Finite Element Numerical Model Research Articles

Simulating the sealing performance of the double rubber cylinder assembly in an intelligent pipeline isolation tool

Intelligent pipeline isolation tools (IPITs) are widely used for pipeline maintenance and repair. Therefore, authors mainly study the sealing performance of double rubber cylinder IPIT. This study first analyzed the material and geometric properties of the rubber cylinders in an IPIT to establish a numerical finite element model of cylinder mechanical behavior. The influence of the cylinder hardness, camber angle, and short-side length on the sealing performance was subsequently investigated by systematically altering the established model according to the control variable method. Next, the response surface methodology was employed to evaluate the change in model sealing performance according to the coupled action of multiple rubber cylinder parameters and identify their optimal values.

Identification method on the vibration properties of a periodic core sandwich: Thermal impact on the band gap

This paper focuses on the thermal impact of filtering properties on sandwich structures with periodic core. The evolution of the bandgap is carefully studied as a function of temperature. Sandwich structure allows to shear the viscoelastic core layer and increases passive damping. Two polymers are selected for their viscoelastic properties and their adhesion properties with metal surfaces. The mechanical properties, shear modulus G(ω) and loss factor η(ω) of these polymers, are determined at temperature by an inverse method. The periodicity of the sandwich structure is achieved by alternating two materials with specific viscoelastic properties in the core, allowing resonant frequencies to be located in beams creating frequency ranges without resonant peaks. Temperature has a strong influence on the mechanical properties of polymer materials. This is why we felt it was important to be able to carry out a temperature investigation. Numerical finite element modelling is developed considering periodicity and temperature. Periodic sandwich fabricated in our laboratory are tested under thermal conditioned. The results show the importance of considering the effect of temperature. It has a direct impact on the filtering properties obtained by periodic structures.

Three-Dimensional Finite Element Modeling of Ultrasonic Vibration-Assisted Milling of the Nomex Honeycomb Structure

Machining of Nomex honeycomb composite (NHC) structures is of critical importance in manufacturing parts to the specifications required in the aerospace industry. However, the special characteristics of the Nomex honeycomb structure, including its composite nature and complex geometry, require a specific machining approach to avoid cutting defects and ensure optimal surface quality. To overcome this problem, this research suggests the adoption of RUM technology, which involves the application of ultrasonic vibrations following the axis of revolution of the UCK cutting tool. To achieve this objective, a three-dimensional finite element numerical model of Nomex honeycomb structure machining is developed with the Abaqus/Explicit software, 2017 version. Based on this model, this research examines the impact of vibration amplitude on the machinability of this kind of structure, including cutting force components, stress and strain distribution, and surface quality as well as the size of the chips. In conclusion, the results highlight that the use of ultrasonic vibrations results in an important reduction in the components of the cutting force by up to 42%, improves the quality of the surface, and decreases the size of the chips.

Glulam frame corner joints built of birch plywood and mechanical fasteners: An experimental, analytical, and numerical study

This study investigates frame corner joints built of birch plywood plates and glulam elements connected via self-tapping screws. Analytical calculations based on the fastener group’s torsional moment resistance, the proposed fastener group’s elastic and post-elastic load-bearing criteria, and the design formulas in Eurocode 5 were performed to predict the connection capacity in both elastic and post-elastic stages. A combined action check formula was adopted to predict the capacity of birch plywood plates and glulam elements. Frame corner specimens constructed with three different plywood thicknesses were planned to study the influence on global behavior and rotational stiffness. The specimens were intentionally designed so that failure occurred either in plywood or in glulam, in order to examine the robustness and validity of analytical calculation models. Another supplementary test group with 21 mm plywood and fewer fasteners was also designed and tested, in which the plastic yield of fasteners was expected. The test results of this supplementary group served to calibrate the analytical model that predicts the elastic and post-elastic capacity of the connection group. As a result of the comparison, the analytical calculations gave reasonable predictions on the failure of plywood, glulam, and the capacity of the fastener group. Only when the exposed moment exceeded the post-elastic limit of the fastener group did the plastic yielding of fasteners become observable. Moreover, numerical finite element models adopting the foundation zone-modeling scheme were constructed, which were proven to capture all test configurations' linear loading stiffness satisfactorily.

