Finite Element Computer Model Research Articles

Matrix curing and stress field development around fiber during the solvent evaporation-induced repolymerization of recycling composites

When recycling fiber-reinforced composites using depolymerized polymer solutions, oligomers reconnect through covalent bond exchange reactions (BERs), which ultimately forms a crosslinked network with mechanical properties comparable to those of virgin materials. This process offers exciting opportunities for the primary recycling of engineering composites, but it is intricately influenced by a few material and process parameters, such as heating temperature, duration, and fiber volume fractions. These parameters collectively determine the matrix's curing degree and the evolution of stress fields around the fiber, which are significant factors determining the quality and mechanical performance of recycled composites. This study introduces a diffusion-reaction-mechanics finite-element computational model to examine the solvent-induced repolymerization process in recycling composites. The model predicts the matrix curing degree, residual stress development around the fiber, and the composite's mechanical properties, aligning with experimental results. Parametric computational studies are then conducted to assess the influences of temperature, fiber content, solvent diffusivity, and the reactivity of BERs. The objective is to identify material and processing conditions that ensure efficient composite recycling while minimizing the development of residual stress. Overall, this study enhances our understanding of the mechanisms behind composite recycling using organic solvents and provides valuable insights for industrial stakeholders looking to optimize processing conditions and advance the commercialization and widespread adoption of this innovative recycling technique.

Predictive Refined Computational Modeling of ACL Tear Injury Patterns.

Anterior cruciate ligament (ACL) ruptures are prevalent knee injuries, with approximately 200,000 ruptures annually, and treatment costs exceed USD two billion in the United States alone. Typically, the initial detection of ACL tears and anterior tibial laxity (ATL) involves manual assessments like the Lachman test, which examines anterior knee laxity. Partial ACL tears can go unnoticed if they minimally affect knee laxity; however, they will progress to a complete ACL tear requiring surgical treatment. In this study, a computational finite element model (FEM) of the knee joint was generated to investigate the effect of partial ACL tears under the Lachman test (GNRB® testing system) boundary conditions. The ACL was modeled as a hyperelastic composite structure with a refined representation of collagen bundles. Five different tear types (I-V), classified by location and size, were modeled to predict the relationship between tear size, location, and anterior tibial translation (ATT). The results demonstrated different levels of ATT that could not be manually detected. Type I tears demonstrated an almost linear increase in ATT, with the growth in tear size ranging from 3.7 mm to 4.2 mm, from 25% to 85%, respectively. Type II partial tears showed a less linear incline in ATT (3.85, 4.1, and 4.75 mm for 25%, 55%, and 85% partial tears, respectively). Types III, IV, and V maintained a nonlinear trend, with ATTs of 3.85 mm, 4.2 mm, and 4.95 mm for Type III, 3.85 mm, 4.25 mm, and 5.1 mm for Type IV, and 3.6 mm, 4.25 mm, and 5.3 mm for Type V, for 25%, 55%, and 85% partial tears, respectively. Therefore, for small tears (25%), knee stability was most affected when the tears were located around the center of the ligament. For moderate tears (55%), the effect on knee stability was the greatest for tears at the proximal half of the ACL. However, severe tears (85%) demonstrated considerable growth in knee instability from the distal to the proximal ends of the tissue, with a substantial increase in knee instability around the insertion sites. The proposed model can enhance the characterization of partial ACL tears, leading to more accurate preliminary diagnoses. It can aid in developing new techniques for repairing partially torn ACLs, potentially preventing more severe injuries.

