Finite Element Method Analysis Research Articles

Size Optimization of Truss Structures Based on Genetic Algorithm by Developing Single-point Crossover with Bit-wise Mutation Using FORTRAN Programming

A truss is a collection of axially loaded structural elements connected through pin joints. Optimization of truss structures indicates the determination of best possible conditions that are necessary for achieving the most economical design in terms of lowest possible weights of the truss elements. According to recent studies, Size, Topology and Shape based optimizations are the three possible independent optimization scopes for finding the optimum weight of a truss. The current study focuses on the size optimization of truss structure and aims to identify the most cost-effective sections of the truss using a powerful evolutionary optimization technique named as Genetic Algorithm (GA). Here single point cross over method and bit wise mutation operator are adopted for expanding the search space with the assigned displacement and stress constraints. Fortran based sub routines are developed for each individual steps of GA such as fitness evaluation, selection, cross-over and mutation. Finaly the complete program is run for validation of its outcome. While comparing with the solution of an existing literature regarding a minimization of objective function having two design variables the outcomes tend to show a good correlation. Further, the study is extended for the weight minimization of two widely used truss having 10 members and 17 members respectively with standard Finite Element Method of analysis. Minimum weight of each truss is obtained via convergence plot and compared with the existing literatures. With this simple but efficient global optimization technique optimum weight of truss structure can easily be achieved.

Friction Characteristics and Lubrication Properties of Spherical Hinge Structure of Swivel Bridge

A spherical hinge structure is a key swivel bridge element that must be considered when evaluating friction characteristics and lubrication properties to meet the rotation requirement. Polytetrafluoroethylene (PTFE)-based spherical hinge sliders and lubrication coating have been employed for over 20 years, but with the growing tonnage of swivel bridge construction, their capacity to accommodate the required lubrication properties can be exceeded. In this manuscript, the optimal friction coefficient of the spherical hinge is obtained through the finite element analysis method. Four lubrication coatings and four spherical hinge sliders are prepared and tested through a self-developed rotation friction coefficient test, four-ball machine test, dynamic shear rheological test, and compression and shear performance test to evaluate the lubrication and friction properties of the spherical hinge structure. The results of the finite element analysis show that the optimum rotation friction coefficient of the spherical hinge structure is 0.031–1.131. The test results illustrate that the friction coefficient, wear scar diameter, maximum non-seize load, phase transition point, and thixotropic ring area of graphene lubrication coating are 0.065, 0.79 mm, 426 N, 14.6%, and 64,878 Pa/s. The graphene lubrication coating has different degrees of improvement compared with conventional polytetrafluoroethylene lubrication coating, showing more excellent lubrication properties, bearing capacity, thixotropy, and structural strength. Compressive and shear tests demonstrate that polyether ether ketone (PEEK) has good compressive and shear mechanical properties. The maximum compressive stress of PEEK is 87.7% higher than conventional PTFE, and the shear strength of PEEK is 6.07 times higher than that of PTFE. The research results can provide significantly greater wear resistance and a lower friction coefficient of the spherical hinge structure, leading to lower traction energy consumption and ensuring smooth and precise bridge rotation.

Finite Element Analysis for Linear Viscoelastic Materials Considering Time-Dependent Poisson’s Ratio: Variable Stiffness Method

For linear viscoelastic materials, this paper proposes a finite element analysis method based on an integral constitutive relationship that can simultaneously consider the relaxation behavior of the elastic modulus and the creep Poisson’s ratio. Firstly, the generalized Maxwell model is employed to depict the relaxation characteristics of the elastic modulus, while the generalized Kelvin model is used to represent the creep Poisson’s ratio. Subsequently, the element relaxation stiffness matrix is established, thereby forming a convolutional finite element equation. Furthermore, the recursive calculation of the convolutional integral is derived, and the calculation steps of the finite element for viscoelasticity considering the time-dependent nature of both the elastic modulus and Poisson’s ratio are established. Finally, the accuracy of the proposed algorithm is verified through two numerical examples with linear viscoelastic material. The results indicate that the proposed variable stiffness method for the finite element analysis of linear viscoelastic materials can simultaneously consider the changes in the elastic modulus and Poisson’s ratio over time, thereby establishing a new path and idea for the more accurate simulation of viscoelastic materials’ mechanical properties. Compared with the initial strain method for linear viscoelastic materials, the variable stiffness method proposed in this paper effectively avoids the assumption of constant stress during the micro time interval, thus significantly enhancing the finite element calculation accuracy of linear viscoelastic materials. The proposed method establishes a simulation algorithm that matches existing commercial software with viscoelastic material experiments by considering the elastic modulus and Poisson’s ratio as material parameters.

