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In this paper, a ground-based experimental system for solar array active vibration suppression has been established. Firstly, in order to establish an accurate model of the solar array, the solar array is regarded as a flexible cantilevered thin plate, and the corresponding dynamical equations are derived using the absolute nodal coordinate method. In addition, in this paper, the more advanced MFC piezoelectric patch is used instead of the traditional PZT piezoelectric ceramic patch. The electromechanical coupling finite element model of the P1-type MFC patch is established and substituted into the kinetic equation of the solar array. Finally, the accuracy of the electromechanical coupling modeling and the control effect of active vibration suppression were verified using the PID control. A set of experimental frameworks for evaluating the active vibration suppression effect, including the free vibration test, sinusoidal perturbation test, and white noise perturbation test, as well as the analysis strategy of the test data, are established. [ABSTRACT FROM AUTHOR]

In order to further study the cushioning performance of concave hexagonal cores (CHCs) and expand their application range, the in-plane finite element model of CHCs is established in this paper. A dynamic cushioning coefficient method was proposed to characterize the cushioning performance of CHCs. The dynamic cushioning coefficient curve and minimum dynamic cushioning coefficient (MDCC) of CHCs with different impact velocities and structural parameters are obtained. The influence rules of structural parameters and impact velocities on the MDCC are analyzed; the deformation mode and transformation empirical formula are also obtained. The results show that when other parameters are constant, the MDCC of CHCs decreases with the increase of impact velocity, increases with the increase of wall thickness and side length ratio, and decreases with the increase of expansion angle. The theoretical analysis is consistent with the finite element results, which further verifies the reliability of the model. This paper provides a solid theoretical basis for the industrial application of the cushioning performance of CHCs and forms a key technical support. [ABSTRACT FROM AUTHOR]

The multiple intersecting stiffeners on the chemical milling stiffened panel (CMSP) limit the application of active health monitoring methods on it. An imaging algorithm based on electromechanical impedance (EMI) and probability-weighting is proposed to achieve quantitative evaluation and localization of the damage on CMSP. The proposed algorithm compensates for the difference in sensor performance with coefficients and there is no need to determine the key parameters of the algorithm through prior experiments. In the paper, the applicability of ultrasonic guided wave (GW) and EMI on CMSP was first studied through the finite element method. Based on EMI and the mean absolute percentage deviation (MAPD), the selected damage indicator (DI), a probability-weighted damage imaging algorithm are proposed and experimentally verified. The results indicate that due to the reflection and attenuation effects of stiffeners on GW, the signal characteristics of damage scattering waves are contaminated, making it difficult to quantitatively characterize the damage from GW signals through DIs. MAPD is positively correlated with the damage degree and has consistency in characterizing the signal of different PZTs under the same working condition. The feasibility and accuracy of the proposed algorithm are verified through experiments which show a strong engineering application capability. [ABSTRACT FROM AUTHOR]

This paper presents a study on the numerical solutions of the Burgers' equation with forcing effects. The article proposes three hybrid methods that combine two-point, three-point, and four-point discretization in time with the Galerkin finite element method in space (TDFEM2, TDFEM3, and TDFEM4). These methods use backward finite difference in time and the finite element method in space to solve the Burgers' equation. The resulting system of the nonlinear ordinary differential equations is then solved using MATLAB computer codes at each time step. To check the efficiency and accuracy, a comparison between the three methods is carried out by considering the three Burgers' problems. The accuracy of the methods is expressed in terms of the error norms. The combined methods are advantageous for small viscosity and can produce highly accurate solutions in a shorter time compared to existing numerical schemes in the literature. In contrast to many existing numerical schemes in the literature developed to solve Burgers' equation, the methods can exhibit the correct physical behavior for very small values of viscosity. It has been demonstrated that the TDFEM2, TDFEM3, and TDFEM4 can be competitive numerical methods for addressing Burgers-type parabolic partial differential equations arising in various fields of science and engineering. [ABSTRACT FROM AUTHOR]

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 ( L e q ) 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. [ABSTRACT FROM AUTHOR]

Timely wear evaluation is crucial in maintaining the functionality of bridge expansion joints (BEJs), ultimately ensuring the safety of bridges. Despite the significance of traffic load simulation (TLS) in simulation-based evaluation methods, existing TLS approaches face challenges in accurately modeling in situ traffic flow at a high fidelity. This paper presents a novel methodology and its application for evaluating the wear performance of BEJs, employing a Transformer-enhanced TLS approach. Initially, a tailored dataset is crafted for data-driven car-following modeling, leveraging an established spatial-temporal traffic load monitoring system. High-fidelity TLS with a mean absolute error (MAE) of 0.1738 m/s is then achieved using Transformer modules equipped with an attention mechanism. To evaluate the final wear life of BEJs, transient dynamic analysis and a calibrated finite element model of the bridge are employed to extract cumulative displacement. Additionally, a surrogate model is developed to depict the relationship between the hourly traffic weight on the entire bridge deck and the cumulative displacement of BEJs, yielding an impressive R-squared value of 0.96619. Comparative results demonstrate the superior performance of our proposed TLS approach over other data-driven approaches, with the linear model derived from our TLS approach outperforming the model generated by the conventional Monte Carlo-based TLS approach. To conclude, our proposed TLS emerges as a comprehensive and precise methodology for the wear evaluation of BEJs. [ABSTRACT FROM AUTHOR]

Tooth flank fracture (TFF) and tooth interior fatigue fracture (TIFF) usually occur on case-harden gears in electromechanical coupling systems, both starting from the core caused by metal fatigue. The cracks propagate rapidly compared with the total life of a gear, so that it is necessary to detect and identify the faults in time when they take place in order to avoid danger. In this paper, the time-varying mesh stiffness model of two types of faults is established by the potential energy method and validating by the finite element method. Based on the stiffness model, the influence of faults on the electromechanical system and their fault characteristics are analyzed, which provides a theoretical basis for the health detection of electromechanical coupling systems. The results indicate that in the early stage of the three faults, i.e., tooth root fracture, tooth interior fatigue fracture, and tooth flank fracture, it is hard to discriminate the faults. But after the second stage, the faults can be distinguished by the vibration amplitude, frequency band components, and phase diagrams. The TFF can be discerned into different stages by frequency domains and phase diagrams. When the fracture occurs completely, three faults can be easily distinguished by the time domain and phase diagram. In the frequency domain, the TRF can also be distinguished from the other two faults by referring to the sideband component near the meshing frequency. [ABSTRACT FROM AUTHOR]

