Numerical Simulation Test Research Articles

Impact load identification method based on artificial neural network for submerged floating tunnel under collision

In order to minimize economic and human losses due to collisions that may cause serious problems, such as severe damage and collapse, in a submerged floating tunnel (SFT), an impact load identification method that can estimate the magnitude, as well as the location of the impact as the point, is proposed. The proposed method is based on an artificial neural network, specifying multi-layered perceptron (MLP), and its performance is verified by numerical simulation and experimental tests. The structural response data in the time domain obtained from the SFT when collisions occur within an ocean current is used to train the neural network model. The MLP-based identification system is investigated to establish each purpose of impact points and magnitude estimation considering the classification and regression model. In the numerical simulation, a finite element model of the SFT simplified as the beam on an elastic foundation is established in ABAQUS and the time history of impact is used to simulate the impact as a collision in hydraulic resistance. The time-series acceleration responses of the simulation are extracted to convert to input variables. The experiment with an SFT model, a set of accelerometers, and an impact hammer is conducted for the identification system validation. Only using the time-series acceleration as input variables for the neural network shows an accurate estimation of the impact points and the magnitude over 97%, and provides reasonable results using the minimal amount of data.

Mechanical Behavior of Anchor Bolts for Shallow Super-Large-Span Tunnels in Weak Rock Mass.

Based on the Xiabeishan No.2 tunnel project of the Hang-Shao-Tai high-speed railway in China, the mechanical behavior of the anchor bolts for shallow super-large-span (SSLS) tunnels in weak rock mass is comprehensively investigated through laboratory tests, numerical simulation, and field tests. Firstly, an eight-month field test is conducted in the Xiabeishan No.2 tunnel, and it is discovered that the blasting vibration created by the construction of the middle pilot tunnel caused serious damage to the temporary support, seriously affecting the development of the bolt axial force and causing great construction risks. Then, the refined finite difference model of the SSLS tunnels is formulated, and a series of field and laboratory tests are conducted to acquire the calculation parameters. By comparing the monitored and simulated bolt axial force, the reliability of the numerical model is verified. Subsequently, the influence of the rock condition, construction scheme and bolt length on the mechanical behavior of anchor bolts is discussed. It is revealed that the rock grade significantly affects the bearing characteristics of anchor bolts. The construction scheme can greatly affect the magnitude and development mode of the bolt axial force, but the final distribution characteristics of the bolt axial force do not change regardless of the construction sequence. The axial force of the anchor bolts grows rapidly with the bolt length when the bolt length is within 18 m; meanwhile, when the bolt length exceeds 18 m, increasing the bolt length has a limited effect on the improvement in the bolt support performance. Finally, some optimization measures are proposed according to the monitoring data and simulation results.

Cyclic response and parametric study of a self-centering coupled shear wall system with disc spring devices

The use of the disc spring device (DSD) to provide a superior self-centering ability and ductility for shear walls has been investigated in both numerical simulation and pseudo-static cyclic loading tests. In the current study, the DSD is adopted to improve the resilience of the coupled shear walls. A finite element model of a present coupled shear wall is developed and verified by the experiment. Based on the prototype model, a model of the self-centering coupled shear wall system is built by installing two DSDs in the bottom corners of the wall piers. A parametric study is performed to provide a holistic evaluation on the effect of the stiffness, friction, and installation layout of the DSD. Results prove the resilience promotion of the traditional coupled shear wall by installing DSDs. The sufficient initial stiffness of DSDs can provide high overturning moment capacity and the second stiffness of DSDs is key in mitigating the residual displacement for the self-centering coupled shear wall. The friction between disc springs can enhance energy dissipation ability of the system. More installed DSDs would be beneficial for the ductility of the coupled shear walls.

