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The Velocity Synchronizing Control on the Electro-Hydraulic Load Simulator 被引量:39
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作者 焦宗夏 高俊霞 +1 位作者 华清 王少萍 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2004年第1期39-46,共8页
This paper builds up an accurate nonlinear mathematical model of anelectro-hydraulic force/ torque servo control system, and provides a thorough theoretical analysison the feedforward compensation for extraneous force... This paper builds up an accurate nonlinear mathematical model of anelectro-hydraulic force/ torque servo control system, and provides a thorough theoretical analysison the feedforward compensation for extraneous force/torque, whose limitation is analyzed andrevealed. The nonlinear factors and the servo valve dynamics have much influence on the systemcharacteristics. Subsequently a velocity syn-chronizing-compensation method by using the controlsignal of the control actuator is proposed, which can reduce the lagging effects for the betterperformance. For the reason of similarity between the model of control actuator and that of the loadsimulator, the proposed method performs well against the influence of nonlinear factors. Thesimulations and the experiments confirm that this control scheme results in a quick response,robustness, and excellent ability against disturbance. 展开更多
关键词 load simulator synchronizing control extraneous force/torque
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Determination method of mesh size for numerical simulation of blast load in near-ground detonation
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作者 Doudou Si Zuanfeng Pan Haipeng Zhang 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2024年第8期111-125,共15页
In order to improve the overall resilience of the urban infrastructures, it is required to conduct blast resistant design for important building structures in the city. For complex terrain in the city, it is recommend... In order to improve the overall resilience of the urban infrastructures, it is required to conduct blast resistant design for important building structures in the city. For complex terrain in the city, it is recommended to determine the blast load on the structures via numerical simulation. Since the mesh size of the numerical model highly depends on the explosion scenario, there is no generally applicable approach for the mesh size selection. An efficient method to determine the mesh size of the numerical model of near-ground detonation based on explosion scenarios is proposed in this study. The effect of mesh size on the propagation of blast wave under different explosive weights was studied, and the correlations between the mesh size effect and the charge weight or the scaled distance was described. Based on the principle of the finite element method and Hopkinson-Cranz scaling law, a mesh size measurement unit related to the explosive weight was proposed as the criterion for determining the mesh size in the numerical simulation. Finally, the applicability of the method proposed in this paper was verified by comparing the results from numerical simulation and the explosion tests and was verified in AUTODYN. 展开更多
关键词 Blast load Mesh size effect Numerical simulation Scaled mesh size VERIFICATION
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Blast waveform tailoring using controlled venting in blast simulators and shock tubes
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作者 Edward Chern Jinn Gan Alex Remennikov David Ritzel 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2024年第7期14-26,共13页
A critical challenge of any blast simulation facility is in producing the widest possible pressure-impulse range for matching against equivalent high-explosive events.Shock tubes and blast simulators are often constra... A critical challenge of any blast simulation facility is in producing the widest possible pressure-impulse range for matching against equivalent high-explosive events.Shock tubes and blast simulators are often constrained with the lack of effective ways to control blast wave profiles and as a result have a limited performance range.Some wave shaping techniques employed in some facilities are reviewed but often necessitate extensive geometric modifications,inadvertently cause flow anomalies,and/or are only applicable under very specific configurations.This paper investigates controlled venting as an expedient way for waveforms to be tuned without requiring extensive modifications to the driver or existing geometry and could be widely applied by existing and future blast simulation and shock tube facilities.The use of controlled venting is demonstrated experimentally using the Advanced Blast Simulator(shock tube)at the Australian National Facility of Physical Blast Simulation and via numerical flow simulations with Computational Fluid Dynamics.Controlled venting is determined as an effective method for mitigating the impact of re-reflected waves within the blast simulator.This control method also allows for the adjustment of parameters such as tuning the peak overpressure,the positive phase duration,and modifying the magnitude of the negative phase and the secondary shock of the blast waves.This paper is concluded with an illustration of the potential expanded performance range of the Australian blast simulation facility when controlled venting for blast waveform tailoring as presented in this paper is applied. 展开更多
