-driven cavity

The purpose of this study is to explore the characteristics of fluid-structure interaction and heat transfer enhancement from a hot flexible thin plate during mixed convection. The mixed convection condition of the plate heater is assumed by placing it inside a lid driven cavity with top and bottom cavity walls being fixed and insulated while left and right cavity walls maintained at constant low temperature move in downward and upward direction respectively. The Galerkin Finite Element Approach has been used to numerically solve equations describing unsteady flow, thermal and stress fields in the Arbitrary Lagrangian-Eularian (ALE) framework. Key parameters include Reynolds number ( Re) and Richardson number ( Ri), and Cauchy number ( Ca) which are varied in the range of 100 ≤ Re ≤ 500, 0.1 ≤ Ri ≤10, and 10−4 ≤ Ca ≤ 10−7 respectively. To investigate the effect of the heater’s geometry, the plate length ( l) has been varied within 0.1 ≤ l ≤ 0.7. The results have been presented in terms of the distribution of streamline and isotherm, heat transfer rate from the flexible heater as well as its deformation. The outcomes reveal that heat transfer enhances with the increase in Reynolds number and Richardson number while it degrades with the extension of the heater. Moreover, thermal frequency obtained by Fast Fourier Transform (FFT) indicates dominant peaks at higher Reynolds number and Richardson number although these become insignificant as the plate becomes rigid.

Potential of waste woven polypropylene fiber and textile mesh for production of gypsum-based composite

The huge production of woven polypropylene bags has led to an increase generation of plastic waste. The recycling of waste woven polypropylene bags and textiles in construction applications can be a viable option. Therefore, an attempt has been made to utilize the woven polypropylene fibers and textiles in the production of gypsum-based composite false ceiling tile for an economical and sustainable construction product. In the current research work, different water-to-powder ratios (0.6 %, 0.7 %, 0.8 %, 0.9 %) and fiber contents (0.25 %, 0.35 %, 0.45 %, 0.55 %) in the gypsum-based composite were prepared. Flexural plates with different thicknesses (18, 15, 12, and 9 mm) incorporating different recycling fibers and reinforced with different types of meshes were manufactured to produce sustainable gypsum-based plates. The physical properties, compressive and flexural strength properties of the fiber-reinforced gypsum-based composite were also evaluated. The textile and woven polypropylene fiber mesh reinforced gypsum false ceiling plates were compared with the control specimen. The results revealed that the density of gypsum-based composite decreased up to 26 % with the increase in the proportion of waste fiber contents. The compressive and flexural strength of gypsum-based composites exhibited a decrease with an increase in fiber contents and water-to-powder ratio. However, all the specimens satisfied the acceptable limit of 1 MPa and 2 MPa, respectively, according to BS EN 14246. The bending strength of all the plates incorporating different fiber content and thicknesses satisfied the minimum specified flexural strength criteria according to BS EN 14246. Moreover, the plates with different thicknesses and fiber contents also satisfied the minimum specified flexural criteria except for the plate with a thickness of 9 mm. However, all the plates with varying thicknesses and reinforced mesh have also satisfied the minimum load criteria specified by BS EN 14246. Thus, it can be envisioned that the woven polypropylene fibers and textiles can be effectively utilized to produce sustainable gypsum-based composite leading to reduce waste generation.

A biomimetic approach to improve convective heat transfer using self-excited flaps

Bio-inspired flexible plates have shown promising results as a passive method to enhance convective heat transfer and mixing in flow. Flap fluttering is a self-excited phenomenon caused by the fluid-structure-interaction between the main flow and the flap. Among all the parameters, the direction of the flap relative to the incoming flow appears to be the key factor in determining the transition into the flapping mode. In this study, flaps made of a 50-micron thick polyester sheet were cut into rectangular shapes and placed at the centerline of the channels of a shrouded straight fin heatsink. Both hanging and vertical positions of the flap in the axial flow were investigated using a custom-built testbed in our lab. We measured the convective heat transfer rates and pressure drop in the heatsink for both arrangements. We observed that: i) the rectangular cantilevered flap is more unstable in the hanging flap configuration compared to the vertically installed flap, i.e., the transition to the fluttering mode occurs at a lower airflow velocity; ii) the critical flow velocity – the velocity at which the flap becomes unstable– is lower for the flap aspect ratio of 0.5. We attribute this behavior to the longer viscous boundary layer around the vertical case, which stabilizes the flap; iii) from a thermal performance point of view, the hanging configuration outperforms the vertical one with the same flap dimensions; iv) at a Reynolds number of 8,940, large amplitude vibrations and coherent fluttering in a hanging configuration render a superior thermal performance of 39 percent improvement in the Nusselt number compared to when bare channels are measured. On the contrary, at higher flowrates, the difference falls in the range of measurement uncertainty; and v) as for the pressure drop, unlike the hanging configuration, the vertical flap creates a higher pressure drop as it tends to block half the channel at the end of the trailing edge stroke. Furthermore, the presence of the flap holder adds to the pressure drop increase, which is eliminated in the hanging position and therefore, flaps could be connected to the shroud directly.