Strata Movement of Overburden-Separation Grouting Working Face and Its Influence on Gas Emission during Mining

Due to its excellent effect of surface subsidence reduction, the overburden-separation grouting (OSG) technology has been widely applied to green mining. However, OSG changes the mine pressure, and the resultant gas emission in the stope remains unclear. Therefore, with the 22301 working face of Tunlan Coal Mine as an example, the overburden deformation and stress distribution in the absence and presence of OSG were studied through numerical simulation and on-site tests. Furthermore, the gas emission law in the stope was contrastingly analyzed. The following results were obtained. With the rise of grouting pressure (GP), the subsidence of strata above the separation layer decreases while that below the separation layer increases; the heave displacement of floor strata below the coal seam gradually decreases. OSG significantly changes the geometric shape and range of the overburden stress relief zone. As the GP rises, the gas enrichment area moves downward continuously and shrinks spatially. Horizontally, the ranges of the stress relief zone and the free space in the goaf shrink, while the range and compaction degree of the compaction area gradually grow. After OSG, the total amount of gas emission in the working face falls by 52.2%.

Deep hierarchical reinforcement learning based formation planning for multiple unmanned surface vehicles with experimental results

In this paper, a novel multi-USV formation path planning algorithm is proposed based on deep reinforcement learning. First, a goal-based hierarchical reinforcement learning algorithm is designed to improve training speed and resolve planning conflicts within the formation. Second, an improved artificial potential field algorithm is designed in the training process to obtain the optimal path planning and obstacle avoidance learning scheme for multi-USVs in the determined perceptual environment. Finally, a formation geometry model is established to describe the physical relationships among USVs, and a composite reward function is proposed to guide the training. Numerous simulation tests are conducted, and the effectiveness of the proposed algorithm are further validated through the NEU-MSV01 experimental platform with a combination of parameterized Line of Sight (LOS) guidance.

Analysis and control of self stable balance circle of surrounding rock of roadway in inclined coal seam

The asymmetric deformation of surrounding rock in inclined coal seam roadway is serious, and its stability is difficult to control. Based on the PU's arch theory and considering the development process of the progressive formation of the self stable balance circle (SSBC), this paper establishes a mechanical model of the SSBC for the right-angle trapezoidal roadway in the inclined coal seam. The mechanical analysis and morphological characterization of the forming process were carried out, and the numerical simulation and physical similarity simulation test were carried out to verify. On this basis, the stability control method of roadway in inclined coal seam is improved, and the asymmetric support scheme of roadway is optimized, which is verified by numerical simulation and field monitoring. The results show that the roadway surrounding rock forms a quasi elliptical SSBC after self stabilization, and the mechanical formula of the shape of the SSBC is derived and characterized. Through numerical simulation and physical similarity simulation experiments, the dynamic evolution process of SSBC is depicted, and the gradual forming evolution characteristics of SSBC are revealed. With the increase of the deformation of the surrounding rock, the effective height and width of the roadway gradually increase, and finally a quasi elliptical SSBC deflecting to the left side of the roadway is formed. Based on this, the asymmetric support principle that can control the stability of surrounding rock by improving the asymmetric stress concentration is proposed, and the asymmetric support scheme is designed, that is, "the anchor bolts (cables) are arranged to the right sidewall, and the sidewall angle weakening area is intensively supported". Through numerical simulation and field monitoring, the support effect is remarkable.

Numerical Simulation and Field Test of a PDC Bit with Mixed Cutter Arrangement to Break Non-Homogeneous Granite

