Search Results (24)

The aim of this work is to present an original, relatively simple, and elegant approach to the analysis of long rectangular plates subjected to uniformly distributed vertical loads acting on various surfaces. Plate analysis is important in many fields, especially where components are either rectangular plates or can be approximated as such. The Transfer Matrix Method is increasingly used in research, as evidenced by the references cited. The advantages of this method lie in the simplicity of its algorithm, the ease of implementation in programming, and its straightforward integration into optimization software. The approach consists of discretizing the rectangular plate by sectioning it with planes parallel to the short sides—i.e., perpendicular to the two long edges. This results in a set of beams, each with a length equal to the width of the plate, a height equal to the plate’s thickness, and a unit width. Each unit beam has support at its ends that replicate the edge conditions of the plate along its long sides. In the study presented, the rectangular plate is embedded along its two long edges, meaning the unit beam is considered embedded at both ends. The Transfer Matrix Method is particularly valuable because it lends itself well to iterative calculations, making it easy to develop software capable of analyzing long rectangular plates quickly. This makes it especially useful for shape optimization applications, which we intend and hope to pursue in future studies. Full article

One of the effective types of heat-resistant insulating products with an operating temperature of 1050 °C is made from calcium silicates or their hydrates. These materials are made from synthetic xonotlite and 1.13 nm tobermorite. Various wastes and by-products from other industries can be used for the synthesis of the latter compound. However, such raw materials often contain various impurities, especially Al-containing compounds, which strongly influence the kinetics of 1.13 nm tobermorite formation and its properties. Using XRD, DSC, TG, and SEM/EDX methods, it was found that at the beginning of the hydrothermal synthesis, the Al₂O₃ additive promotes the formation of 1.13 nm tobermorite; however, it later begins to inhibit the recrystallization of semi-crystalline C-S-H(I)-type calcium silicate hydrate and pure, high-crystallinity 1.13 nm tobermorite is more easily formed in mixtures without the aluminum additive. Aluminum oxide also influence the morphology of 1.13 nm tobermorite. When hydrothermally curing the CaO–SiO₂ mixture, long, thin fibers (needles) are formed within 24 h. Later, they thicken and form rectangular parallelepiped crystals. After adding alumina, the product produced by 24 h synthesis is dominated by agglomerates, the surface of which is partially covered with crystal plates. By extending the synthesis duration, amorphous aggregates are absent and the crystal shape becomes increasingly square. Full article

This article presents the Transfer Matrix Method as a mathematical approach for the calculus of different structures that can be discretized into elements using an iterative calculus for future applications in the vehicle industry. Plate calculus is important in construction, medicine, orthodontics, and many other fields. This work is original due to the mathematical apparatus used in the calculus of long rectangular plates embedded in both long borders and required by a uniformly distributed force on a line parallel to the long borders. The plate is discretized along its length in unitary beams, which have the width of the rectangular plate. The unitary beam can also be discretized into parts. As applications, the long rectangular plates embedded on the two long borders and charged with a vertical uniform load that acts on a line parallel to the long borders are studied. A state vector is associated with each side. For each of the four cases studied, a matrix relationship was written for each side, based on a transfer matrix, the state vector corresponding to the origin side, and the vector due to the action of external forces acting on the considered side. After, it is possible to calculate all the state vectors for all sides of the unity beam. Now, the efforts, deformations, and stress can be calculated in any section of the beam, respectively, for the long rectangular plate. This calculus will serve as a calculus of resistance for different pieces of the components of vehicles. Full article

Owing to the long-standing statement that natural frequency-based crack detection is not sensitive enough to localised damage to identify small cracks, many natural frequency-based crack detection methods are validated by detecting cracks of moderate size. However, a direct comparison between the crack severity causing a measurable natural frequency change and the crack severity reaching the initiation of crack propagation or leading to brittle fracture is constantly ignored. Without this understanding, it is debatable whether the presented crack detection methods are feasible in practical situations. Through natural frequency calculation and linear elastic fracture mechanics, this study is dedicated to filling the above gap in knowledge. To directly utilize the solution of stress intensity factor, common fracture toughness test specimens featuring a single-edge crack are used. These specimens are essentially cracked rectangular plates under uniform uniaxial tension. Considering the stress resultants obtained via the extended finite element method, the natural frequency of the loaded cracked plates is calculated using the Rayleigh–Ritz method incorporating corner functions. In addition, assuming the specimens as structural components under remote uniform tension, the development of critical load versus crack length is derived based on the solution of the stress intensity factor. Thus, critical crack lengths corresponding to a series of safety factors are obtained by equating service load with critical load. After obtaining natural frequencies of the cracked plates with critical crack lengths, the natural frequency drop caused by a critical crack can be computed. Hence, the critical crack length can be compared with the crack length when the frequency drop is measurable. It is found that the brittleness of the employed metals plays a vital role in the feasibility of natural frequency-based crack detection. Full article

