Cross-sectional Side Length Research Articles

A Fast Method of High-Frequency Induction Cladding Copper Alloy on Inner-Wall of Cylinder Based on Simulation and Experimental Study

To quickly repair the inner-surface damage to the hydraulic support cylinder caused by frequent scratches, corrosion, and wear in the process of fully mechanized coal mining, this paper proposes a method of high-frequency induction cladding (HIC) copper alloy on inner-wall of cylinder (IWC) to improve the corrosion, sealing and pressure retention performance of hydraulic cylinders combined with numerical simulation and experimental study. Firstly, a numerical temperature field model for HIC of copper alloy on the IWC is established to investigate various distribution patterns and influencing factors including frequency of induction heating, gap between coil and cladding, power supply rating, cladding thickness and side length of square section of induction coil, etc. Subsequently, an HIC test experiment is conducted to rigorously validate the numerical temperature field model and the experiment employs a meticulously collected dataset of temperature measurements, confirming the model’s accuracy and consistent alignment with anticipated changing trends. In addition, the experiment results were verified through microstructure observation, microhardness testing, friction-wear testing, and electrochemical corrosion parameters, which shows that the factors of induction heating frequency and others have obvious effects on the temperature field distribution of HIC copper alloy on the IWC. Under these working conditions (cladding thickness 1.5 mm, power supply rating 120 kW, heating frequency 120 kHz, gap between the cylindrical workpiece and the induction coil 3 mm, induction coil cross-sectional side length of 10 mm), the thermal impact on the cylinder barrel matrix is minimal, the metallurgical bonding between the cladding layer and the matrix is good, and there are no over burning and porosity defects.

Prediction and design of mechanical properties of origami-inspired braces based on machine learning

In order to rapidly and accurately evaluate the mechanical properties of a novel origami-inspired tube structure with multiple parameter inputs, this study developed a method of designing origami-inspired braces based on machine learning models. Four geometric parameters, i.e., cross-sectional side length, plate thickness, crease weakening coefficient, and plane angles, were used to establish a mapping relationship with five mechanical parameters, including elastic stiffness, yield load, yield displacement, ultimate load, and ultimate displacement, all of which were calculated from load-displacement curves. Firstly, forward prediction models were trained and compared for single and multiple mechanical outputs. The parameter ranges were extended and refined to improve the predicted results by introducing the intrinsic mechanical relationships. Secondly, certain reverse prediction models were established to obtain the optimized design parameters. Finally, the design method of this study was verified in finite element methods. The design and analysis framework proposed in this study can be used to promote the application of other novel multi-parameter structures.

Experimental and numerical evaluation of axial compression strengthening for corroded square reinforced concrete columns by carbon textile reinforced concrete

This research focuses on analyzing the behavior of reinforced concrete (RC) columns under axial compression, both in their uncorroded and corroded states, through a combination of experimental and numerical investigations. For the experiment, seven specimens were prepared and manufactured subjecting to centric compression. The cross-sectional side length of the square columns was 200 mm. The column height was selected as 800 mm based on the dimensions of the testing machine. The specimens were divided into three groups: (i) the control columns, (ii) the corroded columns without strengthening, and (iii) the corroded columns strengthened with an external carbon textile reinforced concrete (TRC) layer. The experimental results showed that when the corroded columns had approximately 10% mass loss in longitudinal reinforcement and stirrups, the ultimate load was reduced by 5.7%. Meanwhile, the axial compression capacity of corroded columns strengthened by TRC layer was approximately 28% higher than the corroded unstrengthened ones. All tested specimens failed due to the buckling of the longitudinal reinforcement. The strengthened columns failed at the corners due to the rupture of the textile reinforcement. To validate the experimental results, a finite element (FE) modeling was presented.

