Precise Finite Element Model Research Articles

Analysis of Damage Factors of Reinforced Concrete Frame Under Internal Explosion

To explore the mechanisms of the damage to reinforced concrete (RC) frame structures subjected to internal explosions, this paper establishes a precise finite element model (FEM) of an RC frame utilizing ANSYS/LS-DYNA software 14.5. The influence of four important damage factors on the degree of structural damage is systematically analyzed. Specifically, the vertical displacement at the top center of the frame serves as the primary evaluation metric, while the four damage factors are treated as independent variables. An empty column is incorporated as an error term, facilitating a five-factor, four-level orthogonal optimization design for the simulation experiments. Based on this design, a variance analysis of the simulation outcomes is conducted. The results show that by increasing the reinforcement ratio of the beam section and reducing the charge weight, when the explosion point is located at the higher part of the building floor and near the external window, the vertical displacement of the building after the internal explosion can be reduced. The order of the influence degree of each damage factor on the damage to the reinforced concrete frame structure is as follows: explosion floor, charge weight, beam section reinforcement ratio, and explosion horizontal position.

Circular Spline Tooth Longitudinal Modification Design and Contact Analysis for Harmonic Drives with Short Flexspline

Harmonic drives (HDs) with short flexspline (FS) always suffer from small meshing areas and severe stress concentration caused by large cone angles when a short FS is assembled and loaded. To address this issue, a tooth longitudinal modification method for the circular spline (CS) with a double circular arc common-tangent tooth profile (DCTP) is proposed. Using neutral layer and envelope conjugation theories, a mathematical model of the conventional straight CS tooth was developed. A shaping cutter for this tooth profile was then designed through coordinate transformation and meshing principles. The proposed longitudinal modification for the CS was achieved by adjusting the cutter’s trajectory. A precise finite element model of the HD was developed, revealing that tooth longitudinal modification can reduce the maximum contact pressure by 69.6% and significantly increase the contact area for HDs with short FS. This work provides valuable technical references for improving the contact state of HDs with short FS.

Finite Element Model Calibration with Surrogate Model-Based Bayesian Updating: A Case Study of Motor FEM Model

This paper introduces an advanced methodology for the calibration of Finite Element Models (FEM) utilizing a surrogate model-based Bayesian updating framework. The approach is exemplified through a case study on motor design, where precise FEM calibration is essential for predicting and optimizing motor performance. Traditional calibration techniques are often computationally expensive due to the iterative nature of the simulation process. To mitigate this, the proposed method integrates surrogate models to approximate FEM simulations, significantly reducing the computational burden without sacrificing accuracy. Bayesian updating is then employed to iteratively refine the surrogate model by incorporating new data, thereby enhancing prediction accuracy. This dual approach not only accelerates the calibration process but also ensures a high level of precision, making it highly suitable for complex engineering applications requiring both efficiency and reliability. The case study underscores the effectiveness of this methodology, demonstrating its potential to streamline the design process in motor development and other FEM-dependent engineering fields. The findings suggest that the surrogate model-based Bayesian updating approach achieves robust calibration with significantly fewer simulations, thereby optimizing both time and computational resources.

Sparse regularized graph pooling network optimal sensor placement method for diesel engine vibration fault perception system

Vibration sensor network optimization increases monitoring effectiveness and reduces sensor quantity and transmission burden. However, the traditional model-driven methods depend on precise finite element models, challenging for complex machinery. This paper presents a data-driven approach using the Sparse Regularized Graph Pooling Network (SRGPN), which conceptualizes sensor networks as graphs and uses graph pooling to identify optimal sensor combinations. A sparsity regularization term related to the number of sensors is included in the loss function, aiming for the minimal yet effective sensor combination. Additionally, a monitoring capability metric suited for diesel engines with multi-source impulse signals is proposed, reflecting the sensors’ monitoring capacity. Validated through simulations and tests on a diesel engine test bench, the results show that SRGPN optimally places sensors near excitation sources, balancing sensor count and monitoring needs. This approach shows potential for optimizing sensor placements in condition monitoring.