关键词 Advanced blast simulator Shock wave propagation Far-field explosion Blast loads Blast waves Computational fluid dynamics
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Numerical Simulation of Combustion in 660MWTangentially Fired Pulverized Coal Boiler on Ultra-Low Load Operation
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作者 Xuehui Jing Junchen Guo Zhiyun Wang 《Frontiers in Heat and Mass Transfer》 EI 2024年第3期919-937,共19页
In this paper,the combustion conditions in the boiler furnace of a 660 MWtangential fired pulverized coal boiler are numerically simulated at 15%and 20%rated loads,to study the flexibility of coal-fired power units on... In this paper,the combustion conditions in the boiler furnace of a 660 MWtangential fired pulverized coal boiler are numerically simulated at 15%and 20%rated loads,to study the flexibility of coal-fired power units on ultra-low load operation.The numerical results show that the boiler can operate safely at 15%and 20%ultra-low loads,and the combustion condition in the furnace is better at 20%load,and the tangent circles formed by each characteristic section in the furnace are better,and when the boiler load is decreased to 15%,the tangent circles in the furnace begin to deteriorate.The average flue gas temperature of different areas of the furnace shows that when the boiler furnace operates under ultra-low load conditions,the average smoke temperature of the cold ash hopper at 20%load is basically the same as the average smoke temperature at 15%load;in the burner area,the average smoke temperature of the cold ash hopper at 20%load is about 50 K higher than that at 15%load;in the burned out area,the average smoke temperature of the cold ash hopper at 20%load is slightly higher than that at 15%load.The average temperature of flue gas in the furnace showed a tendency to increase rapidly with the height of the furnace,then slow down and fluctuate the temperature in the burner area,and finally increase slightly in the burnout area due to the further combustion of combustible components to release heat,and then began to decrease. 展开更多
关键词 Boiler combustion deep peak shaving ultra-low load numerical simulation
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Precise Compound Control of Loading Force for Electric Load Simulator of Electric Power Steering Test Bench 被引量:1
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作者 Changhua Dai Guoying Chen +1 位作者 Changfu Zong Buyang Zhang 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2022年第1期255-265,共11页
Electric load simulator(ELS) systems are employed for electric power steering(EPS) test benches to load rack force by precise control. Precise ELS control is strongly influenced by nonlinear factors. When the steering... Electric load simulator(ELS) systems are employed for electric power steering(EPS) test benches to load rack force by precise control. Precise ELS control is strongly influenced by nonlinear factors. When the steering motor rapidly rotates, extra force is directly superimposed on the original static loading error, which becomes one of the main sources of the final error. It is key to achieve ELS precise loading control for the entire EPS test bench. Therefore, a three-part compound control algorithm is proposed to improve the loading accuracy. First, a fuzzy proportional–integral plus feedforward controller with force feedback is presented. Second, a friction compensation algorithm is established to reduce the influence of friction. Then, the relationships between each quantity and the extra force are analyzed when the steering motor rapidly rotates, and a net torque feedforward compensation algorithm is proposed to eliminate the extra force. The compound control algorithm was verified through simulations and experiments. The results show that the tracking performance of the compound control algorithm satisfies the demands of engineering practice, and the extra force in the ELS system can be suppressed by the net torque corresponding to the actuator’s acceleration. 展开更多
关键词 Electric load simulator Electric power steering Extra force Compound control
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Dynamic response of UHMWPE plates under combined shock and fragment loading 被引量:1
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作者 Chun-Zheng Zhao Lu-Sheng Qiang +4 位作者 Rui Zhang Qian-Cheng Zhang Jun-Yang Zhong Zhen-Yu Zhao Tian Jian Lu 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2023年第9期9-23,共15页
