Finite Element Numerical Calculation Research Articles

A hemodynamic model of artery bypass graft considering microcirculation function.

The incidence of arterial stenosis is increasing year by year. In order to better diagnose and treat arterial stenosis, numerical simulation technology has become a popular method. A novel model is constructed to investigate the influence of microcirculation on the hemodynamics of artery bypass graft. In this paper, a severely narrow artery bypass graft model is considered. The geometric shape includes a narrow artery tube and a bypass graft of the same diameter with a 45° suture angle. The fluid-structure interaction model is considered by finite element numerical calculation, and the flow is simulated with microcirculation as the outlet boundary condition. The changes of blood flow velocity, pressure and wall shear stress are analyzed. The results show that blood almost entirely flows into the graft tube and there is no recirculation area at the anastomosis. The artery bypass graft model considering microcirculation function could simulate the physiological characteristics of blood flow more reasonably, and it provide helps for clinicians to diagnose and treat arterial stenosis.

Understanding the mechanisms behind ultrasonic vibration in resistance spot welding of aluminum and steel

An ultrasonic-assisted resistance spot welding process, which can improve the quality of aluminum/steel spot-welded joints, has been developed. However, the mechanism of the thermal-electrical-mechanical behavior caused by the ultrasonic longitudinal vibration to welding process has not been clarified. In this study, the role and impact mechanisms of ultrasonic longitudinal vibration during the welding process to form joints were confirmed by combining the microstructural characterization of the formed joints with the signal analysis of the process, as well as the analysis of the independent finite element numerical calculation results. Additionally, the interface metallurgical reaction behavior, welding defects, fracture behavior, and joint strength characteristics of ultrasonic-assisted aluminum/steel resistance spot welding joints were comprehensively analyzed, and the results indicated that the sizes of the aluminum/steel nuggets decreased. It could be attributed to the competition among multiple ultrasonic effects. Specifically, ultrasonic vibration decreased the contact resistance between the aluminum/steel sheets, whereas the acoustic cavitation and acoustic streaming effects increased the electrical conductivity of molten steel and thermal conductivity of molten aluminum, respectively. Moreover, ultrasonic vibration promoted the radial creep of molten and near-molten aluminum, which expanded in the effective bonding area between the two workpieces. Furthermore, ultrasonic vibration effectively reduced the thickness of the intermetallic compound layer (<3.0 µm), concurrently inhibited the formation of interfacial welding defects. Finally, the peak tensile-shear load of aluminum/steel joints is significantly increased under multiple ultrasonic optimization mechanisms.

Determination of Replacement Cable Force of in-Service Suspension Bridge Based on Refined Modelling Approach

In this paper, the replacement cable force of suspension bridge slings in service is systematically analyzed by adopting the coupling analysis model of internal force influence matrix and displacement influence matrix. The sling replacement project of an existing bridge serves as the basis for considering the technical condition and stress state of slings and other components comprehensively. Key control indexes, such as internal force, offset, linear or adjacent cable force change, are defined according to vehicle traffic requirements and structural safety considerations. Refined finite element numerical calculation is employed to determine the target cable force applied to the replacement sling, while analyzing changes in key control indexes of relevant components and structures during adjustment. The target cable force of the replacement sling is adjusted and determined based on a comparison with the target demand index. Compared with the traditional influence matrix method, the double matrix method also has the advantage that it does not need to select the initial adjustment cable force, which avoids the problem that the convergence result may not be obtained, and aims to provide a basis for the subsequent calculation of cable force replacement when the suspension bridge is in service.

