Multipoint Loading Research Articles

Short-term load forecasting based on multi-frequency sequence feature analysis and multi-point modified FEDformer

Given the complexity and dynamic nature of short-term load sequence data, coupled with prevalent errors in traditional forecasting methods, this study introduces a novel approach for short-term load forecasting. The method integrates multi-frequency sequence feature analysis and multi-point correction using the FEDformer model. Initially, variational mode decomposition (VMD) technology decomposes the load sequence into multiple subsequences, each exhibiting distinct frequency characteristics. Subsequently, for each frequency band of the load sequence, the LightGBM algorithm quantifies the correlation between the load and various influencing factors. The filtered features are then input into the FEDformer model, providing preliminary short-term and long-term sequence prediction results. Finally, a point-by-point forecasting method based on a tree model generates multi-point load prediction results by training multiple LightGBM models. Throughout the forecasting process, a weighted threshold α is set, and a hybrid weighting method is utilized to combine the forecast results from different models, culminating in the final short-term load forecast results. Validation of the proposed hybrid model was conducted on an actual dataset from a specific area, The results exhibit higher prediction accuracy, affirming the proposed method as a novel and effective approach for short-term load forecasting.

High efficient predictive model for deformation of large panels with interaction effect of multi-point loads

High efficient predictive model for deformation of large panels with interaction effect of multi-point loads

FDEM investigation on the crack propagation characteristics of walnut shell under multi-contact loadings

Walnut shell breaking is an important aspect of post-harvest processing. However, shell-breaking results differ significantly from ideal uniaxial compression results. In this paper, the effect of multipoint loading on the walnut shell-breaking mechanism by combining FDEM with cohesive elements was investigated. The model for walnuts was created using micro-X-ray CT scans and experimental data. Simulation parameters describing mechanical properties were calibrated through modeling the uniaxial compression experiment. The loading point locations were quantitatively described in terms of top and azimuthal angles. The results show that the crack ex-tension rate increases with the number of loading points and the singularity value, and the maximum value of the four-point loading speed is about 450 m/s. The number of cracks is only related to the number of loading points and is not related to the location of the loading point. In addition, three loading methods are proposed, and the fastest crack propagation rate is achieved when the azimuthal angle of four-point loading is 0, 150, 180, and 330, respectively. These findings may serve as a theoretical foundation for studying shell crushing.

Biomechanical Properties of Maxillary Second Molar with Different Endodontic Cavity Designs - A Finite Element Analysis.

To evaluate the biomechanical properties of maxillary second molars with three different cavity designs - Traditional, Conservative, and Extended - endodontic cavities using the finite element analysis method. Three finite element models of a maxillary second molar with three different types of endodontic cavities were designed and restored. Each model was subjected to three different force loads directed at the occlusal surface. The stress distribution patterns and the maximum von Mises (VM) stresses were calculated and compared. Vertical force of multipoint load on the occlusal surface and lateral forces to the palatal cusp showed the maximum stress values in the extensive cavity design, followed by the traditional cavity design and then the conservative cavity design. The VM stress distribution in the conservative endodontic cavity was minimal when compared to other access cavity designs.

Static stability test and simulation of a large-scale modular carbon fiber reinforced polymer wheel-spoke-shaped stiffening ring subjected to multi-point radial loading

To enhance the hoop stiffness of the rigid-flexible integrated airship, a new large-scale wheel-spoke-shaped stiffening ring composed of modular carbon fiber reinforced polymer (CFRP) standard trusses was designed in this work. Particularly, by using the modular assembly technology, the CFRP stiffening ring with a diameter of 40.0 m was integrated assembly, which verified the feasibility of the proposed structural design method. Based on the applied uniformly distributed load form of the CFRP wheel-spoke-shaped stiffening ring during the flight of the rigid-flexible integrated airship, the standard truss module was subjected to a multi-point loading static stability test through a self-developed loading device, while the in-plane buckling failure position and buckling load of the CFRP wheel-spoke-shaped stiffening ring were also determined. Based on the refined multi-layered shell model, the combined eigenmode imperfection method was used for the nonlinear buckling analysis of the CFRP truss module. The buckling failure mode and the buckling load obtained from the simulation results were in good agreement with the test results. The proposed and verified large-scale modular CFRP wheel-spoke-shaped stiffening ring improved the hoop stiffness of the rigid-flexible integrated airship and achieved structural weight reduction and the design goal of the large-scale structure. The refined multi-layered shell model based on the combined eigenmode imperfection method has an important application value and guiding significance for investigating the buckling property of CFRP wheel-spoke-shaped stiffening rings, which provides valuable technical support for the structural design of rigid-flexible integrated airships.

