With the continuous development of artillery,the disadvantages of hydraulic recoil brakes gradually appear.At the same time,the appearance of high-performance Nd Fe B permanent magnet makes it possible to apply electr...With the continuous development of artillery,the disadvantages of hydraulic recoil brakes gradually appear.At the same time,the appearance of high-performance Nd Fe B permanent magnet makes it possible to apply electromagnetic braking technology to recoil mechanism.In this paper,prototype tests of a certain artillery were carried out to verify the feasibility of the electromagnetic brake(EMB)and obtain the electromagnetic braking force.Due to the brittleness of Nd Fe B,in order to eliminate the worry about the safety of EMB,SHPB experiments of Nd Fe B were carried out.Then,based on the assumption of uniform crack distribution,the law of crack propagation and damage accumulation was described theoretically,and the damage constitutive model suitable for brittle materials was proposed by combining the Zhu-Wang-Tang(ZWT)equation.Finally,the numerical simulation model of the artillery prototype was established and through calculation,the dynamic mechanical characteristics of Nd Fe B in the prototype were analyzed.The calculation results show that the strength of Nd Fe B can meet the requirements of the use in the working process.From the perspective of damage factor,the damage value of the permanent magnet on the far right is larger,and the damage value of the inner ring gradually decreases to the outer ring.展开更多
In this paper,the subdomain analysis model of the eddy current brake(ECB)is established.By comparing with the finite element method,the accuracies of the subdomain model and the finite element model are verified.Furth...In this paper,the subdomain analysis model of the eddy current brake(ECB)is established.By comparing with the finite element method,the accuracies of the subdomain model and the finite element model are verified.Furthermore,the resistance characteristics of radial,axial,andHalbach arrays under impact load are calculated and compared.The axial array has a large braking force coefficient but low critical velocity.The radial array has a low braking force coefficient but high critical velocity.The Halbach array has the advantages of the first two arrays.Not only the braking force coefficient is large,but also the critical speed is high.The parameter analysis of the Halbach array is further carried out.The inner tube thickness and air gap length are the sensitive factors of resistance characteristics.The demagnetization effect is significantly enhanced by the increase of the inner tube thickness.In order to ensure that the ECB does not overheat,the electromagnetic-thermal coupling model is established based on the heat transfer theory.The temperature rise of the inner tube is obvious while that of the permanentmagnet is small.The temperature rise of the inner tube is more than 20 K each time,and that of the permanent magnet is less than 1 K each time.展开更多
A multi-body dynamic rigid-flexible coupling model of landing gear is established to study the gear walk instability caused by the friction characteristics of the brake disc.After validating the model with the experim...A multi-body dynamic rigid-flexible coupling model of landing gear is established to study the gear walk instability caused by the friction characteristics of the brake disc.After validating the model with the experimental results,the influence of the landing gear structure and braking system parameters on gear walk is further investigated.Among the above factors,the slope of the graph for the friction coefficient of the brake disc and the relative velocity of brake stators and rotors is the most influential factor on gear walk instability.Phase trajectory analysis verifies that gear walk occurs when the coupling of multiple factors causes the system to exhibit an equivalent negative damping trend.To consider a more realistic braking case,a back propagation neural network method is employed to describe the nonlinear behavior of the friction coefficient of the brake disc.With the realistic nonlinear model of the friction coefficient,the maximum error in predicting the braking torque is less than 10%and the effect of the brake disc temperature on gear walk is performed.The results reveal that a more negative friction slope may contribute to a more severe unstable gear walk,and reducing the braking pressure is an effective approach to avoid gear walk,which provides help for future braking system design.展开更多
C/C-SiC braking composites,based on reinforcement of carbon fibers and matrices of carbon and silicon carbide,were fabricated by warm compaction and in situ reaction process.The tribological characteristics of C/C-SiC...C/C-SiC braking composites,based on reinforcement of carbon fibers and matrices of carbon and silicon carbide,were fabricated by warm compaction and in situ reaction process.The tribological characteristics of C/C-SiC braking composites under dry and wet conditions were investigated by means of MM-1000 type of friction testing machine.The influence of dry and wet conditions on the tribological characteristics of the C/C-SiC composites was ascertained.Under dry condition,C/C-SiC braking composites show superior tribological characteristics,including high coefficient of friction (0.38),good abrasive resistance (thickness loss is 1.10 μm per cycle) and steady breaking.The main wear mechanism is plastic deformation and abrasion caused by plough.Under wet condition,frictional films form on the worn surface.The coefficient of friction (0.35) could maintain mostly,and the thickness loss (0.70 μm per cycle) reduces to a certain extent.Furthermore,braking curves are steady and adhesion and oxidation are the main wear mechanisms.展开更多
为进一步提高制动能量回收率,考虑不同工况下驾驶员不同制动意图所需的制动效果,提出了一种四驱电动汽车制动控制策略。首先,针对常规制动工况,基于常规制动意图识别,从制动能量回收率、稳定性和安全性角度分别设计控制策略;其次,针对...为进一步提高制动能量回收率,考虑不同工况下驾驶员不同制动意图所需的制动效果,提出了一种四驱电动汽车制动控制策略。首先,针对常规制动工况,基于常规制动意图识别,从制动能量回收率、稳定性和安全性角度分别设计控制策略;其次,针对滑行工况下的不同滑行制动意图,判断电机制动力是否介入及何时介入,并根据驾驶员所需的滑行距离计算电机制动力的大小;然后,由台架试验获得前后电机外特性并建立前后电机最优利用效率模型;最后,利用Carsim和Simulink进行了联合仿真分析。仿真结果表明,在新欧洲驾驶循环(New European Driving Cycle,NEDC)工况下,与并联控制策略相比,能量回收率提升了13.64百分点;在滑行工况下可有效识别驾驶员需求滑行距离,提升了整车滑行经济性。展开更多
