The aim of this study is to address the issues associated with traditional magnetorheological fluid(MRF)dampers,such as insufficient damping force after power failure and susceptibility to settlement.In order to achie...The aim of this study is to address the issues associated with traditional magnetorheological fluid(MRF)dampers,such as insufficient damping force after power failure and susceptibility to settlement.In order to achieve this,a bidirectional adjustable MRF damper was designed and developed.Magnetic field simulation analysis was conducted on the damper,along with simulation analysis on its dynamic characteristics.The dynamic characteristics were ultimately validated through experimental testing on the material testing machine,thereby corroborating the theoretical simulation results.Concurrently,this process generated valuable test data for subsequent implementation of the semi-active vibration control system.The simulation and test results demonstrate that the integrated permanent magnet effectively accomplishes bidirectional regulation.The magnetic induction intensity of the damping channel is 0.2 T in the absence of current,increases to 0.5 T when a maximum forward current of 4 A is applied,and becomes 0 T when a maximum reverse current of 3.8 A is applied.When the excitation amplitude is 8 mm and the frequency is 2 Hz,with the applied currents varying,the maximum damping force reaches 8 kN,while the minimum damping force measures at 511 N.Additionally,at zero current,the damping force stands at 2 kN,which aligns closely with simulation results.The present paper can serve as a valuable reference for the design and research of semi-active MRF dampers.展开更多
The aim of this work is to propose a 3D FE model of a theoretical assembling straight bevel gear pair to analyze the contact fatigue on the tooth surface and the bending fatigue in the tooth root. Based on the cumulat...The aim of this work is to propose a 3D FE model of a theoretical assembling straight bevel gear pair to analyze the contact fatigue on the tooth surface and the bending fatigue in the tooth root. Based on the cumulative fatigue criterion and the stress-life equation, the key meshing states of the gear pair were investigated for the contact fatigue and the bending fatigue. Then, the reliability of the proposed model was proved by comparing the calculation result with the simulation result. Further study was performed to analyze the variation of the contact fatigue stress and the bending fatigue stress under different loads. Furthermore, the roles of the driving pinion and the driven gear pair were evaluated in the fatigue life of the straight bevel gear pair and the main fatigue failure mode was determined for the significant gear. The results show that the fatigue failure of the driving pinion is the main fatigue failure for the straight bevel gear pair and the bending fatigue failure is the main fatigue failure for the driving pinion.展开更多
Facing the problems lack of considering the non-uniform distribution of the static bias magnetic field and computing the panicle displacements in the simulation model of electromagnetic acoustic transducer （EMAT）, a...Facing the problems lack of considering the non-uniform distribution of the static bias magnetic field and computing the panicle displacements in the simulation model of electromagnetic acoustic transducer （EMAT）, a multi-field coupled model was established and the finite element method （FEM） was presented to calculate the entire transduction process. The multi-field coupled model included the static magnetic field, pulsed eddy current field and mechanical field. The FEM equations of the three fields were derived by Garlerkin FEM method. Thus, the entire transduction process of the EMAT was calculated through sequentially coupling the three fields. The transduction process of a Lamb wave EMAT was calculated according to the present model and method. The results show that, by the present method, it is valid to calculate the particle displacement under the given excitation signal and non-uniformly distributed static magnetic field. Calculation error will be brought about if the non-uniform distribution of the static bias magnetic field is neglected.展开更多
A shield machine with freezing function is proposed in order to realize tool change operation at atmospheric pressure. Furthermore, the transformation project of freezing cutterhead and tool change maintenance method ...A shield machine with freezing function is proposed in order to realize tool change operation at atmospheric pressure. Furthermore, the transformation project of freezing cutterhead and tool change maintenance method are put forward. Taking the shield construction of Huanxi Power Tunnel as an example, a numerical analysis of the freezing cutter head of the project was carried out. The results show that when the brine temperature is-25 °C, after 30 d of freezing, the thickness of the frozen wall can reach 0.67 m and the average temperature drops to-9.9 °C. When the brine temperature is-30 °C, after 50 d of freezing, the thickness of the frozen wall can reach 1.01 m and the average temperature drops to-12.4 °C. If the thickness of the frozen wall is 0.5 m and the average temperature is-10 °C, as the design index of the frozen wall, the brine temperature should be lower than-28 °C to meet the excavation requirements in 30 d. Analyzing the frozen wall stress under 0.5 m thickness and-10 °C average temperature condition, the tensile safety factor and compressive safety factor are both greater than 2 at the most dangerous position, which can meet the tool change requirements for shield construction.展开更多
To investigate the effects of billet geometry on the cold precision forging process of a helical gear, six different billet geometries were designed utilizing the relief-hole principle. And the influences of the bille...To investigate the effects of billet geometry on the cold precision forging process of a helical gear, six different billet geometries were designed utilizing the relief-hole principle. And the influences of the billet geometry on the forming load and the deformation uniformity were analyzed by three-dimensional （3D） finite element method （FEM） under the commercial software DEFORM 3D. The billet geometry was optimized to meet lower forming load and better deformation uniformity requirement. Deformation mechanism was studied through the distribution of flow velocity field and effective strain field. The forging experiments of the helical gear were successfully performed using lead material as a model material under the same process conditions used in the FE simulations. The results show that the forming load decreases as the diameter of relief-hole do increases, but the effect of do on the deformation uniformity is very complicated. The forming load is lower and the deformation is more uniform when do is 10 mm.展开更多
The roll contour pattern and variety of work and backup rolls in service and its effect on profile and flatness control performance in 1 700 mm hot strip mill at Wuhan Iron and Steel(Group) Corporation were tested and...The roll contour pattern and variety of work and backup rolls in service and its effect on profile and flatness control performance in 1 700 mm hot strip mill at Wuhan Iron and Steel(Group) Corporation were tested and analyzed by the developed finite element models of different typical roll contours configurations.A rather smooth local work roll contour near strip edges and an increase in rolled length can be obtained by application of long stroke work roll shifting system with conventional work roll contours that is incapable of the crown control.In comparison with the conventional backup and work roll contours configuration,the crown control range by the roll bending force enhances by 12.79% and the roll gap stiffness increases by 25.26% with the developed asymmetry self-compensating work rolls(ASR) and varying contact backup rolls(VCR).A better strip profile and flatness quality,an increase in coil numbers within the rolling campaign and a significant alleviated effect of severe work roll wear contours on performance of edge drop control are achieved by the application of ASR with crown control and wear control ability in downstream stand F5 and VCR in all stands of 1 700 mm hot strip mill.展开更多