Design and Treatment Case Analysis of Continuous T-beam External Prestressed Composite Reinforcement Based on Finite Element Model Calculation

The second section of a highway bridge is a 3×30m prestressed concrete continuous T-beam, of which the 5th span 4# T-beam was found to have multiple structural cracks, such as U-shaped cracks and vertical cracks, during regular inspections after one year of operation. Analysis has shown that this was attributed to the fact that the insufficient prestressing during construction caused inadequate prestressing in the beam body. In this sudy, Midas/Civil software is utilized to establish a spatial finite element model to estimate the loss of prestress in damaged T-beams, yielding results consistent with the inspected conditions. On this basis, an external prestressing reinforcement design plan is proposed. The innovative plan considers the impact of reinforcement on the hogging moment of continuous T-beams and optimizes the layout of prestressed steel strands. The layout and fixing methods of steel turning blocks and anchoring blocks are also optimized in accordance with the stress characteristics of continuous T-beams, with the bearing capacity and safety reserve improved. After checking and analyzing the crack width of the reinforced T-beam, it was found that the plan fully meets the requirements for prestressed concrete Class A components. According to plan, the damaged T-beam was repaired and reinforced, and continuous observation of the reinforced T-beam was conducted for two years. No new development of bridge defects was observed in the later stages, indicating a satisfactory reinforcement effect. This provides technical reference for similar projects.

Study on the Ultimate Load-Bearing Capacity of Disc Buckle Tall Formwork Support Considering Uncertain Factors

Disc buckle steel pipe brackets are widely used in building construction due to the advantages of its simple structure, large-bearing capacity, rapid assembling and disassembling, and strong versatility. In complex construction projects, the uncertainties affecting the stability of disc buckle steel pipe support need to be considered to ensure the safety of disc buckle steel pipe supports. A surrogate model based on a deep neural network is built and trained to predict the ultimate load-carrying capacity of a stent. The results of the finite element model calculations are used to form the sample set of the surrogate model. Then, we combined the computationally efficient DNN surrogate model with the Monte Carlo method to consider the distribution of the ultimate load capacity of the disc buckle bracket under the uncertainties of the bracket node pin wedge tightness, the wall thickness of the steel pipe, and the connection of the connecting wall member. At the same time, based on the DNN model, the SHapley Additive exPlanations (SHAP) interpretability analysis method was used to study the degree of influence of various uncertainty factors on the ultimate bearing capacity of the stent. In practical engineering, the stability analysis of a disc buckle tall formwork support has shown that a surrogate model based on a deep neural network is efficient in predicting the buckling characteristic value of the support. The error rate of the prediction is less than 2%. The buckling characteristic values of the bracket vary in the range of 17–25. Among the various factors that influence the buckling characteristic value of the bracket, the joint wedge tightness has the greatest impact, followed by the bottom and top wall-connecting parts.

Impact of prior axonal injury on subsequent injury during brain tissue stretching – A mesoscale computational approach

Epidemiology studies of traumatic brain injury (TBI) show individuals with a prior history of TBI experience an increased risk of future TBI with a significantly more detrimental outcome. But the mechanisms through which prior head injuries may affect risks of injury during future head insults have not been identified. In this work, we show that prior brain tissue injury in the form of mechanically induced axonal injury and glial scar formation can facilitate future mechanically induced tissue injury. To achieve this, we use finite element computational models of brain tissue and a history-dependent pathophysiology-based mechanically-induced axonal injury threshold to determine the evolution of axonal injury and scar tissue formation and their effects on future brain tissue stretching. We find that due to the reduced stiffness of injured tissue and glial scars, the existence of prior injury can increase the risk of future injury in the vicinity of prior injury during future brain tissue stretching. The softer brain scar tissue is shown to increase the strain and strain rate in its vicinity by as much as 40% in its vicinity during dynamic stretching that reduces the global strain required to induce injury by 20% when deformed at 15 s−1 strain rate. The results of this work highlight the need to account for patient history when determining the risk of brain injury.

