Finite Element Model For Numerical Simulation Research Articles

An automated computation method for flexible protection systems based on neural networks

An automated computation method is proposed in this paper to address the problems of enormous computational difficulty and low efficiency in flexible protection systems. This method uses neural networks to demonstrate the complex nonlinear mapping relationships between the system’s specifications and performance. Use the finite element numerical simulation model validated by a full-scale impact test on the 750 kJ passive flexible protection system for massive parametric analysis, and extract the critical computation results as the label space. Conducted mechanical tests on critical components, analyzed the mechanical characteristics of each component, and extracted training features to form a sample space. The label space and sample space formed a dataset containing 1828 sets of data and used 1700 sets of data to train a neural network while using the remaining 128 sets of data to test. The maximum predicted error was 8.33 %, and the maximum average error was 3.73 % from the test. The proposed method can complete the computation in just 6 s, with a computation speed of 520 times that of the fastest finite element method, significantly improving the computation efficiency of the flexible protection system and reducing the computational difficulty.

Characteristics of hydraulic fracture penetration behavior in tight oil with multi-layer reservoirs

The tight oil reservoirs of Fuyang and Gaotaizi in the Daqing Oilfield exhibit characteristics such as thin layers and distributed barriers, which pose challenges for maintaining drilling accuracy within the desired geological sweet spot. Hydraulic fracturing has emerged as the optimal method to connect production wells with target layers effectively. Understanding the behavior of hydraulic fracture propagation in multiple thin layers with significant differences in mechanical properties is crucial for assessing the extent of effective drainage. In this study, a finite element numerical simulation model incorporating cohesive elements is employed to investigate and quantify the effects of stress differences and rock mechanical parameters on fracture penetration. The results indicate that the stress difference between the reservoir and barrier layers plays a key role in controlling hydraulic fracture penetration and height. Moreover, the flow rate and viscosity of the fracturing fluid have a noticeable impact on fracture progression. Hydraulic fractures tend to propagate along the interface of layers with low flow rate and fluid viscosity, thereby hampering the penetration performance in those layers. To achieve a comparable penetrated fracture length in low permeability reservoirs, it is necessary to increase the volume of fracturing fluid in high permeability reservoirs. Furthermore, the barriers layers, which possess relatively weaker mechanical properties, can constrain the width development of hydraulic fractures. This limitation may result in the risk of excessive liquid without sufficient proppant (commonly known as “over liquid but no sand”). Therefore, appropriate measures should be implemented to increase the net pressure and avoid encountering this complex situation.

Fast inversion method for seepage parameters of core earth-rock dam based on LHS-SSA-MKELM fusion surrogate model

The inversion of seepage parameters is an important research topic in the safety evaluation of earth-rock dams. Core earth-rock dam is a commonly used structural type in earth-rock dams. Most of the existing inversion methods focus on concrete dams, and few of them are aimed at earth-rock dams. These methods have the problems of slow inversion speed or low accuracy. Aiming at the above problems, this paper proposes a novel fast inversion method for the seepage parameters of core earth-rock dams based on the LHS-SSA-MKELM fusion surrogate model. The proposed fusion inversion model optimizes the selection of combination models based on the surrogate model framework, making it more suitable for the inversion calculation of seepage parameters in earth-rock dams. First, based on the seepage theory of earth-rock dams, the finite element numerical simulation model of core earth-rock dam seepage is constructed. The Latin Hypercube Sampling (LHS) method is used to obtain the parameter sample dataset according to the range of the seepage parameters, and the sample dataset is substituted into the finite element model to obtain the corresponding theoretical seepage pressure of different datasets. Then, the Mixed Kernel Extreme Learning Machine (MKELM) is used to establish the mapping relationship between seepage parameters and the theoretical seepage pressure. The MKELM parameters were optimized by using the Sparrow Search Algorithm (SSA) to further improve the accuracy of the surrogate model. Finally, taking the minimum error between the theoretical value and the measured value of the surrogate model as the objective function, the SSA algorithm is used to derive the optimal inversion value of seepage parameters. The results of engineering examples show that the mean absolute percentage error between the measured value of the core earth-rock dam seepage pressure and the simulated value after inversion is only 4.958%. In addition, the average inversion time of the proposed surrogate model is only 6.6 s, which greatly reduces the time-consuming problem of numerical simulation. The proposed method provides a new way for accurate and fast inversion of seepage parameters of core earth-rock dams after long-term operation.