Superelastic ferroelectric micropillar with large hysteresis and super-durability

Hysteresis and durability are generally on the opposite sides of a trade-off for superelastic materials. We herein break this trade-off and report that BaTiO3 (BT) micropillars present size-dependent superelasticity and possess simultaneous large hysteresis and super-durability, sustaining up to 108 superelastic cycles without functional degradation and structural failure. TEM results reveal that the as-fabricated BT pillars are composed of inner BT crystal part and surface BT amorphous layer. In addition, it is found that after high temperature annealing, the BT pillar with cross sectional side length d of 2 µm loses superelasticity. Based on these results, a model was developed to explain the size dependent behavior of BT pillars by considering the constitutive behavior difference of BT crystal and BT in amorphous phase, and their interaction during compressive stress loading and unloading. The super-durability was attributed to the small ferroelastic switching stress, which are much smaller than the dislocation nucleation activation stress and the compression strength of BT pillars, and the moderate mismatch stress between different ferroelectric variants as well as the stress relaxation by the high surface area of the small volume BT pillar. These discoveries enable ferroelectric micropillars many promising applications such as microdampers, and also provide significant insight into developing superelastic materials with enhanced durability.

Specimen size and shape dependent yield strength in micropillar compression deformation of Mo single crystals

The deformation behavior of [1¯25]-oriented Mo micropillars with rectangular cross-sections having the [111] primary slip direction parallel to one of the two orthogonal side-surfaces has been investigated as a function of specimen size and shape (with varying ratios for two side-edge lengths of the cross-section). Micropillars with square-shaped cross-sections exhibit a size dependence of the critical resolved shear stress τCRSS approximated by τCRSS∝L−m with a power-law exponent of m ∼0.5 (L: cross-section side length). For a series of micropillars with a fixed length for the side-edge perpendicular to [111] (CE series), the CRSS also exhibit a power-law relationship with a relatively small exponent of m = 0.3. In contrast, an unexpected size-dependence is observed with two strength plateaus being connected by a strongly size dependent region (m ∼ 1) for a series of micropillars having a fixed length for the other cross-section side (CS series). The observed specimen size and shape dependence of CRSS of Mo micropillars is discussed based on the stochastic dislocation source length model and the dislocation kinetics model.

Experimental Study on Temperature Distribution of Concrete Filled Steel Tube Reinforced Concrete Square Short Columns

The temperature distribution of concrete filled steel tube reinforced concrete (CFSTRC) square short columns was analyzed. Test results of four CFSTRC square short columns were reported in this paper. The specimens exposed to the ISO-834 standard fire without initial loads. The fire test lasted 180minutes. The influential factors included the side length of cross-section, slenderness ratio and steel tube area ratio. Finite element method (FEM) simulation was used to calculate temperature distribution of CFSTRC square short columns at elevated temperature. The test results show that the larger side length of cross-section, the lower temperature inside the specimens with the same fire exposure time and steel tube area ratio and height of specimens. Under the same fire exposure time and side length of cross- section and steel tube area ratio, the slenderness ratio was larger, and the temperature inside the specimens was lower. With the same fire exposure time and side length of cross-section and slenderness ratio, the steel tube area ratio had slight influence on temperature distribution inside the specimens. The FEM simulation results agreed well with the experimental results. The FEM simulation was capable of calculating temperature distribution of CFSTRC square short columns with an accuracy that was sufficient for design purposes.

Static, free vibration and stability analysis of three-dimensional nano-beams by atomistic refined models accounting for surface free energy effect

This work presents several higher-order atomistic-refined models for the static, free vibration and stability analysis of three-dimensional nano-beams. Stemming from a one-dimensional approach and thanks to a compact notation for the a priori kinematic field approximation over the beam cross-section, the model derivation is made general regardless the approximation order. This latter is a free parameter of the formulation. Several higher-order beam theories can be obtained straightforwardly. Classical beam models, such as Euler–Bernoulli’s and Timoshenko’s, are obtained as particular cases. The assumed constitutive equations for orthotropic materials account for the surface free energy effect as well as the third-order elastic constants. The resulting stiffness coefficients depend upon the cross-section side length. The governing equations and boundary conditions are variationally obtained through the Principle of Virtual Displacements. A Navier-type, strong form solution is adopted. Simply supported beams are, therefore, investigated. Static, free vibration and buckling analyses are carried out in order to investigate the effect of the cross-section side as well as the crystallographic plane orientation on the mechanical response. Beams with different values of the length-to-thickness ratio are considered. Results are validated in terms of accuracy and computational costs towards three-dimensional FEM solutions. Numerical investigations show the advantages of refined beam models over the classical ones demonstrating that accurate results can be obtained with reduced computational costs.