Transmission Line Icing Prediction Based on Dynamic Time Warping and Conductor Operating Parameters

Aiming to improve on the low accuracy of current transmission line icing prediction models and ignoring the objective law of icing of transmission lines, a transmission line icing prediction model considering the effect of transmission line tension on the bundle of icing thickness is proposed, based on a convolutional neural network (CNN) and bidirectional gated recurrent unit (BiGRU). Firstly, the finite element calculation model of the conductor and insulator system was established, and the change rule between transmission line tension and icing thickness was studied. Then, the convolutional neural network and bidirectional gated recurrent unit were used to construct a transmission line icing thickness prediction model The model incorporated a weighted fusion of soft−dynamic time warping (Soft−DTW) and the icing change rule as the loss function. Optimal weights were determined through the utilization of the grid search algorithm and cross−validation, contributing to an enhancement of the model’s generalization capabilities and a reduction in prediction errors. The results indicate that the proposed prediction model can consider the impact of line operating parameters, avoiding the shortcomings of prediction results conflicting with actual physical laws. Compared with traditional non−mechanical models, the proposed model showed reductions in root mean square error (RMSE), mean absolute error (MAE), and mean absolute percentage error (MAPE) by 0.26–0.51%, 0.24–0.44%, and 5.77–13.33%, respectively, while the coefficient of determination (R2) increased by 0.07–0.13.

Simulation Research on Local Settlement of Kiln Foundation Based on Winkler Theory

The masonry structure is one of the main types of modern industrial buildings in China because of its local materials and simple economy. However, these buildings often suffer damage and cracks due to uneven settlement of the foundation and disrepair, which affects the safe and normal use of the structure. It is urgent to maintain and strengthen the structure to restore the safety of the structure. This paper takes Baoji Shenxin Yarn Factory - Kiln Factory as the actual engineering background, and use the finite element software ABAQUS based on Winkler’s theory to establish a finite element calculation model that can more conveniently respond to the effects of different foundation settlements. Through the simulation analysis, the influence law of the local settlement of the kiln foundation on the overall structural force state was obtained, which can provide an important reference basis for the maintenance and reinforcement of the structure.

An Initial Case Study of the Computational Modeling of Cord–Rubber Segments

This paper presents an initial study of the computational modeling for determining the stress–strain behavior of the cord–rubber segment, tailored to be used as a flexible member in the construction of torque transfer coupling in railway vehicles. The presented computational models use the multibody simulation approach for the assessment of segment deformation under diverse loading characteristics. The results are then used in the finite element computational models of the cord–rubber segment. The computational model is validated through tension tests of cord–rubber segments. The homogenized and microstructural models show their ability to simulate the overall stiffness of the segment relatively accurately in tension, but they are limited in not being able to include the influence of the segment’s manufacturing technology. The micro-scale computational model then incorporates realistic representations of cord bundles, considering various cross-sectional shapes, whereas a very important factor significantly influencing the correlation of the results of the technical experiment and simulation is the consideration of the manufacturing technology in the process of building the computational model. The results show that the computational modeling approach in this work can be used for the determination of the optimal manufacturing technology conditions with regard to the stress–strain behavior of the given segment.

The Mechanical Behavior and Constitutive Model Study of Coarse-Grained Soil under Cyclic Loading–Unloading in Large-Scale Plane Strain Conditions

To address loading and unloading issues in civil and hydraulic engineering projects that employ coarse-grained soil as fill material under plane strain conditions during construction and operation, cyclic loading–unloading large-scale plane strain tests were conducted on two types of coarse-grained soils. The effects of coarse-grained soil properties on shear behavior and various modulus relationships were analyzed. The research results showed that coarse-grained soils with better particle roundness exhibit significant shear dilation deformation; it was also found that low parent rock strength can lead to strain softening, and an increase in confining pressure suppresses shear dilation deformation. During the cyclic loading–unloading process, the initial unloading modulus (Eiu) > unloading–reloading modulus (Eur) > initial reloading modulus (Eir) > initial tangent modulus (Ei), with the unloading modulus considerably greater than the others. In finite element simulations and model calculations, it is essential to select appropriate modulus parameters based on the stress conditions of the soil to ensure calculation accuracy. In this work, an elastoplastic and nonlinear elastic theory was used to establish a cyclic loading–unloading constitutive model. By comparing the values obtained using this model with experimental measurements, it was found that the model can reasonably predict stress–strain variations during cyclic loading–unloading of coarse-grained soils under plane strain conditions.