Design and Development of Solar Powered Electric Cart for on Campus Application

Electric vehicles (EVs) are becoming increasingly popular due to their eco-friendliness and low operational costs. However, the use of fossil fuels to generate electricity to charge these EVs undermines their sustainability goals. Combining solar energy with EV charging can create a sustainable and clean transportation system, which can reduce our dependency on non-renewable energy sources. The overall objective of the project is to design an efficient solar powered electric cart that can be used on campus in transporting and carrying Stationery loads. This is accomplished through the design of subsystems such as the frame, drivetrain, power, suspension, Brakes and steering, and integrated into a master assembly model using soft wares namely SolidWorks, a computer aided design (CAD), and finite element method (FEM). The FEM analysis is carried out to study the stress and displacements of the cart in order to ensure the safety. The basic performance of cart is evaluated in terms of its range, acceleration and maximum achievable speed. The cart is designed for 250kg load carrying capacity, acceleration of 1.2 m/s2 and maximum achievable speed of 15km/h with a power rating of about 1.5kW. Secondary support software such as Excel, and solar analyzing software were used to assist in the planning of the various subsystems as well as data collection and assortment. Keywords : Solar / electric cart, electronic differential speed control, Lithium-ion battery, transportation, photovoltaic.

Analysis of vibration response characteristics of composite pipeline based on finite element method

In order to ensure the good stability of the composite pipeline under fluid dynamic loads, finite element analysis method was applied to simulate and calculate the modal characteristics under dry and wet mode conditions. According to the working principle and structural characteristics of composite pipelines, the model was parameterized and simplified to improve computational efficiency and convergence. The modal testing platform is constructed, consisting of a combination of pipeline structure and pipeline support structure. The movement direction of the slider is limited by the guide rail used, allowing the horizontal section of the branch to move only along its own pipeline axis direction. The fluid structure coupling analysis technology was applied to obtain the vibration mode and spectral response results of the composite pipeline, which was verified through an experimental platform. The research results indicate that the natural frequency in wet mode was about 16 % lower than that in dry mode. In addition, it could be proven that the simulation scheme had good computational accuracy, with a maximum error of 9.2 %.

Modal and vibration response characteristics of rotating support platform

In order to improve the strength and stability of the rotating support platform, modal and stress characteristics were simulated and calculated based on finite element analysis method. In Hypemesh, the model of the rotating support platform was established. In Abaqus, boundary conditions and loads were defined, and the natural frequencies and vibration modes of the first four orders were obtained. Based on the structure and stress characteristics of the crossbeam, different damping technologies were compared and analyzed, and rubber damping scheme was selected and designed. Through time mileage analysis, the load response and damping effect of damping scheme were verified. The results show that the rubber damping scheme can reduce the maximum stress by more than 15 % without changing the natural frequency substantially.

A Novel Method to Enhance the Mechanical Properties of Polyacrylonitrile Nanofiber Mats: An Experimental and Numerical Investigation.

