Finite Element Numerical Model Research Articles

Feasibility Study on the Effect of FRP Shear Reinforcements on the Behaviour of FRP-Reinforced Concrete Deep Beams

Unlike steel reinforcements in concrete, Fiber Reinforced Polymer (FRP) materials are light and free from corrosion. Therefore, FRP materials are increasingly being used in structural engineering as a replacement for steel reinforcements. While the use of FRP bars as longitudinal reinforcements in concrete deep beams has been studied somewhat widely, their use and effectiveness as web reinforcements are not well studied. In this study, the effect of the FRP web reinforcements on the behaviour and strength of FRP-reinforced concrete deep beams were investigated in an experimental study. Four glass fiber-reinforced concrete (RC) simply supported deep beam specimens were tested under a concentrated load with different shear span-to-depth ratios and web reinforcement ratios. The behaviour of the deep beams was described in terms of load–deflection behaviour, crack developments, strain in FRP reinforcements, and failure modes. The experimental investigation emphasized the significance of web reinforcements in determining the reinforced concrete deep beam behaviour, such as mid-span deflection, crack breadth, failure modes, and ultimate strengths. Furthermore, to predict the behavior of deep beams, numerical Finite Element models using Abaqus software were created. The present test results were compared to those predicted using the Finite Element models. This investigation shows that web reinforcement is quite important for FRP-RC deep beams to achieve a robust behaviour by enhancing its capacity and deformability.

Influence of landform on the pressure distribution of explosion shock wave

The explosion site terrain and geomorphic environment will directly affect the shock wave pressure propagation and attenuation law and the shock wave test results uncertainty evaluation. In this study, the explosion site topographic and geomorphic parameters were analyzed, and the slope ratio and elevation difference within the region were proposed to parameterize the test site topographic and geomorphic characteristics. Using multi-physical field coupling simulation software, the finite element numerical simulation model of acoustic-solid structure coupling with different elevation difference and slope ratio is established and relevant research is carried out. The results show that when the pressure monitoring point is located at the test site low position, the elevation difference plays a role in attenuation of the shock wave pressure peak value, and vice versa; With the increase of the test site slope ratio, the shock wave pressure peak value at different test points gradually increases, and with the increase of the distance between the test points, the impact degree gradually decreases. Therefore, the elevation difference and slope ratio of the site shall be reduced as much as possible during the explosion shock wave pressure test, so as to improve the shock wave pressure test accuracy and the test data reliability, and provide theoretical support for the shock wave pressure test results uncertainty evaluation in the explosion field.

Experimental Study on Repairing the Mechanical Characteristics of Oil-Contaminated Silty Clay in Ancient Dike with Modified Lime Mortar.

Flood-controlled ancient dikes play a significant role in flood control and have received widespread attention as historical and cultural symbols. Flood-controlled ancient dikes often undergo disasters, and research on their repair is receiving increasing attention from experts and scholars. This article studies the control of seepage and bank slope instability in flood-controlled ancient dikes. Starting from the repair of ancient dike materials, three types of work are carried out: a test of soil's mechanical properties, finite element numerical simulation, and repair technology research. The research results show that the soil of the ancient dike site has hardened after being contaminated with waste oil from catering. The strength index of the ancient dike soil decreases and shows brittleness when the water content is 15% and the oil content exceeds 6%. The strength index and permeability coefficient of oil-contaminated soil improved using modified lime mortar (MLM), which was achieved using the method of MLM to repair oil contaminated soil. When the MLM content was 10% and the oil content was 6%, the friction angle of the soil sample reached its maximum value. When the MLM content was the same, the higher the density of the soil sample, the greater the friction angle and cohesion and the smaller the permeability coefficient. Establishing a finite element numerical model, through comparative analysis, it was found that after MLM remediation of oil-contaminated soil, the extreme hydraulic gradient of the ancient dike decreased by 31.3%, and the extreme safety factor of the bank slope stability increased by 31.2%. MLM pressure grouting technology was used to improve the soil during the remediation of contaminated soil at the ancient dike site. Through on-site drilling inspection, the effective diffusion radius of MLM grouting was obtained, and the plane layout and grouting depth of MLM pressure grouting were determined. The on-site water injection permeability test showed that using MLM pressure grouting technology can effectively repair oil-contaminated soil in the ancient dike while reducing the permeability coefficient by 8-15%.