In order to broaden the muffler frequency band in the low-frequency range of the exhaust muffler and to achieve the purpose of broadband noise reduction, in this paper, a model of an annular connecting pipe muffler is proposed using the finite element method (FEM) to simulate the nonreflection boundary condition and to solve the transmission loss (TL). In addition, the experimental value is obtained by the spatial five-point measurement method and compared with the simulated value, and the validity and reliability of the solution model are verified. Compared with a simple expansion muffler, the average TL of the annular connecting pipe muffler is increased by 11.86 dB, and the maximum TL is increased by 18.31 dB, effectively widening the muffler frequency area, and the overall performance is effectively improved. Finally, the influence of structural factors is analyzed, including the width (W) of the annular connecting pipe, the length (L) of the annular connecting pipe, and the length ratio (m) of the front and rear chambers on the TL and on the width of the anechoic frequency band. The results reveal that the width and length of the annular connecting pipe and front-to-back cavity length ratio are the most significant factors to influence the TL, muffler frequency band, and elimination or reduction of the passing frequency, respectively. [ABSTRACT FROM AUTHOR]

The aim of this study is to compose a corotational finite element formulation for space frames with geometrically nonlinear behavior under dynamic loads. Using a moving frame through three successive rotations similar to Euler angles is one of the oldest techniques; however, there are still some gaps that require attention, mainly due to singularity. Hence, alternative techniques had been developed, sometimes elusive and computationally expensive. In this paper, we went back to the old technique and filled the gaps. Three-coordinate systems are used, i.e., the fixed global coordinate system, the fixed local coordinate system that is attached individually to every element, and the corotational local frame for each element that moves and rotates with the element. The deformation is always small relative to the corotational frame. The successive rotations between different coordinate systems are expressed using Tait–Bryan angles. Lagrange's equation is used to derive the equation of motion, and the stiffness and mass matrices are obtained using the Euler–Bernoulli beam model. A MATLAB code is developed based on the Newton–Raphson method and the Newmark direct integration implicit method. In traditional techniques, singularity is attained when any rotation angle in the fixed local frame approaches π / 2 , and if any is greater than π / 2 , the techniques could fail to specify the location of the element. In this paper, each case is treated with a proper procedure, and special handling of trigonometric formulations prevents singularity and correctly specifies the location of elements in all situations. Different examples of beams and frames are analysed. While the method is not intricate, it is timesaving, is highly effective, provides more stable and robust analysis, and gives sufficiently accurate results. Compared to the parametrization of the finite rotations technique, the method has a significant reduction in the convergence rate because it avoids the storage of joint orientation matrices. [ABSTRACT FROM AUTHOR]

This paper presents the development of a numerical model able to track in time the behavior of nonlinear focused ultrasound when interacting with tiny gas bubbles in a liquid. Our goal here is to analyze the frequency components of the waves by developing a model that can easily be adapted to the geometrical restrictions and complexities that come out in several application frameworks (sonochemistry, medicine, and engineering). We thus model the behavior of nonlinear focused ultrasound propagating in a liquid with gas bubbles by means of the finite-element method in an axisymmetric three-dimensional domain and the generalized- α method in the time domain. The model solves a differential system derived for the nonlinear interaction of acoustic waves and gas bubble oscillations. The high nonlinearity and dispersion of the bubbly medium hugely affect the behavior of the finite-amplitude waves. These characteristics are used here to generate frequency components of the signals that do not exist at the source through nonlinear mixing (parametric antenna). The ability of the model to work with complex geometries, which is the main advantage of the method, is illustrated through the simulation of nonlinear focused ultrasound in a medium excited from two spherical sources in opposite directions. [ABSTRACT FROM AUTHOR]

The residual strain generated in grains during the propellant manufacturing process can significantly impact the safety and stability of solid rocket motors. Pressure curing molding technology has been employed as an effective approach to mitigate residual strain. This research paper focuses on deriving a strain prediction function for grains based on continuum mechanics, taking into account the influence of pressure curing molding technology. The accuracy of the prediction function is verified through finite element analysis. The results show that the proposed function accurately predicts strain distribution at critical positions within the grains. And the effects of curing pressure and the elastic modulus of the case on residual strain are analysed. Specifically, for a given material of case, an optimal curing pressure is identified that minimizes residual strain in the grains. Moreover, it is observed that materials with lower hoop elastic modulus, such as composites, tend to require lower optimal curing pressures. The outcomes of this study provide valuable guidance for grain shape design and the selection of optimal curing pressure. [ABSTRACT FROM AUTHOR]

Vortex-induced force (VIF) identification and modelling of a long-span bridge are often conducted in terms of aeroelastic sectional model tests in wind tunnels. However, there are uncertainties inherent in wind tunnel model tests so that vortex-induced vibration (VIV) still occurs in real long-span bridges designed according to wind tunnel test results. This paper presents a framework for VIF identification of a long-span bridge based on field-measured wind and acceleration data. The framework is composed of the four steps: (1) decompose field-measured acceleration response time histories using variational mode decomposition (VMD) method; (2) obtain velocity and displacement response time histories using frequency domain integration (FDI) method; (3) establish and update the finite element model and identify the generalized VIF time histories of the bridge; and (4) identify the parameters in the polynomial VIF models and decide the most suitable VIF model. The proposed framework is finally applied to a real suspension bridge with a recent VIV event. The results show that the proposed framework can accurately identify the generalized VIF acting on the bridge from the field-measured acceleration and wind data, and the derived most suitable VIF model can produce almost the same vortex-induced response (VIR) as the measured ones. [ABSTRACT FROM AUTHOR]