Experimental study on the fatigue and freeze-thaw properties of geotextile isolation layer in CRTS III ballastless tracks

To investigate the fatigue and freeze-thaw properties of the geotextile isolation layer in CRTS III ballastless track, a new type of disc multi-point load distribution device was manufactured. The experimental study was carried out on the geotextile isolation layer subjected to the fatigue load and freeze-thaw cycles. The results showed that the mechanical properties of the geotextile isolation layers were affected by the harsh environment and cyclic load. With the increase of fatigue loading cycles, the dynamic stiffness of the geotextile isolation layers increased and tended to be stable, and the nonlinear performance of the geotextile isolation layer gradually weakened. The freeze-thaw cycle greatly influenced the dynamic stiffness of the geotextile isolation layer compared with the fatigue loadings, and the freeze-thaw cycle action could accelerate the elastic loss of the geotextile isolation layer. Under the fatigue load and freeze-thaw cycles, the tensile strength of the geotextile isolation layer decreased and caused damage to the geotextile isolation layers, which should be paid attention to in long-term service.

One-dimensional numerical model for unsteady solute transport in open channels under multi-point loading

A numerical method for solving the unsteady-one-dimensional advection-dispersion equation for solute transport in streams and channels imposed with multiple point-loading is presented. The numerical technique proposes to solve the equation, which also includes a first-order decay term and a loading term, using techniques similar to those employed by the finite volume method (FVM). The channel length is segmented into cells and the solution aims at evaluating the concentrations at the cell interfaces or the internal nodes, at prescribed time steps for the steady condition of the flow. The results are computed commencing from a specified time level with known spatial concentration within the domain. It is assumed that the boundary nodes at the two ends of the channel, one each at the upstream and the downstream, are specified with solute concentration values or its spatial gradient at all times. Unlike the standard within-the-cell spatial approximations of a variable assumed in the finite volume or finite element schemes, the proposed method models the spatial variation of the solute concentration within a cell by an analytical expression in terms of the concentrations at the two boundary nodes of the cell and the influx rate of point-loading, if any, located within the cell. Using such a closed-form function based upon the true nature of the problem not only helps in capturing the spatial variation of concentration within a cell more precisely but also allows a better approximation of its spatial gradients at the cell interfaces, thus helping to achieve a more accurate computation of the inter-cell dispersive fluxes. The performance of the proposed algorithm is evaluated against analytical benchmarks, a standard finite difference scheme, and one public-domain computational package. Data sets reported from field tests are used for demonstrating the potential of the technique in simulating real situations.

Development of the piezoelectric dynamometer for brittle material drilling

ABSTRACT When processing deep and small holes in optical glass with a diamond core drill, the cutting force is minimal and very variable. It is challenging to measure the cutting force because of the high cutting frequency and small value of the cutting operation. In this study, a piezoelectric three-component dynamometer with excellent axial sensitivity is developed based on the measuring properties of quartz wafers and characteristics of cutting forces during processing. The dynamometer’s four sensors are positioned vertically, which could increase the dynamometer’s axial sensitivity. The dynamometer’s calibration studies were conducted in both static and dynamic modes. The output consists of the dynamometer was verified using a multi-point loading experiment. According to the experimental findings, the dynamometer’s linearity error and repeatability error are both less than 0.5%. Less than 1.6% and 2.9%, respectively, are found in the output error and crosstalk of multi-point loading experiment. The frequency of nature is higher than 1500 Hz. An experiment measuring cutting force was completed lastly. The findings of the experiment confirm the viability of the dynamometer by demonstrating that it performs well and can identify changes in cutting force caused by two distinct cutting tools when operating under various conditions.

Multi-equipment coordinated scheduling strategy of U-shaped automated container terminal considering energy consumption

In order to meet the green development trend of today's ports and accelerate the formation of green and low-carbon transportation modes. In this paper, the coordinated scheduling efficiency of quay crane, automatic double cantilever, intelligent guided transport vehicle and external truck in the multi-point loading and unloading mode of U-shaped automated container terminal is optimized to reduce the overall operation energy consumption of the terminal. A decision tree learning based on heuristic Monte Carlo tree search algorithm with the objectives of minimizing road conflicts and minimizing the total task energy consumption is proposed to solve the mixed integer planning model. The proposed regional coordinated scheduling strategy and flexible neighborhood search strategy effectively reduces operational conflicts and improves the optimal container scheduling sequence in the yard. The proposed predictive-based pruning strategy and other pruning strategy effectively improves the operational efficiency. This paper conducted experiments comparing the algorithms on a large scale and a small scale scheduling problems, and the total energy consumption value gap rate was reduced by 0.03%-14.15%. The results show that the proposed algorithm and model can not only effectively handle the conflicts between transportation equipment, but also further improve the transportation efficiency and reduce energy consumption.