In this article, a miniaturized and highly stable frequency-selective rasorber (FSR) incorporating an embedded transmission window is designed. This FSR consists of a lossy layer loaded with resistors, an air layer, and a bandpass layer. The lossy layer is provided with a rectangular, square ring structure loaded with four $180 \Omega$ resistors and four quadrilateral metal plates. The four metal plates are connected to the four corners of the inner ring around the square ring and are radially distributed along the diagonal. The bandpass layer is a square metal patch that a cross-ring slot structure is loaded inside of, and the cross points lie in the direction along the diagonal of the unit. The inner boundary of the cross-ring is composed of two mutually perpendicular and long rectangular elements. This FSR shows an embedded transmission window from 3.63 GHz to 3.80 GHz and has a transmission rate of 93% at 3.72 GHz. Moreover, both sides of the transmission band, namely, 1.86–3.35 GHz and 3.99–8.28 GHz, have an absorption rate of more than 80% and bilateral relative bandwidth of more than 50%. In addition, this structure exhibits excellent miniaturization performance, polarization insensitivity, and angular stability. Finally, a prototype of the designed FSR is processed and measured. The measured results are basically consistent with the simulation results. Full article

The supersonic–supersonic ejector–diffuser system is employed to suck supersonic low-pressure and low-temperature flow into a high-pressure environment. A new design of a supersonic–supersonic ejector–diffuser was introduced to verify pressure control performance under different operating conditions and vacuum background pressure. A 1D analysis was used to predict the geometrical structure of an ejector–diffuser with a rectangular section based on the given operating conditions. Different numbers and types of nozzle plates were designed and installed on the ejector to study the realizability of avoiding or postponing the aerodynamic choking phenomenon in the mixing section. The effects of different geometrical parameters on the operating performance of the ejector–diffuser system were discussed in detail. Experimental investigation of the effects of different types of nozzle plates and the back pressures on the pressure control performance of the designed ejector–diffuser system were performed in a straight-flow wind tunnel. The results showed that the position, type and number of the nozzle plates have a significant impact on the beginning of the formation of aerodynamic choking. The geometry of the ejector and the operating conditions, especially the backpressure and inlet pressure of the ejecting stream, determined the entrainment ratio of the two supersonic streams. The experimental results showed that long nozzle-plate had a better performance in terms of maintaining pressure stability in the test section, while short a nozzle-plate had a better pressure matching performance and could maintain a higher entrainment ratio under high backpressure conditions. Full article

Thin rectangular plates are considered basic structures in various sectors like aerospace, civil, and mechanical engineering. Moreover, isotropic and laminated composite plates subjected to transverse normal loading and undergoing small and large deflections have been extensively studied and published in the literature. Yet, it seems that the particular case of long thin plates having a high aspect ratio appears to be almost ignored by various scholars despite its engineering importance. The present study tries to fill this gap, yielding novel findings regarding the structural behavior of long thin plates in the small- and large-deflection regimes. In contrast to what is normally assumed in the literature, namely that a long plate with a high aspect ratio can be considered an infinitely long plate, the present results clearly show that the structural effects of the ends continue to exist near the remote ends of the long plate. An innovative finding is that long plates would (only on movable boundary conditions for the large-deflection regime) exhibit a larger mid-width displacement in comparison with deflections of infinitely long plates. This innovative higher deflection appears for both small and large-deflection regimes for both all-around simply supported and all-around clamped boundary conditions. This new finding was shown to be valid for both isotropic and orthotropic materials and presents a novel engineering approach for the old assumption well quoted in the literature that a relatively long plate on any boundary condition can be considered an infinite plate. Based on the present research, it is recommended that this assumption should be used carefully as the largest plate mid-deflection might occur at finite aspect ratios. Full article