As the depth of petroleum drilling increases, the strata environment becomes more complex. The efficiency and lifespan of Polycrystalline Diamond Compact (PDC) drill bits fail to meet current drilling demands. However, the structure and arrangement of PDC cutters are valuable determinants of drilling efficiency, although related research still has gaps and deficiencies. This study focuses on PDC cutters in axe, triangular prism, and circular forms. It establishes an inhomogeneous granite model based on the actual measurements of granite and verifies the accuracy of this model through uniaxial compression simulation. Finite element models of three types of cutters in various combination schemes are constructed to examine rock-breaking effects, with the best scheme optimized using Box-Behnken response surface methodology. The rock-breaking process of the optimal PDC drill bit layout has been compared to that of a single cutter bit. Field drilling has demonstrated the effectiveness of a mixed cutter arrangement. The results show that the inhomogeneous granite model can be trusted. The optimal arrangement involves axe cutters in the front row and an alternate arrangement of triangular prism cutters and axe cutters in the back row. The optimal lateral and longitudinal distances for the triangular cutters from the front row of axe cutters are 10 mm and 7 mm, respectively, while those for the back row of axe cutters from the front row are 10.06 mm and 7 mm, respectively. The ROP standard deviation in the drilling process of mixed cutter bits decreases by 53.06% and 43.08% compared to axe and triangular prism cutter bits, respectively. The drilling efficiency increases by 16.8% and 16.6%, respectively, demonstrating higher efficiency and stability. Field drilling results indicate that a mixed cutter bit increases efficiency by 23.5% compared to a bit with only triangular prism cutters. This study posits that research on the combination schemes and parameters of PDC cutters can significantly enhance drilling efficiency, thereby reducing the drilling cycle and costs.

Dynamics and performance evaluation of wind-induced vibration of a cuboid bluff body with two ornaments

The geometric design of the bluff body has a decisive effect on the wind-induced vibration energy harvesting performance. Aiming to enhance the properties of the wind-induced vibration energy harvester at the low-speed wind, we presented a wind-induced vibration energy harvester with two symmetrical additional ornaments, and the effects of installation location and size of ornaments on a cuboid bluff body are comprehensively studied. A distributed parameter model is developed based on the Euler-Lagrange equation. Corresponding numerical simulation and wind tunnel tests are implemented to evaluate the dynamics and performance of wind-induced vibration. The results show that the wind-induced vibration energy harvesters with various bluff bodies may exhibit galloping or vortex-induced vibrations (VIV) based on the position of ornaments and h/DB (h is the height of the ornament and DB is the diameter of the cuboid bluff body. For both Square-Front-h/DB (S–F-h/DB) and Square-Middle-h/DB (S-M-h/DB), the aeroelastic energy harvesting performance and the root-mean-square output voltage (Vrms) are improved in the low-speed wind. Compared with the cuboid bluff body, the critical wind speed (the smallest wind speed for triggering vibration) of S-M-0.25 is reduced by 18.18%, and the maximum voltage output reaches 10.89 V, which is increased by 105.72%. Afterwards, the three-dimensional computational fluid dynamics (3D-CFD) studies are conducted by Xflow to investigate the inherent physical mechanism of performance improvement. The results of vorticity vectors and vorticity contours verify the experimental results and reveal the insight mechanism of aerodynamic change. This work could provide a theoretical basis for optimizing wind-induced vibration energy harvesters and improving the performance of aeroelastic energy harvesting.

Stress and permeability evolution of high-gassy coal seams for repeated mining

Coal bed methane reservoirs in China are generally characterized by high stress and low gas permeability coefficient. Protected layer mining has the effect of unloading pressure and increasing gas permeability coefficient. There are few studies in the case of repeated mining with an orthogonal arrangement of the protected layer. Based on the engineering practice of the high gas coal seams group in Xinjing coal mine, a combination of numerical simulation and field test was used. The distribution law of plastic zone, stress-strain and gas permeability coefficient of the protected layer under the two states of single mining and repeated mining were obtained. The stress and gas permeability coefficient distribution of the protected layer was divided into 5 and 6 zones in plane for single and repeated mining cases. The field test tested the distribution law of stress, gas pressure, deformation, and gas permeability coefficient, and verified the reliability of the numerical simulation results. According to the characteristics of gas permeability coefficient distribution under the condition of repeated mining, a method for accurate gas extraction is proposed. The results of the study have important implications for the design of gas extraction schemes in orthogonal repeated mining situations.