The topography and the incident angle of seismic waves both have considerable effects on the seismic ground motions of canyons in a half-space. In this paper, the theory of wavefield decomposition and the artificial boundary is used to develop a method for inputting obliquely incident SV waves. Formulas for the equivalent nodal forces applied to the truncated boundary are derived and implemented in the finite element method. The validity of the proposed method is verified by a test case. A parametric study is then performed to investigate the influence of canyon geometry and incident angle of SV waves on the seismic response of trapezoidal canyons. The numerical results indicate that the canyon inclination has a more significant effect on the ground motion amplification than its height and width. The amplification effects are strongly related to the canyon inclination and the incident angle of SV waves. Additionally, the dominant frequency corresponding to the acceleration of the canyon crests is not sensitive to the incident angle of SV waves. [ABSTRACT FROM AUTHOR]

The tubing used in a gas well rarely collapses and fails during applying annulus pressure. In this study, the failure causes of tubing collapse were analyzed by means of data verification, macroscopic observation, magnetic particle inspection, physical and chemical inspection, optical microscopy, and tubing collapse test. Mechanical analysis of the string and full-scale physical simulation test simulating downhole working conditions. Finally, the verification analysis of the collapse test is carried out by the finite element analysis (FEA). The results showed that (1) the physical dimension, physical and chemical properties, and collapse resistance of this batch of tubing met the requirements of the tubing ordering technical standard. (2) Assuming that the well packer slip was unsealed and could slide freely, the mechanical theoretical analysis of collapsed tubing string and collapse test under simulated working condition load was carried out, which reproduced the load when the tubing collapsed. It can be seen from this that the packer did fail. (3) The FEA calculation results showed that when the external pressure was greater than 30.75 MPa, it would inevitably lead to collapse failure in case of packer unsealed. In conclusion, the root cause for the collapse failure of the 105th underground tubing string was that the packer lost its sealing function, resulting in an abnormal axial load. While under the action of external pressure, the tubing was overloaded and collapsed. It is recommended to carry out verification tests on the material performance of packer slip, the dimensional changes of packer tool outer diameter and inner diameter under actual well conditions, the creep behavior of packer seal, and the performance of shear pin under actual working conditions, especially in the well containing H2S, so as to prevent the pressure leakage of gas well annulus caused by packer unsealing and the reoccurrence of such downhole string collapse accidents. The first collapse test under simulated working condition load is conducted in this paper. Analyzing the collapse failure work and putting forward suggestions to effectively prevent similar failures from happening again are of great significance to the oilfield. [ABSTRACT FROM AUTHOR]

This paper proposes an electric propulsion system model for computationally efficient multiobjective optimization considering overall driving cycles using coupled electromagnetic–thermal 1D simulation. The proposed system model uses equivalent circuit networks rather than finite element method to obtain high computational efficiency because considering both driving cycles and motor temperature change during optimization requires considerable computational cost. The magnetic saturation effect and temperature change of traction motor during operation are examined by constructing look-up tables. This study first integrated the lumped parameter thermal network into the system model to consider the motor temperature change without any iterative process. The 1D simulation results over urban and highway driving cycles indicate that the changes in the induced current, efficiency, and motor temperature could be predicted while driving. The Pareto optimal solution of traction motor cross-sectional geometry including reduction ratio is successfully obtained by multiobjective optimization with the maximum output torque constraint. Constructing the proposed system model once, optimal design for multiple target driving cycles can be obtained without any driving cycle analysis. In addition, high computational efficiency indicates that the proposed system model is practical in the early design stage of various electric propulsions. [ABSTRACT FROM AUTHOR]

In this paper, a model to predict the residual shear capacity of RAC beams with corroded stirrups was established, and the simulation analysis was conducted on recycled concrete beams with different corrosion level using ANSYS. The reliability of the finite element analysis model was verified by comparing the finite element results with experimental results. [ABSTRACT FROM AUTHOR]

The electromagnet pneumatic proportional servo valve is widely used in industrial automation, medical equipment, scientific composition detectors, and other fields that require precise adjustment of high-pressure air flow due to its simple working structure, large output power, large working frequency response, and good control performance. However, the output pressure of the valve is small, making it vulnerable to the impact of the external environment. Based on the practical electromagnet-type pneumatic proportional servo valve, this paper establishes a finite element dynamic mathematical model, conducts finite element analysis on the electromagnet magnetic field in the valve, then improves the structural parameters of the original proportional valve through the analysis of the valve performance parameters and structural optimization, and finally, the physical experiment proves that the optimized electric proportional valve can effectively reduce the hysteresis within the working pressure range and has good response characteristics to step signals. This paper can provide support for performance analysis and structural parameter improvement of the electric proportional valve. [ABSTRACT FROM AUTHOR]

In wind turbine systems, bolted connections are frequently subjected to gravitational and centrifugal loads transmitted by the blades during operation. This can lead to the attenuation of bolt preloading, resulting in bolt loosening or uneven loading, which in turn affects the service life of the generator unit. Therefore, the study of bolt preloading variations is crucial. However, there are numerous factors influencing bolt preloading, and the existing techniques struggle to precisely assess bolt preloading. This paper proposed a bolt preloading evaluation technique based on the hammer modal method. Focusing on the 42CrMo4 bolted connection of a pitch bearing, a test platform for bolt preloading assessment is constructed. Hammer modal tests are conducted under various preloading forces. By combining finite element modal analysis, the correspondence between preloading changes and the bending frequencies and modes of the bolted connection is obtained. The research illustrated that with changes in bolt preloading, variations occur in coherence, phase, and natural frequencies of frequency response functions. The fundamental correlation between bolt preloading and the second-order bending frequency can be utilized to assess changes in preloading. Furthermore, the applicability of this method has been validated, offering a reference for evaluating bolt preloading. [ABSTRACT FROM AUTHOR]