Multiscale evaluation of tunnel construction safety risk: a case study of an offshore tunnel construction in Ningbo

Based on the WBS-RBS method, in this study, the risk factors corresponding to the construction risk events of an offshore tunnel foundation pit in Ningbo were identified, and the fuzzy comprehensive evaluation method was used to evaluate the construction safety risk of the project. The system-level risk value was obtained by using the risk event deformation resulting from changes in two factors, namely, “mechanical property of soil” and “stiffness of the envelope structure”, to calculate the new event-level risk value corresponding to the deformation using a finite element numerical model. The findings indicate that the tunnel project has a risk evaluation score of 62.78 and thus falls within the category of high-risk projects. A change in risk factors will alter the likelihood that risk events will occur, which affects the safety risk status of the entire project. When two factors are coupled, a project’s system-level risk can increase dramatically.

Method for vibration and acoustic radiation analysis of underwater stiffened plates with acoustic coatings

Based on the effective medium theory as well as the three-dimensional viscoelastic theory, a semi-analytical model of the three-dimensional underwater vibration and acoustic radiation with cavity-type stiffened plate structures covered with acoustic coatings is established to solve the issues related to underwater vibration and acoustic radiation calculation of the stiffened plate and shell structure with complex acoustic coatings. By comparing the far-field acoustic radiation characteristics of the proposed semi-analytical model and the finite element numerical model, this research verifies the validity and accuracy of the proposed model. On such a basis, this research preliminarily investigates the coupling effect exerted by stiffeners and parent plates in stiffened plates as well as the vibroacoustic characteristics of acoustic coatings, thereby providing a valuable idea for the prediction of vibroacoustic characteristics concerning underwater structures.

Seismic Performance of Precast Steel Fiber Reinforced Lightweight Aggregate Concrete Shear Walls Assembled with a Socket Horizontal Joint

Seismic Performance of Precast Steel Fiber Reinforced Lightweight Aggregate Concrete Shear Walls Assembled with a Socket Horizontal Joint

Enhancing the Machining Performance of Nomex Honeycomb Composites Using Rotary Ultrasonic Machining: A Finite Element Analysis Approach.

Nomex honeycomb composites (NHCs) are commonly used in various industrial sectors such as aerospace and automotive sectors due to their excellent material properties. However, when machining this type of structure, problems can arise due to significant cutting forces and unwanted cell vibrations. In order to remedy these shortcomings, this study proposes to integrate RUM (rotary ultrasonic machining) technology, which consists of applying ultrasonic vibrations along the axis of rotation of the cutter. To fully understand the milling process by ultrasonic vibrations of the NHC structure, a 3D numerical finite element model is developed using Abaqus/Explicit software. The results of the comparative analysis between the components of the simulated cutting forces and those from the experiment indicate a close agreement between the developed model and the experimental results. Based on the developed numerical model, this study comprehensively analyzes the influence of the ultrasonic vibration amplitude on various aspects, such as stress distribution in the cutting zone, chip size, the quality of the machined surface and the components of the cutting force. Ultimately, the results demonstrate that the application of ultrasonic vibrations leads to a reduction of up to 50% in the components of the cutting force, as well as an improvement in the quality of the machined surface and a reduction in the size of chips.

Numerical analysis of a pressure distribution field and fluid flow velocity vectors near cumulative perforation holes