P.8.a.017 The revolving door phenomenon: an epidemiologic characterisation at a psychiatric department of a Portuguese university hospital

This work presents several higher-order atomistic-refined models for the static, free vibration and stability analysis of three-dimensional nano-beams. Stemming from a one-dimensional approach and thanks to a compact notation for the a priori kinematic field approximation over the beam cross-section, the model derivation is made general regardless the approximation order. This latter is a free parameter of the formulation. Several higher-order beam theories can be obtained straightforwardly. Classical beam models, such as Euler–Bernoulli’s and Timoshenko’s, are obtained as particular cases. The assumed constitutive equations for orthotropic materials account for the surface free energy effect as well as the third-order elastic constants. The resulting stiffness coefficients depend upon the cross-section side length. The governing equations and boundary conditions are variationally obtained through the Principle of Virtual Displacements. A Navier-type, strong form solution is adopted. Simply supported beams are, therefore, investigated. Static, free vibration and buckling analyses are carried out in order to investigate the effect of the cross-section side as well as the crystallographic plane orientation on the mechanical response. Beams with different values of the length-to-thickness ratio are considered. Results are validated in terms of accuracy and computational costs towards three-dimensional FEM solutions. Numerical investigations show the advantages of refined beam models over the classical ones demonstrating that accurate results can be obtained with reduced computational costs.

Experimental Study on Size Effect of Compressive Strength and Deformation Properties of Large Size Fly Ash Concrete

The authors experimentally studied the size effect of axial compressive properties of concrete cube and slenderness ratio of 2:1 prism with cross-section side length of 100mm to 800mm in this paper. Commercial concrete was used for test specimens. Specimens were cast and cured outdoors. To highlight the size factors, accumulation of sand on the end surface of the specimen was used to eliminate the end cyclo-hoop effect. The test results show that, in the case of eliminating the end restraint, failure modes of the prism and the cube are the same. There isn’t determined relationship between the cubic compressive strength and cylinder axial compressive strength of concrete, in the case of the specimen slenderness ratio not more than 2 to 1. However, the decline trend of cylinder axial compressive strength with size is slightly greater than the cubic strength. Fly ash concrete, ordinary concrete without fly ash and fiber reinforced fly ash concrete show different size effects. Size effect for concrete with 40% fly ash replacement of cement significantly reduced. The experimental results also show that, strength, elastic modulus and ultimate strain of concrete are all size-dependent. But there are different size effect trends between strength and deformation properties. Ultimate strain of concrete decreases as size increases, and more attention should be taken to this point.

Thin-walled curved hexagonal beams in crashes – FEA and design

This paper focuses on the crashworthiness analysis and crash responses of thin-walled curved beams with hexagonal cross sections. An optimal design of hexagonal cross-sectional profile of such curved beams are obtained based on the observations of typical crash responses of a series of thin-walled curved hexagonal beam samples. The optimised curved beam achieves maximum energy-absorption capability. Detailed finite element (FE) models and finite element analysis (FEA) method are employed to investigate the crash behaviour of the curved hexagonal beams and provide the observations for the optimum design. In this design optimisation problem, the specific energy absorption is set as the objective, and the cross-sectional side length and wall thickness are selected as two design variables. The design samples are selected from design space using factorial design method, and the design problem is formulated based on the FEA results of the design samples, by the use of design of experiments method. Afterwards, simplified FE models are developed for the design samples of the curved hexagonal beams and are applied for the same design problem. It is verified that the developed simplified models lead to the same optimal design as the detailed models. A parametric study is also performed to reveal the influences of the selected design variables on the overall structures' crash responses.