6σ Robust Lightweight Design of the GIL/GIS Bus Based on Co‐Simulation of Insulation, Current Flow, and Mechanical Stress

GIL/GIS bus is widely used in the field of power transmission and distribution, and the demand for lightweight is becoming more and more prominent. To reduce the weight of the bus and ensure the safety and reliability of the structure, a new 6σ robust design method of the GIL/GIS bus based on electric‐thermal‐mechanical co‐simulation is proposed. Taking a 550 kV/5000A bus as the initial structure, considering the uncertainty of product size and performance, a 6σ robust lightweight model of bus insulation electric field strength, current temperature rise, and mechanical stress multi‐performance co‐simulation is established. The finite element numerical calculation method is used to calculate and analyze the performance parameters of the bus. The Kriging surrogate model is used to form the response surface, and the optimal bus structure is obtained by genetic algorithm. The results show that after the robustness optimization, the performance of the bus meets the design requirements, the weight per meter decreased from 65.11 to 39.12 kg, and the lightweight effect is remarkable. Compared with the traditional deterministic optimization design, the reliability of the structure is improved. The new method of the GIL/GIS bus lightweight design proposed in this study has high feasibility and application prospects, which can provide new ideas for the development of gas‐insulated electrical equipment. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

A Computational Model for Analysing the Dry Rolling/Sliding Wear Behaviour of Polymer Gears Made of POM.

This study presents a computational model to determine the wear behaviour of polymer gears. Using PrePoMax finite element numerical calculation software, a proposed computational model was built to predict dry rolling/sliding wear behaviour based on Archard's wear model. This allows the calculation of the wear depth in each loading cycle with constant mesh updating using the finite element method. The developed computational model has been evaluated on a spur gear pair, where the pinion made of POM was meshed with a support gear made of steel. The computational results obtained were compared with the analytical results according to the VDI 2736 guidelines. Based on this comparison, it was concluded that the proposed computational model could be used to simulate the wear behaviour of contacting mechanical elements like gears, bearings, etc. The main advantage of the model, if compared to the standardised procedure according to the VDI 2736 guidelines, is the geometry updating after a chosen number of loading cycles, which enables a more accurate prediction of wear behaviour under rolling/sliding loading conditions.

Axial compressive stability design of longitudinal asymmetrical shuttle-shaped columns

Longitudinal asymmetrical shuttle-shaped column (LA-SSC) has found its wide application when subjected to combined axial compression and horizontal point load in practical engineering. This paper focuses on elastic and elasto-plastic buckling behaviors of the LA-SSC only under axial compression and the resulting outcome could provide an indispensable basis for further establishing buckling strength prediction of LA-SSC under axial compression and horizontal point load. At first, the elastic buckling behavior of tapered columns (TC) and longitudinal symmetrical shuttle-shaped columns (LS-SSC) are derived in theory and verified by finite element numerical results, and corresponding elastic buckling modes are discussed. Subsequently the elastic buckling load prediction of LA-SSCs is established first and the corresponding normalized slender ratio, as a key design parameter, is generalized. Finally, the stability capacity of LA-SSCs is involved in theoretical analysis and finite element (FE) numerical calculation under axial pressure. Through investigating the axial load-lateral displacement curves and axial stress distributions the buckled LA-SSCs, the effects of different parameters (such as overall length, plate thickness, and steel strength) on the axial compression stability capacity of LS-SSCs are explored. As a result, the complete design formulas for axial compression stability capacity of LA-SSCs are presented first and compared with current major design codes in various countries. It is observed that the proposed strength design formulas are in good correspondence with the FE numerical results. The proposed formulas could provide references and guidance for the axial compression buckling strength of LA-SSCs under axial compression and they further supply fundamentals for establishing the strength design recommendation of LA-SSCs under axial compression and bending moments.

Research on integrated technology of integral aerial building formwork equipment and large tower crane

The integrated aerial building formwork equipment is an independently developed support apparatus by China, which is primarily and importance for the construction of concrete structures in ultra high buildings exceeding 200 m. The novelty of this paper focuses on optimizing and improving the load transmission system and its critical large bearing support structure connecting the tower crane through theoretical analysis and finite element numerical calculation. By obtaining the stress ratio and maximum deformation before and after integrated optimization design, a local strengthening scheme for the tower crane support tube is proposed to simplify the structural connection while significantly reducing self-weight and steel consumption without compromising mechanical performance requirements, thus improving the overall performance of the integrated formwork equipment for aerial building construction.