Bending levitation control of flexible steel plate: Consideration of effect of magnetic properties on electromagnetically levitated steel plate vibration

Recently, demand for thin steel plates has increased. In the manufacturing of thin steel plates, surface quality deterioration due to contact between the rollers and steel plate involved is problematic. We are investigating magnetic levitation conveyance to propose a noncontact conveyance system using electromagnets. However, the magnetic levitation of thin steel plates is unstable because of the deflection in the range where the electromagnetic force is not affected. Therefore, to improve the levitation stability, we are investigating a bending magnetic levitation system in which a thin steel plate is bent during magnetic levitation but not deformed plastically. In this study, a dynamic analysis using the finite difference method is performed to understand the behavior of a thin steel plate during magnetic levitation. In the dynamic analysis, vibration is evaluated based on the displacement standard deviation. The dynamic simulation visualizes the dynamic behavior of a levitated flexible steel plate.

Effect of permanent magnets in optimized arrangement for levitation support on vibration characteristics of levitated flexible steel plate

In the production line of thin steel plates, contact conveyance by rollers causes deterioration in the surface quality of the plates. To solve this problem, our research group has been continuously investigating the optimal placement of permanent magnets in hybrid magnetic levitation systems. In this study, when a thin steel sheet was magnetically levitated, the effect of the horizontal electromagnet position on the gap between the steel sheet and the permanent magnet was investigated through a permanent magnet configuration optimized using a genetic algorithm.

Fluid-structure interaction of a sweeping impingement jet for cooling hot flat target

Normal impingement jets remove heat from a hot target locally and cause non-uniform temperature due to the limited covered distance on the target. The current numerical study suggests an approach for sweeping impingement laminar jets to cover a wider distance on a hot flat plate. The approach is based on oscillating a slot impingement jet composed of two flexible plates. A sinusoidal excitation is imposed to the flexible plates to create two oscillation modes, sweeping jet (in-phase) and converging-diverging jet (out-of-phase). The study focused on the characteristics of the jet oscillation in addition to the Reynolds number. The problem is solved using the finite element method with moving mesh. The results show that the suggested oscillating jets offer an enhancement of the average Nusselt number. It is noticed a pronounced role of the amplitude of the oscillation in enhancing the Nusselt number in the out-of-phase mode where about 11.2% and 4.6% enhancements are attained with out-of-phase and in-phase modes, respectively at Reynolds number of 400 and amplitude ratio of 0.1875. It is also found that the pressure drop cannot be avoided in sweeping oscillating jets.

Flexible Metamaterial Quarter-Wave Plate and Its Application in Blocking the Backward Reflection of Terahertz Waves.

A terahertz flexible metamaterial quarter-wave plate (QWP) is designed and fabricated using polyimide as the substrate in this paper, with a 3 dB axial ratio bandwidth of 0.51 THz and high polarization conversion efficiency and transmittance. The effect of the incidence angle on the polarization conversion performance of the QWP is discussed by measuring the transmissions at multiple incidence angles. The blocking effect of this QWP combined with a polarizer on the backward reflection of terahertz waves is investigated by terahertz time-domain spectral transmission experiments. By adjusting the angle of the QWP and polarizer with respect to the incident light in the optical path, a blocking efficiency of 20 dB can be achieved at a 20° incidence angle, with a bandwidth of 0.25 THz, a maximum blocking efficiency of 58 dB at 1.73 THz, and an insertion loss of only 1.4 dB. Flexible terahertz metamaterial QWPs and polarizers can effectively block harmful reflected waves in terahertz communication and other systems. They have the advantages of a simple structure, ultra-thinness and flexibility, easy integration, no external magnetic field, and no low-temperature and other environmental requirements, thus having broad application prospects for terahertz on-chip integrated systems.

13.1: The design and preparation of flexible MiniLED plate with nano‐Ag paste

The development and preparation process of a flexible MiniLED line subgrade board on a white reflective sheet was carried out in this paper using silk‐printing nanoscale silver paste assisted bonding technology. The design of the line conductivity parameter ‐ nanoscale silver paste parameter model, printing plate selection, and process verification were systematically completed, as well as the preparation and reliability confirmation of flexible MiniLED lamp board. The flexible MiniLED lamp board with disposable sintered nano silver slurry lines was successfully prepared, and the 65" backlight module was constructed.