Influence of landform on the pressure distribution of explosion shock wave

The explosion site terrain and geomorphic environment will directly affect the shock wave pressure propagation and attenuation law and the shock wave test results uncertainty evaluation. In this study, the explosion site topographic and geomorphic parameters were analyzed, and the slope ratio and elevation difference within the region were proposed to parameterize the test site topographic and geomorphic characteristics. Using multi-physical field coupling simulation software, the finite element numerical simulation model of acoustic-solid structure coupling with different elevation difference and slope ratio is established and relevant research is carried out. The results show that when the pressure monitoring point is located at the test site low position, the elevation difference plays a role in attenuation of the shock wave pressure peak value, and vice versa; With the increase of the test site slope ratio, the shock wave pressure peak value at different test points gradually increases, and with the increase of the distance between the test points, the impact degree gradually decreases. Therefore, the elevation difference and slope ratio of the site shall be reduced as much as possible during the explosion shock wave pressure test, so as to improve the shock wave pressure test accuracy and the test data reliability, and provide theoretical support for the shock wave pressure test results uncertainty evaluation in the explosion field.

Numerical Investigation of the Performance of Segmental CFST Piers with External Energy Dissipators under Lateral Cyclic Loadings.

In order to improve the construction efficiency of piers and reduce the local damage of piers, concrete-filled steel tubes (CFST) are used to precast pier segments. Aiming at the problems of the poor integrity and insufficient energy dissipation capacity of dry joint segmental assembled piers, segmental assembled concrete-filled steel tubular piers with external replaceable energy dissipators are being developed. Based on the low cyclic test of a segmental assembled CFST pier, the finite element numerical simulation model of a CFST pier is established based on ABAQUS software, and the validity of the numerical model is verified by the experimental results. The effects of the section ratio, axial compression ratio, and initial prestress on the seismic performance of piers are studied through a pseudostatic analysis. The results show that an increase in the section ratio can improve the lateral bearing capacity and energy dissipation capacity of the pier. When the section ratio is increased to 4%, the energy dissipation capacity of a CFST pier is increased by 77.8% and the lateral bearing capacity is increased by 33.9% compared with a section ratio of 2%, but the residual displacement of the pier top also increases. With an increase in the axial compression ratio, the energy dissipation capacity of the pier is significantly improved; when the axial compression ratio is increased to 0.30, the energy dissipation capacity of CFST piers is increased by 27.5% compared with a section ratio of 0.05, the residual displacement of the pier top is reduced, and the self-resetting effect of the pier is improved. A change in the initial prestress has no effect on the energy dissipation capacity of piers. Finally, based on an analysis of mechanical theory, a formula of bending capacity suitable for this type of pier is proposed, and the error is within 10%.

Unmanned aerial vehicle transport of frozen blood samples using phase change materials

Appropriate cryopreservation of blood samples during transit from the point of collection to testing sites is an important element of quality sample management in clinical and veterinary diagnostics and research. Here, a heat-insulated design that employs 23.3% w/w salt water as the phase change material (PCM) for encapsulating a 1.5-mL vial of frozen blood sample was studied to assess its efficacy in maintaining sub-zero temperatures during transport. A two-dimensional finite element numerical simulation model with 5457 elements was found to exhibit mesh independence with 10% convergence error. For the PCM pre-cooled in dry ice and vial sample kept initially at 20 °C before flight, this model is predicted to maintain a stable transport temperature of −20 °C for at least 70 min. It also predicted to have uniform temperature distribution across the PCM holder, PCM, sample vial and sample. Experimental data obtained using a thermocouple confirmed the accuracy of the simulation model. Sensor data collected from a bespoke unmanned aerial vehicle (UAV) allowed mapping of the acceleration forces during flight and facilitated the development of a mechanical setup to experimentally show that frozen samples are protected from shear forces generated under mimicked transport conditions. The capability of real-time sample temperature monitoring with feedback control on UAV flight path demonstrates the viability of the drone delivery system for quality transport of thermal-sensitive samples. • UAV transport of frozen blood samples done here with salt water phase change material. • 2D finite element model achieved mesh independence with 10% convergence error. • 70 min stable transfer at −20 °C attained after 30 min of dry ice pre-cooling. • Sensor data from UAV mimicked the flight conditions in a sloshing test setup. • Preliminary tests with frozen sheep's blood show lower coagulation from sloshing.