Structure Research of Resistance Shunt Type Piezoelectric Composite and Underwater Sound Absorption Performance Analysis

The high-efficiency sound absorption of underwater sound-absorbing materials under "low frequency" and "wide frequency" conditions has become a hot topic in current research. Underwater semi-active sound absorption can help to improve low frequency sound absorption performance by designing the structure of the piezoelectric composite and the shunt circuits, and it is also advantageous due to its simplicity, compactness, ease of installation, low cost, and high stability. In this paper, a kind of resistance shunt type piezoelectric composite is designed, and its underwater sound absorption performance is analyzed. Theoretical analytical formulas and finite element numerical calculation are used to calculate the electro-elastic constants of the piezoelectric composite. The theoretical model based on the Mason equivalent circuit and transfer matrix theory is used to calculate the sound absorption coefficient. Through the study of 0-3 and 1-3 composites used in the existing research work, it was found that the piezoelectric composite which is suitable for resistance shunt type underwater semi-active sound absorption should have a low longitudinal wave velocity and high electromechanical conversion coefficient. According to this design objective, the structure of the piezoelectric composite has been gradually modified, and finally it is determined that the sparse oblique 2-1-3 composite is an appropriate type of piezoelectric composite. Theoretical calculations and simulation experimental measurement verifies that when the inclination angle is 21 deg and the shunt resistance is 10 kOhm or the inclination angle is 24 deg and the shunt resistance is 10 kOhm, the sound absorption coefficient within the low frequency band 1--3~kHz can be significantly improved.

Comparative Study on Numerical Calculation of Modal Characteristics of Pump-Turbine Shaft System

Because a pump-turbine mainly undertakes the role of energy conversion and pumped storage in the field of hydropower engineering, the complex transition process and frequent conversion between different working conditions lead to the increase in the stress and strain of core components such as the unit shaft system, and even cause resonance phenomena. Based on ANSYS finite element numerical calculation software, this paper adopts the acoustic fluid–structure coupling method to study the influence of the shaft of the pump-turbine on the dynamic characteristics of the runner. At the same time, the paper analyses the influence of different contact modes between the runner and the shaft on the modal characteristics of the shaft system. The numerical simulation results have shown that the runner is affected by the added mass of the water. The natural frequency reduction rate of each order of wet modal is ranged from 19% to 64%. The main shaft has a greater influence on the simplification of the shaft system calculation method. The type of contact surface between the main shaft and the runner has a smaller influence on the modal characteristics and the natural frequency of the shaft system. The research in this paper contributes an evaluation of the dynamic characteristics of the runner of a hydraulic turbine unit, which is of great significance for the optimization of the analysis algorithm of the runner structure for large pumped storage units.

Multi‐Objective Optimization Design of Vacuum Interrupter Structure Based on Improved Artificial Jellyfish Search Algorithm

An improved multi‐objective optimization method based on artificial jellyfish search algorithm is proposed to solve the multivariable and multi‐objective optimization problem of vacuum interrupter with mutual coupling of structural parameters and mutual restriction of performance indexes. The finite element model of 40.5 kV/31.5kA vacuum interrupter is established. The structural parameters of seven important parts such as contact diameter and contact sheet thickness in vacuum interrupter are taken as optimization variables. The optimization objective is to maximize the longitudinal magnetic field strength and minimize the conductor resistance at the peak breaking short‐circuit current of vacuum interrupter. The artificial jellyfish search algorithm is improved on the population position initialization strategy and the population mutation cross‐update strategy. The Pareto front solution of the structural parameters of the vacuum interrupter is obtained by the joint simulation of finite element analysis and numerical calculation software. Finally, the multi‐parameter and multi‐objective optimization design of vacuum interrupter structure is realized. The comprehensive performance index is introduced into the optimal parameter group of jellyfish on the Pareto front. Under the constraint of weight variables, the optimal structural parameters of contact system are obtained. The axial magnetic induction intensity of the optimized vacuum interrupter contact is increased by 13.2%, and the conductor resistance is reduced by 25.4%. The comprehensive performance of vacuum interrupter is improved by 17.8%, and the stability and reliability of the power system are further improved. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