3D dynamic analysis models of 1000 m deep-ocean mining pipeline, including steel lift pipe, pump, buffer and flexible hose, were established by finite element method (FEM). The coupling effect of steel lift pipe and f...3D dynamic analysis models of 1000 m deep-ocean mining pipeline, including steel lift pipe, pump, buffer and flexible hose, were established by finite element method (FEM). The coupling effect of steel lift pipe and flexible hose, and main external loads of pipeline were considered in the models, such as gravity, buoyancy, hydrodynamic forces, internal and external fluid pressures, concentrated suspension buoyancy on the flexible hose, torsional moment and axial force induced by pump working. Some relevant FEM models and solution techniques were developed, according to various 3D transient behaviors of integrated deep-ocean mining pipeline, including towing motions of track-keeping operation and launch process of pipeline. Meanwhile, an experimental verification system in towing water tank that had similar characteristics of designed mining pipeline was developed to verify the accuracy of the FEM models and dynamic simulation. The experiment results show that the experimental records and simulation results of stress of pipe are coincided. Based on the further simulations of 1 000 m deep-ocean mining pipeline, the simulation results show that, to form configuration of a saddle shape, the total concentrated suspension buoyancy of flexible hose should be 95%?105% of the gravity of flexible hose in water, the first suspension point occupies 1/3 of the total buoyancy, and the second suspension point occupies 2/3 of the total buoyancy. When towing velocity of mining system is less than 0.5 m/s, the towing track of buffer is coincided with the setting route of ship on the whole and the configuration of flexible hose is also kept well.展开更多
In recent years,a new type of foundation named composite piled raft foundation (also called long short composite piled raft) has been developed.Where designing shallow foundations would mean unacceptable settlement,or...In recent years,a new type of foundation named composite piled raft foundation (also called long short composite piled raft) has been developed.Where designing shallow foundations would mean unacceptable settlement,or other environmental risks exist which could impair the structure in the future,composite piled raft foundations could be used.Finite element method was applied to study the behavior of this type of foundation subjected to vertical loading.In order to determine an optimal pile arrangement pattern which yields the minimum settlement,various pile arrangements under different vertical stress levels were investigated.Results show that with increasing the vertical stress on the raft,the effectiveness of the arrangements of short and long piles become more visible.In addition,a new factor named "composite piled raft efficiency" (CPRE) has been defined which determines the efficiency of long short piles arrangement in a composite piled raft foundation.This factor will increase when short piles take more axial stresses and long piles take less axial stresses.In addition,it is found that the changes in settlements for different long short piles arrangement are in a well agreement with changes in values of CPRE ratio.Thus,CPRE ratio can be used as a factor to determine the efficiency of piles arrangements in composite piled raft foundation from the view point of reducing raft settlements.展开更多
A working shaft for pipe-jacking is going to be excavated into a sand stratum with high hydraulic pressure in Guangzhou, China. A newly assembled pre-stressed retaining system has been proposed to support the shaft fo...A working shaft for pipe-jacking is going to be excavated into a sand stratum with high hydraulic pressure in Guangzhou, China. A newly assembled pre-stressed retaining system has been proposed to support the shaft for its efficiency, safety and sustainability. Full-scale field tests and numerical analysis were conducted to analyze the base failure of the circular shaft with confined water. The failure process of the shaft was observed on site. The construction process of step-by-step excavation of shaft and layer-by-layer assembly of pre-stressed structure was simulated in detail. Simulation results agree well with the phenomenon on site. The base failure modes present that tensile damage generates at the center of the base due to non-uniform uplift and shear failure occurs along the soil-structure interface. The effects of shaft size and confined water head were also discussed. As a result, a critical ratio of diameter to shaft depth is put forward to assess the size effect of circular shaft. A conclusion that the soil strength should be partially considered in anti-inrushing safety factor calculation is drawn by analysis and comparison of various calculation methods. This research provides a reference for the base stability evaluation of similar shaft subjected to hydraulic uplift.展开更多
A new structure design method of elastic composite cylindrical roller bearing is proposed, in which PTFE is embedded into a hollow cylindrical rolling element, according to the principle of creative combinations and t...A new structure design method of elastic composite cylindrical roller bearing is proposed, in which PTFE is embedded into a hollow cylindrical rolling element, according to the principle of creative combinations and through innovation research on cylindrical roller bearing structure. In order to systematically investigate the inner wall bending stress of the rolling element in elastic composite cylindrical roller bearing, finite element analysis on different elastic composite cylindrical rolling elements was conducted. The results show that, the bending stress of the elastic composite cylindrical rolling increases along with the increase of hollowness with the same filling material. The bending stress of the elastic composite cylindrical rolling element decreases along with the increase of the elasticity modulus of the material under the same physical dimension. Under the same load, on hollow cylindrical rolling element, the maximum bending tensile stress values of the elastic composite cylindrical rolling element after material filling at 0° and 180° are 8.2% and 9.5%, respectively, lower than those of the deep cavity hollow cylindrical rolling element. In addition, the maximum bending-compressive stress value at 90° is decreased by 6.1%.展开更多