The influence of sensor installation angle on explosive shock wave overpressure test

In the engineering measurement of explosion shock wave pressure, the installation method of shock wave pressure sensor is of great significance to accurately obtain shock wave pressure. Based on the actual shooting range explosion shock wave overpressure test program, this paper uses AUTODYN to establish a finite element numerical simulation model. The distance from the ground reflection pressure sensor to the explosion center is 3 m, 4 m, 5 m, and 6 m. The shock wave overpressure data in the range of 8° and 10° are acquired and analyzed. The analysis results show that the shock wave overpressure obtained when the sensor installation angle is absolute zero is the ideal value. When the sensor installation plate is within a certain range, the overpressure value of the explosion shock wave increases with the increase of the installation angle of the plate, and the installation angle of the sensor is positively correlated with the overpressure of the explosion shock wave.

Dynamic numerical simulation analysis of a large caliber artillery projectile extrusion process

Taking a large-caliber gun as the research object, a projectile and gun coupling finite element numerical simulation model during the extrusion process is established according to the finite element simulation technology. The dynamic simulation of the extrusion process is carried out by using ABAQUS/EXPLAICT solver, and the stress variation law of the projectile belt during the groove and the barrel during the extrusion process is obtained. In the post-processing module of the finite element software, the data of displacement, velocity and acceleration at the center of mass of the projectile in the extrusion process are extracted, and the motion law of the projectile in the extrusion process is analyzed, which provides some reference value for the study of the extrusion process of large caliber artillery projectile.

Modelling and design method for static resistance of a new connection between steel tubular column and flat concrete slab

This paper presents the results of a numerical and analytical investigation into the punching shear behaviour of an innovative simple and effective shear connection between steel tubular column and flat concrete slab using welded shear studs, steel plates and bent-up rebars. The finite element numerical simulation model was validated against two full-scale physical tests carried out by the authors. The validated numerical simulation model was used to perform extensive numerical parametric studies to investigate the effects of changing different design parameters including flat slab depth, concrete grade, bent-up rebar design, shear stud dimensions (length and diameter) and steel tube size, so as to develop thorough understanding of their punching shear behaviour and to provide comprehensive data for development of an analytical method for design. The developed analytical design method can be used to check capacities of shear studs, bent-up rebars and slab punching shear resistance. For this shear connection system, it is easy to prevent shear stud yield failure and bent-up rebar failure so that the system behaves as an enlarged column for calculating punching shear resistance of the slab. For the enlarged column, punching shear resistance calculation method in Eurocode 2 [2] can be used.

Taguchi Grey Relational Approach for Optimizing Process Parameters of Laser Peening on Titanium Alloy to Induce Enhanced Compressive Stress based on Finite Element Simulation

Laser Shock Peening (LSP) turned out to be the most efficient surface engineering process for advanced materials to induce beneficial deep compressive residual stress which helps in improving mechanical, fatigue properties and surface damage resistance. But, analyzing the nonuniform distribution of residual stresses in the treated sample with X-ray diffraction (XRD) is much time taking and a costly process. This problem can be resolved with LSP finite element numerical simulation model which is feasible with the realistic experimental process. The FE model allows the user to control the laser parameters in order to achieve the optimal level of all controllable parameters. This study is intended to analyze and optimize the influence of laser processing parameters that assists in inducing the residual compressive stress with minimal surface deformation. A Ti6Al4V material model with Johnson–Cook’s visco-elastic–plastic material behavior law is prepared for LSP simulation. Gaussian pressure profile is utilized for uniform loading of the targeted zone for the proposed model. Taguchi Grey Relational Analysis (TGRA) with L27 orthogonal array is applied to LSP simulation, and the results were analyzed with consideration of multiple response measures. It is noted that surface deformation is increased with the rise in a number of laser shots and pressure pulse duration. Maximum compressive residual stresses are falling for higher levels of laser spot diameter, laser spot overlap and laser power density. The correlation is observed between the FE simulation and the published results. The optimal set of process parameters are obtained for improving the LSP on Ti alloys.