Ultra-high molecular weight polyethylene(UHMWPE)fiber composite has been extensively used to construct lightweight protective structures against ballistic impacts,yet little is known about its performance when subject... Ultra-high molecular weight polyethylene(UHMWPE)fiber composite has been extensively used to construct lightweight protective structures against ballistic impacts,yet little is known about its performance when subjected to combined blast and fragment impacts.Built upon a recently developed laboratory-scale experimental technique to generate simulated combined loading through the impact of a fragment-foam composite projectile launched from a light gas gun,the dynamic responses of fullyclamped UHMWPE plates subjected to combined loading were characterized experimentally,with corresponding deformation and failure modes compared with those measured with simulated blast loading alone.Subsequently,to explore the underlying physical mechanisms,three-dimensional(3D)numerical simulations with the method of finite elements(FE)were systematically carried out.Numerical predictions compared favorably well with experimental measurements,thus validating the feasibility of the established FE model.Relative to the case of blast loading alone,combined blast and fragment loading led to larger maximum deflections of clamped UHMWPE plates.The position of the FSP in the foam sabot affected significantly the performance of a UHMWPE target,either enhancing or decreasing its ballistic resistance.When the blast loading and fragment impact arrived simultaneously at the target,its ballistic resistance was superior to that achieved when subjected to fragment impact alone,and benefited from the accelerated movement of the target due to simultaneous blast loading. 展开更多
关键词 UHMWPE composite Ballistic performance Combined blast and fragment loading Impact test Finite element simulation
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State-of-the-art on the anchorage performance of rock bolts subjected to shear load 被引量:2
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作者 Yu Chen Haodong Xiao 《International Journal of Coal Science & Technology》 EI CAS CSCD 2024年第1期1-30,共30页
Rock bolts are extensively utilized in underground engineering as a means of offering support and stability to rock masses in tunnels,mines,and other underground structures.In environments of high ground stress,faults... Rock bolts are extensively utilized in underground engineering as a means of offering support and stability to rock masses in tunnels,mines,and other underground structures.In environments of high ground stress,faults or weak zones can frequently arise in rock formations,presenting a significant challenge for engineering and potentially leading to underground engineering collapse.Rock bolts serve as a crucial structural element for the transmission of tensile stress and are capable of withstanding shear loads to prevent sliding of weak zones within rock mass.Therefore,a complete understanding of the behavior of rock bolts subjected to shear loads is essential.This paper presents a state-of-the-art review of the research progress of rock bolts subjected to shear load in three categories:experiment,numerical simulation,and analytical model.The review focuses on the research studies and developments in this area since the 1970s,providing a comprehensive overview of numerous factors that influence the anchorage performance of rock bolts.These factors include the diameter and angle of the rock bolt installation,rock strength,grouting material,bolt material,borehole diameter,rock bolt preload,normal stress,joint surface roughness and joint expansion angle.The paper reviews the improvement of mechanical parameter setting in numerical simulation of rock bolt shear.Furthermore,it delves into the optimization of the analytical model concerning rock bolt shear theory,approached from the perspectives of both Elastic foundation beam theory coupled with Elastoplasticity theory and Structural mechanic methods.The significance of this review lies in its ability to provide insights into the mechanical behavior of rock bolts.The paper also highlights the limitations of current research and guidelines for further research of rock bolts. 展开更多
关键词 Rock bolt Shear load Shear test Numerical simulation Analytical model
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Modeling,Simulation and Experiment of Electro-hydraulic Screw Down Servo System of Seamless Tube Rolling Mill 被引量:4
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作者 XU Xiaoqing QUAN Long +1 位作者 LI Bin GUO Jibao 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2011年第1期113-120,共8页