Relevance. The need to determine a reliable pressure distribution field and fluid filtration velocity vectors inside the perforation hole and the reservoir rock surrounding it. Aim. On the basis of numerical finite element modeling of the fluid flow inside the perforation holes and its filtration in the surrounding reservoir rock, to reveal the patterns of pressure distribution and fluid filtration vectors in the perforation hole, on its walls and in the near-wellbore zone. Objects. Near-wellbore zone of a limestone reservoir of one of the oil fields in the south of the Perm Region, including perforations. Methods. Numerical finite element method for calculating the flow and filtration of liquid in the near-wellbore zone, taking into account the geometry of perforation holes. Results. The paper considers the main relationships used in numerical simulation of fluid flow and filtration in the ANSYS finite element modeling software package. The authors have developed the finite element scheme of the near-wellbore zone, including cumulative perforation holes and taking into account their geometric parameters, as well as the fact that inside the holes the fluid flow is modeled in open space using the Navier–Stokes equations, and in the surrounding reservoir rock based on the filtration equations and Darcy's law. Numerical calculations were carried out, on the basis of which the distribution of pressure, flow velocities and fluid filtration inside the holes and in the near-wellbore zone as a whole was obtained. Calculations were made with varying pressure in the well (or pressure drawdown), as well as for different values of reservoir permeability. The calculation results showed that for the actual drawdown values of 10 MPa and the reservoir permeability of 50 mD, the value of pressure change inside the perforation holes will not exceed 0.01 MPa, i.e. it can be assumed that it practically does not change inside the hole. It is noted that the maximum value of the filtration rate corresponds to the top of the perforation holes and then its value decreases as it approaches the borehole wall. It is concluded that in further modeling of the stress-strain state of the near-wellbore zone, taking into account the holes of cumulative perforation on the surface of the holes, it is permissible to set a constant pressure value equal to the pressure in the well, and not logarithmic or any other distribution of it.

Bayesian data-driven framework for structural health monitoring of composite structures under limited experimental data

Ultrasonic-guided waves can be used to monitor the health of thin-walled structures. However, the run of experimental damage tests on materials like carbon fiber-reinforced plastics can be impractical and costly. Instead, numerical models can be used to create hybrid datasets to train machine learning algorithms, integrating data from numerical and experimental tests. This paper presents a Bayesian-driven framework to compensate for limited experimental data regarding Lamb wave propagation in composite plates. Using Bayesian inference, the framework updates a numerical finite element model, considering observed uncertainties by sampling posterior probability density functions for input parameters using Markov–Chain Monte Carlo simulations with the Metropolis-Hastings algorithm. A neural network surrogate model speeds-up these simulations, leading to a model that replicates the uncertain experimental setup. This model then generates data to augment true experimental data. Finally, a one-dimensional convolutional neural network is trained on a three different datasets to analyze Lamb wave signals and assess damage. Comparing training strategies shows the hybrid dataset augmented by samples generated by the updated FE model gives the most accurate damage size predictions.

Fatigue-Life Prediction of the Optimized Savonius Vertical-Axis Wind Turbine Composite Blades

Abstract The sustainability of modern human civilization is significantly concerned with enhancing sustainable energy resources. Vertical-Axis Wind Turbines (VAWTs) gained a promising impact on the global energy mix due to their belief in sustainable energy solutions. This paper presents an integrated study of the dynamic performance and fatigue-life characteristics of the optimized Savonius-rotor VAWT composite blades. Furthermore, this paper introduces an experimental validation, numerical modeling, and visualization/verification study of the optimized VAWT composite blades and assesses its impact on the whole performance of the optimized Savonius VAWTs. Four combination levels of the optimal settings of the S-VAWT composite blade configurations are designed, modeled, simulated, and fabricated of Carbon/Glass—Polyester. The modal parameters such as natural frequency, mode shape, and damping factor are investigated using fast Fourier transformer (FFT) analyzer. The numerical finite element models (FEM) are generated to model, visualize, simulate, and predict the dynamic nature and fatigue-life characteristics of the optimal S-VAWT composite blade configurations. A correlation between the experimental and numerical results is established. The study findings highlight the significant impact of VAWT composite blades in enhancing the dynamic performance and fatigue-life characteristics of Savonius VAWTs. Furthermore, a small damage percentage of 2.8% predicted by the finite element analysis (FEA) for the optimal S-VAWT composite blade configuration validated the sustainability of the VAWT composite blade configurations in dynamic loading conditions.