An Efficient and High-Precision Electromagnetic–Thermal Bidirectional Coupling Reduced-Order Solution Model for Permanent Magnet Synchronous Motors

The traditional electromagnetic–thermal bidirectional coupling model (EMTBCM) of permanent magnet synchronous motors (PMSMs) requires a long time to solve, and the temperature-induced torque change is not accounted for in the finite element (FE) numerical calculation of the EM field. This paper presents a precise and efficient EMTBC reduced-order solution model. The specific methods are as follows: First, a torque control technology based on the current injection method is proposed for determining the effect of temperature on the properties of EM materials and EM torque in an EM field, and the accuracy of the FE numerical calculation model is improved. Second, we use the improved EM field finite element numerical calculation model (FEMNCM) to analyze the correlation between the EM loss, the temperature, and the load, and we replace the FEMNCM with the EM field reduction model using the least-squares method. Then, we analyze the law of the PMSM’s internal temperature distribution. We choose the GA-BP algorithm with as few samples as possible and a high accuracy and stability to build the regression prediction model of the temperature field. We use this regression prediction model to replace the complex temperature field calculation. After analyzing the EMTBCM solution strategy, the original complex EMTBC numerical calculation model is substituted with iterations of the magnetic field reduction model and the temperature field regression prediction model. The FE numerical calculation is then used to validate the reduced-order model. The proposed model is validated through numerical simulations. The numerical results indicate that the proposed reduced-order EMTBC model in this paper is accurate and computationally efficient.

An explosion field inversion algorithm combining finite element calculation and tomography

The finite element numerical calculation can get the shock wave velocity and overpressure at any point in the explosion field, but some factors such as the parameter value of the state equation influence the calculation results. The tomography inversion can acquire the velocity and overpressure distribution of shock wave; however, the initial model and constraints can affect the inversion results. Aiming at the shortcoming of the two algorithms, this article combines the two methods and presents a new algorithm to reconstruct the explosion field. First, The LS-DYNA finite element program is applied to establish a numerical model and calculate the shock wave velocity and superpressure in air explosion. Second, generalized inversion with regularization tomography inversion algorithm is used to invert the shock wave field. In the inversion, the finite element calculation results are used as the initial model of inversion and constrain the inversion. The experiment results prove that the proposed algorithm can greatly improve the inversion accuracy and the iterative convergence speed. The inversion image can better depict the internal details of the explosion field and eliminate noise.

Non-invasive analysis of macro-crack on the characteristics of ultrasonic guided wave

The effects of macro-crack in plates on the characteristic of ultrasonic guided wave were studied. Using the Finite Element Model and numerical calculation method, the finite element mesh models of various macro-crack in aluminum plate were established. The single S0 or A0 mode Lamb wave was excited in plate by the wave structure loading method. The propagation time and amplitude of wave packet in the received signal were analyzed to study the phenomenon of mode transformation and the relationship between macro-crack size and signal amplitude. The simulation results show that there is mode conversion when the single mode Lamb wave interacts with an asymmetric macro-crack, and no mode conversion with a symmetric macro-crack. The energy of reflected wave increases with the increase of the depth and width of macro-crack, and the energy of transmitted wave decreases correspondingly. The size and inclined angle of macro-crack can be quantitatively estimated by the fitting function from the energies of reflected and transmitted waves. The variation of crack depth, width and angle is approximately linear with the amplitudes of reflected and transmitted wave packets. A fitting function is constructed by using the amplitude ratio of reflected wave packet or transmitted wave packet to total wave packet, which can be used to estimate the macro-crack depth, width and angle. This conclusion is helpful to the detection of macro-crack in the actual production and service of plate structures.