The influence of different features of natural soft clays,namely anisotropy,destructuration and viscosity,on modelling the time-dependent behaviour of Murro embankment was investigated.The newly developed elasto-visco...The influence of different features of natural soft clays,namely anisotropy,destructuration and viscosity,on modelling the time-dependent behaviour of Murro embankment was investigated.The newly developed elasto-viscoplastic models were enhanced for determining viscosity parameters in a straightforward way and adopted for the finite element analysis.The same set of common parameters determined from conventional triaxial and oedometer tests was employed for all models,with additional parameters required for representing different soil features.The finite element predictions by using models coupled with BIOT's consolidation theory were compared with each other and with field data for settlement,horizontal displacement and excess pore pressures.In addition,the stress paths under the embankment loading were also compared with each other to improve the understanding of the effect of different soil features.All simulations demonstrate that all three features significantly influence the predictions.As a consequence,accounting for soil features needs to be carefully considered when they are applied to a construction site.展开更多
In-service hydrocarbons must be transported at high temperature and high pressure to ease the flow and prevent the solidification of the wax fraction. The pipeline containing hot oil will expand longitudinally due to ...In-service hydrocarbons must be transported at high temperature and high pressure to ease the flow and prevent the solidification of the wax fraction. The pipeline containing hot oil will expand longitudinally due to the rise in temperature. If such expansion is resisted, for example by frictional effects over a kilometer or so of pipeline, compressive axial stress will be built up in the pipe-wall. The compressive forces are often so large that they induce vertical buckling of buffed pipelines, which can jeopardize the structural integrity of the pipeline. A typical initial imperfection named continuous support mode of submarine pipeline was studied. Based on this type of initial imperfection, the analytical solution of vertical thermal buckling was introduced and an elastic-plasticity finite element analysis （FEA） was developed. Both the analytical and the finite element methodology were applied to analyze a practice in Bohai Gulf, China. The analyzing results show that upheaval buckling is most likely to build up from the initial imperfection of the pipeline and the buckling temperature depends on the amplitude of initial imperfection. With the same amplitude of initial imperfection, the triggering temperature difference of upheaval buckling increases with covered depth of the pipeline, the soil strength and the friction between the pipeline and subsoil.展开更多
The finite element analysis （FEA） software Ansys was employed to study the stress state of the dies of both plane and non-plane parting face structures with uniform interference and the die of plane parting face str...The finite element analysis （FEA） software Ansys was employed to study the stress state of the dies of both plane and non-plane parting face structures with uniform interference and the die of plane parting face structure with non-uniform interference. Considering the symmetry of the die, a half gear tooth model of the two-ring assembled die with 2.5 GPa inner pressure was constructed. Four paths were defined to investigate the stress state at the bottom comer of the die where stress concentration was serious. FEA results show that the change of parting face from non-plane to plane can greatly reduce the stress at the teeth tips of the die so that the tip fracture is avoided. The interference structure of the die is the most important influencing factor for the stress concentration at the bottom comer. When non-uniform interference is adopted the first principal stress at the comer on the defined paths of the die is much lower than that with uniform interference. The bottom hole radius is another important influencing factor for the comer stress concentration. The first principal stress at the comer of the plane parting face die with non-uniform interference is reduced from 2.3 to 1.9 GPa when the hole radius increases from 12.5 to 16.0 mm. The optimization of the die structure increases the life of the die from 100 to 6 000 hits.展开更多
A new method for optimizing a butterfly-shaped linear ultrasonic motor was proposed to maximize its mechanical output. The finite element analysis technology and response surface methodology were combined together to ...A new method for optimizing a butterfly-shaped linear ultrasonic motor was proposed to maximize its mechanical output. The finite element analysis technology and response surface methodology were combined together to realize the optimal design of the butterfly-shaped linear ultrasonic motor. First, the operation principle of the motor was introduced. Second, the finite element parameterized model of the stator of the motor was built using ANSYS parametric design language and some structure parameters of the stator were selected as design variables. Third, the sample points were selected in design variable space using latin hypercube Design. Through modal analysis and harmonic response analysis of the stator based on these sample points, the target responses were obtained. These sample points and response values were combined together to build a response surface model. Finally, the simplex method was used to find the optimal solution. The experimental results showed that many aspects of the design requirements of the butterfly-shaped linear ultrasonic motor have been fulfilled. The prototype motor fabricated based on the optimal design result exhibited considerably high dynamic performance, such as no-load speed of 873 ram/s, maximal thrust of 27.5 N, maximal efficiency of 43%, and thrust-weight ratio of 45.8.展开更多
Top structure and basement will confront the risk of being damaged on account of large stress and strain fields incurred by differential uplift and settlement between inner column and diaphragm wall in top-down method...Top structure and basement will confront the risk of being damaged on account of large stress and strain fields incurred by differential uplift and settlement between inner column and diaphragm wall in top-down method. Top-down excavation of the Metro Line 10 in Shanghai was modeled with finite element analysis software ABAQUS and parameters of subsoil were obtained by inverse analysis. Based on the finite element model and parameters, changes in the following factors were made to find more effective methods to restrain differential uplift and settlement: length of diaphragm wall, thickness of jet-grouting reinforcement layer, ways of subsoil reinforcement, sequence of pit excavation, connection between slabs and diaphragm wall or column and width of pit. Several significant results are acquired. The longer the diaphragm wall is, the greater the differential uplift between column and diaphragm wall is. Rigidity of roof slab is in general not strong enough to keep diaphragm wall and column undergoing the same uplift during excavation; Uplift at head of column and differential uplift between column and diaphragm wall decrease when subsoil from-16.6 to-43 m in pit is reinforced through jet-grouting. But, as excavation proceeds to a lower level, benefit from soil reinforcement diminishes. During the process applying vertical load, the larger the depth of diaphragm wall is, the smaller the settlement is at head of column and diaphragm wall, and the greater the differential settlement is between column and diaphragm wall. When friction connection is implemented between column, diaphragm wall and floor slabs, uplifts at head of column and diaphragm wall are larger than those of the case when tie connection is implemented, and so does differential uplift between column and diaphragm wall. The maximum deflection of diaphragm wall decreases by 58% on account of soil reinforcement in pit. The maximum deflection of diaphragm wall decreases by 61.2% when friction connection is implemented instead of tie connection.展开更多