Bolted connections have become the most widely used connection method in steel structures. Over the long-term service of the bolts, loosening damage and other defects will inevitably occur due to various factors. To ensure the stability of bolted connections, an efficient and precise method for identifying loosened bolts in a given structure is proposed based on computer vision technology. The main idea of this method is to combine deep learning with image processing techniques to recognize and label the loosening angle from bolt connection images. A rectangular steel plate was taken as the test research object, and three grade 4.8 ordinary bolts were selected for study. The analysis was conducted under two conditions: manual loosening and simulated loosening. The results showed that the method proposed in this article could accurately locate the position of the bolts and identify the loosening angle, with an error value of about ±0.1°, which proves the accuracy and feasibility of this method, meeting the needs of structural health monitoring. Full article

Due to their high bending stiffness, high torsional stiffness, and high local stability, rectangular section members of Al alloy space structures are frequently utilized as load-bearing elements. However, the joint construction is more complex because of the closed cross-section. To join rectangular section members without drilling holes in them, a variety of blind bolts that can be placed and fastened on one side have been devised. The blind bolts researched in this paper is known as BOM bolt. The shear resistance of BOM-bolted Al alloy connections is investigated using shear testing and finite element calculations of individual bolts and bolt groups. According to the test and numerical simulation results, the formulas for the compressive strength of the aluminum plate and the shear capacity reduction factor of BOM-bolted long connections are derived. Full article

A comb-type floating breakwater is a new wave dissipation structure with particular force and dissipation performance advantages due to the two wave-reflecting surfaces. In this article, physical model experiments are used to study the hydrodynamic characteristics of a fixed floating comb breakwater and two structural optimization-based measures under the combined action of regular waves, irregular waves, and wave currents. The effects of factors such as the relative width, relative wave height, water flow velocity, and irregular waves on the transmission coefficient of the breakwater are analyzed. In addition, the characteristics of the transmission wave waveform are analyzed based on the time and frequency domains. The results show that (1) the wave transmission coefficient of a comb-type floating breakwater is lower than that of a rectangular floating box for long-period waves, while the transmission coefficient is larger than that of a rectangular floating box for short-period waves. (2) Under combined current and waves, the superimposition of bidirectional currents can increase the transmission coefficient, and the transmission coefficient increases with increasing current speed. The superimposition of the anti-directional current can decrease the transmission coefficient. (3) Moreover, with the same wave parameters, the transmission coefficient for irregular waves is larger than that of regular waves. (4) Finally, extending the bottom plate and adding lower baffles can effectively enhance the wave dissipation effect of the comb-type floating breakwater while also stabilizing the transmitted wave waveform. Full article

Bird strikes have long been a source of concern for all airlines across the world. It is the most significant design criterion for aircraft engine fan blades. As it is not practical to manufacture and test aviation engines repeatedly for minor design modifications, simulation analysis can be used to investigate strategies to reduce the influence of a bird strike on a jet engine by employing proper design and manufacturing processes for blades. This study proposes using two fibers (hybrid) instead of the single-fiber composite blade presently in use to address delamination problems. As an idea validation test, the coupon-level analysis results are validated using a four-point bend test of similar-size coupons. Following this validation, dynamic analysis is used to investigate the impact behavior of a rectangular plate subjected to a bird strike. The current research focuses on analyzing bird strikes on a hybrid composite fan blade using blade-level models. This study concentrates on the position of the bird’s impact and the joint region length of two materials. The results show that the joint region with a 40% length of glass composite shows the optimum level of normalized interlaminar shear strain in all three impact locations. Full article

To address the problem of low efficiency and automatically sense the phenotypic characteristics of wheat seeds, a wheat seed phenotype detection device was designed to predict thousand seed weight. Five commonly used varieties of wheat seeds were selected for the study, and a wheat seed phenotype detection system was built with a 2 mm sampling hole plate. Grayscale, image segmentation, area filtering and other methods were used to process the image in order to extract and analyse the correlation between thousand seed weight and seven phenotypic characteristics: wheat seed area, perimeter, long axis, short axis, ellipticity, rectangularity, and elongation. The results showed that different varieties of wheat seeds were significantly correlated with different phenotypic characteristics. Among them, the area and short axis for Luomai 26; the area, long axis, short axis, perimeter, and rectangularity for Jinqiang 11; the area and perimeter for Zhoumai 22; the area of Luomai 42; the area, short axis, and perimeter for Bainong 207 were significantly correlated with the thousand seed weight. A multiple linear regression model of thousand seed weight prediction was developed by selecting the significantly correlated phenotypic characteristic. The models showed that the R² values of the thousand seed weight prediction models for Jinqiang 11 and Bainong 207 were 0.853 and 0.757, respectively; and the R² values for Luomai 26, Zhoumai 22, and Luomai 42 were less than 0.5. Subsequently, PCA-MLR was used to build a thousand seed weight prediction model, and K-fold cross-validation was used for comparative analysis. Afterwards, three kinds of wheat seeds with 40–50 g thousand seed weight were selected to validate the model. The validation results showed that the more significantly correlated the phenotypic parameters were, the higher the accuracy of the thousand seed weight prediction model. The study provided a set of detection devices and methods for the rapid acquisition of the phenotypic characteristics of wheat seeds and thousand seed weight prediction. Full article

