Variation Of Deflection Research Articles

Cohesive zone approach to the cyclic response of cracked concrete beams reinforced with externally bonded FRP plate

To predict the cyclic response of concrete strengthened with FRP, this paper presents a new analytical solution, which uses the cohesive zone model (CZM). Based on the CZM, for intermediate crack-induced debonding, with intermediate flexural cracking of concrete beams repaired with FRP plate, the deteriorative effect of cyclic loading on the adhesive joints (interface) is investigated. To accomplish this aim, a cyclic damage process is coupled with a CZM to predict the cumulative damage evolution along the FRP-to-concrete interface as a function of the number of cycles. Comparing the results from the present model with those found in the literature shows that the constitutive model is able to accurately predict the overall cyclic loading response of concrete strengthened with FRP composites. The main advantage of the proposed model is that it gives the variation of the mid-span deflection, damage development, and interfacial stress distribution with increasing load cycles, and number of loading cycles. We conclude that cyclic degradation of the component materials significantly reduces the resistance and lifespan of the repaired structures.

Neural fields for rapid aircraft aerodynamics simulations

This paper presents a methodology to learn surrogate models of steady state fluid dynamics simulations on meshed domains, based on Implicit Neural Representations (INRs). The proposed models can be applied directly to unstructured domains for different flow conditions, handle non-parametric 3D geometric variations, and generalize to unseen shapes at test time. The coordinate-based formulation naturally leads to robustness with respect to discretization, allowing an excellent trade-off between computational cost (memory footprint and training time) and accuracy. The method is demonstrated on two industrially relevant applications: a RANS dataset of the two-dimensional compressible flow over a transonic airfoil and a dataset of the surface pressure distribution over 3D wings, including shape, inflow condition, and control surface deflection variations. On the considered test cases, our approach achieves a more than three times lower test error and significantly improves generalization error on unseen geometries compared to state-of-the-art Graph Neural Network architectures. Remarkably, the method can drastically accelerate high fidelity numerical solver, achieving a five order of magnitude speedup on the RANS transonic airfoil dataset.

Assessment of dynamic response of armor grade steel plates and FMLs under air-blast loads

This numerical study represents an effort to characterize the dynamic behavior of distinct armor-grade steel plates and fiber metal laminates (FMLs) of the same masses under blast loads. The blast resistance of finite element models of square steel plates and FMLs is evaluated by applying conventional weapon effects program air-blast loading ranging from 1 to 3 kg of trinitrotoluene (TNT) at a fixed stand-off distance (SoD) of 0.1 m. A user-defined subroutine is used to implement a failure criterion to determine realistic failures in the composite. A variation of kinetic energy, radial deflection, and energy absorptions of the steel plates and FMLs are determined to discover their blast mitigation performance. The deformation modes and equivalent plastic strain of both the steel plate and FMLs are also compared. The obtained results show that the armor-grade AISI 4340 steel has up to 50.5% smaller peak deflection than the other armor-grade steels. The use of FML with multi-thin layers of composite laminate and steel sheets instead of equivalent AISI 4340 steel plate significantly reduces the peak deflection up to 23.9% under similar blast loading conditions. The findings of steel plates and FMLs also represent their applicability for making complex protective structures.

Effect of bioprosthetic leaflet anisotropy on stent dynamics of Transcatheter Aortic Valve Replacement devices

The assessment of stent fatigue in Transcatheter Aortic Valve Replacement (TAVR) systems is critical for the design of next-generation devices, both in vitro and in vivo. The mechanical properties of the bioprosthetic heart valves (BHVs) have a significant impact on the fatigue life of the metallic stent and thus must be taken into consideration when evaluating new TAVR device designs. This study aims to investigate the relationship between BHV anisotropic behaviour and the asymmetric deflections of the stent frame observed during in vitro testing.An explicit dynamics finite element model of the nitinol stent with attached bioprosthetic valve leaflets was developed to evaluate the deflections of the TAVR device under haemodynamic loading. Our results demonstrate that pericardium behaviour plays a dominant role in determining stent frame deflection. The anisotropic behaviour of the leaflets, resulting from collagen fibre orientation, affects the extent of deflection encountered by each commissure of the frame. This leads to asymmetric variation in frame deflection that can influence the overall fatigue life of the nitinol stent. This study highlights the importance of considering both the flexible nature of the metallic stent as well as the leaflet anisotropic behaviour in the design and fatigue assessment of TAVR systems.