Many high earth-rockfill dams are constructed in the west of China. The seismic intensity at the dam site is usually very high, thus it is of great importance to ensure the safety of the dam in meizoseismal area. A 3D...Many high earth-rockfill dams are constructed in the west of China. The seismic intensity at the dam site is usually very high, thus it is of great importance to ensure the safety of the dam in meizoseismal area. A 3D FEM model is established to analyze the seismic responses of Shiziping earth-rockfill dam. The nonlinear elastic Duncan-Chang constitutive model and the equivalent viscoelastic constitutive model are used to simulate the static and dynamic stress strain relationships of the dam materials, respectively. Four groups of seismic waves are inputted from the top of the bedrock to analyze the dynamic responses of the dam. The numerical results show that the calculated dynamic magnification factors display a good consistency with the specification values. The site spectrum results in larger acceleration response than the specification spectrum. The analysis of relative dynamic displacement indicates that the displacement at the downstream side of the dam is larger than that at the upstream side. The displacement response reduces from the center of river valley to two banks. The displacement responses corresponding to the specification spectrum are a little smaller than those corresponding to the site spectrum. The analysis of shear stress indicates that a large shear stress area appears in the upstream overburden layer, where the shear stress caused by site waves is larger than that caused by specification waves. The analysis of dynamic principal stress indicates that the minimum dynamic stresses in corridor caused by specification and site waves have little difference. The maximum and minimum dynamic stresses are relatively large at two sides. The largest tensile stress occurs at two sides of the floor of grouting corridor, which may result in the crack near the corridor side. The numerical results present good consistency with the observation data of the grouting corridor in Wenchuan earthquake.展开更多
A three-dimensional finite element simulation was carried out to investigate the effects of tunnel construction on nearby pile foundation.The displacement controlled model (DCM) was used to simulate the tunneling-indu...A three-dimensional finite element simulation was carried out to investigate the effects of tunnel construction on nearby pile foundation.The displacement controlled model (DCM) was used to simulate the tunneling-induced volume loss effects.The numerical model was verified based on the results of a centrifuge test and a set of parametric studies was implemented based on this model.There is good agreement between the trend of the results of the centrifuge test and the present model.The results of parametric studies show that the tunnelling-induced pile internal force and deformation depend mainly on the pile?tunnel distance,the pile length to tunnel depth ratio and the volume loss.Two different zones are separated by a 45° line projected from the tunnel springline.Within the zone of influence,the pile is subjected to tensile force and large settlement;whereas outside the zone of influence,dragload and small settlement are induced.It is also established that the impact of tunnelling on a pile group is substantially smaller as compared with a single pile in the same location with the rear pile in a group,demonstrating a positive pile group effect.展开更多
The seismic behavior of planar frames with concrete-filled T-section columns to steel beam was experimentally and numerically studied. A finite element analysis （FEA） model was developed to investigate the engineeri...The seismic behavior of planar frames with concrete-filled T-section columns to steel beam was experimentally and numerically studied. A finite element analysis （FEA） model was developed to investigate the engineering properties of the planar frames. Two 1：2.5 reduced-scale specimens of T-section concrete-filled steel tubular column and steel beam of single-story and single-bay plane frames were designed and fabricated based on the design principles of strong-column, weak-beam and stronger-joint. One three-dimensional entity model of the investigated frame structure was built using a large-scale nonlinear finite-element analysis software ABAQUS. Experimental results show that the axial compression ratio has no effect on the failure mode of the structure, while with the increase of axial compression ratio and the dissipated energy ability increasing, the structural ductility decreased. The results from both experiments and simulations agree with each other, which verifies the validity and accuracy of the developed finite element model. Furthermore, the developed finite element model helps to reflect the detailed stress status of the investigated frame at different time and different positions.展开更多
According to the basic emotional theory, the artificial emotional model based on the finite state machine（FSM） was presented. In finite state machine model of emotion, the emotional space included the basic emotiona...According to the basic emotional theory, the artificial emotional model based on the finite state machine（FSM） was presented. In finite state machine model of emotion, the emotional space included the basic emotional space and the multiple emotional spaces. The emotion-switching diagram was defined and transition fimction was developed using Markov chain and linear interpolation algorithm. The simulation model was built using Stateflow toolbox and Simulink toolbox based on the Matlab platform. And the model included three subsystems： the input one, the emotion one and the behavior one. In the emotional subsystem, the responses of different personalities to the external stimuli were described by defining personal space. This model takes states from an emotional space and updates its state depending on its current state and a state of its input （also a state-emotion）. The simulation model realizes the process of switching the emotion from the neutral state to other basic emotions. The simulation result is proved to correspond to emotion-switching law of human beings.展开更多
文摘The aim of this study is to address the issues associated with traditional magnetorheological fluid(MRF)dampers,such as insufficient damping force after power failure and susceptibility to settlement.In order to achieve this,a bidirectional adjustable MRF damper was designed and developed.Magnetic field simulation analysis was conducted on the damper,along with simulation analysis on its dynamic characteristics.The dynamic characteristics were ultimately validated through experimental testing on the material testing machine,thereby corroborating the theoretical simulation results.Concurrently,this process generated valuable test data for subsequent implementation of the semi-active vibration control system.The simulation and test results demonstrate that the integrated permanent magnet effectively accomplishes bidirectional regulation.The magnetic induction intensity of the damping channel is 0.2 T in the absence of current,increases to 0.5 T when a maximum forward current of 4 A is applied,and becomes 0 T when a maximum reverse current of 3.8 A is applied.When the excitation amplitude is 8 mm and the frequency is 2 Hz,with the applied currents varying,the maximum damping force reaches 8 kN,while the minimum damping force measures at 511 N.Additionally,at zero current,the damping force stands at 2 kN,which aligns closely with simulation results.The present paper can serve as a valuable reference for the design and research of semi-active MRF dampers.