This study addresses the challenge of enhancing the transverse mechanical properties of oriented polyacrylonitrile (PAN) nanofibers, which are known for their excellent longitudinal tensile strength, without significantly compromising their inherent porosity, which is essential for effective filtration. This study explores the effects of doping PAN nanofiber composites with varying concentrations of polyvinyl alcohol (PVA) (0.5%, 1%, and 2%), introduced into the PAN matrix via a dip-coating method. This approach ensured a random distribution of PVA within the nanofiber mat, aiming to leverage the synergistic interactions between PAN fibers and PVA to improve the composite's overall performance. This synergy is primarily manifested in the structural and functional augmentation of the PAN nanofiber mats through localized PVA agglomerations, thin films between fibers, and coatings on the fibers themselves. Comprehensive evaluation techniques were employed, including scanning electron microscopy (SEM) for morphological insights; transverse and longitudinal mechanical testing; a thermogravimetric analysis (TGA) for thermal stability; and differential scanning calorimetry (DSC) for thermal behavior analyses. Additionally, a finite element method (FEM) analysis was conducted on a numerical simulation of the composite. Using our novel method, the results demonstrated that a minimal concentration of the PVA solution effectively preserved the porosity of the PAN matrix while significantly enhancing its mechanical strength. Moreover, the numerical simulations showed strong agreement with the experimental results, validating the effectiveness of PVA doping in enhancing the mechanical properties of PAN nanofiber mats without sacrificing their functional porosity.

Finite element analyses of failure of fiber reinforced polymer-concrete interface considering the concrete tension–compression softening effect

The concrete near the shear failure surface of the FRP (fiber reinforced polymer)-concrete interface is subjected to both tensile and compressive biaxial stress. However, existing finite element methods of the interfacial failure behavior of FRP-concrete interface to describe the tension–compression softening effect of concrete failure are not sufficiently accurate, and some detailed results may not be reflected. To address these issues, a finite element analysis method is proposed that accurately considers the tension–compression softening effect on concrete failure. The effectiveness of the method is demonstrated through analysis of literature data from experiments on plain concrete failure, FRP-concrete interface shear, and three-point bending. The method accurately reflects the generation of interfacial discontinuous micro-cracks, the oscillation singularity of stress field near the interfacial crack tip, the phenomenon of interface mismatch, the dispersion observed in the bond-slip curves, and the phenomenon of interfacial shear stress reversal. Moreover, this finite element analysis method is applied to the double shear experiments of the fully-bonded FRP-concrete interface under different boundary conditions, and the reasons for the different failure modes observed in the specimens are explained. The results indicate that considering the biaxial effect on concrete failure strength in numerical analysis can more accurately and comprehensively describe the shear failure behavior of the FRP-concrete interface.

Microscopic-plastic deformation behavior of grain boundary precipitates in an Al-Zn-Mg alloy

The nano-precipitates with minimal misfit strengthen Al-Zn-Mg alloys by impeding dislocation motion. However, grain boundary precipitates (GBPs) are known to have a completely incoherent relationship with the matrix, making them less effective in strengthening the alloys. Instead, GBPs are recognized for preoccupying elements such as Zn or Mg, thereby diminishing the quantity of nano-strengthening phases. GBPs significantly influence the deformation and fracture behaviors of Al-Zn-Mg alloys by accelerating stress localization and crack formation. In this study, we investigated how the accumulation of dislocations in the GBP areas leads to stress localization and subsequent cracking, using micropillar tests and crystal plasticity finite element method (CP-FEM) analysis. The dislocation pile-up in the GBPs causes stress localization around the grain boundaries, inducing crack initiation and leading to intergranular fracture. These findings enhance our understanding of the role of GBPs in the deformation and cracking of Al-Zn-Mg alloys and may pave the way for new concepts in managing GBPs.

Математическое моделирование и визуализация сложнонапряженного состояния при переломе диафиза бедренной кости

The purpose of this work is to establish the possibility of using the finite element analysis method to study complex stress states in case of a femur fracture with subsequent data visualization. Experimental data were obtained on a solid-state mathematical parametric model of the femur, created on the basis of computer tomogram data, and repeating studies on native biological objects. As a result of mathematical modeling, oblique transverse and helical fractures of the diaphysis of the femur with elements of helical deformation were studied. The application of finite element analysis made it possible to visualize and predict the stresses arising in bone tissue under the impact of a blunt solid object in a complex stress state and the morphological features of femoral shaft fractures under different torsional loading forces of the proximal part of the femur. The data on the mechanism and morphology of the femoral shaft fracture obtained during modeling are confirmed by the results of original full-scale experiments.