Effect of Al7075 and activated carbon reinforced composite on optimizing WEDM responses

This paper presents wire cut electrical discharge machining (WEDM) response characteristics of Aluminium 7075 (Al7075) reinforced with powdered activated carbon (PAC) composite. In recent days WEDM has become a significant machining process in targeting its benefits of contributing improved material removal rate (MRR) and low surface roughness (SR). This is due the rising need for intricate, accurate, and superior structural components, the WEDM process emerges as a formidable alternative to traditional machine tools. In this work Pulse-on time (Ton), pulse-off time (Toff), discharge current (IA) and servo speed rate (SS) are the variables to be given as input and machining responses such as MRR and SR are studied. From Analysis of Variance (ANOVA) study it is found that discharge current and servo speed is the significant parameters. The optimal desirability condition is obtained with input parameters Ip: 2000 mA; Ton: 8.9 μs; Toff: 25 μs and SS: 150 rpm for the precision machining. The optimum response parameters are found as MRR 10.46 mm3/min and SR 3.32 μm. Results shows that the model designed for the prediction of MRR produces an above 98.27% and the prediction of SR is above 97.17%. The error percentage among the experimental and predicted MRR and SR were estimated. Additionally confirmatory test is performed with optimal results achieved from response surface methodology (RSM) and desirability technique. Metallurgical tests like electron backscatter diffraction analysis (EBSD) and microstructure are conducted to confirm the surface properties and atomic force morphology (AFM) analysis is applied to clarify the structural features of machined composites. The results revealed that the variation of hard deflection is caused by depression of eroded materials on the top layers of machined surface.

Numerical investigation of the effect of longitudinal steel reinforcement ratio on the ductility of concrete beams

Abstract This research aims to use numerical methods to analyze concrete beams with different reinforcement ratios. Two software packages – ABAQUS and OpenSeesPy – were employed to achieve this task. Empirical stress–strain relationships were utilized to forecast the concrete’s stress–strain behavior. The numerical analysis results were compared with previously published experimental results, and the findings showed a reasonable similarity. The results were consistent with the published laboratory results, particularly for ultimate and yield loads, with no more than 10% differences. However, the ultimate deflection variation was higher. For the first control beam, denoted as B 2−12, ABAQUS predicted a 24.64% difference in ultimate deflection, while OpenSeesPy predicted a 35.83% difference for the second beam, sampled as B 2–16. However, the ultimate deflection for the remaining beams differed by less than 10%. Meanwhile, the difference in yield deflection was greater than in ultimate deflection, with OpenSeesPy showing a maximum difference of 18.51%. The maximum ductility was found to occur at a reinforcement ratio equal to 0.0016. Additionally, OpenSeesPy was faster than ABAQUS in computation while still producing satisfactory agreement with experimental results.