Research on a fiber Bragg grating hydrostatic level based on elliptical ring for settlement deformation monitoring.

The hydrostatic leveling system based on the connecting pipe principle has important application value in the field of settlement monitoring. In this paper, a novel fiber Bragg grating (FBG) hydrostatic level based on elliptical ring is proposed. In this study, the vertical and lateral deformations of elliptical ring under concentrated force is analyzed using force method and Mohr integral. Thereby, the deformation-coordination equation of the elliptical ring and the diaphragm is constructed. The temperature self-compensation model for the elliptical ring is established from the three levels of material, structure, and device. A complete set of theories and methods for the designed FBG hydrostatic level is proposed. Furthermore, the tests of the sensitivity, resolution, and temperature self-compensation for the encapsulated sensors are carried out by multi-point loading experiment. The experimental results show that in the range of 0∼100 mm, the sensitivity of the sensor is close to the theoretical analysis, which is about 12 pm/mm. The effective resolution can reach 0.025∼0.05 mm, with the sensitivity coefficient to temperature as low as only 1.46 pm/°C.

FBG pressure sensor in pressure distribution monitoring of ship.

In order to realize the multi-point load measurement of ship hull during wave experiments, an FBG pressure sensor was developed to monitor ship bottom liquid level. The principle is to measure the responses of optical fiber sensing units caused by hydraulic pressure. By utilizing a designed steel diamond structure and reasonable selected material, the sensor realized the temperature self-compensation function of a single FBG. The theoretical models and experimental methods are analyzed in detail. Lots of sensing tests showed that, the sensor had a sensitivity of 58.94 pm/kPa and a precision of 1.7 Pa. The temperature sensitivity was only 2.7 pm/°C, which basically achieved the effect of temperature self-compensated. Finally, 15 sensors were installed at the bottom of the hull and a series of wave load experiments were carried out, which further showed that the pressure sensor had good measuring ability and wide application prospect.

A micro‐macromechanical compression model of crushing in granular materials based on a probabilistic approach and energy aspects

AbstractThis paper presents a micro and macromechanical model to estimate the grading evolution and plastic strain caused by particle crushing in the isotropic compression of granular materials. A joint‐probability particle crushing criterion of the maximum contact force and the particle strength is proposed to calculate the incremental particle crushing probability. The dependence of the contact force and particle strength during a multistage loading process is recognized. The distribution of the maximum contact force and the magnitude of the mean contact force are strictly derived from the stress‐force relationship and maximizing the statistical entropy. The coordination number of polydisperse particles is derived from the geometric relationship and applies to any grading curve, which enables the consideration of the coupling effects of particle crushing and grading evolution during a multistage loading process. A multipoint load particle crushing criterion involving the particle strength size effect is adapted. To simulate the grading evolution, the fractal distribution assumption and Markov chain model are applied to describe the fragmentation mess after crushing. Finally, following the work equation by Mcdowell and Bolton, the energy consumption of particle crushing and the corresponding plastic strain are correlated with the increase in the particle surface area. The model is verified by published experimental data of silica sand with different initial grading curves and carbonate sand with different grain sizes.

Electromechanical modeling and analysis of a piezocomposite multi-point loaded beam vibration energy harvester

In this paper, vibration energy harvesting from a piezocomposite beam with unconventional boundary conditions is investigated. The beam in consideration has multi-point constraints and consequently has concentrated multi-point loading along its length. It is shown that the natural frequencies, strain uniformity along the beam, and strain node positions can be adjusted by shifting the support locations, allowing for a significant range of mechanical tuning. To model the electromechanical system, the Euler-Bernoulli beam assumptions are adopted, and by Hamilton’s principle and Gauss’ law, the governing equations are derived. Frequency response functions of the output voltage and beam transverse displacement are solved for harmonic base excitation, and the maximum output power is calculated both numerically and analytically. A set of experimental results are used to validate the model. A detailed parametric analysis is conducted by varying tunable system parameters such as resistive load, tip mass, and the intermediate support location. All interesting operational conditions of the system, and the corresponding tuning parameters are quantified. It is shown that the multi-point loaded beam concept can produce higher strain-normalized-output-power when compared to a cantilevered or a simply supported beam.