In this paper, considering combined excitations of the steady current, surface wave, internal solitary wave as well as, the vessel's surge and heave motions, a time-domain model is established to investigate the lateral dynamic response of marine drilling risers. The finite element and Newmark-β methods are used to solve the nonlinear partial differential equation in the time-domain. The entire numerical solution process is realized by a self-developed program based on MATLAB. The reliability of the numerical solution program is verified by comparing it with published numerical results. The lateral dynamic responses of a real-scale marine drilling riser, usually used in the deep water oil/gas industry in the South China Sea, are studied. The impact level of each factor in the riser's lateral dynamic response is discussed. [ABSTRACT FROM AUTHOR]

Rapid development of offshore wind foundation models has resulted in a large number of built structures with generally underestimated foundation stiffness properties and a need to update and validate both the individual structural models and the underlying foundation design frameworks. This paper outlines a structural health monitoring approach, based on the combination of output only structural health monitoring methods and model updating, to estimate foundation stiffness parameters using field monitored data. Field monitoring data from an offshore wind turbine under idling conditions, over a large monitoring period, are presented and operational modal analysis is applied to estimate the modal parameters. Those are compared to modal properties predicted by finite element models, employing either old (API/DNVGL) or new (PISA) foundation design properties, which are calibrated using geotechnical site investigation data. A new approach to interpret seabed level statically equivalent foundation stiffness, in terms of effective lateral and rotational stiffness against load eccentricity, is presented. Seabed level statically equivalent foundation properties are updated by comparison against the observed modal behaviour and the optimised foundation parameters are presented, demonstrating a close match to the predictions of the PISA method. [ABSTRACT FROM AUTHOR]

With the continuous increase in building types, people's demand for buildings is increasing. In addition to focusing on the work of the building itself, high requirements are also placed on the safety, stability, and durability of the building. Especially in other earthquake-prone areas, it is even more necessary to strengthen seismic isolation research to reduce vibration. Rapid construction of environmental protection walls pays attention to environmental protection and efficiency during construction, which can effectively solve problems in the construction process, but the seismic resistance of rapid construction environmental protection walls is unknown. Therefore, this paper used artificial intelligence technology to study the seismic performance of rapid construction environmental protection walls and analyzed its vibration control. This paper firstly established the seismic performance analysis model of the environmental protection wall, used the finite element method to construct the environmental protection wall model, and then used the artificial intelligence algorithm to analyze the seismic performance of the rapid construction environmental protection wall. The experimental results showed that the peak load of the rapid construction environmental protection wall was about 250 KN, and the seismic performance was good. [ABSTRACT FROM AUTHOR]

The finite element method divides the existing solid structure into a finite number of elements. It integrates and analyzes the divided elements according to preset criteria, and then solves the equilibrium equation of the overall structure according to the corresponding boundary conditions. The problem is analyzed through a finite element model. A large amount of data from the experiment are derived, and then data mining technique is used to find out the data that are useful for the experiment. The purpose of this paper is to test bridge engineering through data mining technology, and then simulate different fiber-reinforced concrete models through finite element method. In this paper, three kinds of nanofibers, carbon fiber (CFRP), glass fiber (GFRP), and aramid fiber (AFRP) are used to make concrete bridges. Loading experiments are also carried out with different degrees of load on the bridge and 100 experiments on the error interval. The experimental results show that the displacement is proportional to the load to a certain extent. The carbon fiber concrete has a stronger positive correlation than the other two materials. Its finite element simulation experimental data have 78% error difference between 0 and 10, while the other two are around 40%. [ABSTRACT FROM AUTHOR]

Transmission lines in the desert are exposed to the desert environment, which includes sandstorms as one of its hallmarks. A conductive layer develops with prolonged sand deposition and the presence of moisture, ambient humidity, and dew. The ensuing leakage current causes surface discharge, which limits the life of the insulator and interrupting the power supply. The locations of power lines in the Egyptian Sinai desert, where sandstorms are known to occur frequently, are exposed to such a risk. In order to estimate the danger of insulator failure, this paper studies the flow of leakage current on porcelain insulators that have been contaminated with sand. This work relies on accurate data collected and published in a prior study regarding Sinai, which mainly focused on contaminating sand's grain sizes. Porcelain insulator is simulated using finite element method to determine the leakage current that results on its contaminated surface. The probabilistic characteristics of the insulator's leakage current are derived using Monte Carlo technique, allowing for the risk assessment of insulator failure. This assessment can be used to justify the suitability of using this kind of insulator in Sinai. [ABSTRACT FROM AUTHOR]

In this paper, based on the theory of elastic structure analysis, considering the rotational softening and centrifugal stiffening of the blade, the dynamic model of the fir-tree rotating blade and the macroslip hysteresis model of the dry friction on the contact surface of fir-tree tenon are established. Based on elastic mechanics, the pressure distribution model of fir-tree tenon is innovatively established and the relationship between fit clearance and contact pressure has been derived. After the blade is discretized by the finite element method, the dynamic equation of the blade is solved iteratively by the Newmark-β numerical integration method. According to the dynamic equation of the blade, the influence of the change of the tenon angle on the forced response and contact stress of the blade is derived. Finally, some novel conclusions are obtained by analyzing the influence of pressure distribution, tenon angle, friction coefficient, rotational speed, and aerodynamic excitation on blade vibration characteristics. It provides a scheme and relevant basis for the design and development of tenon blades with the most damping effect at different speeds in industrial practice. [ABSTRACT FROM AUTHOR]

Focusing on the phenomenon of the crack on the autoclave flange, a three-dimensional model of the autoclave was established based on the Ansys Workbench platform. A new finite element analysis flow for optimizing the design of autoclave teeth was established using the Fluent, Static Structure, and Direct Optimization modules. The paper analyzed and discussed the maximum stress and minimum fatigue life at the corresponding position. The variation trend of stress and fatigue life at the corresponding position after fillet optimization was also discussed. The results showed that the equivalent stress of autoclave teeth without fillet optimization reached the maximum under different fillet sizes. The equivalent stress and fatigue life of the autoclave tooth were the same as the rounded corner size obtained by the optimization design. The optimal global solution could be obtained through the optimization design process. [ABSTRACT FROM AUTHOR]