Characteristic Analysis of Transformer Loss with Subsynchronous Components by Field-Circuit Coupled Time Periodic FEM

A field-circuit coupled finite element calculation model embedded loss separation theory is proposed, which can effectively deal with the nonlinear core loss of transformer caused by subsynchronous frequency components injection. In order to deal with the increased time period due to the subsynchronous frequency components, and the problem of excessive loss current and too small parallel resistance due to zero-crossing point of voltage, the Parareal algorithm is introduced to solve the model. The algorithm is verified by the experiments of the physical transformer under the conditions of rated fundamental voltage and with subsynchronous components, respectively.

Seismic Analysis of Large-span Steel Truss Structure Based on PKPM

In the construction industry, large-span steel truss structures are widely used. In order to test their seismic performance under different structures, select truss structures with better seismic performance, and use PKPM software to establish two cross-sectional triangular arch truss models with different web member arrangements, one cross-sectional trapezoidal arch truss model. Using the mode decomposition response spectrum method, simulate and analyze the displacement and stress changes of three sets of finite element calculation models under different load combinations during earthquakes. The results showed that all truss models meet seismic requirements. The change in the arrangement of the web members did not significantly improve the seismic performance of the cross-sectional triangular truss, the seismic performance of the cross-sectional trapezoidal arch truss was significantly better. The lower chord of the triangular arch truss support and the mid-span top chord are under compression, while the top chord is only compressed on one side and tensioned on the other side. The top chord of the trapezoidal arch truss is mainly under pressure.

Finite Element Analysis of Geotechnical Isolation System Finite-Element Analysis on the Geotechnical Seismic Isolation (GSI) System

In order to verify the effectiveness of the Geotechnical Seismic Isolation (GSI), a series of finite element parameter studies were carried out. The finite element calculation model of the GSI system and superstructure is established. The finite element analysis conditions consist of two kinds of confining pressures, three kinds of RSM ratios and three kinds of seismic wave inputs, a total of 32 kinds of conditions. Comparing the analysis results of the parameters, it can be seen that the dynamic shear modulus of the RSM sample increases with the increase of the confining pressure, but the degree is affected by the input of seismic waves. The greater the peak value of the input acceleration, the more obvious the isolation effect; As the RSM ratio increases, it decreases, but it is not greatly affected by the input of seismic waves, and the isolation effect remains basically the same. The numerical simulation results verify the isolation effect of GSI, which can be used as a reference for practical engineering applications in the future.

Research on the Influence of Compression and Offset of Cushion Blocks on the Axial Strength of Transformers

The instability of the winding-cushion structure is one of the primary causes of transformer failures. Insulation cushion compression and offset are the predominant forms leading to structural instability. Therefore, this paper, using the SFSZ7-31500/110 transformer as an example, first derives the theoretical formula for mechanical stress calculation. It clarifies the key influencing parameters of the winding-cushion block structure on the axial bending stress of the winding. Subsequently, an electromagnetic force finite element calculation model is established to obtain the axial force distribution in the winding and the distribution of unbalanced displacement during short-circuit processes. Based on the force and offset distribution, a specific cushion block compression and offset test platform is constructed. By setting different cushion block variables, the effects of cushion block unbalanced height and cushion block offset on the winding’s bending elastic modulus are determined. Finally, a simulation model for stress calculation of the winding-cushion block structure is established, revealing the influence pattern of cushion block compression and offset instability on the axial strength of the winding. The results of this study indicate that the greater the uneven cushion block height, the lower the axial strength of the winding. Under the same cushion block offset angle, winding structures with non-uniform cushion block offsets exhibit the worst axial stability. When the offset angles are 30°, 45°, and 60°, the maximum axial bending stress of the winding increases by 1.73%, 3.46%, and 7.82%, respectively. Increasing the offset angle exacerbates the decrease in the axial strength of the winding up to a certain extent. The findings in this study have significant implications for enhancing a transformer’s short-circuit resistance.