Round-ended rectangular concrete-filled steel tube (RRCFST) columns are prone to local buckling that are close to straight steel plates when used as piers of a bridge and affect its long-term use. In order to solve this problem, tie bars were used in this research to stiffen RRCFST columns. Eleven specimens with tie bars and three specimens without tie bars were tested to analyze influences of cross-sectional aspect ratio, longitudinal spacing, limb numbers and diameter of the tie bar on failure model, confined effect, bearing capacity and ductility of RRCFST stub columns. Finite element models (FEM) with different concrete constitutive models for rectangular and circle parts were established and validated to reveal the mechanism of the constrained effect of tie bars. Experimental and FEM results show that the local buckling scope was decreased and gradually moved to middle height with decreased longitudinal spacings tie bars. The addition of tie bars in RRCFST columns with large aspect ratios slightly enhanced the ultimate bearing capacity, the diameter of tie bars changing from 8 mm to 12 mm greatly enhanced displacement and energy ductility by 58.4% and 85.1%, respectively. However, more tie bars (e.g., two or three limbs) utilization could not further improve the bearing capacity and failure mode. While, the tie bars had very limited contribution to bearing capacity and ductility for RRCFST columns with small aspect ratios, because the outer steel tubes already individually provided for enough confinement on inner concrete. By considering different concrete confined models for rectangular and round-ended parts, an analytical model was proposed and validated to predict the ultimate bearing load for RRCFST stub columns with tie bars. Full article

The periodic flexural-gravity waves propagating along a frozen channel are investigated. The channel has a rectangular cross section. The fluid in the channel is inviscid, incompressible and covered with ice. The ice is modeled by a thin elastic plate whose thickness varies linearly. Two cases have been considered: the ice thickness varies symmetrically across the channel, being the smallest at the center of the channel and the largest at the channel walls; the ice thickness varies from the smallest value at the one wall to the largest value at another wall. The periodic 2D problem is reduced to the problem of the wave profiles across the channel. The solution of the last problem is obtained by the normal mode method of an elastic beam with linear thickness. The behavior of flexural-gravity waves depending on the inclination parameter of the ice thickness has been studied and the results have been compared with those for a constant-thickness plate. Dispersion relations, profiles of flexural-gravity waves across the channel and distributions of strain in the ice cover have been determined. In the asymmetric case, it is shown that for long waves, the most probable plate failure corresponds to transverse strains at the thin edge of the plate, which can lead to detachment of the ice from the corresponding bank. For short waves, the longitudinal stresses within the plate, localized closer to the thick edge, become maximum. This can lead to cracking of the plate in transverse direction. In the symmetric case, the maximum strains are achieved inside the plate—close to the center, but not necessarily in the midpoint. Full article

This paper presents a design of a radio frequency identification (RFID) tag antenna in the ultra-high-frequency (UHF) range, which is applicable to a vehicular license plate attached to a vehicle bumper. The main goals are to first improve the identification ratio by controlling the radiation beam pattern and, second, to control the beam direction. Since every vehicle has a license plate, the available plate structure is used to design the antenna. The shape of the tag is rectangular and has a dimension of 525 mm × 116 mm, which is smaller than the typical size of standard plates, 540 mm × 120 mm, used in Europe and Korea. The fabricated tag antenna, the license plate, and the vehicular bumper are fixed by volt and nut. For vehicle tracking and identification, RFID readers are deployed on the road side. For efficient identification, a long distance passive UHF RFID license plate with a patch antenna is proposed to provide not only line-of-sight identification but also left and right beams. Unlike the general UHF tag antennas, in this paper, the patch antenna is designed to attach to the metal part of the car, the license plate holder. The beam patterns of the RFID tag antenna can be controlled by the patch antenna parameter values. The simulation result demonstrates that the proposed UHF RFID tag antenna has a beam radiation pattern as required at 920 MHz. In addition, the estimated read range of the proposed plate meets the requirement of RFID systems. Full article