Reduction of the warping of a silicon wafer coated with two thin layers by minimal geometric modifications

Purpose The aim of this study is to make a contribution towards reducing the deflections of silicon wafers. The deformation of silicon wafers used in the manufacture of electronic micro-components is one of the most common problems encountered by industrialists during manufacturing. Stack warping is typically produced during the process of depositing thin layers on a substrate. This is due to the thermal-mechanical stresses caused by the difference between the thermal expansion coefficients of the materials. Reducing wafer deformation is essential to increase reliability and improve quality. In this paper, the authors propose an approach based on minimal geometrical modifications to reduce the deformation of a silicon wafer coated with two thin layers. Numerical finite element models have been developed to evaluate the impact of geometrical modifications on warping amplitude. Finite element models have been validated compared with experimental models. The results obtained are encouraging and clearly show a considerable reduction in wafer deformation. Design/methodology/approach Reducing wafer deformation is essential to increase reliability and improve quality. In this paper, the authors propose an approach based on minimal geometrical modifications to reduce the deformation of a silicon wafer coated with two thin layers. Numerical finite element models have been developed to evaluate the impact of geometrical modifications on warping amplitude. Finite element models have been validated compared with experimental models. Findings The results obtained are encouraging and clearly show a considerable reduction in wafer deformation. Originality/value This paper describes the influence of geometric modification on wafer deformation. The work show also the cruciality of stress reduction in the purpose to obtain less wafer deformation.

An efficient deep learning model to predict the structural response of CFRP isogrid tubes

Several sectors have increased the use of lattice structures due its great capacity to reduce the structural mass with reasonable rigidity loss. However, these structures can present complex mechanical behaviors, impossible to be determined analytically. Surrogate models obtained from design of experiments have been shown to be promising but insufficient. Numerical models using finite elements are computationally expensive when optimization model updating is considered. In order to solve these problems, in this paper a deep learning model is trained in order to predict 16 different structural responses (static, dynamic and stability) of a complex composite isogrid structure tube. All input data were generated from a numerical finite element model. The results demonstrated substantial capacity of the deep learning model to fit the isogrid physical behavior and also predict the structural responses. In addition, it was also to predict the design parameters of the isogrid structure from the desired results, also demonstrating the good performance (R2 > 90 %) of the artificial intelligence model to perform this prediction.

Analysis of a Motocross Knee Brace: From the Real Model to the Numerical Finite Element Model via 3D Scanning and Reverse Engineering

Musculoskeletal injuries often occur when performing motocross; almost half of the overall ligamentous injuries (42%) are knee ligaments injuries. Lesions can be greatly reduced with knee braces. Commercial knee braces are expected to oppose and limit unwanted and potentially harmful movements such as hyperextension and excessive rotation of the knee joint. However, this aspect has not been fully investigated from a biomechanical point of view. This would require proper Finite Element Modelling (FEM) and Analysis (FEA). However, to perform FEA and evaluate the efficacy of the brace simulating sportive conditions, numerical models need to be built. It requires a dedicated setup and several preprocessing steps, for which no industrial standard or widely accepted better practise is available as of today. Firstly, the brace and the lower limb are scanned using a 3D scanner. The geometry is reconstructed using reverse engineering techniques. These allow us to obtain a smooth, reliable 3D model starting from the points cloud acquired during scanning. A lower limb model was created using a mixed approach, combining MRI data and 3D scanning. Finally, a simulation of the impact condition after a jump using the developed model was carried out.