This paper presents a systematic study in reviewing the application of finite element method for the analysis of correction mechanism of spine deformity due to scoliosis. The study is aimed at systematically (1) reviewing the use of finite element analysis in spine deformity case, (2) reviewing the modelling of pedicle screw and rod system in scoliosis surgery, and (3) analysing and discussing gap between the studies. Using the restricted key phrases, the review gathered studies from 2001 to 2021 from various electronic databases (Scopus, ScienceDirect, PubMed, Medline, and WorldCAT). Studies were included if they reported a finite element study on spine deformity. Studies that did not fully disclose their methodology and results had significant discrepancies, not published in English or not yet published were all disqualified. Regardless of inconsistencies in the methodological design of the studies, the quality of all papers was above the acceptable level. A total of fifteen manuscripts were considered for inclusion and were given a comprehensive review. This study indicates that analysing the forces acting on the spine, as well as the interrelationship between the force, stress, and degree of correction (which measured as the Cobb angle), could help to improve the corrective mechanism procedure of spine deformity. Pedicle screws and its placement strategies are also important as it influence the corrective forces for scoliosis treatment. Hence, the findings of this study could potentially be used as a guidance to develop a reliable finite element analysis that can predict the biomechanics responses during the corrective spine deformity treatment. [ABSTRACT FROM AUTHOR]

Concrete expanded-plate piles have significant advantages in the bearing capacity, settlement, and construction period. The added bearing expanded plate is the key reason for their many advantages; moreover, the slope angle (α angle: the maximum diameter of the bearing expanded plate and the angle formed on the plate) of the bearing expanded plate is the main factor to control the longitudinal symmetry. However, the concrete expanded-plate piles in practical engineering do not exist in a rigid body state, and elastic deformation will occur under variable engineering conditions. In addition, the research in this paper mainly focuses on a flexible concrete expanded-plate pile (F-CEP pile). The flexible pile mentioned in this paper refers to the bending deformation of the pile body under horizontal load, which produces large pile top displacement. This study uses the two methods of small-scale half-plane pile model test and finite element simulation analysis of ANSYS, after referring to the equipotential pile test at the actual site. In this paper, the variation law of the displacement curve and the failure law of the soil around the pile under the horizontal force when the α angle changes are analyzed, and the calculation model of the bearing capacity of F-CEP pile under the α angle change is put forward. This research aims to verify the reliability of existing research and provides strong support for the application, promotion, design, and research of F-CEP piles in construction engineering. [ABSTRACT FROM AUTHOR]

The influence of load rate and other factors is not considered in the temperature rise monitoring process of traditional motor, which will lead to the wrong diagnosis of motor health status. In this paper, the characteristics of motor temperature rise under different ambient temperatures and different load factors are studied. Taking an 11 kW three-phase asynchronous motor as an example, the temperature rise model of the motor is based on the finite element method established using ANSYS software. The thermal conductivity coefficient and surface heat dissipation coefficient of each part of the motor are determined. According to the electromagnetic field calculation, the motor loss distribution is obtained, and the temperature rise distribution curve of the motor is obtained by the simulation of the three-dimensional steady temperature field of the motor. In this paper, the temperature rise variation law of the motor considering the influence of environmental temperature and load factors is proposed, and combined with the temperature rise threshold curve of the motor under different load rates, a dynamic threshold judgment system is established to accurately warn the motor of overheating under any load rate. When the motor's health status changes after running for a long time, it provides an important theoretical basis for accurate diagnosis of the motor's health status. [ABSTRACT FROM AUTHOR]

In order to study the die wear law of rotary fine blanking helical cylindrical gear, a three-dimensional rigid plastic finite element model of rotary fine blanking helical cylindrical gear is established on the Deform-3D software platform. Based on the Archard wear model, this paper analyzes the die wear in the fine blanking process, obtains the wear distribution of each point on the working surface of the die, determines the maximum wear area, and makes a comparative analysis with the fine blanking die wear of spur gear. Through the single factor variable method, this paper studies the effects of reverse jacking force, blank holder force, blanking speed, punch and die clearance, die fillet radius, and die initial hardness on die wear. The test results show that when the punch reduction is the same, the wear of the female die of fine blanking helical cylindrical gear is greater than that of fine blanking spur cylindrical gear. When the counter jacking force increases from 100 kN to 200 kN, the maximum wear of the die gradually increases from 6.91 × 10–6 mm to 9.38 × 10–6 mm; when the blank holder force increases to 3/4 of the blanking force, the die wear decreases with the increase of blank holder force; it is ideal when the blanking clearance is 0.5% t (0.02 mm). Conclusion. The wear model can accurately predict the relationship between main process parameters and wear in the process of rotary fine blanking, and the measures to reduce die wear are put forward from the aspect of process design. [ABSTRACT FROM AUTHOR]

In order to deal with the bottleneck of poor plasticity and low formability of magnesium alloys at room temperature, a numerical simulation and a die process optimization method based on hot stamping of AZ series magnesium alloys were proposed. Firstly, based on the PAM-STAMP finite element analysis platform, the thermomechanical coupling numerical simulation is carried out for the cross cup-shaped deep drawing, and the changes in the stress and temperature field during the forming process are analyzed. Aiming at the influence of various process parameters on the plastic formability of magnesium alloys, the effects of sheet metal shape, die fillet size, friction factor, and blank holder force on the forming quality were analyzed through experiments. The experimental results show that under the same conditions such as temperature and blank holder force, the numerical simulation method and the mold process optimized in this paper can be used to form parts that are 25% deeper than the traditional process, and the sheet material can be thinned to the maximum at this time. The amount is 0.152 mm, which verifies the correctness and superiority of the method and process in this paper. [ABSTRACT FROM AUTHOR]

At this stage, the varieties and specifications of aluminum profiles continue to increase, and the scope of application continues to expand. The extrusion forming process is the key technology to realize the production of aluminum profiles, and its technological level determines the quality of the profile products and the service life of the mold. However, in actual production, the quality of the die is difficult to guarantee, and it takes multiple die trials and die repairs to produce qualified products. The numerical simulation technology is used to simulate the actual extrusion process, which can track and describe the flow behavior of the metal in real time, reveal the real flow law of the metal, predict the possible defects of the profile during the extrusion process, and adjust the mold structure and process parameters in time. It can not only improve the quality of extruded profiles, but also reduce production costs and shorten the mold production cycle. Based on this, this paper established an extrusion die optimization design model integrating finite element simulation technology and artificial intelligence algorithm. The prediction models were established with the mean square deviation of the section velocity, the maximum extrusion force and the maximum temperature of the section, respectively, and the optimal design of the structure was realized by using the particle swarm algorithm. The experimental results show that the model in this paper can realize the function well, which verifies the validity of the model. [ABSTRACT FROM AUTHOR]