Effects of Tool Geometry Parameters on Clinched Joint Strength Using FEM

Abstract Clinching joining is one of the predominant techniques used to join aluminium alloys in the automotive industry. Although the technique can be easily automated, cost-effective, and not affect the material’s mechanical properties during the joining process, the tool geometry parameters significantly affect the strength of the clinched joint. Therefore, a precise finite element model is critical to improve the strength and reduce the cliched joint’s production cost. This study investigated the effect of the punch fillet radius, the punch angle, the die diameter and the die depth on the strength of the clinched joint of 5754 aluminium alloys. The clinched joint was produced with different geometry parameters. The cross-section of the clinched joints was observed. In the meantime, the interlocking value, the neck thickness, and tool parameters were measured to investigate the joinability of the aluminium alloys. The static tensile shear tests were also conducted using the universal tensile machine. Numerical studies have been conducted to analyse the influence of the geometrical parameters using a 2D axisymmetric model. As a result, the numerical results agreed with the experimental results. Additionally, the result showed that the tool geometry significantly impacted the strength of the clinched joint of aluminium alloys. The study concluded that the neck thickness and the interlocking value have played a vital role in the enhancement of the cliched joint strength.

Type Id versus type IId three-level hybrid surgery for the treatment of noncontiguous cervical spondylosis: A finite element analysis

The objective of the research is to simulate different forms of three-level hybrid surgeries, aiming to establish a foundational reference for the selection of suitable treatment strategies for multilevel noncontiguous cervical degenerative disease (CDD). For the development of precise finite element models (FEMs), this study utilized computed tomography (CT) data. Two cross-segment surgical approaches were primarily investigated: C3/4 cervical disc arthroplasty (CDA), C5/6 anterior cervical discectomy and fusion (ACDF), and C6/7 ACDF in the type Id model; C3/4 CDA, C5/6 CDA, and C6/7 ACDF in the type IId model. The follower load technique was employed to apply an initial axial load of 73.6 N at the motion center. Subsequently, a moment of 1.0 Nm was introduced at the center of the C2 vertebra to simulate the overall motion of the model. In contrast to type IId, type Id exhibited lower average intervertebral disc pressure in C4/5 across various motions. The average intervertebral disc pressure in C2/3 was higher in type Id compared to type IId in flexion and axial rotation, whereas the reverse was observed in lateral bending. Type IId exhibited notably lower facet joint contact stresses during extension in C2/3 and C4/5 when compared to type Id. Type Id has a better protective effect on IS, and can significantly reduce the average pressure of the intervertebral disc in IS compared with type IId. Type IId has a significant protective effect on the post-column structure of non-fused segments.

Impact response of SCS sandwich slabs with ultra-high performance concrete: Failure mechanism and influence of shear connector configuration

In the typical steel-concrete-steel (SCS) sandwich structure, the normal-strength concrete core fills the external steel skeleton. This paper describes a program of drop-weight tests and finite element investigations on reduced-scale SCS sandwich slabs with ultra-high performance concrete (UHPC) core material as a novel protective layer construction. Test results demonstrated that the steel-ultra-high performance concrete-steel (SUHPCS) sandwich slabs were adequate for forming enhanced dynamic resistance through the high strength of UHPC and tensile stiffening membrane of the steel skins. Also, this construction was found to perform a highly ductile behavior and sustain obvious bulges without penetration through the whole slab. Precise finite element models for sandwich slabs under impact loading conditions were established and the simulated time histories were verified against the test data. Furthermore, a parametric study of sandwich slabs designed with different configurations of shear connectors was subjected to a spherical hammer weighing 540 kg dropping from the height of 5 m. The simulation results showed that the failure mode of SUHPCS sandwich slab changed with various degrees of composite interaction. Moreover, a theoretical methodology was proposed to classify the failure mode involving stiffness, flexural and punching resistances. SUHPCS sandwich slabs with a reasonable layout of shear connectors were found to provide a means for effective energy absorption against severe impact attacks.