基金Project(51105287) supported by the National Natural Science Foundation of ChinaProject(2012BAA08003) supported by the Key Research and Development Project of New Products and New Technologies of Hubei Province, ChinaProject(2011-P05) supported by the State Key Laboratory of Materials Processing and Die & Mould Technology, Huazhong University of Science and Technology,China
文摘The aim of this work is to propose a 3D FE model of a theoretical assembling straight bevel gear pair to analyze the contact fatigue on the tooth surface and the bending fatigue in the tooth root. Based on the cumulative fatigue criterion and the stress-life equation, the key meshing states of the gear pair were investigated for the contact fatigue and the bending fatigue. Then, the reliability of the proposed model was proved by comparing the calculation result with the simulation result. Further study was performed to analyze the variation of the contact fatigue stress and the bending fatigue stress under different loads. Furthermore, the roles of the driving pinion and the driven gear pair were evaluated in the fatigue life of the straight bevel gear pair and the main fatigue failure mode was determined for the significant gear. The results show that the fatigue failure of the driving pinion is the main fatigue failure for the straight bevel gear pair and the bending fatigue failure is the main fatigue failure for the driving pinion.
基金Project(10974115) supported by the National Natural Science Foundation of China
文摘Facing the problems lack of considering the non-uniform distribution of the static bias magnetic field and computing the panicle displacements in the simulation model of electromagnetic acoustic transducer （EMAT）, a multi-field coupled model was established and the finite element method （FEM） was presented to calculate the entire transduction process. The multi-field coupled model included the static magnetic field, pulsed eddy current field and mechanical field. The FEM equations of the three fields were derived by Garlerkin FEM method. Thus, the entire transduction process of the EMAT was calculated through sequentially coupling the three fields. The transduction process of a Lamb wave EMAT was calculated according to the present model and method. The results show that, by the present method, it is valid to calculate the particle displacement under the given excitation signal and non-uniformly distributed static magnetic field. Calculation error will be brought about if the non-uniform distribution of the static bias magnetic field is neglected.
基金Project(2014FJ1002)supported by the Science and Technology Major Project of Hunan Province,ChinaProject(2012AA041803)supported by National High Technology Research and Development Program of China。
文摘A shield machine with freezing function is proposed in order to realize tool change operation at atmospheric pressure. Furthermore, the transformation project of freezing cutterhead and tool change maintenance method are put forward. Taking the shield construction of Huanxi Power Tunnel as an example, a numerical analysis of the freezing cutter head of the project was carried out. The results show that when the brine temperature is-25 °C, after 30 d of freezing, the thickness of the frozen wall can reach 0.67 m and the average temperature drops to-9.9 °C. When the brine temperature is-30 °C, after 50 d of freezing, the thickness of the frozen wall can reach 1.01 m and the average temperature drops to-12.4 °C. If the thickness of the frozen wall is 0.5 m and the average temperature is-10 °C, as the design index of the frozen wall, the brine temperature should be lower than-28 °C to meet the excavation requirements in 30 d. Analyzing the frozen wall stress under 0.5 m thickness and-10 °C average temperature condition, the tensile safety factor and compressive safety factor are both greater than 2 at the most dangerous position, which can meet the tool change requirements for shield construction.
基金Project(51105287)supported by the National Natural Science Foundation of China
文摘To investigate the effects of billet geometry on the cold precision forging process of a helical gear, six different billet geometries were designed utilizing the relief-hole principle. And the influences of the billet geometry on the forming load and the deformation uniformity were analyzed by three-dimensional （3D） finite element method （FEM） under the commercial software DEFORM 3D. The billet geometry was optimized to meet lower forming load and better deformation uniformity requirement. Deformation mechanism was studied through the distribution of flow velocity field and effective strain field. The forging experiments of the helical gear were successfully performed using lead material as a model material under the same process conditions used in the FE simulations. The results show that the forming load decreases as the diameter of relief-hole do increases, but the effect of do on the deformation uniformity is very complicated. The forming load is lower and the deformation is more uniform when do is 10 mm.