Electro-hydraulic screw down servo system(HSDS) is widely used in seamless tube rolling mill in western companies.But in Chinese companies,mechanical screw down system(MSDS) is popularly equipped and has a serious... Electro-hydraulic screw down servo system(HSDS) is widely used in seamless tube rolling mill in western companies.But in Chinese companies,mechanical screw down system(MSDS) is popularly equipped and has a serious disadvantage that the roller would often be locked when it is overloaded.For the purpose of designing the first set of domestic twin-roller,four-cylinder and six-framework electro-hydraulic HSDS of seamless tube rolling mill,an experiment system that can simulate the process of seamless tube rolling is constructed.A digital simulation model of the experiment system is built with AMESim software and validated by comparing the simulation results with experiment results.The sudden load response of the screw piston position is studied with the built model and the experiment system.To improve the HSDS's positioning accuracy with large load,a hybrid control scheme of combining load disturbance feedforward compensation(LDFC) method based on servo valve's pressure-stroke feature and anti-saturation integral control(ASIC) is proposed.Both results of simulation and experiment indicate that the transient response time of the single-roller HSDS with the proposed scheme decreases from 0.65 s to less than 0.2 s without static error.To improve the system dynamic stiffness and production qualified rate,a flow rate feedforward compensation(FFC) control strategy based on oil compressibility to dynamic position error is proposed.This FFC strategy is validated with experiments in which the transient error caused by sudden load is reduced to less than 25% of that without FFC.By extending the simulation model to HSDS of a twin-roller,four-cylinder rolling mill,analyzing the mill deformation,and applying the LDFC,ASIC and FFC to the HSDS,the dynamic performance and positioning accuracy of compensated multi-roller HSDS at biting moment are predicted.The research results provide a theoretical and experimental basis for the design of HSDS of seamless steel tube rolling mill. 展开更多
关键词 tube rolling mill servo system digital simulation load stiffness
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Effects of loading waveforms on rock damage using particle simulation method 被引量:5
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作者 XIA Ming GONG Feng-qiang 《Journal of Central South University》 SCIE EI CAS CSCD 2018年第7期1755-1765,共11页
The particle simulation method is used to study the effects of loading waveforms (i.e. square, sinusoidal and triangle waveforms) on rock damage at mesoscopic scale. Then some influencing factors on rock damage at t... The particle simulation method is used to study the effects of loading waveforms (i.e. square, sinusoidal and triangle waveforms) on rock damage at mesoscopic scale. Then some influencing factors on rock damage at the mesoscopic scale, such as loading frequency, stress amplitude, mean stress, confining pressure and loading sequence, are also investigated with sinusoidal waveform in detail. The related numerical results have demonstrated that: 1) the loading waveform has a certain effect on rock failure processes. The square waveform has the most damage within these waveforms, while the triangle waveform has less damage than sinusoidal waveform. In each cycle, the number of microscopic cracks increases in the loading stage, while it keeps nearly constant in the unloading stage. 2) The loading frequency, stress amplitude, mean stress, confining pressure and loading sequence have considerable effects on rock damage subjected to cyclic loading. The higher the loading frequency, stress amplitude and mean stress, the greater the damage the rock accumulated; in contrast, the lower the confining pressure, the greater the damage the rock has accumulated. 3) There is a threshold value of mean stress and stress amplitude, below which no further damage accumulated after the first few cycle loadings. 4) The high-to-low loading sequence has more damage than the low-to-high loading sequence, suggesting that the rock damage is loading-path dependent. 展开更多
关键词 rock damage failure process crack initiation and propagation loading waveform cycle loading particle simulation method
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Velocity Feedback in Load Simulator with a Motor Synchronizing in Position 被引量:2
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作者 于慈远 刘庆和 赵克定 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 1998年第3期78-81,共4页
The velocity feedback in a load simulator with a motor synchronizing in position is achieved by installing a tachometer generator between tile shaft and shell of the loading motor, and thes not only decreases the dist... The velocity feedback in a load simulator with a motor synchronizing in position is achieved by installing a tachometer generator between tile shaft and shell of the loading motor, and thes not only decreases the disturbance torque of tile load simlilator greatly but also improves its dynamic performance. 展开更多
关键词 Velocity feedback load simulator SYNCHRONIZING at POSITION DISTURBANCE TORQUE