A dynamic stiffness-based two-step method for damage identification of joints in hinged slab bridges using support vector machine

As critical components of hinged slab bridges, joints are of great importance to the bearing capacity and serviceability of bridges. The existing model-based joint damage detection methods are based on precise finite element models, and their identification accuracy is significantly affected by construction uncertainty. In this paper, dynamic stiffness is introduced into joint damage detection and a two-step framework is proposed for the damage localization and quantification of joints in hinged slab bridges. The dynamic stiffness-based data-driven method is suitable for the evaluation of bridges with incomplete information or bridges with serious damage. Firstly, the second-order difference of dynamic stiffness (SDDS) calculated by slabs’ responses is used an indicator to locate the damage. Secondly, Bayesian optimization is utilized to optimize the model hyperparameters of the support vector machine (SVM), where the dynamic stiffness serves as the characteristic vector for training the optimized SVM network. The applicability of this method was numerically validated using a grillage model of a hinged slab bridge, taking into consideration factors such as noise interference, impact location, sensor placement, and impact force characteristics. Additionally, on-site experiments were conducted on an in-service bridge to verify the effectiveness of the proposed method. Analysis results demonstrate that the proposed two-step method can properly evaluate joint damage with less dependence on the impact locations, force amplitude and environmental factors, and thus can be used for rapid damage identification of in-service hinged slab bridges and quantitative evaluation of repair effect.

A novel machine learning-based framework for predicting impact force in ship-bridge pier collisions

The escalating occurrence of ship-pier collisions poses a substantial threat to coastal bridge infrastructures. To avert such accidents, various specifications have introduced several impact force models, yet engineers strive for accurate predictions. This study presents a framework for predicting impact forces by combining a precise finite element (FE) model, machine learning algorithms, and fast Fourier transform (FFT). Firstly, a reliable FE model is constructed to simulate barge collisions with a double-column pier, encompassing analyses of energy transformation, structural damage, time-frequency impact forces, and structural response. Subsequently, a machine learning approach combined with FFT is employed to predict the impact force, with a discussion on the impact force's sensitivity to barge weight and velocity. The study also presents two potential applications of the proposed framework. Numerical results demonstrate that the framework accurately predicts the duration and frequency series of impact forces. The sensitivity analysis reveals the importance of closely monitoring barge weight in comparison to velocity during the design and management stages. Additionally, the study reveals that increasing barge velocity and weight prolongs the impact duration and amplifies the response peak, with time-series responses primarily concentrated in a limited low-frequency band. In summary, this study not only proposes a novel and accurate framework for predicting the time-history of impact forces through time-frequency analysis but also offers valuable insights into preventing catastrophic ship-pier collisions and mitigating their impact on coastal bridge infrastructure.

Effects of bond-slip on flexural behavior of reinforced nano-material modified UHPC beams: Experimental and numerical investigation

A series of central pull-out tests were carried out to assess the bond performance between steel bar and nano-material modified ultra-high performance concrete (nano-UHPC). The effects of parameters, such as the type of concrete and steel bar, the diameter of steel bar, bond length, the thickness of concrete cover, the length and content of steel fiber, and the nanomaterial type and content, on the failure mode and the bond stress-slip relationship were analyzed in detail. Subsequently, a constitutive model was proposed based on the experimental results for the precise prediction of the bond stress-slip relationship. Furthermore, to illustrate the effectiveness of the constitutive model, a reinforced nano-UHPC beam under the monotonic lateral loading was tested, and numerically simulated by a precise finite element model incorporating the constitutive model. Parametric studies were also conducted to evaluate the effect of critical parameters of the constitutive model on the flexural behavior of the reinforced nano-UHPC beam. The experimental results revealed that there was a superior bond performance between the steel bar and nano-UHPC. The increase in the bond length and the ribbed steel bar diameter were not conducive to the bond performance, and so did the decrease in the concrete cover thickness, steel fiber length and content. Nano-SiO2 and nano-CaCO3 had a positive impact, whereas nano-Al2O3 showed a negative effect. The numerical results indicated that both the bond strength and modulus had a significant effect on the flexural behavior of the reinforced nano-UHPC beam, whereas the slope of descending segment of the bond stress-slip relationship had an insignificant effect.