Thermal design and performance of low beta cryomodule for CAFe

China initiative Accelerator Driven System (CiADS) has developed several kinds of cryomodules for superconducting proton linac at IMP. The low beta cryomodules had been designed, fabricated, assembled, and tested for the linac. To meet the requirements of minimizing heat transfer and operational stability, the thermal design and performance of low beta cryomodules have been studied. In this paper, finite element analysis and numerical calculation have been carried out on the design of important components such as thermal insulating support, bellows, thermal shield, power coupler, current leads and so on. Then the heat loads at various temperature levels have been summarized. Besides, the performance of the cryomodules including the cool down, equipment operating data, and heat load measurements are reported. The trial test result of low beta cryomodules shows that the various technical indexes satisfied the technical requirements.

Investigation on Performance of Hydraulically Expanded Joint of Titanium-Steel Clad Tubesheet.

The performance of a hydraulically expanded joint between tubesheet and titanium tube was analyzed using a finite element numerical calculation. The connection strength of Q345R tubesheet and TA2-Q345R clad tubesheet was studied using a tight expansion method. The results proved that the residual contact pressure and pullout force of the tight expansion joint of TA2-Q345R clad tubesheet were greater than those of the Q345R tubesheet. However, the residual contact pressure of the expanded joint without a groove for the TA2-Q345R tubesheet and the pullout force failed to meet the requirement of connection strength. Hence, the groove was employed on the contact surface. The influences of groove position and groove width on the connection strength of the expanded joint with grooves in tubesheet hole were studied. The results show that the residual contact pressure of the clad tubesheet of grooving in the cladding layer was higher than that of grooving in the base layer. The effect of the position of groove in the cladding layer and base layer on the residual contact pressure could be neglected. A wider groove led to a higher residual contact pressure, which increased significantly when the groove width was 4 mm.

Mechanical Properties of Polyurethane Mixture and Load Response Behaviour of Polyurethane Composite Pavement

Finite element numerical simulation calculation of pavement structure load response is widely applied; however, there is still a lack of research on the polyurethane (PU) mixture composite pavement load response. The mechanical characteristics of PU mixture composite pavement are not well understood, and there is a lack of research on typical pavement structures of PU mixtures, which limits their application in pavement structures. Therefore, herein, the mechanical properties of PU mixtures are analysed using the dynamic modulus test, uniaxial penetration test, and fatigue test. Further, the finite element theory calculation method is used to realize the load response calculation of orthogonal design composite pavement structure. The results show that PU mixtures exhibit more obvious elastic characteristics and have good shear resistance, fatigue stability, and temperature stability, and can be used as shear and anti-fatigue layers. The structure of '4 cm SMA-13 + 5 cm PUM-20 + 6 cm PUM-25 + semi-rigid base' is recommended for the PU mixture composite structure. In comparison to typical asphalt pavement, the analysis shows that except for shear stress, temperature has little effect on the load response of PU composite pavement structures, while high temperatures lead to a significant increase in the load response of typical asphalt pavement structures. The PU composite pavement can bear greater loads and has a reduced thickness of its surface layer by about 3 cm in comparison to conventional pavement. The results of this study provide theoretical support for the design of PU mixture pavement structures and promote the popularization and application of PU mixture pavement.

Analysis of load-bearing safety and reliability of solid rocket motor flexible joint structure

Flexible nozzle is the thrust vector control system of a solid rocket engine, and flexible joint is the key component of its load-bearing and changing behavior. It is composed of composite rubber elastic parts with spherical annular structure and metal reinforcing parts with spherical annular structure alternately adhesive. Under the action of complex loads, the flexible nozzle exhibits highly nonlinear mechanical properties. The traditional flexible joint structure with uniform thickness is easily damaged during loading and has large negative mass and short system range. However, the load-bearing swing performance of the system, such as swing center displacement, swing moment, and fatigue life, is difficult to predict, and the safety and reliability of the joint structure cannot be guaranteed. To this end, on the basis of the measured material properties of elastic parts, the Lagrangian structural dynamics algorithm coupling material and geometrically nonlinear, the Design of Experiment multi-objective optimization algorithm and the multi-axial stress fatigue finite element numerical calculation method based on crack propagation combined to design a new lightweight variable-thickness joint. From the mechanical point of view, the failure mechanism and mode of the two joint structures are compared and analyzed, the safety factor is determined, and the load-bearing swing performance of the system is predicted. Results of the ground experiment test of the system prove that variable-thickness flexible joint has better safety and reliability.