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Effective loading algorithm associated with explicit dynamic relaxation method for simulating static problems 被引量:4
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作者 赵崇斌 彭省临 +2 位作者 刘亮明 HOBBS B E ORD A 《Journal of Central South University》 SCIE EI CAS 2009年第1期125-130,共6页
Based on the fact that a static problem has an equivalent wave speed of infinity and a dynamic problem has a wave speed of finite value, an effective loading algorithm associated with the explicit dynamic relaxation m... Based on the fact that a static problem has an equivalent wave speed of infinity and a dynamic problem has a wave speed of finite value, an effective loading algorithm associated with the explicit dynamic relaxation method was presented to produce meaningful numerical solutions for static problems. The central part of the explicit dynamic relaxation method is to turn a time-independent static problem into an artificial time-dependent dynamic problem. The related numerical testing results demonstrate that: (1) the proposed effective loading algorithm is capable of enabling an applied load in a static problem to be propagated throughout the whole system within a given loading increment, so that the time-independent solution of the static problem can be obtained; (2) the proposed effective loading algorithm can be straightforwardly applied to the particle simulation method for solving a wide range of static problems. 展开更多
关键词 numerical simulation static systems dynamic relaxation loading algorithm
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Numerical Simulation of Bed Load and Suspended Load Sediment Transport Using Well-Balanced Numerical Schemes
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作者 J.C.González-Aguirre J.A.González-Vázquez +2 位作者 J.Alavez-Ramírez R.Silva M.E.Vázquez-Cendón 《Communications on Applied Mathematics and Computation》 2023年第2期885-922,共38页
Sediment transport can be modelled using hydrodynamic models based on shallow water equations coupled with the sediment concentration conservation equation and the bed con-servation equation.The complete system of equ... Sediment transport can be modelled using hydrodynamic models based on shallow water equations coupled with the sediment concentration conservation equation and the bed con-servation equation.The complete system of equations is made up of the energy balance law and the Exner equations.The numerical solution for this complete system is done in a seg-regated manner.First,the hyperbolic part of the system of balance laws is solved using a finite volume scheme.Three ways to compute the numerical flux have been considered,the Q-scheme of van Leer,the HLLCS approximate Riemann solver,and the last one takes into account the presence of non-conservative products in the model.The discretisation of the source terms is carried out according to the numerical flux chosen.In the second stage,the bed conservation equation is solved by using the approximation computed for the system of balance laws.The numerical schemes have been validated making comparisons between the obtained numerical results and the experimental data for some physical experiments.The numerical results show a good agreement with the experimental data. 展开更多
关键词 Sediment transport Suspended load Bed load Finite volume method Numerical simulation Well-balanced schemes
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Finite element simulation of aluminum alloy cross valve forming by multi-way loading 被引量:2
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作者 张大伟 杨合 孙志超 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2010年第6期1059-1066,共8页
Deformation behavior,temperature evolution and coupled effects have a significant influence on forming process and quality of component formed,which are very complex in forming process of aluminum alloy 7075 cross val... Deformation behavior,temperature evolution and coupled effects have a significant influence on forming process and quality of component formed,which are very complex in forming process of aluminum alloy 7075 cross valve under multi-way loading due to the complexity of loading path and the multiplicity of associated processing parameters.A model of the process was developed under DFEORM-3D environment based on the coupled thermo-mechanical finite element method.The comparison between two process models,the conventional isothermal process model and the non-isothermal process model developed in this study,was carried out,and the results indicate that the thermal events play an important role in the aluminum alloy forming process under multi-way loading.The distributions and evolutions of the temperature field and strain filed are obtained by non-isothermal process simulation.The plastic zone and its extension in forming process of cross valve were analyzed.The results may provide guidelines for the determination of multi-way loading forming scheme and loading conditions of the forming cross valve components. 展开更多