Stand for accelerated tests of rail vehicles wheelsets

Tests and research can be greatly accelerated by applying a multi-point load to the test wheel. The aim of this work is to substantiate rational parameters of the stand for accelerated life tests of railway wheelsets, in which a multi-point load applies to the rolling surface of the test wheel. On the basis of the laws of the theory of elasticity, we performed analytical calculations of the contact stresses created by the rolling bodies of the load mechanism of the test stand. Research has shown that the dependence of the contact stresses on the wheel rolling surface on the ball’s diameter is nonlinear. The decrease in stress is due to an increase in the contact area. We obtained the analytical and graphical dependencies, which make it possible to evaluate the influence of the parameters of the stand for accelerated life tests of railway wheelsets on contact stresses on the wheel rolling surface, taking into account the shape and dimensions of this surface. The authors have proposed a stand design for accelerated life tests of railway wheelsets. The use of a stand with the parameters justified in this work will reduce the test duration by 10-15 times.

Full-scale multi-functional test platform for investigating mechanical performance of track\u2013subgrade systems of high-speed railways

Motivated by the huge practical engineering demand for the fundamental understanding of mechanical characteristics of high-speed railway infrastructure, a full-scale multi-functional test platform for high-speed railway track–subgrade system is developed in this paper, and its main functions for investigating the mechanical performance of track–subgrade systems are elaborated with three typical experimental examples. Comprising the full-scale subgrade structure and all the five types of track structures adopted in Chinese high-speed railways, namely the CRTS I, the CRTS II and the CRTS III ballastless tracks, the double-block ballastless track and the ballasted track, the test platform is established strictly according to the construction standard of Chinese high-speed railways. Three kinds of effective loading methods are employed, including the real bogie loading, multi-point loading and the impact loading. Various types of sensors are adopted in different components of the five types of track–subgrade systems to measure the displacement, acceleration, pressure, structural strain and deformation, etc. Utilizing this test platform, both dynamic characteristics and long-term performance evolution of high-speed railway track–subgrade systems can be investigated, being able to satisfy the actual demand for large-scale operation of Chinese high-speed railways. As examples, three typical experimental studies are presented to elucidate the comprehensive functionalities of the full-scale multi-functional test platform for exploring the dynamic performance and its long-term evolution of ballastless track systems and for studying the long-term accumulative settlement of the ballasted track–subgrade system in high-speed railways. Some interesting phenomena and meaningful results are captured by the developed test platform, which provide a useful guidance for the scientific operation and maintenance of high-speed railway infrastructure.

The hybrid action tool for operations of cleaning of turbine units cavities

The paper deals with the hybrid action tool for cleaning of cavities and elements of turbine units whose operation is based on a combination of action of a water-ice flow with mechanical shock influence of the small concentrated masses mounted on elastic suspensions. Receiving energy from the flow, the masses, performing self-oscillating motion, come into contact with the treated surface having a layer of strong contamination, and create a multipoint shock-cyclic loading of the surface, which results in active development of initial defects of the contamination film, due to which the following action of the water-ice stream produces better and more productive cleaning. It is shown that the generated local stresses, determined on the basis of Hertz contact problems, reach 15-20 MPa, do not have a significant effect on the surface of the base, which is a thin curves shell, do not change the state of its surface in the plane of adhesion, but result in defects in surface film in the form of cracks and delaminations . In this case the film is eliminated by water-ice flow more dynamically. The use of water-ice jet, formed by the original tubeless device, enables the formation of a wide flow (with the top angle of p/12… p/6) and the work of its ice particles is spent on grinding the surface film. The jet stream cleans the surface and removes the products of destruction beyond the impact.The use of a hybrid tool has increased the productivity of treatment with the wetting angles of the jet flow, different from p/2, by more than 30%, while the consumption of cryogenic liquid (liquid nitrogen) is reduced by 20-25%.The process modeling is performed, the conditions of the destruction of the adhesive bond of the contaminant film with the surface are estimated, the conditions of its rational execution are determined.