The introduction of hierarchical structures into conventional honeycomb structure materials can increase the mechanical properties of honeycomb materials. This paper studies the in-plane collapse response of a new second-order diamond-shaped hierarchical honeycomb (DHH) (the cell walls are composed of equilateral triangles) and systematically studies the quasi-static collapse response and dynamic collapse response of the DHH in two directions through the finite element method. The quasi-static collapse response of the DHH is analyzed by a two-scale research method, and combined with momentum conservation law, the study is extended to dynamic collapse response. This paper also studies the collapse response of the DHH with different number of substructures, different relative densities, and different impact speeds, and the results are verified by theoretical analysis and numerical simulation. The results show that adding hierarchical structure can greatly increase the collapse stress of the diamond honeycomb structure and make the structure have better energy absorption effect. [ABSTRACT FROM AUTHOR]

In this paper, we propose a two-level nonconforming rotated finite element (TNRFE) method for solving the Navier–Stokes equations. A new nonconforming rotated finite element (NRFE) method was proposed by Douglas added by conforming bubbles to velocity and discontinuous piecewise constant to the pressure on quadrilateral elements possessing favorable stability properties. The TNRFE method involves solving a small Navier–Stokes problem on a coarse mesh with mesh size H and a large linearized Navier–Stokes problem on a fine mesh with mesh size h by the NRFE method. If we choose h = O H 2 , the TNRFE method gives the convergence rate of the same order as that of the NRFE method. Compared with the NRFE method, the TNRFE method can save a large amount of CPU time. In this paper, the stability of the approximate solutions and the error estimates are proved. Finally, the numerical experiments are given, and results indicate that the method is practicable and effective. [ABSTRACT FROM AUTHOR]

SiC fiber-reinforced silicon matrix (SiCf/SiC) composites are of significant interest for the aircraft engine. The thermal conductive behaviors of [0-90-0]s SiCf/SiC composites along in-plane and out-of-plane (thickness) directions were reported in this paper. The thermal conductivity of the SiCf/SiC composite was tested by using the steady-state measuring apparatus. Then, the thermal conductivity of the SiC matrix was predicted by finite element analysis (FEA). The representative volume element (RVE) models of SiCf/SiC composites were built, and FEA was used to investigate thermal conductive behaviors. It was found that the thermal conductivity along the fiber radial direction was greater than it was in the axial direction in the SiCf/SiC composite and that the thermal conductivity of the out-of-plane direction is lower than that of the in-plane one. The thermal conductivity of the SiCf/SiC composite in the in-plane direction at room temperature was 31.1 Wm−1K−1 and 28.5 Wm−1K−1, and the thermal conductivity in the thickness direction was 24.9 Wm−1K−1. The experimental thermal conductivity showed a good agreement with the thermal conductivity of FEA. [ABSTRACT FROM AUTHOR]

Nasal bone is a long, paired series of small bones, which is narrow at the top and broad at the bottom, that forms the base of the nasal dorsum. Together with the nasal part of the frontal bone, the frontal process of the maxilla and the middle plate of the ethmoid bone constitute the bone scaffold of the external nose. In this paper, the DICOM image data file was imported into the Mimics software for 3D reconstruction. At the same time, the Geomagic software was used for relevant image processing, and the finite element software ANSYS was used to establish a finite element model to analyze the stress characteristics of the nasomaxillary complex. Results. The maximum principal stress and maximum strain force at the lower segment of nasal bone and the junction of nasal bone and maxilla were relatively large. When the same external force acts on the lower segment of the nasal bone and the angle is 0° (sagittal force), the maximum principal stress and maximum strain force are the smallest. When the angle continues to increase, the maximum principal stress and maximum strain force continue to increase. [ABSTRACT FROM AUTHOR]

An accurate and reasonable finite element model is essential for bridge structural health monitoring and safety assessment. To improve the accuracy and efficiency of the finite element model updating, this paper proposes a finite element model updating method for bridge structures based on an improved response surface method. By introducing the radial basis function as the augmentation term of the polynomial function, a response surface model based on the augmentation polynomial is established, and the fitting accuracy of the global response surface model is improved. The convergence speed and accuracy of the response surface model optimization solution are improved by improving the regression step and annealing strategy in the simulated annealing algorithm. The method is validated using the numerical case of a simply supported beam and the finite element model of the main bridge of the Tonghe Songhua River Highway Bridge (Tonghe Bridge), and the safety condition of the main bridge of the Tonghe Bridge is evaluated using the updated finite element model. The results show that the maximum relative error of the updated parameters of the simply supported beam decreased from 13.011% before improvement to 0.719% after improvement, and the maximum relative error of the natural frequencies decreased from 0.728% before improvement to 0.225% after improvement; the maximum relative error of the natural frequencies of the finite element model of the Tonghe Bridge main bridge decreased from 21.68% before improvement to 4.23% after improvement. In April, May, and June of 2021, the main bridge of the Tonghe Bridge operated well and had a good security reserve. [ABSTRACT FROM AUTHOR]

At present, the traditional phase unwrapping algorithm is difficult to balance the accuracy and unwrapping efficiency. The traditional phase unwrapping algorithm is difficult to balance the accuracy and efficiency in the phase unwrapping experiments of simulated and measured topographic interferograms. In this paper, the phase unwrapping technology will be studied under the framework of deep learning theory according to the development trend of InSAR intelligence. A phase unwrapping algorithm based on deep GAN is proposed. The model structure includes dense convolution layer blocks and series structure, so that the network can achieve a better balance between feature extraction and detail preservation of interferogram. This is helpful to improve the phase unwrapping accuracy and training efficiency of the network. The experimental results show that the algorithm has a good expansion effect on the interferogram with high signal-to-noise ratio. The synthesis algorithm makes full use of the advantages of the branch cutting method and the finite element method. The phase reliable region and unreliable region are determined, and the transmission of phase error from the unreliable region to reliable region is effectively avoided. The accuracy of the phase unwrapping results in the reliable region is ensured, and the overall phase unwrapping convergence accuracy is greatly improved. [ABSTRACT FROM AUTHOR]