Monitoring damage of concrete beams via self-sensing cement mortar coating with carbon nanotube-nano carbon black composite fillers

Self-sensing concrete used in coating form for structural health monitoring of concrete structures has the merits of cost-effectiveness, offering protective effect on structural components, enabling electrical measurements unaffected by steel reinforcement and is also convenient to maintain and replace. This paper investigates the feasibility of using self-sensing cement mortar coating containing carbon nanotube-nano carbon black (CNT-NCB) composite fillers (CNCFs) for damage monitoring of concrete beams. The self-sensing cement mortar coated to concrete beams demonstrated outstanding electrical conductivity (resistivity ranging from 18 to 85 Ω·cm). Under monotonic flexural loadings, self-sensing cement mortar coating with 1.8 vol.% CNCFs featured sensitive self-sensing performance in terms of capturing the initiation of vertical cracks at pure bending span of concrete beams, with fractional change in resistivity (FCR) reaching up to 60.6%. Moreover, FCR variations of self-sensing cement mortar coating exhibited good synchronization and stability with the variation of mid-span deflections of concrete beams during cyclic flexural loadings irrespective of the contents of CNCFs and cyclic amplitudes. Remarkably, it was found that FCR of cement mortar coating basically showed a progressive upward tendency, representing irreversible increase in the resistance during cyclic loading. The irreversible residual FCR indicated the crack occurrence and damage accumulation of concrete beams.

The Influence of the Variation in Arch Height of the Main Tayan Bridge on the Member Forces

The height of the bridge arch significantly impacts the strength and structural efficiency. Research on the height of the Tayan Bridge arch was conducted to determine the values and behaviour of member forces, structural weight, and deflection and to design the optimal arch height geometry. This research involved five variations of the arch height. The bridge structure was modelled using AutoCAD software. Relevant bridge loading data based on the SNI 1725-2016 standard was inputted into AutoCAD for structural design, and then the structure was modelled and analysed using SAP2000. The analysis results provided information on the bridge weight, deflection, and member forces. The analysis results were then compared with the bridge arch height, and this comparison was presented in the form of graphs. From the analysis results, it can be concluded that the bridge arch height has a positive linear relationship with the bridge weight. Tensile and compressive forces exhibit opposite behaviour. Increasing the arch height with constant value results in weight, deflection, and member force variations. Constantly expanding the arch height also does not lead to an increase in the stiffness of the bridge. Structurally, the optimal arch height is 42.134 meters.

Bending Behavior of Clamped Skew Plates

The deflection analyses performed using MSC/NASTRAN on skew plates under different loads such as (concentrated and uniformly distributed loads) for clamped boundary conditions are presented in the present study. The CQUAD4 and CQUAD8 components of MSC/NASTRAN are verified using values from the literature. The CQUAD8 element was employed in the present experiments because it had been found to produce more effective results than the CQUAD4 element. For isotropic skew plates, the variation of deflection with regards to aspect ratio and length to thickness ratio is provided. With an increase in the skew angle, it appears that the deflections decrease.

Study on the Influence of Geometric Parameters and Shape Optimization of Single Tenon Joint in Assembled Subway Station

The various components of fully prefabricated metro stations are mainly connected using grouted tenon and mortise joints. Therefore, studying the mechanical properties of the joint locations is of significant importance for the overall safety and stability of the station. This paper focuses on the single tenon-long joint as the research object and applies an orthogonal experiment plan to investigate the relationship between the lower bottom length, upper bottom length, and height of the joint and its flexural load carrying capacity. After comparing various loading methods, uniformly distributed loads are chosen as the method for applying axial forces and bending moments. The objective is to determine the dimensions of the tongue and groove that exhibit optimal mechanical properties based on the law of opening displacement and maximum deflection variation with bending moment. The influence of geometrical parameters on the flexural strength of tenon joints is analyzed by means of range analysis in order to find the combination of geometrical parameters with the best mechanical properties. The degree of influence of each geometrical parameter was also ranked. Using these insights, the authors proposed a modified cross-shaped tenon based on the optimal combination of geometrical parameters, which was verified by comparing the M–θ curves of the optimal combination and the optimum working condition. The main conclusions are as follows: (1) the ranking of the geometric parameters of the joint in terms of their influence on the flexural capacity is as follows: height has a greater impact than the bottom length, and the bottom length has a greater impact than the top length. Among these parameters, the influence factor of the height is significantly greater than the other two. (2) The optimum geometry for the tenon and mortise joint is 385 mm for the lower bottom length, 230 mm for the upper bottom length, and 200 mm for the height; the joint’s ratio of height to total width should be 25%, the ratio of lower bottom length to total width should be 48%, and the ratio of upper bottom length to total width should be 29%. (3) The load carrying capacity of the cross-shaped tenon is significantly higher than that of the optimal combination and optimum working condition, providing a significant improvement. This research’s results will serve as a valuable reference for designing assembly nodes in prefabricated assembly metro stations.