Simulation and analysis of hot cylindrical flow forming process of titanium alloy

The spinning process of cylindrical titanium alloy parts was studied using a three-dimensional model and finite element simulation. The forming conditions and stress changes under different spinning process parameters have been analyzed. Based on the numerical simulation test, the blank’s state in the processing process is analyzed and predicted, providing a process reference for the spinning trial.

Simulation study of crack parameters’ effects on the vibration characteristics of a bladed disk system

As a key component of the turbo machine rotor in harsh operating conditions, high cycle fatigue failure and even cracks are common in bladed disks. In this paper, modal analysis was carried out for a single cracked bladed disk system, the effects of crack depth, crack height and rotating speed on its vibration characteristics were studied by the method of both numerical simulation and orthogonal test, and the effects of crack distribution on the vibration characteristics of multi-crack bladed disk systems were also studied. Finally, some conclusions have been drawn, they provide a fundamental understanding of blade health monitoring and fault prediction, and are important to improve the reliability and safety of turbine operation.

Altitude influence on the explosion shock wave pressure distribution

The explosion shock wave pressure distribution law is significantly affected by the altitude. It is very important to clarify the altitude impact on the explosion shock wave pressure propagation law for guiding the shock wave pressure test and accurately evaluating the ammunition damage power. The paper reviews the finite element numerical simulation and actual testing results of researchers at home and abroad regarding the propagation of explosive shock wave pressure through different air and water mediums, and clarifies the impact of altitude on characterization parameters of shock wave pressure such as peak pressure, impulse, and positive pressure duration. Based on the current research status both domestically and internationally, we have pointed out the main problems that still exist in the current research process and proposed research directions that need to be focused on in subsequent studies.

Numerical simulation and experimental investigation of heat transfer performance of turbine blade with ribbed channel

A combination of numerical simulation and experimental test is carried out, and the vortex core visualization technology is adopted to visualize vortex in the flow field and study the heat transfer mechanism. The heat transfer characteristics of air flow in 45° ribbed straight channel with aspect ratio of 1 and the other 6 new ribbed channels are studied. The results show that the average heat transfer performance of the new ribbed channel with all the fins 3.8 mm cut at the far end of fins along the flow direction is the best by comparing with the original ribbed straight channel under the same conditions. The average Nu, the average Nu/Nu0 and the average heat transfer enhancement factor FT of the ribbed wall is increased respectively by 25.1%, 24.8%, 22.7% on the average by comparing with the original ribbed channel. The experimental results show that the error between the experimental value and the simulated is about 10% for the outer wall temperature of ribbed channel.

Non-contact model test and numerical simulation of plastic zone in sandy soil foundation

Reasonable determination of the ultimate bearing capacity of the foundation is of great significance in engineering applications. Based on the self-developed non-contact testing device for the plastic zone of shallow foundation, this paper carries out model test research on the plastic zone of sandy soil shallow foundation and analyzes the development law of plastic zone under the action of foundation load. The main advantages and functional characteristics of the foundation plastic zone test system are that it can realize the non-contact test of displacement deformation of soil, the dynamic development process of shear deformation, and the plastic zone of model foundation can be obtained intuitively. The development process, morphological boundary characteristics, and foundation failure mode of the plastic zone of the sand foundation are obtained. The plastic zone of the foundation starts from the edges of both sides of the bearing plate; with the increase of the load, the plastic zone gradually develops downward and approaches to the center line, and finally crosses through at the bottom until the local shear failure of the foundation occurs. The measured plastic zone is a symmetrical spindle shape with thin ends and a bulge in the middle; the sand on both sides of the bearing plate partially bulges, forming a “V” shaped shear failure zone, and the bottom of bearing plate forms a triangular compression zone, the foundation failure mode of sandy soil represents a typical punching shear failure mode. In order to study the distribution characteristics of the plastic zone range of foundation under different foundation loads and foundation widths, the Universal Distinct Element Code (UDEC) based on the discrete element method is used for numerical simulation research. By conducting parameterized numerical simulation test for the plastic zone of foundation and analyzing the results, with the changes in the foundation load and the foundation width, the variation law of (1) the depth of the plastic zone on the foundation bottom, (2) the width of the plastic zone on both sides of the foundation, (3) the ratio for the depth of plastic zone to the width of foundation, (4) the ratio for the width of plastic zone to the width of foundation and (5) the ratio for the width of plastic zone to the depth of plastic zone is obtained. The research has significant guiding significance for the study of the development law of plastic zone and foundation design.