Considering the stringent requirement of the pointing accuracy up to 2.5″ of the world's largest full steerable radio telescope, this paper studies the welding experiment of the azimuth track of the antenna. First, the opposite deformation jig and welding process were designed for the QTT's azimuth track. Then, the welding process was numerically simulated using a finite element model. The simulation results show that a better welding effect will be obtained by appropriately reducing the opposite force on the basis of the original. The three deformation processes of the track are regulated by the opposite deformation jig. The results show that the opposite deformation jig designed for QTT's azimuth track can make the amount of deformation and flatness meet the design requirements. Finally, nondestructive testing was carried out to check the welding quality of the track surface and interior. The results show that there are no obvious defects in the welds of the azimuth track. The constraint jig and welding processes designed for QTT are effective and feasible. [ABSTRACT FROM AUTHOR]

Techniques used for breast cancer detection usually incorporate Infrared Thermography (IRT) to locate abnormal hotspots or asymmetry in a thermal texture map. This can be unreliable due to various individual differences from one person to another. In this paper, a detection method that is independent of the aforementioned limitations is proposed. This technique is a combination of thermal imaging and high-frequency excitation. This technique is based on the fact that the differences in electromagnetic and thermal properties of abnormal (malignant) tissue and the surrounding normal tissue will result in a noticeable difference in temperature increase after exposure to high-frequency excitation. A three-dimensional (3-D) finite-element method (FEM) has been used to simulate the thermal behavior of breast tissue exposed to antenna excitations. Finally, the effectiveness of this technique was tested in a series of experiments using a life-sized breast phantom. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of the field winding interturn short-circuit (FWISC) position on the rotor vibration properties in turbo generators. Different from the previous studies which focused on the influence of the short-circuit degree, this work pays much attention to the impact of the short-circuit position on the rotor unbalanced magnetic pull (UMP) properties and vibration characteristics. The theoretical UMP model is firstly deduced based on the analysis of the magnetic flux density (MFD) variation. Then, the finite element analysis (FEA) is performed to calculate the UMP data. Finally, the rotor vibrations are tested on a CS-5 prototype generator which has two poles and a rated capacity of 5 kVA. It is shown that the occurrence of FWISC will greatly increase the UMP as well as the rotor vibration. In addition to the short-circuit degree, the short-circuit position will also affect the UMP and vibration. The nearer the short-circuit position is to the big rotor teeth, the larger the UMP and vibration will be. The proposed study in this paper will be beneficial for the monitoring and diagnosis of FWISC faults. [ABSTRACT FROM AUTHOR]

The functionally graded honeycomb has the characteristic of light weight, low density, high impact resistance, noise reduction, and energy absorption as a kind of new composite inhomogeneous materials. It has the advantages of both functionally graded materials and honeycombs. In this paper, a functionally graded honeycomb sandwich plate with functionally graded distributed along the thickness of the plate is constructed. The equivalent elastic parameters of the functionally graded honeycomb core are given. Based on Reddy's higher-order shear deformation theory (HSDT) and Hamilton's principle, the governing partial differential equation of motion is derived under four simply supported boundary conditions. The natural frequencies of the graded honeycomb sandwich plate are obtained by both the Navier method from the governing equation and the finite element model. The results obtained by the two methods are consistent. Based on this, the effects of parameters and graded on the natural frequencies of the functionally graded honeycomb sandwich plate are studied. Finally, the dynamic responses of the functionally graded honeycomb sandwich plate under low-speed impacts are studied. The results obtained in this paper will provide a theoretical basis for further study of the complex dynamics of functionally graded honeycomb structures. [ABSTRACT FROM AUTHOR]

Liquid storage tanks are lifeline structures and strategically very important. Heavy damages or even collapse of these facilities subjected to strong earthquakes may cause disastrous consequences. In this paper, the seismic response of a multistage series liquid storage tank was simulated by a finite element method and verified by a scaled-down experiment. The structural flexibility of the tank and the liquid-structure coupling characteristics between the liquid and tank wall were considered in the research. A multimass-block and spring model was employed to be equivalent to the longitudinal vibration of the liquid in the storage tank. The relationships between the connection springs and the elements of the stiffness matrix were explicitly deduced. The seismic response analysis of a four-stage series liquid tank was carried out, and the acceleration response, the stress response of the tank, and the vertical vibration of the liquid were obtained. The experimental results are in good agreement with the simulation results, which verifies the effectiveness of the modeling method in this paper. [ABSTRACT FROM AUTHOR]

Switched reluctance generator (SRG) has become the key focus of research for its usage in wind power generation. The sizing and performance of SRG depend on the core material used for the stator and rotor. This paper analyses the impact of the magnetic loading of different core materials on the performance of SRG in terms of self-inductance, torque, iron losses, ohmic losses, and generated voltage. 1 kW SRG with different pole configuration 8/6 SRG and 12/8 SRG for the wind speed of 3 m/s to 6 m/s has been designed. Static and dynamic analyses using the finite element analysis (FEA) were carried out for analytically designed 1 kW SRG with different core materials with the same lamination thickness. Prototypes of 8/6 SRG and 12/8 SRG are fabricated. The output of simulation results has been validated by experimental measurements. [ABSTRACT FROM AUTHOR]