Numerical Simulation of Flood Control Levee Deformation by Shield Tunnel Excavation through the Liuyang River: A Case Study

The interval section of the Liuyang River flood control levee project of the Changsha Metro Line 6 is used as the engineering background of this study. A three-dimensional finite element numerical model of a tunnel shield containing complex interfaces is established by using the multifield coupling software COMSOL. The paper studied the deformation of flood control levees under shield tunnel excavation working conditions. The results show that when the left line shield machine is excavated below the Liuyang River flood control levee, the deformation of the flood control levee and the surrounding rock of the tunnel is biased towards the built right line tunnel. And it has an impact on the bridge pile near the tunnel. When the shield of the left line crosses the flood control levee, it can easily cause a large deformation and displacement of the levee above the area between the two shields. To ensure the controlled deformation of the levee, the construction should ensure the spacing between the two tunnel palm faces as far as possible and should be far away from other structures on the levee. When the shield crosses the levee, the deformation that occurs at the base of the levee is significantly higher than the deformations that occur at other locations of the levee. Displacement monitoring and secondary reinforcement at the base of the flood control levee appear to be necessary. The numerical simulation results validate the feasibility of using the multifield coupling software COMSOL to study the construction modeling of shield tunnels through rivers and its advantages. This method provides a practical framework for similar tunnel performance engineering or displacement monitoring in future projects.

A Numerical Study of the Damage Mechanisms for CT Tensile Specimens of P265GH Steel Material

The aim of this paper is to determine the damage mechanisms of P265GH steel, commonly used for pressure equipment. First, an experimental study using tensile and Charpy tests allowed us to determine the mechanical properties (Young modulus E = 200 GPa, elongation ε = 35%, yield se = 320 MPa, ultimate stress su = 470 MPa, and KIC = 96 MP√m). Then, numerical finite element modeling on a CT specimen using the CASTEM calculation code allowed us to determine the damage of the material when the notch depth varies. The analysis of the results shows that the numerical values of the stress concentration coefficient Kt and the stress intensity factor KI are comparable with the analytically calculated values, thus validating our numerical study. The numerical results obtained revealed that the maximum stress σmax is located in the vicinity of the notch bottom and the high probability density corresponds to a high loading level.

Theoretical and numerical modeling of Rayleigh wave scattering by an elastic inclusion

This work presents theoretical and numerical models for the backscattering of two-dimensional Rayleigh waves by an elastic inclusion, with the host material being isotropic and the inclusion having an arbitrary shape and crystallographic symmetry. The theoretical model is developed based on the reciprocity theorem using the far-field Green's function and the Born approximation, assuming a small acoustic impedance difference between the host and inclusion materials. The numerical finite element (FE) model is established to deliver a relatively accurate simulation of the scattering problem and to evaluate the approximations of the theoretical model. Quantitative agreement is observed between the theoretical model and the FE results for arbitrarily shaped surface/subsurface inclusions with isotropic/anisotropic properties. The agreement is excellent when the wavelength of the Rayleigh wave is larger than, or comparable to, the size of the inclusion, but it deteriorates as the wavelength gets smaller. Also, the agreement decreases with the anisotropy index for inclusions of anisotropic symmetry. The results lay the foundation for using Rayleigh waves for quantitative characterization of surface/subsurface inclusions, while also demonstrating its limitations.

ANALYTICAL MODEL AND NUMERICAL FINITE ELEMENT MODEL FOR A SUBMERSIBLE SYNCHRONOUS HYDROGENERATOR

The main objective of the paper is to demonstrate the functionality and reliability of a hydrokinetic turbine system – a submersible electric generator, suitable for very low watercourses. To achieve this goal, it is necessary to design and build a prototype of a hydrokinetic turbine, coupled with an electric generator with excitation made with permanent magnets. This paper presents an analytical model and a finite element numerical model for estimating the electrical parameters of the generator (voltage, current, power, etc.). The two models were compared, and the results were extrapolated, in the analytical model, for several speed values.

Study of flow field and vibration characteristics of supersonic centrifugal impellers based on fluid-structure interaction