A Multi-Objective Finite-Element Method Optimization That Reduces Computation Resources Through Subdomain Model Assistance, for Surface-Mounted Permanent-Magnet Machines Used in Motion Systems

Surface-mounted permanent-magnet (PM) motors are widely used in motion control systems because of their high peak torque-to-inertia ratio. These motors exhibit high magnetic saturation to produce high peak torque. A precise finite-element model (FEM) is needed to optimize these motors. It requires high computation power, especially for multi-objective optimizations. On the contrary, subdomain models require low computing power but are inaccurate when magnetic saturation occurs. To solve this problem, we use a subdomain-assisted FEM optimization method (SAFEMOM) that combines subdomain models for preoptimization and FEM for refined optimization. We provide the quantitative measurement methods to compare SAFEMOM with FEM-only optimization. If the constraints in the magnetic fluxes in the subdomain part of SAFEMOM are based on the actual saturation value of the materials, then the advantage of SAFEMOM is not significant. The machines in this study use non-linear material with a knee point at 1.3 T and hence show heavy magnetic saturation above 1.5 T. In that case, contrary to what could be intuitively thought, we need to increase the magnetic flux density limit to 2.6 T - 3.0 T in SAFEMOM to have a significant advantage. SAFEMOM reduces about 80% of computing time to obtain a slightly better convergence than the one using FEM only. Also, if limited computing resource is allowed, SAFEMOM gives an error reduced by a factor of nearly eight compared to the optimization error using FEM only. Those results are validated on a family of surface-mounted permanent-magnet machines with a wide range of design parameters.

Effect of fibre volume on the natural frequencies of laminated composite plate

Resonance is an important phenomenon related to natural frequencies that could lead to catastrophic failure, and therefore investigating this phenomenon is crucial. There have been many studies regarding the effect of stiffness on the natural frequencies of laminated composite plates; however, studies relating the fibre volume to the natural frequencies have still not been established. This paper aims to investigate the effect of fibre volume on the natural frequencies of laminated composite plates. A 300 mm × 300 mm plate model made of carbon/epoxy composite laminates under Clamp-Free-Clamp-Free (CFCF) boundary conditions was developed using Finite Element Software (ANSYS). Different lamination schemes (fibre orientations, symmetry and anti-symmetry lay-up) with various fibre volume fractions were the analysed parameters. The natural frequencies were calculated for each scenario using finite element simulations. The mode shapes of vibration of the plates were also examined. To establish the precise finite element model for free vibration analysis of laminated composite plates, convergence analysis and numerical verification were conducted. The present numerical simulation results were in good agreement with published numerical results. The findings demonstrated that increasing the fibre capacity results in an increase of all vibrational modes and their shapes. Aside from that, the fibre orientation at 90°had the highest natural frequency value (910.52 Hz, 915.66 Hz and 1332.2 Hz) and the lowest natural frequency value at 0° (244.84 Hz, 245.90 and 627.95 Hz) for the first three modes shape of vibrations. In general, this study has made important contributions on how a fibre volume affects the natural frequencies of laminated composite plates.

A 3D finite element model updating of spinal lumber segment applying experimental modal data and particle swarm optimization algorithm

The dynamic loadings can be more harmful than static ones for the human lumbar spine health. Consequently, the prediction of the spine behavior under dynamic and vibration loads is vital and can be achieved by creating a precise finite element model in which the dynamic mechanical properties of the components need to be estimated. For this purpose, noninvasive experimental modal analysis can be applied to evaluate the dynamic mechanical properties of the spine in the numerical simulation by supplying the structural dynamic characteristics (natural frequencies, mode shapes, and damping ratio) of the system. Since the most adequate model for the human lumbar segment is a sheep model, in this paper, a 3D finite element model of a fresh spinal lumber segment of a sheep is generated based on the poroelasticity theory via Abaqus and is updated utilizing particle swarm optimization (PSO) algorithm and experimental modal analysis. In this regard, the frequency response function (FRF) of the specimen is obtained by performing the experimental modal test and the modal parameters are derived by using the rational fraction polynomial method. Afterward, the sensitivity analysis is carried out to determine the appropriate design variables. Finally, the PSO algorithm using experimental data is employed to update the design variables, including the elastic material properties and the structural damping factors of the specimen components, and the stiffness and damping coefficient of the suspension system. According to the results, the error percentage between the numerical FRF and the experimental one decreases remarkably after model updating indicating the high efficiency of the methods used.