Study on floor instability law of cemented filling mining above a confined aquifer

To solve the problem of floor water inrush in the process of coal mining on a confined aquifer and study the law of floor instability, a cemented filling mining method is proposed in the paper. Using river sand and cement as filling materials, the cementitious material with a concentration of 75% and cement content of 15% has the best flow and mechanical properties. Based on the elastic half-space theory and the bearing characteristics of the backfill, the mechanical model of floor stability is established, the critical criterion of floor instability is proposed, and the relationship between the failure depth of floor and the location and pressure of confined aquifer is obtained. The numerical simulation test scheme is designed, and the FLAC3D fluid-structure coupling element is used to explore the instability characteristics of the floor in the mining process. The research results show that the failure depth of the floor will gradually decrease with the increase of the strength of filling materials, the increase of aquifer distance, and the decrease of water pressure. The research results provide a useful reference for the study of safe mining of coal resources on a confined aquifer.

Biomechanical analysis of different osteosynthesis configurations in the pin and plate fixation method for distal humerus fractures

Distal humerus fractures commonly occur in adults with low bone mineral density causing major technical challenges for orthopedic surgeons. Persian fixation method was introduced as a novel technique to stabilize small fragments in comminuted distal humerus fractures using a set of K-wires and a reconstruction plate. The present study aims to measure this technique's stiffness and stability of this technique and analyze the effect of influential parameters with numerical simulation and biomechanical testing on a cadaveric specimen. Validation of the finite element (FE) model was conducted based on results of experiments. The results indicated that Delta configuration mainly led to a higher stiffness in the case of axial loading and anterior bending compared to L configuration. Analyzing the influential factors of this technique suggests that changes in diameter and number of K-wires have a similarly significant effect on the construct stiffness while the height of plate had a slight influence. Also, the diameter of wires was the most effective parameter for implant failure, particularly in the 3-pin construct, which caused a reduction in failure risk by about 60%. The results revealed that the Persian fixation method would achieve suitable stability compared to the dual-plating technique.

Investigation of a novel ceramic coating for graphite electrodes in electric ARC furnaces using numerical simulation, experimental method, and industrial testing

Electric ARC furnaces (EAF) are referred to as a set of furnaces in which the process of melting metal materials takes place using an electric ARC. The temperature of melting and discharging in these furnaces is different and can vary between 1600 and 3000 ℃. These furnaces can use lime, fluorine, iron, etc., and ferroalloys to produce metal products such as steel or cast iron. The production of EAF metal products depends on various factors, including graphite electrodes. Electric electrodes are one of the main components of EAF, which transfer the current by creating an electric ARC from the electrode arms to the furnace load. Nowadays, a growing need is felt for using graphite electrodes in electric ARC furnaces (EAF). The validity of SiO2/ TiO2 productive coating is evaluated to decrease the corrosion resistance of graphite electrodes through the experiments. The corrosion of the graphite samples was simulated using finite element (FE) simulation in ANSYS software. FE simulation was used to model the actual working condition of electrodes in the EAF. The validity of SiO2/TiO2 productive coating is evaluated to decrease the corrosion of electrodes by using numerical simulation, experimental methods, and industrial testing in the EAF. All the tests and experiments performed in this study were to obtain a more precise consideration of the corrosion of electrodes. Also, using the TGA (Thermo-gravimetric analysis), the results show that this ceramic coating has a prominent role in decreasing the corrosion of electrodes at high temperatures. Finally, it was realized that coating the surface of graphite electrode with two layers of SiO2/ TiO2 would effectively decrease the consumption of graphite electrodes.