基金Project(20040311890) supported by the Science and Technology Development Foundation of University of Science and Technology Beijing
文摘The roll contour pattern and variety of work and backup rolls in service and its effect on profile and flatness control performance in 1 700 mm hot strip mill at Wuhan Iron and Steel(Group) Corporation were tested and analyzed by the developed finite element models of different typical roll contours configurations.A rather smooth local work roll contour near strip edges and an increase in rolled length can be obtained by application of long stroke work roll shifting system with conventional work roll contours that is incapable of the crown control.In comparison with the conventional backup and work roll contours configuration,the crown control range by the roll bending force enhances by 12.79% and the roll gap stiffness increases by 25.26% with the developed asymmetry self-compensating work rolls(ASR) and varying contact backup rolls(VCR).A better strip profile and flatness quality,an increase in coil numbers within the rolling campaign and a significant alleviated effect of severe work roll wear contours on performance of edge drop control are achieved by the application of ASR with crown control and wear control ability in downstream stand F5 and VCR in all stands of 1 700 mm hot strip mill.
基金Project(DY105-3-2-2) supported by China Ocean Mineral Resources Research and Development Association(COMRA)Project(50675226) supported by the National Natural Science Foundation of China
文摘3D dynamic analysis models of 1000 m deep-ocean mining pipeline, including steel lift pipe, pump, buffer and flexible hose, were established by finite element method (FEM). The coupling effect of steel lift pipe and flexible hose, and main external loads of pipeline were considered in the models, such as gravity, buoyancy, hydrodynamic forces, internal and external fluid pressures, concentrated suspension buoyancy on the flexible hose, torsional moment and axial force induced by pump working. Some relevant FEM models and solution techniques were developed, according to various 3D transient behaviors of integrated deep-ocean mining pipeline, including towing motions of track-keeping operation and launch process of pipeline. Meanwhile, an experimental verification system in towing water tank that had similar characteristics of designed mining pipeline was developed to verify the accuracy of the FEM models and dynamic simulation. The experiment results show that the experimental records and simulation results of stress of pipe are coincided. Based on the further simulations of 1 000 m deep-ocean mining pipeline, the simulation results show that, to form configuration of a saddle shape, the total concentrated suspension buoyancy of flexible hose should be 95%?105% of the gravity of flexible hose in water, the first suspension point occupies 1/3 of the total buoyancy, and the second suspension point occupies 2/3 of the total buoyancy. When towing velocity of mining system is less than 0.5 m/s, the towing track of buffer is coincided with the setting route of ship on the whole and the configuration of flexible hose is also kept well.
基金Imam Khomeini International University(IKIU)for providing financial support during the research undertaken in the Civil Engineering Department at IKIU,Iran
文摘In recent years,a new type of foundation named composite piled raft foundation (also called long short composite piled raft) has been developed.Where designing shallow foundations would mean unacceptable settlement,or other environmental risks exist which could impair the structure in the future,composite piled raft foundations could be used.Finite element method was applied to study the behavior of this type of foundation subjected to vertical loading.In order to determine an optimal pile arrangement pattern which yields the minimum settlement,various pile arrangements under different vertical stress levels were investigated.Results show that with increasing the vertical stress on the raft,the effectiveness of the arrangements of short and long piles become more visible.In addition,a new factor named "composite piled raft efficiency" (CPRE) has been defined which determines the efficiency of long short piles arrangement in a composite piled raft foundation.This factor will increase when short piles take more axial stresses and long piles take less axial stresses.In addition,it is found that the changes in settlements for different long short piles arrangement are in a well agreement with changes in values of CPRE ratio.Thus,CPRE ratio can be used as a factor to determine the efficiency of piles arrangements in composite piled raft foundation from the view point of reducing raft settlements.
基金Project(2017YFC0805008)supported by the National Key Research and Development Program of ChinaProject(265201708)supported by the Fundamental Research Funds for the Central Universities,China
文摘A working shaft for pipe-jacking is going to be excavated into a sand stratum with high hydraulic pressure in Guangzhou, China. A newly assembled pre-stressed retaining system has been proposed to support the shaft for its efficiency, safety and sustainability. Full-scale field tests and numerical analysis were conducted to analyze the base failure of the circular shaft with confined water. The failure process of the shaft was observed on site. The construction process of step-by-step excavation of shaft and layer-by-layer assembly of pre-stressed structure was simulated in detail. Simulation results agree well with the phenomenon on site. The base failure modes present that tensile damage generates at the center of the base due to non-uniform uplift and shear failure occurs along the soil-structure interface. The effects of shaft size and confined water head were also discussed. As a result, a critical ratio of diameter to shaft depth is put forward to assess the size effect of circular shaft. A conclusion that the soil strength should be partially considered in anti-inrushing safety factor calculation is drawn by analysis and comparison of various calculation methods. This research provides a reference for the base stability evaluation of similar shaft subjected to hydraulic uplift.
基金Project(51175168)supported by the National Natural Science Foundation of ChinaProjects(2011GK3148,2012GK3092)supported by Science and Technology Program of Hunan Province,China
文摘A new structure design method of elastic composite cylindrical roller bearing is proposed, in which PTFE is embedded into a hollow cylindrical rolling element, according to the principle of creative combinations and through innovation research on cylindrical roller bearing structure. In order to systematically investigate the inner wall bending stress of the rolling element in elastic composite cylindrical roller bearing, finite element analysis on different elastic composite cylindrical rolling elements was conducted. The results show that, the bending stress of the elastic composite cylindrical rolling increases along with the increase of hollowness with the same filling material. The bending stress of the elastic composite cylindrical rolling element decreases along with the increase of the elasticity modulus of the material under the same physical dimension. Under the same load, on hollow cylindrical rolling element, the maximum bending tensile stress values of the elastic composite cylindrical rolling element after material filling at 0° and 180° are 8.2% and 9.5%, respectively, lower than those of the deep cavity hollow cylindrical rolling element. In addition, the maximum bending-compressive stress value at 90° is decreased by 6.1%.