Experimental Investigations on Natural Convection Heat Transfer Around Horizontal Triangular Ducts

Experimental investigations have been reported on steady-state natural convection from the outer surfaces of horizontal ducts with triangular cross sections in air. Two different horizontal positions are considered; in the first position, the vertex of the triangle faces up, while in the other position, the vertex faces down. Five equilateral triangular cross-section ducts have been used with cross-section side length of 0.044, 0.06, 0.08, 0.10, and 0.13 m. The ducts are heated using internal constant-heat-flux heating elements. The temperatures along the surface and peripheral directions of the duct wall are measured. Longitudinal (perimeter-averaged) heat transfer coefficients along the side of each duct are obtained for natural convection heat transfer. Total overall averaged heat transfer coefficients are also obtained. Longitudinal (perimeter-averaged) Nusselt numbers and the modified Rayleigh numbers are evaluated and correlated using different characteristic lengths. Furthermore, total overall averaged Nusselt numbers are correlated with the modified Rayleigh numbers. Moreover, a dimensionless temperature group was developed and correlated with the modified Rayleigh number. For the upward-facing case, laminar and transition regimes are obtained and characterized. However, for the downward-facing vertex case, only the transition regime is observed. The local (perimeter-averaged) or the overall total Nusselt numbers increase as the modified Rayleigh numbers increase in the transition regime. However, Nusselt numbers decrease as the modified Rayleigh numbers increase in the laminar regime.

Numerical study of turbulent heat and fluid flow in a straight square duct at higher Reynolds numbers

This paper presents the large eddy simulation (LES) results of turbulent heat and fluid flows in a straight square duct (SSD) at higher Reynolds numbers ranged from 10 4 to 10 6 , which are based on the bulk mean velocity and the duct cross-sectional side length. A sub-grid model is proposed, which assumes that the sub-grid stress and heat flux are, respectively, proportional to the temporal increments of the filtered strain rate and temperature gradient, with the proportional coefficient determined by calibrating the friction factor. The temperature was taken as passive due to the neglect of buoyancy effect. The Taylor and Kolmogorov scales in the SSD are predicted and the results show that the LES results are better than c-DNS results. The LES results can explain why the c-DNS is applicable to the problem at a moderate Re, and reveal that the largest relative deviation of the overall mean Nusselt number is less than 10% as compared with existing experimental correlations. With the rise of Reynolds number, the mean secondary vortex pairs move towards the corners and have smaller size, while smaller vortices also occur in the instantaneous secondary flow. Empirical mode decomposition (EMD) was carried out to analyze the fluctuation of the x -averaged cross-sectional origin temperature at Re = 10 5 .

Cylinders with square cross-section: wake instabilities with incidence angle variation

The wakes behind square cylinders with variation in incidence angle are computed over a range of Reynolds numbers to elucidate the three-dimensional stability and dynamics up to a Reynolds number of Re = 300, based on the projected height of the inclined square cylinder. Three-dimensional instability modes are predicted and computed using a linear stability analysis technique and three-dimensional simulations, respectively. Depending on the incidence angle, the flow is found to transition to three-dimensional flow through either a mode A instability, or a subharmonic mode C instability. The mode A instability is predicted as the first-occurring instability at incidence angles smaller than 12° and greater than 26°, with the mode C instability predicted between these incidence angles. At a zero-degree angle of incidence, the wake instabilities closely match modes A, B and a quasi-periodic mode predicted in earlier studies behind square and circular cylinders. With increasing angle of incidence, the three-dimensional wake transition Reynolds number first increases from Re = 164 as the mode A instability weakens, before decreasing again beyond an incidence angle of 12° as the wake becomes increasingly unstable to the mode C instability, and then again to the mode A instability as the incidence angle approaches 45°. A spanwise autocorrelation analysis from computations over a cylinder span 20 times the square cross-section side length reveals that beyond the onset of three-dimensional instabilities, the vortex street breaks down with patterns consistent with spatio-temporal chaos. This effect was more pronounced at higher incidence angles.