Precise Finite Element Analysis of Full-Scale Straight-Tenon Joints in Ancient Timber Buildings

ABSTRACT In order to study the seismic performance of full-scale straight-tenon joint, a precise finite element analysis has been conducted based on the orthotropic constitutive relationship of wood and a modified Coulomb friction model. The hysteretic and skeleton curve, stiffness degradation, energy dissipation capacity, deformation capacity, and stress distribution are obtained through the finite element model and test results are utilized for calibration. Besides, parameter analyses considering size effect, friction coefficients, material properties, and axial loads on the column are performed. Results demonstrate that the precise finite element model can well reflect the seismic behavior of the straight-tenon joints. The hysteretic curves in simulation and test results are both anti-“Z” types with an obvious pinching effect. The initial stiffness is large, and stiffness degrades obviously with the increment of rotation. At the same rotation, the larger the scale of the model is, the greater moments and stiffness of the joints are, but the relationship is not linear. Friction coefficients and compressive strength in the parallel-to-grain direction mainly influence flexural capacity of the joint but have little effect on rotational stiffness. The rotational stiffness and flexural capacity are slightly affected by elastic moduli and axial loads.

Optimal sizing design of a 1.5 MW permanent magnets synchronous generator for an onshore wind conversion system

This paper proposes a fast and accurate optimal sizing design of 1.5 MW Permanent Magnets Synchronous Generator (PMSG) for a grid-connected wind application. A design strategy inspired from the output space mapping technique is adopted. A fast analytical model is used and detailed to determine the parameters and the performances of the PMSG. Then, the results are validated by a precise finite element model and adjusted iteratively until coherence between the two models is obtained. A multi-objective particle swarm optimization algorithm is deployed with aim of reducing the total losses and weight of the generator. The algorithm's parameters and results are given and analyzed. Three optimal machines are chosen and tested using a 2D-finite element model. The main design parameters of the optimal generators are given and discussed. Good efficiency and optimal designs are obtained for the sized machines thanks to the adopted design strategy.

Finite element model for static characteristic analysis of rolling linear guide

From the designer’s point of view, the static precise finite element model of the single ball-raceway, the overall and the unit slice of the rolling linear guide (RLG) are established based on the limited data obtained. According to the contact characteristics of a single ball-raceway, Hertz theory and finite element method (FEM) are used to determine the maximum contact stress and deformation of RLG under a specific preload value. The specific modeling process of the overall and unit slice finite element model of the RLG is described in detail as well. The comparative analysis results indicate that the unit slice finite element model can take place of the overall finite element model at the static level. On the basis of previous research, the mapping laws between external load, preload value, curvature ratio, the carriage’s wall thickness, the guide’s width, and static mechanical properties of RLG are studied. The combined application of these precise finite element models can solve the problems of large calculation and low efficiency in statics of RLG. Meanwhile, it also provides a new way to achieve high-efficiency and high-rigidity design of RLG from the source.

Life-cycle cost analysis of pile-supported wharves under multi-hazard condition: aging and shaking

Investigating the economic consequences of the natural hazards on the infrastructures is a crucial task in any risk-based decision-making process. Life-cycle cost (LCC) analysis is an important tool in both design (to choose the most economic configuration) and analysis (to estimate the future cost of ownership) stages. The pile-supported wharves, as one of the main parts in a marine harbor system, may experience significant deterioration (i.e. strength reduction) and seismic shaking during their life time. In this paper, damage cost in multiple limit states of a deteriorated pile-supported wharf due to chloride corrosion is calculated. A precise finite element model is developed to account for structural aging and the simultaneous seismic shaking. Aging-dependent seismic fragility functions are first developed using incremental dynamic analysis. Next, the LCC analysis is conducted considering the crane damage, as well as, inspection and maintenance costs. The results are calculated for three seismic hazard levels. The findings confirm significance of corrosion on LCC of pile-supported wharf. It is observed that corrosion may increase the LCC of the structure and system (i.e. structure and cranes) by 15% and 8%, respectively. Finally, a set of analytical formulations are proposed for performance index as a function of age, damage state, and seismic hazard level.