Influence of Local Deformation Mode of Cable‐Stayed Bridge on Unballasted Tracks: Experimental Research

The complex local deformation modes of the cable‐stayed bridge influence the deformation characteristics of the unballasted tracks laid on it. In this work, a large‐scale segment model of a cable‐stayed bridge was fabricated, and the maximum upward bending deformation mode of the cable‐stayed bridge was realized by multipoint loading on the segment model to study the deformation behaviors of the unballasted tracks. Experimental results indicated that the nonlinear behaviors of the rubber isolation layers are apparent with the loading increased, and the interlayer behaviors of the unballasted track can be improved by the rubber isolation layer. Besides, the relative tensile deformations at interlayers of the unballasted track are inevitable. It is noted that no void and silt form at interlayers of the unballasted tracks with rubber isolation layers due to the precompressions of the rubber material. However, it is entirely possible to produce some diseases such as voids and silts at interlayers of the unballasted track with the geotextile isolation layers paved on the cable‐stayed bridge. Furthermore, it is feasible to use the elastic isolation layer to improve the interlayer deformation characteristics because a particular elastic buffer is provided at interlayers of the unballasted track.

Topology optimization of mechanical structures in stair-climbing assistive technology

The design of ambient assistive technology, such as a wheelchair, is less explored from the engineering design perspective compared with other products of similar platforms, such as bicycles and small vehicles. A generic engineering design of mechanical products is explored using computational tools, such as finite-element analysis and integer programming software. Topology optimization of mechanical structures is a widely explored domain that exploits the union of both finite-element analysis and linear or non-linear convergence algorithms, such as Lagrangian multiplier. Analytical modeling of material properties, such as density, using ‘solid isotropic material with penalization’ helps a design engineer discretize the design domain and solve for the optimization of material properties, such as stiffness, loads and energy. This paper addresses solving a wheelchair-structure-optimization problem with compliance of low energy or minimum deflection of the structure. The wheelchair is designed according to loading patterns that occur in the Indian population using male and female anthropometric data. The wheelchair structures that are optimized in this paper are designed for normal-plane and slant-plane movements. The Lagrangian multiplier convergence algorithm is taken as the constraint function for material removal after obtaining an optimal criterion for multipoint load application and multiple degrees of freedom in the structure.

Laced steel–concrete composite sandwich system in flexure: Experiments, analysis and design

Steel–concrete sandwich composite system consists of steel skin and concrete core. The aim of this paper is to present methods for analysis and preliminary design of a recently developed new class of sandwich composite system laced steel–concrete composite for flexural loads. In laced steel–concrete composite system, continuous lacings are used in place of discrete shear connectors which are generally welded to the skin of the composite. Specimen laced steel–concrete composite systems were subjected to laboratory-controlled experimental investigations. Subsequently, three analytical methods are formulated for evaluating the moment–curvature relation of laced steel–concrete composite system. All the methods exploit the prismatic nature of the laced steel–concrete composite system to derive the moment–curvature relation and employ virtual work principle to evaluate the deflection of the laced steel–concrete composite system. In the first method, the stress–strain relationship of the steel and concrete in tension and compression is utilized to analyse the cross-section of laced steel–concrete composite system. In the second method, fibre-based analysis is used to obtain the response of laced steel–concrete composite system. The third method is based on equivalent transformed section in which the tensile stress–strain behaviour of concrete is represented by an equivalent area under tension. The methods are validated by comparing the predicted values with those of the two- and multi-point loading experiments carried out on laced steel–concrete composite beam and one-way laced steel–concrete composite slab, respectively. All the three methods are found to satisfactorily predict the response of laced steel–concrete composite system. A limited parametric study is carried out by using these analytical methods to identify the role played by the lip and web of the cover plates, tensile strength of concrete and confinement of concrete on the structural response of the laced steel–concrete composite system. In the end, guidelines and charts which can be used for preliminary design of laced steel–concrete composite system for flexure loads are presented.

Static and Dynamic Responses of Reinforced Concrete Structures under Sudden Column Removal Scenario Subjected to Distributed Loading

In this paper, static and dynamic experiments on reinforced concrete beam-column frames under single-column-removal scenario applying a multipoint loading method were conducted. One of the objectives was to investigate structural behavior compared with the single-point loading method, which has been popularly used in previous studies. By equally applying point loads at four locations of the double-span beam structure, the test setup successfully simulated the uniformly distributed loading condition, which is generally applicable for gravity loads in practice. Compared with the previously conducted static tests based on concentrated loading method, structural response from the static tests under multipoint loading condition differed not only on load-bearing capacity but also on failure sequence and displacement profile. On the basis of the test results, the analytical relationship between behaviors of the two loading methods was developed and verified. Compared with the static tests, the dynamic tests highlighted dynamic effects created by the column loss event and confirmed the structural behavior and failure modes observed in the static environment. The dynamic tests also verified the correctness and conservatism of the dynamic assessment framework using a previously proposed energy-based approach. Most important, both the static and the dynamic tests of structures under distributed loads showed less development of catenary action against progressive collapse compared with concentrated loading tests.