Spectral and optical properties of a [formula omitted] molecular complex confined in InAs/GaAs Quantum Camels: A spatial finite element method treatment

The evolution of eigenstates and related optical absorption (sum of linear and nonlinear contributions) of a singly ionized double donor (D2+) confined in InAs/GaAs (quantum-well-dot nanostructure) quantum camels were theoretically investigated. Within the effective mass and the compact density matrix approximations, the energy levels and optical absorption were characterized as a function of a hydrostatic pressure field applied, the sample temperature, and the wetting layer thickness via a spatial finite element method analysis. Results show that an increase of hydrostatic pressure (sample temperature) between 0 to 30 kbar (4 to 300 K) leads to a stabilization (destabilization) of the energy levels and a decrease (increase) of the absorption peak value with a red-shift (blue-shift). On the other hand, an increase in the wetting layer thickness leads to a reduction in the energy levels, and a monotonous evolution from quantum-dot states to wetting-layer states, especially in the excited ones, is seen. In addition, an increase in the absorption peak value is reported, which can be intended as an electron mobility enhancement. The donor-electron interactions reduce the wavefunction’s spatially-extended feature, enhancing the absorption peak in the analyzed |1〉→|6〉 transition. In the |1〉→|2〉 optical transition, the resonant peak can be tuned within the band ≈25–48 meV, slightly beyond the Terahertz frequency range.

Performance of tri-tubular conical energy absorber under axial compression

Quasi static axial compression loading on tri-tubular cone (TC) has been carried out using LS-DYNA finite element analysis method. Tri-tubular cones of three arrangements; the first arrangement (model TC-1) consists of cone heights of 50 mm, 75 mm and 100 mm where the inner cone is the maximum height. The second arrangement (model TC-2) consists of cone heights of 100 mm, 75 mm, and 50 mm where the outer cone is the maximum height. The third arrangement (model TC-3) consists of three cones of the same height of 100 mm. Cone semi vertex angle of 20o was maintained for all tri-tubular cones tested. Materials used for this research are glass, jute and jute-glass/epoxy. Crashworthiness analyses were performed to investigate the effect of material used, and tri-tubular cone arrangement on peak load. Crush efficiency, and absorbed energy were drawn and discussed. Failure mechanism of the fractured specimens was also discussed. Effect of number of layers and fiber stacking sequence were also investigated. Results show that the cone arrangement TC-3 gives better performance than the cone arrangement TC-2 followed by the cone arrangement TC-1. Maximum load obtained by tri-tubular cone type TC-3 was found higher 7.09% and 14.96% than TC-2 and TC-1 respectively for glass/epoxy. Material saving was achieved by using tri-tubular cones of different heights under compression. Material used has significant influence on the absorbed energy. Failure mode of tri-tubular conical energy absorber was presented and discussed.

A Finite Element Analysis Study of Edentulous Model with Complete Denture to Simulate Masticatory Movement

The purposes of this study are to establish and validate a finite element (FE) model using finite element analysis methods and to identify optimal loading conditions to simulate masticatory movement. A three-dimensional FE model of the maxillary and mandibular cortical bone, cancellous bone, and gingiva was constructed based on edentulous cone-beam-computed tomography data. Dental computer-aided design software was used to design the denture base and artificial teeth to produce a complete denture. Mesh convergence was performed to derive the optimal mesh size, and validation was conducted through comparison with mechanical test results. The mandible was rotated step-by-step to induce movements similar to actual mastication. Results showed that there was less than a 6% difference between the mechanical test and the alveolar bone-complete denture. It opened 10° as set in the first stage, confirming that the mouth closed 7° in the second stage. Occlusal contact occurred between the upper and lower artificial teeth as the mouth closed the remaining angle of 3° in the third stage while activating the masseter muscle. These results indicate that the FE model and masticatory loading conditions developed in this study can be applied to analyze biomechanical effects according to the wearing of dentures with various design elements applied.