PurposeThere are three purposes in this paper: to verify the importance of bi-directional fluid-structure interaction algorithm for centrifugal impeller designs; to study the relationship between the flow inside the impeller and the vibration of the blade; study the influence of material properties on flow field and vibration of centrifugal blades.Design/methodology/approachFirst, a bi-directional fluid-structure coupling finite element numerical model of the supersonic semi-open centrifugal impeller is established based on the Workbench platform. Then, the calculation results of impeller polytropic efficiency and stage total pressure ratio are compared with the experimental results from the available literature. Finally, the flow field and vibrational characteristics of 17-4PH (PHB), aluminum alloy (AAL) and carbon fiber-reinforced plastic (CFP) blades are compared under different operating conditions.FindingsThe results show that the flow fields performance and blade vibration influence each other. The flow fields performance and vibration resistance of CFP blades are higher than those of 17-4PH (PHB) and aluminum alloy (AAL) blades. At the design speed, compared with the PHB blades and AAL blades, the CFP blades deformation is reduced by 34.5% and 9%, the stress is reduced by 69.6% and 20% and the impeller pressure ratio is increased by 0.8% and 0.14%, respectively.Originality/valueThe importance of fluid-structure interaction to the aerodynamic and structural design of centrifugal impeller is revealed, and the superiority over composite materials in the application of centrifugal impeller is verified.

Effects of different test methods on the seismic dynamic response in inclined liquefiable soil

According to horizontal liquefiable free-field shaking table test carried out by the research group, a finite element numerical model of horizontal liquefiable free-field is established based on OpenSees finite element platform, and the influence of the model box on dynamic response of soil is considered in this numerical model, and the reliability of numerical model is verified by comparing with the shaking table test results. The inclined liquefiable free-field finite element calculation model is established based on the horizontal numerical model, and three different numerical models of inclined shear box model, inclined soil in shear box model and inclined soil in rigid box model are established to simulate the different test methods adopted in the shaking table test. Through comparison, the dynamic response results of free-field soil calculated by three numerical models under the action of 0.3g Wenchuan earthquake Wolong wave are analyzed, and the influences of three different test methods on the calculation results are discussed, and the results showed that the response of the lateral displacement of soil by two test methods of inclined shear box and inclined soil in shear box have great differences, and the maximum difference value can reach 45%; the response obtained by the two test methods of inclined soil in rigid box and in layer shear box have more obvious differences in pore water pressure lateral displacement and acceleration of soil.

Experimental study on long-term behavior of PSC beams

The present study reports the experimental investigations of the long-term strains in two PSC beams, one bonded and one unbonded, having the same cross-section and concrete mix, subject to the same prestress and environmental conditions. In addition, control specimens in the form of one unloaded prism specimen of the same cross-section, and two standard cylinders, one loaded axially and the other unloaded, were also monitored for the same time duration of 250 days. Electrical strain gauges and fiber optic sensors were used for strain measurement, and the results show that they agree well with each other. The ACI 209 model is found to have the least error in the prediction of axially loaded cylinder creep and shrinkage strains. However, all the prediction models (assuming constant stress) are found, in general, to overestimate the creep and shrinkage strains, and the overall loss in prestress in the two PSC beams. When the loss in prestress is incorporated, using a 3D finite element numerical model, the prediction is found to improve significantly in all the models, and particularly in the case of the GL 2000 and MC2010 models. Alternatively, improved predictions can be obtained by using the compliance from cylinder creep data and the shrinkage strains from a control specimen (having the same volume-to-surface ratio) for predicting the strains in PSC beams; this is found to yield good results.

An Analysis of Numerical Homogenisation Methods Applied on Corrugated Paperboard

Corrugated paperboard is a sandwich structure composed of wavy paper (fluting) bonded between two flat paper sheets (liners). The analysis of an entire package using three-dimensional numerical finite element models is computationally expensive due to the waved geometry of the board that requires the use of a relatively large number of elements in a simulation. Because of this, homogenisation approaches are used to evaluate equivalent homogenous models with similar material properties. These techniques have been successfully implemented by various researchers to evaluate the strength of corrugated paperboard. However, studies analysing the various homogenisation techniques and their ranges of applicability are limited. This study analyses the application of three homogenisation techniques: classical laminate plate theory, first-order shear deformation theory and deformation energy equivalence method in the evaluation of effective elastic material properties. In addition, inverse analysis has been applied to determine the effective properties of the board. Finite element models have been used to evaluate the accuracy of the three homogenisation techniques in comparison to the inverse method in modelling four-point bending tests and the results reported.