Modeling and simulation credibility assessments of whole-body finite element computational models for use in NASA extravehicular activity applications

Computational finite element (FE) models are used in suited astronaut injury risk assessments; however, these models’ verification, validation, and credibility (VV&C) procedures for simulating injuries in altered gravity environments are limited. Our study conducts VV&C assessments of THUMS and Elemance whole-body FE models for predicting suited astronaut injury biomechanics using eight credibility factors, as per NASA-STD-7009A. Credibility factor ordinal scores are assigned by reviewing existing documentation describing VV&C practices, and credibility sufficiency thresholds are assigned based on input from subject matter experts. Our results show the FE models are credible for suited astronaut injury investigation in specific ranges of kinematic and kinetic conditions correlating to highway and contact sports events. Nevertheless, these models are deficient when applied outside these ranges. Several credibility elevation strategies are prescribed to improve models’ credibility for the NASA-centric application domain.

Simulation and experimental studies of mechanical delamination characteristics of REBCO tapes and lap joints under transverse tension

In this study, we investigate the delamination properties of high-temperature superconducting REBa2Cu3O7−x (REBCO) coated conductor (CC) tapes and lap joints under transverse tension by a finite element model (FEM) based on the cohesive zone model. The interfacial cohesive strength and the initial penalty stiffness used in the FEM calculations are adopted based on the experimental data obtained from the anvil tensile tests. Compared to previous theoretical studies, our calculation results of the delamination behaviors for the REBCO CC tapes and the lap joints are more approaching to the experimental data, and the abrupt failure behavior of the transverse load–displacement curves, which appears in the anvil tests, is reproduced by the simulations. Moreover, the effects of welding strength between the upper and lower tapes and internal tape damage during the welding process on the delamination characteristics, including the delamination strength, initial separation, delamination locations, and damage distribution of the CC lap joints, are presented.

High-velocity impact failure modeling of Armox 500T steel: Model validation and application to structural design

As an advanced fracture model, the Generalized Incremental Stress State dependent damage MOdel (GISSMO) provides non-linear damage accumulation formulation to better predict ductile fracture initiation associated with a wider range of material stress states. In this study, we simulate the high-velocity impact failure of Armox 500T steel through computational finite element modeling in the LS-DYNA/Explicit solver. Here, the GISSMO is used to describe the ballistic responses of the Armox 500T steel under dynamic impacts. Two sets of the most important parameters in the GISSMO (i.e., the fracture and instability surfaces) are determined for the Armox 500T steel. The GISSMO is calibrated in terms of the fade exponent and mesh regularization functions using the force–displacement curve of tensile tests extracted from the literature. The calibrated GISSMO is then scaled with the strain rate and validated by comparing quantitative measurements from ballistic experiments provided in the literature. Once validated, the model is then used to investigate the impact failure behaviors of Armox 500T steel by simulating bi-layer configurations consisting of an Armox 500T steel front plate and a rolled homogeneous armor (RHA) steel backing plate impact from a 20 mm fragment simulating projectile. The roles of the standoff distance and impact angle of obliquity on impact failure behaviors of bi-layered steel systems are explored. Altogether, results from this study provide new capabilities and insights into the design of armor structures with respect to lightweight and ballistic performance, and evaluation of impact failure behaviors of Armox 500T/RHA bi-layered systems.

Thermal stress analysis of laser cleaning ofaluminum alloy oxide film.