Structural Modal Analysis and Optimization of SUV Door Based on Response Surface Method

Sensitivity analysis and response surface methods were employed to optimize the structural modal of SUV doors. A finite element numerical simulation model was established and was calibrated by restraint modal tests. To screen out highly sensitive panels, a sensitivity analysis for the thickness of door panels was proposed based on the fifth-order modal frequency of the door. Data points were obtained by a faced central composite design with the design variables from the thickness of the highly sensitive panels, and a second-order explicit response surface function of the fifth-order modal frequency of the vehicle door was established. An optimization model was established according to the response surface method. The final results demonstrate that the modal-frequency matching of the door and body in white was optimized after changing the thicknesses, with a 5.74% material reduction.

Study on Loss and Temperature Increases in Hollow Oil-immersed Reactors

Oil-immersed hollow reactors have been applied to high-voltage frequency-modulated resonant power supplies due to their favorable linearity and high insulation strength. A high-quality reactor is the key component of a high-voltage test system. The characteristics of loss and temperature-rise characteristics are the core factors affecting the quality factor of the reactor. In this paper, a finite-element numerical simulation model was established based on a large capacity series resonance test system for a 500-kV submarine cable in China. The eddy current loss, AC resistance loss, and circulating current loss of the oil-immersed air-core reactor were calculated. With these as a foundation, the flow and temperature field distribution characteristics were obtained for an oil-immersed hollow reactor through the coupling of magnetic heat and flow field. Finally, the temperature distribution characteristics of the reactor were compared with the dates obtained from the release testing, and the reliability of the calculation model was verified.

Ultimate Strength of Pit Corrosion Damnification on Pressure-Resistant Shells of Underwater Glider

The ultimate strength of the pressure-resistant shells is degraded due to corrosion pit on the surface of the shells. The underwater glider is prone to pit corrosion damage after working in the water for a long time. This study is aimed at development of an assessing formula for ultimate strength of pressure-resistant shells with pit damage. Firstly, a parameterized geometry model of the pit is determined under the assumption that the pits are elliptical. Secondly, a finite element numerical simulation model is established and the numerical simulation results are analyzed to find that the effect of pit damage on the pressure-resistant shell is obvious. Thirdly, the influences of some parameters (relative length, relative width, and relative depth) of pit on the ultimate strength are studied. The regular curve of the influence of geometric parameters on ultimate strength is drawn. Lastly, the ultimate strength assessment formula of pressure-resistant shells was obtained from the data by nonlinear FEM based on the regression function of multiple nonlinear regression analysis by nonlinear regression analysis function regress which can provide the foundation to assess the ultimate strength of damaged pressure-resistant shells.

Numerical simulation of the temperature field of cold metal transfer welding pool

A thermal source model of cold metal transfer (CMT) welding is established, and the dynamic behavior of temperature field of CMT welding pool is simulated, and the corresponding distribution rule for temperature field is obtained. By combining the experimental measurement with ANSYS finite element numerical simulation, the thermal cycle curve of 16Mn steel surfacing welding is compared. The result of finite element calculation well consists with that of experimental measurement, demonstrating that this finite element numerical simulation model is reliable. The analysis of temperature field of CMT welding pool is reliably predicted, so as to offer a reference basis for simplifying the CMT welding experiment and choosing the parameters of CMT welding process.DOI: http://dx.doi.org/10.5755/j01.mech.22.4.16163

Cyclic behavior of buckling-controlled braces

A parametric study is presented to quantify essential factors influencing cyclic behavior of a steel buckling-controlled brace (BCB) with a tube carrying axial load surrounded by an outer tube to control buckling of the load-bearing tube. A small-scale experiment helped observe overall cyclic behavior, and develop finite-element models for numerical simulations. The model-based simulations identified the interaction of the friction, gap and thickness ratio between the two tubes as the essential factor. The paper concludes that (1) the gap is a sensitive parameter influencing local and global buckling. The smaller the gap, the less likely the local and global buckling will occur, but the more participation of the outer tube in load bearing due to adverse interaction between the two tubes; (2) Friction between the two tubes is a very delicate factor because its impact on the cyclic behavior of BCB varies depending on thickness ratio and friction; (3) Thickness ratio of the two tubes decides the effectiveness of controlling buckling. The thickness ratio of 1.0 is sufficient to control global buckling, but a larger than 1.0 ratio is needed to control both local and global buckling; (4) Interaction among the gap, friction and thickness ratio is strong, and shall be considered in design; and (5) Optimal performance results from a system with smallest gap possible, low friction, and heavier outer tube. Some less optimal but lower costly design combinations may have moderate gaps and various outer tube sizes to control brace buckling within targeted drift limits in performance-based design.