Finite Element Modelling and Updating of a Thin Plate Structure using Normal Mode Analysis

Structural design and analysis require accurate and precise finite element model in order to have a structure with high safety conditions such as aerospace, offshore and civil structures. However, the predicted results of the finite element model are often considerably different from the experimental results due to the modelling assumptions and simplifications on the properties and parameters of the actual structure. This paper presents the finite element modelling and updating methods on the thin plate structure. The modal parameters obtained from the plate are measured by experimental modal analysis by using an impact hammer and roving accelerometers method under free-free boundary conditions. The initial modal parameters are predicted by numerical analysis using normal mode analysis via NASTRAN SOL 103. The accuracy of the natural frequencies and the mode shapes obtained from the initial finite element model are compared with the measured counterparts. The modal based updating methods using NASTRAN SOL 200 is applied to update the properties of the plate. In conclusion, updating the material properties of the plate is successfully achieved. The total error of the initial finite element model of the plate is reduce from 45.12 percent to 6.28 percent respectively.

The Influence of the Motor Traction Vibration on Fatigue Life of the Bogie Frame of the Metro Vehicle

During the service life of metro vehicles, the cracks frequently appear at the root of motor seats. This indicates the previous antifatigue designs are unable to cover the actual operating environment. Some individual loads, such as motor vibration, have been ignored or wrongly understood, which leads to the occurrence of local insufficient fatigue life of the frame. To illustrate the influence of the motor vibration on the fatigue life of the bogie frame, a metro vehicle was taken as an example: first, the precise finite element model of the frame was established, and its correctness was verified; then, the vibration characteristics of the frame were analyzed by sweep frequency calculation; and finally, considering the vibration acceleration signal of the motor measured on a metro line as the excitation, the influence of the random vibration on the fatigue life of the frame under traction and idle running conditions was compared and analyzed by solving the power spectral density of the dynamic stress response at the weak fatigue nodes of the structure. The results show that the energy of the vibration in the frame is mainly concentrated in modes 6 and 7, which are excited by the motor transverse and vertical vibration, respectively, and contribute a lot to the fatigue damage of the frame; the fatigue life of the vital positions of the frame under the traction condition significantly reduces compared to the idle running condition; and the contribution of the low-amplitude vibration above 300 Hz to the fatigue damage can be ignored. At last, the importance of the influence of the motor traction vibration on the fatigue life should be fully considered in the metro vehicle design was proposed.

Local Mass Addition and Data Fusion for Structural Damage Identification Using Approximate Models

In practical civil engineering, structural damage identification is difficult to implement due to the shortage of measured modal information and the influence of noise. Furthermore, typical damage identification methods generally rely on a precise Finite Element (FE) model of the monitored structure. Pointwise mass alterations of the structure can effectively improve the quantity and sensitivity of the measured data, while the data fusion methods can adequately utilize various kinds of data and identification results. This paper proposes a damage identification method that requires only approximate FE models and combines the advantages of pointwise mass additions and data fusion. First, an additional mass is placed at different positions throughout the structure to collect the dynamic response and obtain the corresponding modal information. The resulting relation between natural frequencies and the position of the added mass is sensitive to local damage, and it is thus utilized to form a new objective function based on the modal assurance criterion (MAC) and [Formula: see text]-based sparsity promotion. The proposed objective function is mostly insensitive to global structural parameters, but remains sensitive to local damage. Several approximate FE models are then established and separately used to identify the damage of the structure, and then the Dempster–Shafer method of data fusion is applied to fuse the results from all the approximate models. Finally, fractional data fusion is proposed to combine the results according to the parametric probability distribution of the approximate FE models, which allows the natural weight of each approximate model to be determined for the fusion process. Such an approach circumvents the need for a precise FE model, which is usually not easy to obtain in real application, and thus enhances the practical applicability of the proposed method, while maintaining the damage identification accuracy. The proposed approach is verified numerically and experimentally. Numerical simulations of a simply supported beam and a long-span bridge confirm that it can be used for damage identification, including a single damage and multiple damages, with a high accuracy. Finally, an experiment of a cantilever beam is successfully performed.