Vibration effect and ocean environmental impact of blasting excavation in a subsea tunnel

Drill-blast method is one of the important methods in the current subsea tunnel excavation construction. Controlling the vibration effect during blasting construction and its impact on the marine environment has been a key topic in the construction of subsea tunnels. This paper takes the Xiamen subsea tunnel excavation and blasting project as the background, combines blast vibration monitoring in the tunnel and underwater sound pressure testing in seawater, analyzes the attenuation law of subsea tunnel blast vibration propagation along the rockmass, studies of the characteristics of shock waves formed in water following the propagation of blast stress waves to seawater. Based on the dynamic finite element numerical calculation, the impact of blasting vibration effect of mainline tunnel on the adjacent built service tunnel structure and the characteristics of shock wave pressure distribution in water excited by blasting vibration are analyzed. Considering the influence of the burial depth of tunnel blasting source, a mathematical prediction model of the attenuation law of underwater sound pressure in water caused by subsea tunnel blasting is established. Based on the pressure control standard of marine organism safety, the control range of marine organism safety under the influence of subsea tunnel blasting is proposed.

Analysis of Process Signals of Resistance Spot Welding for DP590 Steel Using Numerical Calculation

Although the finite element (FE) numerical calculation model has been extensively employed in analyzing metal characteristics, very few works use it to analyze features of the main process signals during the resistance spot welding (RSW) process. Hence, its generality was seriously restricted. In this work, a 2D FE model, which coupled thermal, electrical and mechanical fields, was established with reasonable meshing and parameters and boundary conditions. The parent metal used dual phase (DP) 590 steel, which is commonly employed in automobile lightweight manufacturing process. An actual experiment with the same conditions as the numerical calculation was conducted. The dynamic resistance and electrode displacement obtained from numerical calculation and actual experiment were seriously compared and analyzed. Many important characteristics of process signals have been reasonably explained by combining the results obtained from numerical calculation and experiments. The reasonability and accuracy of the FE numerical calculation were not only verified after the welding process but also examined in depth during the intermediate welding process. Hence, the work can effectively enlarge the applications of the FE model and strengthen the correlation between control strategy design, online quality estimation using main process signals and FE numerical calculation during the RSW process.

Research on design method of metamaterial sound field control barrier based on transformer vibration and noise

In order to analyze the propagation path of vibration noise, and carry out finite element numerical calculation research based on electro-magnetic–solid-acoustic multiphysics coupling, a single-phase two-column dry-type transformer is used as the noise source in this paper. According to the distribution characteristics of the spatial sound field and the vibration noise amplitude–frequency characteristics of the transformer, a topology design method of the space coiled acoustic metamaterial (SCAMM) unit is proposed and the analytical calculation methods of acoustic parameters such as sound pressure reflection/transmission coefficient of various SCAMM units are deduced. Besides, the effects of parameters such as the longitudinal width a, the waveguide width b, the ratio of waveguide width to longitudinal width b/a and transverse width t on the SCAMM unit sound transmission loss (STL) are studied, and the anti-resonance frequencies are adjusted by parameter optimization method to achieve the optimal sound insulation effect. In the end, the sound field control barrier based on the SCAMM for transformer vibration and noise suppression is designed, and relevant experiments are carried out. The experiments show that the sound field control barrier based on the SCAMM can reduce the transformer noise sound pressure level (SPL) of the main noise frequencies by up to 25 dB with a thickness of only 4 cm and ventilation.