Correction of the Vimoke–Taylor Concept Representing Drains in a Numerical Simulation Model

Drains are special internal or boundary conditions in numerical simulation models. Instead of approximating them by a hole surrounded by a very dense grid of finite elements, the single node or single element approach based on the theory of Vimoke and Taylor proposed in 1962 offers a good alternative. Several authors have suggested that the Vimoke and Taylor constant to adapt the hydraulic conductivity of the element representing the drain should be changed by a certain factor. However, different correction factors have been given. Here this correction factor is derived for a control volume finite element numerical simulation model for different ratios of the size of the control volume representing the drain and the effective drain radius. It is shown that this relationship is dependent on the way the hydraulic conductivity is averaged at the interfaces between the neighboring control volumes. The relationships were obtained by optimization against an analytical solution for a steady‐state, saturated situation. By applying the additional correction to a hypothetical transient situation for four soil types it was shown that the application of the additional correction factor resulted in 3 to 13% lower drain discharges compared to uncorrected simulations. Consequently, higher groundwater levels of on average 2 to 4 cm were obtained when applying the additional correction. For situations where exact predictions of drain discharge are needed, typically when solute transport is considered, it is advised to make use of the additional correction. Model specific correction factors may be required.

Numerical Simulation for Shaping Feature of Molten Pool in Twin-Arc Submerged Arc Welding

The notion of ratio of width to length is proposed to describe the shaping feature of molten pool of twin-Arc submerged arc welding accurately, and analyze the law of molten pool variation and weld formation. The temperature field finite element numerical simulation model of twin arc movement is established. The loading form of twin-arc with double ellipsoid heat source is discussed. The molten pool temperature field of twin-arc submerged arc welding is calculated and analyzed under different process parameters. The law of molten pool characteristics influenced by the welding speed, current and voltage of twin-arc submerged arc welding parameters is analyzed. The relation between shaping feature of molten pool and weld formation is discussed according to the ratio of width to length. The results manifested that the width to length ratio of weld pool decreases with the improvement of welding speed, which result in gene- ration of weld defects. The width to length ratio of weld pool is increased by adjusting the proportion of the current, voltage and the distance of the two arcs, which avoids the generation of weld defects.

Asymmetric Diffusional Solidification during Transient Liquid Phase Bonding of Dissimilar Materials

A theoretical analysis of diffusional solidification during transient liquid phase (TLP) bonding of dissimilar materials was performed in conjunction with experimental verification. A fully implicit, two-dimensional, finite element numerical simulation model, without the inherent symmetry assumption, was developed and used for the theoretical calculations, and good correlations between the model predictions and experimental results were observed. The study showed that an asymmetric distribution of residual interlayer liquid during a dissimilar joining of polycrystal and single crystal alloys is attributable to a mismatch between their lattice diffusion coefficients or solute solubility, irrespective of enhanced intergranular diffusion as was assumed previously. Also, notwithstanding increased solute diffusivity with temperature, it was found that an increase in bonding temperature can result in the prolongation of processing time t f that is required to prevent the formation of deleterious eutectic during bonding of dissimilar materials. The occurrence of this seemingly anomalous behavior, however, reduces when a material is coupled with another type that exhibits a higher solute solubility or better capability of accommodating diffusing melting point depressant solute from the liquid interlayer.

A finite element model for liquid phase electroepitaxy

AbstractA finite element numerical simulation model for the liquid phase electroepitaxial growth process of gallium arsenide is presented. The basic equations obtained from the fundamental principles of electrodynamics of continua, the constitutive equations for the liquid and solid phases derived from a rational thermodynamic theory, and the associated interface and boundary conditions are presented for a two‐dimensional axisymmetric growth cell configuration.The field equations are solved numerically by an adaptive finite element procedure. The effect of moving interfaces is taken into account. Numerical simulations are carried out for different convection levels by changing the value of the gravitational constant. Results show that convection has significant effect on the growth process under normal gravity conditions and results in thickness non‐uniformity of the grown layers. The thickness non‐uniformity leads to curved interfaces of growth and dissolution, which enhance convection.