Study on Torsional Vibration Response Characteristics of Marine Propulsion Shafting

_ The paper establishes the lumped parameter vibration mathematical model of shafting and uses the system matrix method to calculate and analyze steady-state frequency domain vibration characteristics of the shaft system in the range of diesel engine speed. Then in order to further study the transient torsional vibration of the shaft system under the resonance speed point, the state space method and finite element analysis method were used to compare and analyze the transient time domain response characteristic curve of the shaft system; finally, the test data of the real ship was compared with the theoretical calculation results, which verified the correctness of the mathematical model and the theoretical calculation method. This study has certain theoretical significance for carrying out the design of low-noise and vibration of shaft systems and improving the safety of ship navigation. Keywords shafting torsional vibration; transient time domain; finite element method; vibration test

Seismic performance of vertex-rotation type self-centering link beam equipped with SMA bars

This paper presented the seismic performance of self-centering energy-dissipating link beams that rotate around the vertex. The effects of the connection types of NiTi shape memory alloy (SMA) bar and the material of energy-dissipating steel angle on the self-centering performance, energy-dissipation capacity, bearing capacity, ductility, rotation mode, and strain distribution of link beams were explored through tests. It was verified through theoretical calculation and finite element analysis method, and the specimens were improved in design. The results show that the self-centering link beams have typical flag-shaped hysteretic curves and have excellent self-resetting performances and energy dissipation capabilities. Plastic deformations were concentrated on the steel angles. LY160 steel angle can enable the link beam to obtain better self-centering performance, while the Q235 steel angle can improve the energy dissipation capacity. The full-length SMA bars link beam has better self-centering performance and energy dissipation capacity than the partition SMA bars link beam. The theoretical calculation and finite element analysis results are consistent with the testing results. The self-centering performances of the improved design specimens were improved, but the energy consumption capacities were slightly reduced. The steel angles of the self-centering link beam after an earthquake are easy to replace and can quickly restore the structural function, which effectively solves the post-earthquake large residual deformation and difficulty of repair of traditional link beam.

Analysis of Kinematics and Dynamics of Rolling Ring Based on Finite Element Method

The working performance of the conductive rolling ring has a crucial impact on the overall energy security and on-orbit life of a satellite. To ensure the real-time transmission of signal and current, it is necessary to control the motion pattern of the rolling ring. In this paper, the finite element analysis method is used to carry out kinematics and dynamics simulation analysis, analyze the motion stability of the rolling ring, and discuss the relationship between the size of the idler gear, the driving torque, and the flexible contact pressure. The research results show that the numerical simulation and theoretical analysis show that the deviation angle is between 0 and 1.52 when the initial installation of the rolling ring is deviated by using the existing camber design of the inner and outer rings. Both have a self-recovery function. The driving torque and the size of the idler gear are nonlinear, and the contact force is proportional to the radius of the idler gear. With the increase in the compression of the radius of the flexible ring, the driving torque and the contact force will increase accordingly. The method of reducing the compression or increasing the size of the idler gear can be used to reduce the driving torque and maintain a certain contact to facilitate the transmission of electrical signals.

Driving Comfort Analysis Method of Highway Bridge Based on Human-Vehicle-Bridge Interaction

Research on evaluating highway bridge performance through vehicle-bridge interaction (VBI) analysis has made significant advancements. However, when assessing driving comfort, using vehicle acceleration instead of human acceleration poses challenges in accurately representing comfort. First, the paper proposes a finite element analysis method for human-vehicle-bridge spatial interactions (HVBSIs). Then, the importance of wheel path roughness difference is explored when assessing driving comfort. Furthermore, a new method for evaluating driving comfort that includes human and vehicle vibration responses has been proposed, and a simulation example of the steel-concrete composite beam bridge (SCCBB) is used to verify the effectiveness of the proposed method. The results demonstrate that the HVBSI analysis method effectively simulates the interconnected vibrations of the human body, the spatial vehicle model, and the three-dimensional (3D) bridge model. Differences in wheel path roughness significantly impact the roll vehicle vibration responses, which are crucial in driving comfort analysis. The driver’s body vibration response is essential for evaluating driving comfort, and its inclusion leads to increased comfort indices values. In comparison to traditional methods, the overall vibration total value (OVTV) increases by a maximum of 109.04%, and the level of weighted vibration (Leq) increases by a maximum of 6.74%. This leads to an upgrade from grade IV to grade V in terms of comfort level, indicating a reduced comfort.