关键词 bulk forming multi-way loading cross valve aluminum alloy finite element simulation
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Investigation on automated loading of dynamic 3D heat source model for welding simulation 被引量:2
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作者 Hu Guangxu Yang Xingya +1 位作者 Yu Xingbin Wei Yanhong 《China Welding》 CAS 2022年第3期48-52,共5页
Since programing complex and dynamic heat source model for welding simulation is a complex job,the parametric methods are studied in this paper.Firstly,an overall flow to achieve automatically modeling welding was int... Since programing complex and dynamic heat source model for welding simulation is a complex job,the parametric methods are studied in this paper.Firstly,an overall flow to achieve automatically modeling welding was introduced.Secondly,an expert module rule for selecting welding heat source model was founded,which is based on simulation knowledge and experiences.Thirdly,a modularity routine method was investigated using writing with C++programing,which automatically creates subroutines of 3D dynamic heat source model for user.To realize the dynamic weld path,the local weld path coordinate system was moved in the global coordinate system and it is used to model the direction of weld gun,welding path and welding pose.The weld path data file was prepared by the automatic tool for the welding heat source subroutines.All above functions were integrated in the user interface and the connection with architecture was introduced.At last,a laser beam welding heat source modeling was automatically modeled and the weld pool geometry was compared with the reported literature.It demonstrated that the automated tool is valid for welding simulation.Since modeling became convenient for welding simulation using the tool proposed,it could be easy and useful for welding engineers to acquire the needed information. 展开更多
关键词 welding heat source welding simulation 3D dynamic heat source model automated loading of heat source
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Macro Meso Response and Stress Wave Propagation Characteristics of MCT High-Voltage Switch Under Shock load
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作者 Yuyang Guo Chuang Chen +1 位作者 Ruizhi Wang Enling Tang 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2024年第2期317-335,共19页
In order to study the dynamic and electrical coupling response characteristics of Metal Oxide Semiconductor Controlled Thyristor(MCT)high-voltage switch under the synergic action of mechanical load and high voltage,th... In order to study the dynamic and electrical coupling response characteristics of Metal Oxide Semiconductor Controlled Thyristor(MCT)high-voltage switch under the synergic action of mechanical load and high voltage,the separated Hopkinson pressure bar(SHPB)test system was used to simulate different impact load environments,and combined with the multi-layer high-voltage ceramic capacitor charging and discharging system,the instantaneous electrical signals of MCT high-voltage switch were collected.Combined with numerical simulation and theoretical analysis,the failure mode and stress wave propagation characteristics of MCT high voltage switch were determined.The mechanical and electrical coupling response characteristics and failure mechanism of MCT high voltage switch under dynamic load were revealed from macroscopic and microscopic levels.The results show that the damage modes of MCT high-voltage switches can be divided into non-functional damage,recoverable functional damage,non-recoverable damage and structural damage.Due to the gap between the metal gate and the oxide layer,the insulating oxide layer was charged.After placing for a period of time,the elastic deformation of the metal gate partially recovered and the accumulated charge disappeared,which induced the recoverable functional damage failure of the device.In addition,obvious cracks appeared on both sides of the monocrystalline silicon inside the MCT high-voltage switch,leading to unrecoverable damage of the device. 展开更多
关键词 MCT Impact load Failure analysis Stress wave Numerical simulation
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A Time-Domain Numerical Simulation for Free Motion Responses of Two Ships Advancing in Head Waves
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作者 PAN Su-yong CHENG Yong 《China Ocean Engineering》 SCIE EI CSCD 2024年第3期519-530,共12页