Analysing Slope Stability in Response to Blast-Induced Dynamic Loading by Pseudo-Static Approach

Regular blasting in opencast coal mines generates significant ground vibrations, impacting mine slope stability and posing risks to life and property. This study focuses on monitoring ground vibrations in an opencast coal mine through near-field monitoring and investigating the impact of blast-induced seismic loading on slope stability. The approach involves a pseudostatic method utilising Strength Reduction Factor (SRF), based on Finite Element (FE) numerical modelling software. The study examines a pit slope with a tension crack under seismic loading, varying the intensity of seismic coefficients (Ks) from 0 to 0.5. These coefficients are determined through field vibration monitoring during production blasts. In numerical modelling, seismic loading is considered in both horizontal (outward of slope face) and vertically downward (in-line with gravity). Numerical modelling incorporates dimensionless horizontal seismic coefficient (Kh) and vertical seismic coefficient (Kv), and both directions which is expressed as Seismic Coefficient Ratio (SCR) which is the ratio of Kv and Kh for interpretation of results. Although SCR induces changes in the Factor of Safety (FoS), its impact is minimal compared to seismic loading solely in the horizontal direction. Consequently, increasing SCR leads to a decrease in FoS. The study observes that Peak Ground acceleration (PGA) in the longitudinal direction has greater dominance than in the transverse direction. Additionally, the seismic wave in the horizontal direction destabilises the slope more than the corresponding vertical seismic wave. These findings are elucidated in the context of the Critical Slip Surface (CSS).

Vibration response analysis of mobile liquid Pb-Bi micro-reactors under transportation with liquid sloshing

Mobile micro-reactors, which used the liquid lead–bismuth eutectic (LBE) as coolants, providing energy to remote regions had become a popular topic in nuclear energy due to their desirable characteristics, including inherent safety and modularity. However, the liquid sloshing effect in a reactor may exhibit fluid–structure interaction (FSI) coupling effects, which could have a significant impact on the relevant internal systems. And the ratio of coolant in liquid to solid form was correlated with the duration of heat dissipation. This paper aimed to investigate the liquid sloshing effect in a micro-reactor that was subject to vehicle vibrations, the objective was to provide recommendations for transportation scenarios involving various liquid sloshing. To achieve this, a full-vehicle dynamic model of the system was developed using multi-body dynamics. Additionally, MATLAB simulation software was utilized to simulate the road roughness loadings that the micro-reactor may encounter during transportation. Moreover, a finite element numerical model of the Mobile Micro-reactor had been developed in order to simulate the sloshing effect that occurred during transportation, the numerical models presented in this study were validated by comparing them with a previously-verified Housner model that involved a cylindrical tank. This study investigated the sloshing effects of the Mobile Micro-reactor under different liquid–solid ratios of coolant, internal component lengths, and liquid surface heights. The results indicated that the internal components within the reactor vessel can alleviate the sloshing effect. The solid ratios of liquid lead–bismuth coolant and the liquid surface height during transportation had an impact on the sloshing effect. These findings provided valuable insights for studying the sloshing response of on-board reactors during liquid sloshing transportation.

Semi-automatic algorithm to build finite element numerical models of the human hearing system from Micro-CT data.

Finite Element modeling has been an extended methodology to build numerical model to simulate the behavior of the hearing system. Due to the complexity of the system and the difficulties to reduce the uncertainties of the geometric data, they result in computationally expensive models, sometimes generic, representative of average geometries. It makes it difficult to validate the model with direct experimental data from the same specimen or to establish a patient-oriented modeling strategy. In the present paper, a first attempt to automatize the process of model building is made. The source information is geometrical information obtained from CT of the different elements that compose the system. Importing that data, we have designed the complete procedure to build a model including tympanic membrane, ossicular chain and cavities. The methodology includes the proper coupling of all the elements and the generation of the corresponding finite element model. The whole automatic procedure is not complete, as we need to make some human-assisted decisions; however, the model development time is reduced from 4 weeks to approximately 3 days. The goal of the modeling algorithm is to build a Finite Element Model with a limited computational cost. Several tasks as contour identification or model decimation are designed and integrated in order to follow a semi-automated process that allows generating a patient-oriented model.