Model validation and dynamic simulation of post-combustion carbon dioxide separation with membranes

This work presents a finite-element numerical model for N2–O2–CO2 separation by hollow fiber membranes, scaled-up to treat the combustion gases coming for a medium-size coal-based power unit. The equation set has been expanded to include, beyond the membranes, also compressors and condensers. Two process layouts have been evaluated: one open loop allowing for high purification level, and a recirculating scheme yielding superior enrichments. The resulting simulation, valid from pilot to full-plant scale, takes then into account the interplay of both active and passive process units besides the active membranes, and is fully dynamic in definition and scope.The results show that the degree of purification is mainly affected by the enrichment-side pressure, while the CO2 concentration depends largely on the CO2:N2 selectivity. Even when this latter value is relatively low, a proper scale-up of series/parallel modules can overcome the limitation without exceeding 7–8 bar pressurisation. Simulating the impact of pressure and flow transients on the plant outflows, the recovery procedure and timescales are identified.

High heat producing granites and prolonged extraction of tungsten and tin from melts

The granites associated with world–class W and Sn deposits generally have high concentrations of U, Th, and K and can be classified as high heat producing (HHP) granites (>5 μW m−3) because of high radiogenic heat production, but how long radiogenic heat can prolong the suprasolidus lifetime of magmas and whether radiogenic heat exerts an impact on W and Sn mineralization is poorly understood. To answer these questions, finite element numerical modeling was established to link magma cooling by heat conduction with diffusion of W, Sn, and H2O from silicate melts to coexisting aqueous fluids before the solidus is reached. The magma in the models is emplaced to a depth of 5 km and its size (vertical thickness of 4–5 km and horizontal length of 20 km) is constrained by the granites associated with world–class W and Sn deposits. Fluid convection was not considered in the models. The sensitivity analysis and comparison results suggest that the suprasolidus lifetimes of HHP magmas are positively correlated with the heat production and magma thickness and negatively correlated with the solidus temperatures and the thermal conductivity of host rocks. Average radiogenic heat of 5–10 μW m−3, together with decreased solidus temperatures due to magmatic differentiation and a moderate thermal conductivity of host rocks, can prolong the suprasolidus lifetime of HHP magmas by 49–427 ka (1 Ma = 1000 ka), corresponding to 11–85% of the suprasolidus lifetime of equally sized magmas with normal radiogenic heat (2 μW m−3). From the available gravity modeling data, over half of the granites associated with world–class W and Sn deposits are at least 1 km thicker than the values calculated from the empirical power–law equation, and the modeling results indicate that an increase of 500–1000 m in magma thickness prolongs the suprasolidus lifetimes of HHP magmas (5 μW m−3) by 50–74%. During magma cooling before solidus is reached, the diffusion of W and Sn is at least several orders of magnitude slower than that of H2O in hydrous melts; thus, the equilibrium partitioning of these two metals between silicate melts and coexisting aqueous fluids is not reached, and the metal diffusion from melts is a rate-limiting step. The prolongation of the suprasolidus lifetimes by radiogenic heat and decreased solidus temperatures can allow extraction of 17–95% more W and Sn from silicate melts before the solidus is reached and increase the possibility of producing W and Sn mineralization at later stages. Therefore, the coexistence of HHP granites and world–class W and Sn deposits is not accidental.

Numerical model characterization of the sound transmission mechanism in the tympanic membrane from a high-speed digital holographic experiment in transient regime.

A methodology for the development of a finite element numerical model of the tympanic membrane (TM) based on experiments carried out in the time domain on a cadaveric human temporal bone is presented. Using a high-speed digital holographic (HDH) system, acoustically-induced transient displacements of the TM surface are obtained. The procedure is capable to generate and validate the finite element model of the TM by numerical and experimental data correlation. Reverse engineering approach is used to identify key material parameters that define the mechanical response of the TM. Finally, modal numerical simulations of the specimen are performed. Results show the feasibility of the methodology to obtain an accurate model of a specific specimen and to help interpret its behaviour with additional numerical simulations. STATEMENT OF SIGNIFICANCE: Improving knowledge of the dynamic behavior of the tympanic membrane is key to understanding the sound transmission system in human hearing and advance in the treatment of its pathologies. Recently we acquired a new tool to carry out experiments in transient regime by means of digital laser holography, capable of providing a large amount of information in a controlled transient test. In this work, these data are used to develop a methodology that generates a numerical model of the tympanic membrane based on numerical-experimental correlations. It is important to be able to develop models that fit specific patients. In this work, additional modal simulations are also presented that, in addition to validating the results, provide more information on the specimen.