A Study on the Ultimate Span of a Concrete-Filled Steel Tube Arch Bridge

In order to study the ultimate span of a concrete-filled steel tube (CFST) arch bridge, taking the structural strength, stiffness, and stability as the limiting conditions, the finite element analysis method is adopted to carry out research on the influence law of a single parameter of the pipe diameter, wall thickness, and cross-section height on the ultimate span of the arch axial shape. The result is used as a sample point to determine the ultimate span of the CFST arch bridge under multifactor coupling based on the response surface method. The finite element method is used to check the strength, stiffness, stability, number of segments and maximum lifting weight, steel content rate, and steel pipe concrete constraint effect coefficient of the CFST arch bridge under the ultimate span diameter. The results show that, when analyzed using a single parameter, the ultimate span diameter of the CFST arch bridge increases with the increase in the steel pipe diameter and the cross-section height, and then decreases. Moreover, it increases with the increase in the wall thickness of the steel pipe, and the CFST arch bridge reaches the ultimate span with the increase in the steel pipe wall thickness. When the pipe diameter is 1.38 m, the CFST arch bridge reaches the ultimate span; according to a multi-parameter coupling analysis, when the pipe diameter is 1.49 m, wall thickness is 37 mm, and cross-section height is 17 m, the CFST arch bridge reaches the ultimate span of 821 m, which meets all of the limiting conditions, and, at this point, the arch axial coefficient is 1.2. The results of the finite element calculation show that the structural strength, prior to the stiffness, stability, and other limitations, just reaches the critical value of the limiting conditions.

Flexural Behavior of Inverted Steel Fiber-Reinforced Concrete T-Beams Reinforced with High-Yield Steel Bars

This study discusses the effectiveness of T-beams reinforced with steel fibers and 600 MPa longitudinal reinforcements on negative flexural responses based on experimental and finite element analysis (FEA) methods. Four T-beams reinforced with 400 MPa or 600 MPa reinforcements were manufactured and inversely loaded. Two of the beams were fabricated with 0.75% (by volume) steel fibers as per JGJ/T465-2019, while the rest were cast following the same design but without steel fibers for comparison. The failure modes, the cracking moment and width, and the stress of the longitudinal reinforcements and concrete were compared between the four tested T-beams. In particular, deflection–load curves indicated the improved flexural ability of the specimens with steel fibers and high-yield steel bars. Models of T-beams with longitudinal reinforcements measuring 6, 8, and 12 mm in diameter were simulated and compared with the results of validated models. The FEA results further demonstrate the better flexural performance of T-beams reinforced with steel fibers and longitudinal reinforcements. Both materials can increase the overall performance of inverted steel fiber-reinforced concrete T-beams, including cracking load, crack width, ultimate load, and deflection. However, the findings showed that different diameters of longitudinal reinforcements generated different levels of effectiveness.

Structural design against brittle fracture: Optimizing energy release rate and experiment

Despite substantial advancements in optimizing structural designs for stiffness, the field of design against fracture is still in its early stages. This paper introduces a fundamental and standardized paradigm for structural design against brittle fracture, achieved through the minimization of the energy release rate G within the framework of linear elastic fracture mechanics (LEFM). By leveraging the Griffith criterion expression and the total potential energy in LEFM, we propose an efficient approach for structural optimization that enhances the toughness of architected materials. The energy release rate G is evaluated a synergistic application of finite element analysis and finite difference methods, yielding a precision of 0.6% compared to benchmarks in published handbooks. We demonstrate significantly reduced G values compared to standard stiffness and stress-oriented topology optimization, which directly contributes to increased toughness. To comprehensively analyze the fracture process encompassing damage, crack initiation, propagation, and failure, we employ post-processing phase field fracture modeling on the optimally designed architected materials. By performing multi-objective optimization of the stiffness and energy release rate G, the toughness and extreme load-bearing capacity can be simultaneously improved. The resulting perforated architecture effectively outperforms homogeneous structures in both toughness and peak load. Additionally, we extend our analysis to various configurations, such as non-center cracks, pure shear loading, and adherence to the standard 3D compact tension ASTM E-399-72. The designed structures are additively manufactured and experimentally validated, demonstrating a toughness increase of over 10 times compared to stress-based design. These contributions offer promising prospects for advancing the design of future engineering structures and materials with a favorable balance of critical fracture resistance characteristics.