Study on load-bearing behaviors of prestressed post-grouting tubular piles in the karst region of northern Fujian Province, China

The karst that is dominated by medium-weathered limestone and caves with various spatial features is widely distributed in the northern Fujian Province. This paper discusses the load-bearing behaviors of post-grouting tubular piles in karst region of north Fujian Province with reference to the prestressed tubular piles adopted in the residential buildings of Haixi Comprehensive Trade City Phase II Project in Sanming City. The load-settlement curve, pile side friction resistance, and pile end resistance of tubular piles are analyzed by finite element numerical simulations and field static load tests. The load-bearing behaviors of prestressed tubular piles under karst geological conditions with two different spatial features are comparatively investigated, and the effectiveness of tubular pile reinforcement is verified by field settlement observation. The results reveal that the finite element numerical model can effectively simulate the tubular pile-soil interaction. The use of pile end post-grouting of prestressed tubular piles in the karst region can significantly increase their load-bearing capacities. The top settlements of grouted tubular piles under the maximum test load can be reduced by 16.8%–22.3% compared with these of ungrouted test piles, and the theoretical simulated ultimate load-bearing capacity can be increased by 27.3%. The adoption of pile end post-grouting technique can reduce the pile end displacement of tubular piles and improve the proportion of pile end resistance. Plastic-hard plastic breccia silty clay can be used as a bearing stratum for post-grouting to achieve excellent grouting performance. The bead-shaped karst caves are more unfavorable to the exertion of load-bearing capacity of the tubular piles than the karst caves filled with plastic-hard plastic breccia silty clay to which the piles have direct access. The field monitored average settlements of the 19# and 17# buildings under karst geological conditions with two different spatial features are −12.88 mm and −8.98 mm, respectively, both of which do not exceed the warning value, indicating that it is feasible for the project to adopt the pile end post-grouting technique of the tubular piles. The achievements of this study help to further reveal the load-bearing mechanism of this type of pile, which can provide a basis for its engineering design and construction optimization.

Experimental and numerical study on seismic behavior of precast shear walls assembled with a socket vertical joint

In the development of precast shear wall structures, reliable and efficient connections of precast units are crucial for their seismic behavior. Meanwhile, the heavy precast units using conventional concrete bring a low lifting efficiency. Considering these issues, the paper proposed a novel type of socket vertical joint for precast shear walls made of steel fiber reinforced lightweight aggregate concrete (SFRLAC). Sixteen socket connection specimens, with four socket depths (100 mm, 150 mm, 200 mm, and 250 mm) and two interface treatments (smooth and exposed aggregate), underwent interface bonding performance tests using uniaxial tensile testing and finite element (FE) numerical models to determine the appropriate socket depth. Three specimens were tested using the low-cyclic loading test, including two reinforced SFRLAC precast shear walls assembled with a socket vertical joint and a cast-in-place reinforced SFRLAC shear wall as a reference. The failure patterns and process of the shear walls were observed, while the load-displacement curves were obtained. Additionally, a parametric analysis of different influencing factors was conducted using finite element (FE) numerical models. This analysis studied the bearing capacity, energy dissipation capability, deformation ability, and stiffness degradation of the shear walls. Results indicate that when the precast shear walls were damaged, the socket vertical joint was integrity and failed in bending-shear. The three specimens exhibited fewer differences in seismic behavior with relatively full hysteretic curves. The seismic mechanisms of the shear wall assembled with a socket vertical joint were elucidated by analyzing the numerical distribution of stress in both SFRLAC and steel bars at different stress levels. Furthermore, an expansion analysis was conducted to assess the impact of axial load ratios and shear to span ratios on the seismic behavior of precast shear walls.