Size-dependent bending and buckling of two-dimensional functionally graded microplates, an artificial neural network approach

The main goal of the present study is to focus on the application of artificial neural network (ANN) in predicting the bending and buckling behaviors of size-dependent small-scale micro-plates. To this end, the recently introduced thick microplates made of two-dimensional functionally graded materials (2D-FGM) with simply supported boundary conditions are considered. Adopting the modified couple stress and third-order shear deformation theories together with the Ritz method, the bending and buckling ANN models, including nine and ten input variables, are trained by two databases containing 8842 and 9980 random data for each of these two analyses, respectively. The selected network has six hidden layers, each of them contains 32 nodes. Employing the present ANN model, whose determination coefficient is 98.6%, the variation of microplate deflection and its buckling load versus the input variables are investigated. It is observed that despite the long run-time and the complexities involved in the solution procedures associated with the governing equilibrium and eigenvalue equations, the ANN models enjoy fast and accurate predictions. The rest of the present work is devoted to optimizing the geometric and material variables of a 2D-FGM microplate with respect to the buckling load via the genetic algorithm (GA) method whose fitness function is evaluated by the trained ANN. The results reveal that the combination of the ANN and GA can be treated as a promising tool for optimizing the geometric and material parameters of a 2D-FGM microplate regarding its buckling load.

Experimental Study on the Damage Mechanism of Reinforced Concrete Beams Based on Acoustic Emission Technique

The purpose of this paper is to investigate the developmental process of internal damage in prestressed concrete beams under static loading conditions. We conducted static loading tests on two prestressed reinforced concrete beams and one ordinary reinforced concrete beam. Acoustic emission (AE) technology was employed to dynamically monitor the entire process of the test beams simultaneously. The energy and ring count AE characteristic parameters were studied, and the frequency domain characteristics of acoustic emission signals from three test beams were analyzed. The actual failure process of the test beams was compared with the AE characteristic parameters and the waveform frequency distribution. Furthermore, the corresponding relationships between the actual failure process and the AE characteristic parameters were analyzed. Additionally, the frequency distribution of waveforms was examined. The obtained data, including deflection, strain, and prestress variation within the beams, were combined with theoretical calculations to explore the damage development law of simply supported reinforced concrete beams during the entire failure process. Comparative studies revealed a strong correlation between the actual failure processes of the three test beams and the AE characteristic parameters as well as the waveform frequency distribution. The strain variation trend of the ordinary reinforced concrete beam closely matched the AE signal characteristics, with the critical load often occurring at around 40% of the ultimate load. The strain and deflection variations of the prestressed reinforced concrete beams exhibited a robust correspondence with the AE signal characteristics. The critical load typically manifested at approximately 80% of the ultimate load. The ultimate load of the prestressed reinforced concrete beams decreased by approximately 20% under cyclic loading conditions compared to hierarchical loading.