A corrected p-y curve model for large-diameter pile foundation of offshore wind turbine

With the development of pile-soil interaction theory, at present the sand p-y model of API specification is adopted to the analysis and calculation of large diameter piles under horizontal static load, but the results of the ultimate soil resistance at different depths is underestimated and the initial foundation reaction modulus is overestimated, thus the calculation results are obtained with large errors. For this problem, a finite element numerical model of pile-soil interaction is established in this study, and the calculation models under horizontal static load with different pile diameters and soil depth are analyzed and the data regression is carried out. A correction coefficient is introduced to consider the size effect of large diameter pile, and the variation law of influence index of different factors is discussed. Finally, a corrected sand p-y curve model for single pile foundation with large diameter more than 2 m is proposed. Compared with the results of model test and field test, the calculation results of ultimate soil resistance and initial foundation reaction modulus from the corrected model is more in accord with the actual situation.

A novel reduced column section approach for the seismic protection of wind turbines

The rapid increase in global energy demand over the coming decades must be sustained by a more consistent increment of energy production from renewable sources of which wind energy is currently one of the fast-growing resources. New onshore and offshore wind farms will be rapidly constructed in challenging environments, especially in earthquake-prone areas. As a result, the mitigation of the dynamic vibrations of the wind turbines becomes a fundamental aspect of the seismic design to guarantee their normal operativity and structural safety. Different from past proposals based on traditional passive control devices such as tuned mass dampers or tuned liquid column dampers, this study aims to propose a novel approach, the Reduced Column Section (RCS), to derive an innovative mitigation device which replaces the traditional transition piece of the wind turbine. Analytical formulas to design the proposed RCS will be established. The benefits of the proposed device will be assessed on a real onshore wind turbine located in Italy. Modal properties obtained from the continuous dynamic monitoring of the wind turbine will be used to characterize the numerical finite element model. Therefore, a direct integration analysis with spectrum-compatible real earthquakes and an incremental dynamic analysis will be conducted to evaluate the dynamic mitigation induced by the proposed RCS. Soil-structure interaction effects will be also considered. This study shows that RCS can efficiently mitigate the effective stresses on the wind tower wall by up to 70% compared to the stresses computed on the existing structure.

Operational Modal Analysis of Historical Buildings and Finite Element Model Updating Using α Laser Scanning Vibrometer

Without affecting the integrity or stability of the heritage monuments, vibration-based techniques provide useful solutions for acquiring global information about them. By studying the dynamic response to suitable excitation sources, it is feasible to define the mechanical characteristics of structures and identify and locate defects in their global behaviour. Laser Doppler vibrometry (LDV), which enables non-contact measurements of the vibration velocity of moving surfaces using a focused laser beam, is a highly desirable technique for qualitative dynamic characterisation and damage assessment. LDV is a simple and non-intrusive approach. It permits remote measurements and has a high degree of sensitivity and frequency adaptation. In addition, the system is entirely computer controlled, providing simple data storage, processing, and analysis. LDV has been originally researched and developed for structural and modal shape analysis of physical prototypes, in-service devices (e.g., machinery components), medical imaging applications, and damage detection and analysis relevant to small-scale non-destructive testing (NDT), and evaluation of micro to meso-targets (e.g., fracture detection and mapping in composites, modal shape and vibration analysis of objects, etc.). In spite of several successful applications in the case of bridges and thin structures, ambient vibration testing in an integrated form that includes dynamic identification, sensitivity analysis, and numerical modelling update employing modern sensor non-contact technologies is still uncommon. In this paper, the authors intend to explore further the possibility of combining ambient vibrations and OMA in combination with the non-contact LDV sensing technique in order to remotely acquire mechanical waves travelling in historical structures, track the actual behaviour of such structures, and calibrate their finite element numerical models.