The constant panel method within the framework of potential flow theory in the time domain is developed for solving the hydrodynamic interactions between two parallel ships with forward speed.When solving problems wit... The constant panel method within the framework of potential flow theory in the time domain is developed for solving the hydrodynamic interactions between two parallel ships with forward speed.When solving problems within a time domain framework,the free water surface needs to simultaneously satisfy both the kinematic and dynamic boundary conditions of the free water surface.This provides conditions for adding artificial damping layers.Using the Runge−Kutta method to solve equations related to time.An upwind differential scheme is used in the present method to deal with the convection terms on the free surface to prevent waves upstream.Through the comparison with the available experimental data and other numerical methods,the present method is proved to have good mesh convergence,and satisfactory results can be obtained.The constant panel method is applied to calculate the hydrodynamic interaction responses of two parallel ships advancing in head waves.Numerical simulations are conducted on the effects of forward speed,different longitudinal and lateral distances on the motion response of two modified Wigley ships in head waves.Then further investigations are conducted on the effects of different ship types on the motion response. 展开更多
关键词 ship motions time domain simulation forward speed different distances wave loads
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Micro defects formation and dynamic response analysis of steel plate of quasi-cracking area subjected to explosive load
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作者 Zheng-qing Zhou Ze-chen Du +5 位作者 Xiao Wang Hui-ling Jiang Qiang Zhou Yu-long Zhang Yu-zhe Liu Pei-ze Zhang 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2024年第1期580-593,共14页
As the protective component,steel plate had attracted extensive attention because of frequently threats of explosive loads.In this paper,the evolution of microstructure and the mechanism of damage in the quasi-crackin... As the protective component,steel plate had attracted extensive attention because of frequently threats of explosive loads.In this paper,the evolution of microstructure and the mechanism of damage in the quasi-cracking area of steel plate subjected to explosive load were discussed and the relationships between micro defects and dynamic mechanical response were revealed.After the explosion experiment,five observation points were selected equidistant from the quasi-cracking area of the section of the steel plate along the thickness direction,and the characteristics of micro defects at the observation points were analyzed by optical microscope(OM),scanning electron microscope(SEM) and electron backscattered diffraction(EBSD).The observation result shows that many slip bands(SBs) appeared,and the grain orientation changed obviously in the steel plate,the two were the main damage types of micro defects.In addition,cracks,peeling pits,grooves and other lager micro defects were appeared in the lower area of the plate.The stress parameters of the observation points were obtained through an effective numerical model.The mechanism of damage generation and crack propagation in the quasicracking area were clarified by comparing the specific impulse of each observation point with the corresponding micro defects.The result shows that the generation and expansion of micro defects are related to the stress area(i.e.the upper compression area,the neutral plane area,and the lower tension area).The micro defects gather and expand at the grain boundary,and will become macroscopic damage under the continuous action of tensile stress.Besides,the micro defects at the midpoint of the section of the steel plate in the direction away from the explosion center(i.e.the horizontal direction) were also studied.It was found that the specific impulse at these positions were much smaller than that in the thickness direction,the micro defects were only SBs and a few micro cracks,and the those decreased with the increase of the distance from the explosion center. 展开更多
关键词 Explosive load Quasi-cracking area Micro defects Steel plate Dynamic response Numerical simulation
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Random vibration analysis of FGM plates subjected to moving load using a refined stochastic finite element method
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作者 Ngoc-Tu Do Trung Thanh Tran 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2024年第4期42-56,共15页
The article introduces a finite element procedure using the bilinear quadrilateral element or four-node rectangular element(namely Q4 element) based on a refined first-order shear deformation theory(rFSDT) and Monte C... The article introduces a finite element procedure using the bilinear quadrilateral element or four-node rectangular element(namely Q4 element) based on a refined first-order shear deformation theory(rFSDT) and Monte Carlo simulation(MCS), so-called refined stochastic finite element method to investigate the random vibration of functionally graded material(FGM) plates subjected to the moving load.The advantage of the proposed method is to use r-FSDT to improve the accuracy of classical FSDT, satisfy the stress-free condition at the plate boundaries, and combine with MCS to analyze the vibration of the FGM plate when the parameter inputs are random quantities following a normal distribution. The obtained results show that the distribution characteristics of the vibration response of the FGM plate depend on the standard deviation of the input parameters and the velocity of the moving load.Furthermore, the numerical results in this study are expected to contribute to improving the understanding of FGM plates subjected to moving loads with uncertain input parameters. 展开更多