基金Project(11PJ1405700) supported by Pujiang Talent Plan of Shanghai,ChinaProject(41002091) supported by the National Natural Science Foundation of ChinaProject(PIAP-GA-2009-230638) supported by the European Community through the Program "People"
文摘The influence of different features of natural soft clays,namely anisotropy,destructuration and viscosity,on modelling the time-dependent behaviour of Murro embankment was investigated.The newly developed elasto-viscoplastic models were enhanced for determining viscosity parameters in a straightforward way and adopted for the finite element analysis.The same set of common parameters determined from conventional triaxial and oedometer tests was employed for all models,with additional parameters required for representing different soil features.The finite element predictions by using models coupled with BIOT's consolidation theory were compared with each other and with field data for settlement,horizontal displacement and excess pore pressures.In addition,the stress paths under the embankment loading were also compared with each other to improve the understanding of the effect of different soil features.All simulations demonstrate that all three features significantly influence the predictions.As a consequence,accounting for soil features needs to be carefully considered when they are applied to a construction site.
基金Project(51021004) supported by Innovative Research Groups of the National Natural Science Foundation of ChinaProject(40776055) supported by the National Natural Science Foundation of china+1 种基金Project(1002) supported by State Key Laboratory of Ocean Engineering Foundation, ChinaProject(NCET 11 0370) supported by the Program for New Century Excellent Talents in Universities of China
文摘In-service hydrocarbons must be transported at high temperature and high pressure to ease the flow and prevent the solidification of the wax fraction. The pipeline containing hot oil will expand longitudinally due to the rise in temperature. If such expansion is resisted, for example by frictional effects over a kilometer or so of pipeline, compressive axial stress will be built up in the pipe-wall. The compressive forces are often so large that they induce vertical buckling of buffed pipelines, which can jeopardize the structural integrity of the pipeline. A typical initial imperfection named continuous support mode of submarine pipeline was studied. Based on this type of initial imperfection, the analytical solution of vertical thermal buckling was introduced and an elastic-plasticity finite element analysis （FEA） was developed. Both the analytical and the finite element methodology were applied to analyze a practice in Bohai Gulf, China. The analyzing results show that upheaval buckling is most likely to build up from the initial imperfection of the pipeline and the buckling temperature depends on the amplitude of initial imperfection. With the same amplitude of initial imperfection, the triggering temperature difference of upheaval buckling increases with covered depth of the pipeline, the soil strength and the friction between the pipeline and subsoil.
基金Project(2006BAF04B06) supported by the National Key Technology R & D Program of ChinaProject(2005AA101B19) supported by the Key Technology R & D Program of Hubei Province, China
文摘The finite element analysis （FEA） software Ansys was employed to study the stress state of the dies of both plane and non-plane parting face structures with uniform interference and the die of plane parting face structure with non-uniform interference. Considering the symmetry of the die, a half gear tooth model of the two-ring assembled die with 2.5 GPa inner pressure was constructed. Four paths were defined to investigate the stress state at the bottom comer of the die where stress concentration was serious. FEA results show that the change of parting face from non-plane to plane can greatly reduce the stress at the teeth tips of the die so that the tip fracture is avoided. The interference structure of the die is the most important influencing factor for the stress concentration at the bottom comer. When non-uniform interference is adopted the first principal stress at the comer on the defined paths of the die is much lower than that with uniform interference. The bottom hole radius is another important influencing factor for the comer stress concentration. The first principal stress at the comer of the plane parting face die with non-uniform interference is reduced from 2.3 to 1.9 GPa when the hole radius increases from 12.5 to 16.0 mm. The optimization of the die structure increases the life of the die from 100 to 6 000 hits.
基金Projects(51275235, 50975135) supported by the National Natural Science Foundation of ChinaProject(U0934004) supported by the Natural Science Foundation of Guangdong Province, ChinaProject(2011CB707602) supported by the National Basic Research Program of China
文摘A new method for optimizing a butterfly-shaped linear ultrasonic motor was proposed to maximize its mechanical output. The finite element analysis technology and response surface methodology were combined together to realize the optimal design of the butterfly-shaped linear ultrasonic motor. First, the operation principle of the motor was introduced. Second, the finite element parameterized model of the stator of the motor was built using ANSYS parametric design language and some structure parameters of the stator were selected as design variables. Third, the sample points were selected in design variable space using latin hypercube Design. Through modal analysis and harmonic response analysis of the stator based on these sample points, the target responses were obtained. These sample points and response values were combined together to build a response surface model. Finally, the simplex method was used to find the optimal solution. The experimental results showed that many aspects of the design requirements of the butterfly-shaped linear ultrasonic motor have been fulfilled. The prototype motor fabricated based on the optimal design result exhibited considerably high dynamic performance, such as no-load speed of 873 ram/s, maximal thrust of 27.5 N, maximal efficiency of 43%, and thrust-weight ratio of 45.8.