A new model-free output-only signal processing-based damage detection procedure was carried out in this paper. First of all, a finite element model as the representative of reinforced concrete (RC) frames was constructed and subjected to a specific loading protocol in OpenSees. The protocol consisted of 9 consequent different near-fault fling-step pulse-type earthquake records with low-amplitude white noises among them to simulate the collapse procedure. The analysis process was complemented in three levels: (a) the Fourier transform was utilized to extract the vibration frequency, (b) the time instants of damage occurrence were detected by using the discrete wavelet transform, and (c) accurate damage detection was made by using the extracted pulse components of the records as loading protocol for earthquake simulation and the discrete wavelet transform. The results revealed that the proposed combinatorial method could efficiently diagnose the damage in the RC frames. Also, applying a pulse component instead of an original record increases the accuracy of damage detection by 70%. [ABSTRACT FROM AUTHOR]

The high-speed train speed has a higher requirement for stability and operating safety with its operating speed increasing. The main focus of this paper is on the fault characteristics analysis of a high-speed train transmission system. The governing equation and boundary conditions of the transmission system are derived using the finite element method, in which a Timoshenko beam element is introduced to represent the wheelset shaft, and a rigid mass element is utilized to represent the gears, bearings, and wheels. To investigate the vibration response mechanism of a high-speed train transmission system, the critical speed of the system and its modal response are given. According to the types of high-speed train component fault features, the local fault features of gear, bearing, and wheelset are given. Healthy and faulty systems with localized faults in gear, bearing, and wheelset are studied. The characteristics of amplitude and frequency are verified numerically and the transmission characteristics of signal and relation are explained when there is local fault defect in the system. The results show that under different fault types, the time domain response of the system has obvious periodic impulse response faults, and the fault frequency band characteristic distribution is different in the frequency domain response. The simulation results are consistent with the experimental results. [ABSTRACT FROM AUTHOR]

This paper proposes a stiffness sensitivity analysis with principal strain application to decrease the out-of-plane vibration, which is the main source of the sound radiation of mechanical structures with thin plate parts. The sensitivity is evaluated as a differential coefficient of the target response with respect to the design variable, e.g., stiffness or mass. For suppressing the out-of-plane vibration, we pay attention to finding an appropriate location on the structure to add local stiffness. The location is decided according to stiffness sensitivity analysis results. The compliance frequency response function (FRF) is considered as the target response, and the thickness of stiffener is considered as the design variable. The validity of the proposed method is examined through numerical simulation with a finite element method (FEM) model of a thin plate. The modal principal strain distributions, stiffness sensitivity, and FRF changes by local thickening are calculated based on 4 selected natural modes. It is also examined by the experimental approach. The expected reduction of the response is attained by adding the stiffener (a thin stainless plate) to the appropriate location on the plate. [ABSTRACT FROM AUTHOR]

The influence of masonry infill walls on the progressive collapse performance of reinforced concrete (RC) frame structures was investigated in this paper, using a nonlinear dynamic analysis approach. Based on ANSYS/LS-DYNA finite element software, two finite element models of RC frame structures with and without masonry infilled walls were established. Then, the collapse modes of the two RC frame structure models were analyzed for different scaled distance blast loads, different locations of column damage, and different span numbers. The results show that with the increase of explosive amount, the collapse degree of the structure is more serious in the same time. Under the condition of destroying the outermost central column, the degree of progressive collapse of the RC frame model with infilled walls in the same time is lower than that of the RC frame model without infilled walls. The RC frame model with infilled walls is more resistant to collapse when the outermost side columns are damaged. With the increase of span number, the structure is more likely to be damaged and collapsed. [ABSTRACT FROM AUTHOR]

A range of titanium diaphragms for spacecraft propellant tanks are designed in detail, and two typical titanium diaphragms were manufactured and corresponding reversal tests were developed. A series of finite element models of the reversal process of these titanium diaphragms is developed based on the arc-length method and a finite element analysis software. With the aid of the models, this paper analyzes the characteristics of pressure drop during the whole reversal process and investigates the effects of the structural parameters on pressure differential to roll titanium diaphragm. The results show that simulated values of the critical pressure and the overturning pressure show good agreement with measured ones. In addition, the critical pressure increases with increasing thickness, decreasing bottom diameter and chamfering radius. The thickness and the bottom diameter are the main influence factors for the critical pressure. The overturning pressure increases with increasing thickness and arc radius. These effects of the bottom diameter, the chamfering radius, and arc radius become sharper with increasing thickness. [ABSTRACT FROM AUTHOR]

The backfill construction of a utility tunnel is as important as its main structure construction. While the existing research on utility tunnels focuses on the construction of the main structure, rare attention has been paid to the backfill construction. In this paper, with a practical comprehensive utility tunnel project as the background, a variety of different backfill construction schemes were designed, and the corresponding numerical simulations were performed with the finite element analysis software Midas. The influence of different backfill construction schemes on the side wall, roof, and floor of the utility tunnel was systematically studied and analyzed, and the displacement and stress variation curves in the process of utility tunnel backfill were obtained. Based on the simulation results and the actual engineering situation, the optimal schemes for utility tunnel backfill construction were determined. The results show that the displacement of the side wall of the utility tunnel increased first and then decreased with increasing backfill soil in the unilateral backfill mode, and there was little displacement in the bilateral backfill mode. The shear stress of the side wall of the utility tunnel in both the unilateral and bilateral backfill modes gradually increased with the backfill process. Within the region 1 m above the roof of the utility tunnel, backfill modes had no effect on the final stress and displacement values, but the layering method made a difference. Accordingly, bilateral backfill mode is suggested for the region below the roof of the utility tunnel, while in the case of region 1 m above the roof, backfilling is recommended to be layered according to height rather than position. [ABSTRACT FROM AUTHOR]

Three-dimensional free bending is a new tube forming technology with continuous variable curvature. In order to improve the forming quality of tube, this paper studies the principle of three-dimensional free forming system and the numerical calculation of bending moment in detail, and it uses the finite element simulation to model the mechanism in the bending process. The simulation model is used to simulate the forming process of copper tube, and the influence of key process parameters on the forming process is analyzed,the shape of the inner cavity of the bending die and the gap between the tube and the bending die are studied, the distance between the bending die and the guide column is studied, the axial feed rate on the forming quality of tubular bending parts has also been studied. The optimum process parameters were determined by finite element simulation and analysis. [ABSTRACT FROM AUTHOR]