关键词 FGM Moving load R-FSDT Q4 element Monte Carlo simulation Random vibration
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Numerical and theoretical study of load transfer behavior during cascading pillar failure
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作者 Hangyu Dong Wancheng Zhu +2 位作者 Leilei Niu Chen Hou Xige Liu 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2024年第8期3014-3033,共20页
To further study the load transfer mechanism of roofemulti-pillarefloor system during cascading pillar failure(CPF),numerical simulation and theoretical analysis were carried out to study the three CPF modes according... To further study the load transfer mechanism of roofemulti-pillarefloor system during cascading pillar failure(CPF),numerical simulation and theoretical analysis were carried out to study the three CPF modes according to the previous experimental study on treble-pillar specimens,e.g.successive failure mode(SFM),domino failure mode(DFM)and compound failure mode(CFM).Based on the finite element code rock failure process analysis(RFPA^(2D)),numerical models of treble-pillar specimen with different mechanical properties were established to reproduce and verify the experimental results of the three CPF modes.Numerical results show that the elastic rebound of roofefloor system induced by pillar instability causes dynamic disturbance to adjacent pillars,resulting in sudden load increases and sudden jump displacement of adjacent pillars.The phenomena of load transfer in the roofemulti-pillarefloor system,as well as the induced accelerated damage behavior in adjacent pillars,were discovered and studied.In addition,based on the catastrophe theory and the proposed mechanical model of treble-pillar specimen edisc spring group system,a potential function that characterizes the evolution characteristics of roof emulti-pillarefloor system was established.The analytical expressions of sudden jump and energy release of treble-pillar specimenedisc spring group system of the three CPF modes were derived according to the potential function.The numerical and theoretical results show good agreement with the experimental results.This study further reveals the physical essence of load transfer during CPF of roof emulti-pillarefloor system,which provides references for mine design,construction and disaster prevention. 展开更多
关键词 Cascading pillar failure(CPF) load transfer Multi-pillar Numerical simulation
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Explosion resistance performance of reinforced concrete box girder coated with polyurea:Model test and numerical simulation
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作者 Guangpan Zhou Rong Wang +2 位作者 Mingyang Wang Jianguo Ding Yuye Zhang 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2024年第3期1-18,共18页
To study the anti-explosion protection effect of polyurea coating on reinforced concrete box girder,two segmental girder specimens were made at a scale of 1:3,numbered as G(without polyurea coating)and PCG(with polyur... To study the anti-explosion protection effect of polyurea coating on reinforced concrete box girder,two segmental girder specimens were made at a scale of 1:3,numbered as G(without polyurea coating)and PCG(with polyurea coating).The failure characteristics and dynamic responses of the specimens were compared through conducting explosion tests.The reliability of the numerical simulation using LS-DYNA software was verified by the test results.The effects of different scaled distances,reinforcement ratios,concrete strengths,coating thicknesses and ranges of polyurea were studied.The results show that the polyurea coating can effectively enhance the anti-explosion performance of the girder.The top plate of middle chamber in specimen G forms an elliptical penetrating hole,while that in specimen PCG only shows a very slight local dent.The peak vertical displacement and residual displacement of PCG decrease by 74.8% and 73.7%,respectively,compared with those of specimen G.For the TNT explosion with small equivalent,the polyurea coating has a more significant protective effect on reducing the size of fracture.With the increase of TNT equivalent,the protective effect of polyurea on reducing girder displacement becomes more significant.The optimal reinforcement ratio,concrete strength,thickness and range of polyurea coating were also drawn. 展开更多
关键词 Explosive load Explosion resistance performance Model test POLYUREA Concrete box girder Numerical simulation
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