Exploring the Potential of Machine Learning in Stochastic Reliability Modelling for Reinforced Soil Foundations

This study introduces a novel application of gene expression programming (GEP) for the reliability analysis (RA) of reinforced soil foundations (RSFs) based on settlement criteria, addressing a critical gap in sustainable construction practices. Based on the principles of probability and statistics, the soil uncertainties were mapped using the first-order second-moment (FOSM) approach. The historical data generated via a parametric study on a validated finite element numerical model were used to train and validate the GEP models. Among the ten developed GEP frameworks, the best-performing model, abbreviated as GEP-M9 (R2 = 0.961 and RMSE = 0.049), in the testing phase was used to perform the RA of an RSF. This model’s effectiveness in RA was affirmed through a comprehensive evaluation, including parametric sensitivity analysis and validation against two independent case studies. The reliability index (β) and probability of failure (Pf) were determined across various coefficient of variation (COV) configurations, underscoring the model’s potential in civil engineering risk analysis. The newly developed GEP model has shown considerable potential for analyzing civil engineering construction risk, as shown by the experimental results of varying settlement values.

Determination of Dynamic Characteristics of Lattice Structure Using Dynamic Mode Decomposition

Abstract In this work, dynamic mode decomposition (DMD) was applied as an algorithm for determining the natural frequency and damping ratio of viscoelastic lattice structures. The algorithm has been developed based on the Hankel alternative view of Koopman (HAVOK) and DMD . In general, the Hankel matrix is based on time-delay embedding, which is meant for the hidden variable in a time-series data. Vibration properties of a system could be then estimated from the eigenvalues of the approximated Koopman operator. Results of the proposed algorithm were firstly validated with those of the traditional discrete Fourier transform (DFT) approach and half-power bandwidth (HPBW) by using an analytical dataset of multi-modal spring-mass-damper system. Afterward, the algorithm was further used to analyze dynamic responses of viscoelastic lattice structures, in which data from both experimental and numerical finite element (FE) model were considered. It was found that the DMD-based algorithm could accurately estimate the natural frequencies and damping ratios of the examined structures. In particular, it is beneficial to any dataset with limited amounts of data, whereby experiments or data gathering processes are expensive.

Comparative Study of Numerical Methods for Predicting Crack Propagation in Reinforced Concrete Hollow Core Slabs

Hollow core slabs are commonly used in prefabricated building construction and are calculated and constructed using gravity loads. The dead loads of the structure are reduced by using this slab system. Different criteria, such as the initiation and propagation of cracks in the hollow core slab, are used to analyze these slabs. Fracture mechanics is the basis for studying crack propagation. The present study was conducted to analyze the propagation of cracks in hollow core slabs under common loading conditions using the finite element method and numerical modeling to analyze cracks in reinforced concrete members. This research is theoretically conducted using finite element software. This research takes into account the potential varieties of cracks in concrete slabs. Slabs should consider all three types of cracks, which are shear, flexural, and flexural-shear cracks obtained from the reference test. Two Contour integral and XFEM methods are used to analyze cracks in Abaqus software. To validate and control the modeling process, the laboratory results of the research of Ibrahim N. Najma, Raid A. Daudb, and Adel A. Al-Azzawi. December 2, 2019, has been used. The outcomes of this study showed that the probability of the formation of a flexural-shear crack in the slab is higher than in other crack forms.

Research on Uplift Mechanism of Shield Tunnel Based on Multi-factor Construction Conditions

In order to investigate the influence degree of each factor on tube sheet uplift and tube sheet uplift law of shield tunneling, this thesis takes the background of Zhengzhou Railway Transit Line 6 Phase I Project Weizhuang Station ~ Cargo Station Street Station Interval Project, and establishes ABAQUS finite element numerical model based on the influence factors such as shield thrust, slurry density, grouting pressure, etc., and analyzes the interaction relationship between the influence factors of tube sheet uplift caused by the shield tunneling construction period. The paper investigates the uplift law of tube sheet and the mechanism of influencing factors during the construction period of shield tunnel, and obtains the relationship between grouting pressure and tube sheet uplift, jack thrust and slurry density and tube sheet uplift under the influence of a single factor; the thesis also discovers the location of the maximum uplift and the basic law, as well as the basic range of the uplift and the reduction of the uplift value in the late stage through the comprehensive analysis and calculation of the uplift and the influencing factors under different working conditions. The paper also finds out the location and basic law of the maximum uplift of the tube sheet under different working conditions, and the basic range of the downsizing value of the uplift in the later stage.