Natural element hierarchical models for static and free vibration analysis of cylindrical panels

Most of studies on the hierarchical models were restricted to beam- and plate-like structures using the finite element method. In this context, this study intends to present the hierarchical models for cylindrical panels and investigate their characteristics using 2-D natural element method (NEM). The displacement field of cylindrical panel is decomposed into the triple-vectored in-plane functions and the assumed thickness polynomials, and the hierarchical models are defined by sequentially increasing the maximum orders of thickness polynomials from (1,1,0). The triple-vectored in-plane functions are approximated by applying 2-D NEM to the unfolded rectangular plane of curved mid-surface of cylindrical panels, for which the stiffness matrices corresponding to the membrane and transverse strains and stresses are calculated using the selectively reduced integration technique to avoid shear-membrane locking. The hierarchical models are demonstrated and validated from the comparative numerical experiments of bending and free vibration of cylindrical panels. The present hierarchical models provide the central deflections and the natural frequencies which are in good agreement with the reference solutions. In addition, the characteristics of hierarchical models such as the limit property and the modeling and approximation errors are investigated with respect to the model level and the width-thickness ratio and the grid density. It is found that the hierarchical models show the locking-free robust and spectral variation in the central deflection and natural frequencies.

Static Behaviour of Laminated Composite Shells Containing Piezoelectric Actuators and Sensors

The behavior of laminated composite shells with piezoelectric actuators and sensors subjected to external load and electric potential is investigated. The analysis is carried out using the finite element method based on first-order shear deformation theory. An eight nodded degenerated isoparametric shell element with five degrees of freedom at each node is considered. Results are presented for the variation of deflection and stresses in the simply supported laminated composite cylindrical shell panel subjected uniform normal pressure and electric potential.

Switchbacks, microstreams, and broadband turbulence in the solar wind

Switchbacks are a striking phenomenon in near-Sun coronal hole flows, but their origins, evolution, and relation to the broadband fluctuations seen farther from the Sun are unclear. We use the near-radial lineup of Solar Orbiter and Parker Solar Probe during September 2020 when both spacecraft were in wind from the Sun's Southern polar coronal hole to investigate if switchback variability is related to large scale properties near 1 au. Using the measured solar wind speed, we map measurements from both spacecraft to the source surface and consider variations with source Carrington longitude. The patch modulation of switchback amplitudes at Parker at 20 solar radii was associated with speed variations similar to microstreams and corresponds to solar longitudinal scales of around 5°–10°. Near 1 au, this speed variation was absent, probably due to interactions between plasma at different speeds during their propagation. The alpha particle fraction, which has recently been shown to have spatial variability correlated with patches at 20 solar radii, varied on a similar scale at 1 au. The switchback modulation scale of 5°–10°, corresponding to a temporal scale of several hours at Orbiter, was present as a variation in the average deflection of the field from the Parker spiral. While limited to only one stream, these results suggest that in coronal hole flows, switchback patches are related to microstreams, perhaps associated with supergranular boundaries or plumes. Patches of switchbacks appear to evolve into large scale fluctuations, which might be one driver of the ubiquitous turbulent fluctuations in the solar wind.

Fatigue fracture mechanics in gold-based MEMS notched specimens: experimental and numerical study

The characterization of fatigue fracture mechanics in gold-MEMS notched specimens is presented in this work. A test microstructure with a central notched specimen is specifically designed and built to perform on-chip fatigue test. The central specimen undergoes cyclic loading due to the application of alternating voltage. The variation in the microstructure deflection is measured using an optical profilometer and is attributed to the crack growth in the gold material, causing the variation in the specimen stiffness. The occurrence of pull-in condition is used as a fracture detector, then the fracture of the specimen can be recognized without performing scanning electron microscope inspections during the fatigue test. Crack propagation in the test specimen is simulated through a coupled-field electromechanical fracture finite element model and the resulting crack path is compared to the experimental measurments performed with scanning electron microscope analyses. Finally, Paris’ law is applied and the number of cycles to failure is computed by exploiting the results of the fracture model and experimental measurements. Both experimental and numerical results demonstrate that the notch acts as a stress and strain raiser, fostering crack nucleation, and that the linear elastic fracture mechanics theory is still valid to describe crack propagation in micro-size samples.