基金Projects(51208071,51108312) supported by the National Natural Science Foundation of China
文摘Top structure and basement will confront the risk of being damaged on account of large stress and strain fields incurred by differential uplift and settlement between inner column and diaphragm wall in top-down method. Top-down excavation of the Metro Line 10 in Shanghai was modeled with finite element analysis software ABAQUS and parameters of subsoil were obtained by inverse analysis. Based on the finite element model and parameters, changes in the following factors were made to find more effective methods to restrain differential uplift and settlement: length of diaphragm wall, thickness of jet-grouting reinforcement layer, ways of subsoil reinforcement, sequence of pit excavation, connection between slabs and diaphragm wall or column and width of pit. Several significant results are acquired. The longer the diaphragm wall is, the greater the differential uplift between column and diaphragm wall is. Rigidity of roof slab is in general not strong enough to keep diaphragm wall and column undergoing the same uplift during excavation; Uplift at head of column and differential uplift between column and diaphragm wall decrease when subsoil from-16.6 to-43 m in pit is reinforced through jet-grouting. But, as excavation proceeds to a lower level, benefit from soil reinforcement diminishes. During the process applying vertical load, the larger the depth of diaphragm wall is, the smaller the settlement is at head of column and diaphragm wall, and the greater the differential settlement is between column and diaphragm wall. When friction connection is implemented between column, diaphragm wall and floor slabs, uplifts at head of column and diaphragm wall are larger than those of the case when tie connection is implemented, and so does differential uplift between column and diaphragm wall. The maximum deflection of diaphragm wall decreases by 58% on account of soil reinforcement in pit. The maximum deflection of diaphragm wall decreases by 61.2% when friction connection is implemented instead of tie connection.
基金Foundation item： Project（IRTl125） supported by the Program for Changjiang Scholars and Innovative Research Team in Universities of China Project（B13024） supported by the ＂111＂ Project Project（BK2012811） supported by the Natural Science Foundation of Jiangsu Province, China
文摘Many high earth-rockfill dams are constructed in the west of China. The seismic intensity at the dam site is usually very high, thus it is of great importance to ensure the safety of the dam in meizoseismal area. A 3D FEM model is established to analyze the seismic responses of Shiziping earth-rockfill dam. The nonlinear elastic Duncan-Chang constitutive model and the equivalent viscoelastic constitutive model are used to simulate the static and dynamic stress strain relationships of the dam materials, respectively. Four groups of seismic waves are inputted from the top of the bedrock to analyze the dynamic responses of the dam. The numerical results show that the calculated dynamic magnification factors display a good consistency with the specification values. The site spectrum results in larger acceleration response than the specification spectrum. The analysis of relative dynamic displacement indicates that the displacement at the downstream side of the dam is larger than that at the upstream side. The displacement response reduces from the center of river valley to two banks. The displacement responses corresponding to the specification spectrum are a little smaller than those corresponding to the site spectrum. The analysis of shear stress indicates that a large shear stress area appears in the upstream overburden layer, where the shear stress caused by site waves is larger than that caused by specification waves. The analysis of dynamic principal stress indicates that the minimum dynamic stresses in corridor caused by specification and site waves have little difference. The maximum and minimum dynamic stresses are relatively large at two sides. The largest tensile stress occurs at two sides of the floor of grouting corridor, which may result in the crack near the corridor side. The numerical results present good consistency with the observation data of the grouting corridor in Wenchuan earthquake.
文摘A three-dimensional finite element simulation was carried out to investigate the effects of tunnel construction on nearby pile foundation.The displacement controlled model (DCM) was used to simulate the tunneling-induced volume loss effects.The numerical model was verified based on the results of a centrifuge test and a set of parametric studies was implemented based on this model.There is good agreement between the trend of the results of the centrifuge test and the present model.The results of parametric studies show that the tunnelling-induced pile internal force and deformation depend mainly on the pile?tunnel distance,the pile length to tunnel depth ratio and the volume loss.Two different zones are separated by a 45° line projected from the tunnel springline.Within the zone of influence,the pile is subjected to tensile force and large settlement;whereas outside the zone of influence,dragload and small settlement are induced.It is also established that the impact of tunnelling on a pile group is substantially smaller as compared with a single pile in the same location with the rear pile in a group,demonstrating a positive pile group effect.
基金Projects(51378077,51478047,51778066)supported by the National Natural Science Foundation of ChinaProject(D20151304)supported by Science and Technology Research Project of Education Department of Hubei Province,ChinaProject(2017CFA070)supported by Hubei Provincial Natural Science Foundation,China
文摘The seismic behavior of planar frames with concrete-filled T-section columns to steel beam was experimentally and numerically studied. A finite element analysis （FEA） model was developed to investigate the engineering properties of the planar frames. Two 1：2.5 reduced-scale specimens of T-section concrete-filled steel tubular column and steel beam of single-story and single-bay plane frames were designed and fabricated based on the design principles of strong-column, weak-beam and stronger-joint. One three-dimensional entity model of the investigated frame structure was built using a large-scale nonlinear finite-element analysis software ABAQUS. Experimental results show that the axial compression ratio has no effect on the failure mode of the structure, while with the increase of axial compression ratio and the dissipated energy ability increasing, the structural ductility decreased. The results from both experiments and simulations agree with each other, which verifies the validity and accuracy of the developed finite element model. Furthermore, the developed finite element model helps to reflect the detailed stress status of the investigated frame at different time and different positions.
基金Project(2006AA04Z201) supported by the National High-Tech Research and Development Program of China
文摘According to the basic emotional theory, the artificial emotional model based on the finite state machine（FSM） was presented. In finite state machine model of emotion, the emotional space included the basic emotional space and the multiple emotional spaces. The emotion-switching diagram was defined and transition fimction was developed using Markov chain and linear interpolation algorithm. The simulation model was built using Stateflow toolbox and Simulink toolbox based on the Matlab platform. And the model included three subsystems： the input one, the emotion one and the behavior one. In the emotional subsystem, the responses of different personalities to the external stimuli were described by defining personal space. This model takes states from an emotional space and updates its state depending on its current state and a state of its input （also a state-emotion）. The simulation model realizes the process of switching the emotion from the neutral state to other basic emotions. The simulation result is proved to correspond to emotion-switching law of human beings.