Quantitative analysis of acoustic black hole property by the catastrophe theory

Acoustic black holes (ABHs) have garnered increasing attention in the field of vibration and noise reduction due to their excellent wave aggregation effect. A large number of studies have been conducted in analyzing ABH structures, these analytical methods such as finite element and semi-analytical modeling, however, still suffer from limitations in the quantitative analysis of ABHs. The majority of the existing methodologies are intricate and computationally burdensome and do not furnish a quantitative assessment of the ABH structure. To meet this need, we design a theoretical analysis model from the catastrophe theory perspective. Based on the Hyperbolic umbilic model, the proposed analytical method can investigate the quantitative relationships among each parameter and their energy aggregation effects in ABHs. Combined with a dimensionless analytical solution, the underlying mechanism and the quantitative property of ABHs are expected to be revealed with significantly reduced computational complexity. Further, the proposed quantitative method is demonstrated by a numerical simulation test and a practical experiment. The findings illustrate a clear presence of a catastrophe effect across the range of ABH parameter variation, and establish a direct correlation between each ABH parameter and the ABH effect in the proposed approach. The proposed theoretical method holds significant potential in analyzing and applying of ABHs.

4D printed shape memory metamaterials with sensing capability derived from the origami concept

Mechanical metamaterials have unprecedented properties that contribute to the development of science and technology. However, once the mechanical metamaterials are fabricated, the single configuration will limit their application, especially in areas requiring rich programmability and efficient shape reconfigurability, etc. To break through this limitation and explore more potential of mechanical metamaterials, this work proposes a novel design strategy for 4D printed metamaterials with programmable stiffness. Deriving from the origami concept, the stiffness of the structure can be adjusted not only by changing the geometric parameters but also by changing the geometric configuration utilizing the shape memory property. Through numerical simulation, theoretical analysis and experimental tests, the design strategy is verified in the 4D printed mechanical metamaterials. With this strategy, the stiffness of the structure can be adjusted, and the mechanical programmability, shape reconfigurability and adaptability can be significantly improved. Utilizing excellent energy absorption performance, we design and fabricate a kind of shoe sole. By integrating the sensor function of the Triboelectric Nanogenerator (TENG) into the sole, gait monitoring is successfully realized. The 4D printed shape memory metamaterials show extraordinary potential in the field of programmable shock absorption and intelligent monitoring.

Effect of Volute-Tongue Clearance on the Aerodynamic Performance and Noise of Multi-Wing Centrifugal Fan for Air Conditioning

Multi-wing centrifugal fans are wildly used in the central air-conditioning. The influence of dimensionless clearance of the volute-tongue on aerodynamic performance and noise is studied by numerical simulation and experimental tests in this paper. The complicated internal flow related to unsteady flow in a centrifugal fan with multiple wings is investigated by numerical simulation. Besides, the influence of circumstance on the noise is analyzed. It is testified that the internal flow of centrifugal fans is ameliorated using appropriate volute tongue clearance. Reduced eddy current decreased the local-flow loss near the volute tongue and exit. The experimental results show that the static pressure of model △t/R2=0.12 rose to 7.5 Pa and the aerodynamics noise value reduced to 4 dB compared with that of a reference model. Meanwhile, an obvious reduction of aerodynamics noise by 3.74 dB is obtained for model △t/R2=0.12 installed in the air conditioning unit. The static pressure of centrifugal fan is significantly improved for the model with a cochlear tongue clearance ratio of △t/R2=0.12. It is further demonstrated that the proper dimensionless distance effectively suppresses the aerodynamic noise of forward multi-wing fans.