In this paper, a theoretical model for laser cleaning of aluminium alloy oxide film is presented from the perspective of thermal stress. Additionally, we developed a two-dimensional axisymmetric finite element model for calculation. Thermal stresses result from thermal expansion. Using thermodynamic equations, numerical calculations enablethe determination of a theoretical cleaning threshold by comparing the thermal stresses to the adhesion between the oxide film and the substrate. Through theory and experiments, it is known that the greater the laser fluence, the better is the cleaning effect. The findings indicate that cleaning of the oxide film on aluminum alloys can be achieved under appropriate parameters. The cleaning threshold for laser cleaning of the oxide film is determined to be 3629.47J/c m 2 (continuous laser fluence is 3628.73J/c m 2; nanosecond laser fluence is 0.74J/c m 2). The thermal stress model of laser cleaning is highly useful for selecting the appropriate laser flux in practical applications. Both a simulation and experimental results can provide an explanation for the mechanism of interaction between the laser and the aluminum alloy oxide film, demonstrating that thermal stress is one of the cleaning mechanisms during the laser cleaning process of the oxide film.

Flood impact on structural response of asphalt pavement: A finite element modeling approach

The frequency and intensity of floods have increased due to climate change. These natural events negatively affect asphalt pavements, submerging their layers and reducing structural resistance. This work introduces a computational finite element model suitable for investigating the impact of floods on asphalt pavement response. Unlike previous works, which consider a multi-layer analysis, in this research, the resilient modulus varies locally as a function of moisture, which could be variable in the transverse direction of the cross-section. The moisture distribution in the pavement structure is found by solving the Richards’ equation through non-linear finite element analysis. This moisture distribution is coupled to the three-dimensional elasticity problem to find the structural response to traffic loads. The structural problem was solved using the semi-analytical finite element method. Results show that the reduction of the resilient modulus in the unbound and subgrade layers is heterogeneous, with the areas near the edges of the pavement being the most affected. It was also found that the increase in elastic surface deflection depends on both the load position and time, which suggests the damage caused by vehicles could be different for each wheel path, depending on the time in which the vehicles circulate. This research presents a valuable tool for evaluating the impact of flooding on asphalt pavement structures.

Деформирование слоистых композитных пластин при низкоскоростном контакте с жестким индентором

The computational finite element model of contact between a steel sphere and a composite plate was developed in the ANSYS software package. The model includes geometric description of the contact, materials management, computational mesh generation using the SOLID186 and SOLID187 finite elements, as well as the surface-to-surface contact model using the CONTA174 and TARGET170 contact elements. The paper identifies influence of the rigid sphere radius on the woven composite structure and shows areas of the local composite destruction. Satisfactory compliance was obtained between the numerical calculation results and full-scale study of a contact between rigid indenter of different radii and the fiberglass laminate. The safety factor values are provided according to four criteria. The developed model of contact between the indenter and the composite plate made it possible to obtain stress fields in the carbon-plastic composite material with the laying layers [45°, –45°]n and [45°, 90°, –45°, 0°]n. Destruction in layers based on the numerical calculation results was analyzed using various stress criteria. Carbon composite had more destroyed layers due to low strength in the transverse direction. Destruction zone in the carbon composite was larger than in the fiberglass composite, and the pattern [45°, –45°]n had a smaller damage area compared to [45°, 90°, –45°, 0°]n.

Study on the fatigue performance of steel-composite grillage deck of large-span arch bridge

In this paper, based on the finite element numerical method, an arch bridge with a main span of 252m was selected as the engineering background, and three standard grillage segments of the bridge deck in the derrick area were selected to establish a refined finite element model, and the fatigue characteristics of the steel-composite grillage deck were studied. The fatigue calculation mode III in General Specification for Design of Highway Bridges and Culverts (JTG D60-2015) was loaded into the finite element model for calculation, and the fatigue key points were determined, the stress time course curves were extracted, and the fatigue damage calculation was carried out. The results indicate that the most unfavorable stress point of the steel-composite structure model is at the bottom plate (outside) of the intersection of the middle longitudinal beam and the secondary crossbeam under the longitudinal loading of vehicle load in the transverse position; the stress amplitude of the maximum critical point in the longitudinal bridge stress course under the standard fatigue vehicle model is less than the fatigue strength limit of the normal amplitude, which meets the design requirements.