ANSYS based Modal Analysis of a Fixed Beam of Uniform Cross Section with a Concentrated Mass at Mid Span

The report outlines ANSYS based modal and structural analysis of a fixed beam of dimension 20mm*20mm*1000mm that was constructed in SOLIDWORKS. Structural steel was selected as the material for analysis. The analysis was done in 3 phases, the first analysis was done without any crack and the other two analysis involved cracked beams with cracks created at different lengths. Suitable boundary and loading conditions were used to find the modes of frequencies. The resulting variation in static deflection, position of mode shapes representing transverse deflection and variation in position of equivalent stress corresponding to varying beam conditions with and without cracks are studied.

Experimental and numerical studies on shear behavior of lattice-web reinforced PET foam sandwich panels

To solve the problem that traditional lightweight core sandwich structure is prone to core brittle failure and interface debonding, innovative sandwich panels with fiber reinforced polymer (FRP) as facings and lattice-webs, and polyethylene terephthalate (PET) structural foam as the core were designed. Five composite sandwich panels with different thicknesses of cores and facings were fabricated by vacuum infusion molding process. Three-point bending test was carried out to survey the shear properties of panels, such as failure modes and load–deflection variation laws, which disclosed that the ultimate shear loads of the sandwich panels could be increased by 96.1% and 25.5% by heightening the thickness of the foam core from 40 mm to 80 mm and adding (0,90°)/(±45o) layers. Theoretical formulas were then put forward to calculate the ultimate loads, and the error between theoretical and test values was within 10%. Finally, the shear mechanical characteristics of the sandwich panels under the three-point bending test were simulated with the finite element software ANSYS, and the change rules of the bearing capacity and deformation of the sandwich panels under various test parameters were obtained. Parametric analysis proved that increasing the lattice-webs thickness by one factor can heighten the ultimate shear value of sandwich panels by 95.9%, and longitudinal lattice-webs spacing greatly influenced the ductility performance of panels.

Sensitivity Analysis of Deflection Variation of the Cable-Stayed Bridge to the Cable Damage

In the context of a single-tower cable-stayed bridge, the effects of the ambient temperature change, stiffness degradation of the main beam and cable damage on the deflection of the main girder under the action of self-weight are investigated. To explore the possibility of identifying cable damage based on the deflection of the main girder, the results show that before and after the cable damage, the variation of the deflection difference of the girder has obvious characteristics: under the action of dead weight, the distribution curve of the deflection difference of the girder is obviously twisted at the anchorage point of the damaged cable and reaches a peak, and the peak value increases with the increase of the cable damage degree. The deterioration of the girder’s performance will make the change of the girder’s deflection more sensitive to the cable damage. The ambient temperature change has a great influence on the deflection of the girder but has no obvious influence on the deflection difference of the girder before and after the cable damage.

Experimental Study on the Influence of Stress Concentration on the Flexural Stability of Aluminum Hollow Tube

Solid sections are gradually replaced by the hollow sections in most of the structural applications in various engineering fields due to their attracting features such as light-weight and high specific strength. In the present investigation, one such attempt was made to investigate in detail about the flexural capability of an aluminum hollow tube (AHT) with square cross section. The objective of the investigation is to study about the influence of stress concentration on the flexural behavior of the hollow tube. The type of stress concentration considered in the investigation was through hole of different cross section and quantity. Three-point bending test with concentrated load is conducted on the specimens of hollow tube with different types of stress concentration such as circular hole, square hole and perforations. The load was applied manually during the bending test. The bending test was carried out on all specimens for various support span of 110, 130, 170 and 200 mm respectively. The output measures of the study are maximum bending load, deflection and flexural stiffness. The maximum bending load capacity around 5.7 kN was observed for AHT with circular hole with support span of 90 mm. The maximum deflection measured at the mid span of the beam increases rapidly when the aspect ratio increases from 73.33 to 93.33, whereas after which the variation of deflection is marginal for the increase in aspect ratio from 113.33 to 133.33. This was due to the effect of spring back, which dominates more on the bending behaviour at shorter span between the supports