基金financially supported by the“National Natural Science Foundation of China”[Grant No.52105106]the“China National Postdoctoral Program for Innovative Talents”[Grant No.BX2021126]+2 种基金the“Jiangsu Province Natural Science Foundation”[Grant No.BK20210342]the“Jiangsu Planned Projects for Postdoctoral Research Funds”[Grant No.2021K008A]the“Nanjing Municipal Human Resources and Social Security Bureau”[Grant No.MCA21121]。
文摘With the continuous development of artillery,the disadvantages of hydraulic recoil brakes gradually appear.At the same time,the appearance of high-performance Nd Fe B permanent magnet makes it possible to apply electromagnetic braking technology to recoil mechanism.In this paper,prototype tests of a certain artillery were carried out to verify the feasibility of the electromagnetic brake(EMB)and obtain the electromagnetic braking force.Due to the brittleness of Nd Fe B,in order to eliminate the worry about the safety of EMB,SHPB experiments of Nd Fe B were carried out.Then,based on the assumption of uniform crack distribution,the law of crack propagation and damage accumulation was described theoretically,and the damage constitutive model suitable for brittle materials was proposed by combining the Zhu-Wang-Tang(ZWT)equation.Finally,the numerical simulation model of the artillery prototype was established and through calculation,the dynamic mechanical characteristics of Nd Fe B in the prototype were analyzed.The calculation results show that the strength of Nd Fe B can meet the requirements of the use in the working process.From the perspective of damage factor,the damage value of the permanent magnet on the far right is larger,and the damage value of the inner ring gradually decreases to the outer ring.
基金supported by the National Natural Science Foundation of China(Grant No.51705253).
文摘In this paper,the subdomain analysis model of the eddy current brake(ECB)is established.By comparing with the finite element method,the accuracies of the subdomain model and the finite element model are verified.Furthermore,the resistance characteristics of radial,axial,andHalbach arrays under impact load are calculated and compared.The axial array has a large braking force coefficient but low critical velocity.The radial array has a low braking force coefficient but high critical velocity.The Halbach array has the advantages of the first two arrays.Not only the braking force coefficient is large,but also the critical speed is high.The parameter analysis of the Halbach array is further carried out.The inner tube thickness and air gap length are the sensitive factors of resistance characteristics.The demagnetization effect is significantly enhanced by the increase of the inner tube thickness.In order to ensure that the ECB does not overheat,the electromagnetic-thermal coupling model is established based on the heat transfer theory.The temperature rise of the inner tube is obvious while that of the permanentmagnet is small.The temperature rise of the inner tube is more than 20 K each time,and that of the permanent magnet is less than 1 K each time.
基金the National Natural Science Foundation of China(No.11872312)the Program of Introducing Talents of Discipline to Universities,China(No.BP0719007)the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University,China(No.CX2022002)。
文摘A multi-body dynamic rigid-flexible coupling model of landing gear is established to study the gear walk instability caused by the friction characteristics of the brake disc.After validating the model with the experimental results,the influence of the landing gear structure and braking system parameters on gear walk is further investigated.Among the above factors,the slope of the graph for the friction coefficient of the brake disc and the relative velocity of brake stators and rotors is the most influential factor on gear walk instability.Phase trajectory analysis verifies that gear walk occurs when the coupling of multiple factors causes the system to exhibit an equivalent negative damping trend.To consider a more realistic braking case,a back propagation neural network method is employed to describe the nonlinear behavior of the friction coefficient of the brake disc.With the realistic nonlinear model of the friction coefficient,the maximum error in predicting the braking torque is less than 10%and the effect of the brake disc temperature on gear walk is performed.The results reveal that a more negative friction slope may contribute to a more severe unstable gear walk,and reducing the braking pressure is an effective approach to avoid gear walk,which provides help for future braking system design.
基金Project(2006AA03Z560) supported by the Hi-tech Research and Development Program of ChinaProject(06JJ1007) supported by Excellent Youth of Hunan Province, China
文摘C/C-SiC braking composites,based on reinforcement of carbon fibers and matrices of carbon and silicon carbide,were fabricated by warm compaction and in situ reaction process.The tribological characteristics of C/C-SiC braking composites under dry and wet conditions were investigated by means of MM-1000 type of friction testing machine.The influence of dry and wet conditions on the tribological characteristics of the C/C-SiC composites was ascertained.Under dry condition,C/C-SiC braking composites show superior tribological characteristics,including high coefficient of friction (0.38),good abrasive resistance (thickness loss is 1.10 μm per cycle) and steady breaking.The main wear mechanism is plastic deformation and abrasion caused by plough.Under wet condition,frictional films form on the worn surface.The coefficient of friction (0.35) could maintain mostly,and the thickness loss (0.70 μm per cycle) reduces to a certain extent.Furthermore,braking curves are steady and adhesion and oxidation are the main wear mechanisms.
文摘为进一步提高制动能量回收率,考虑不同工况下驾驶员不同制动意图所需的制动效果,提出了一种四驱电动汽车制动控制策略。首先,针对常规制动工况,基于常规制动意图识别,从制动能量回收率、稳定性和安全性角度分别设计控制策略;其次,针对滑行工况下的不同滑行制动意图,判断电机制动力是否介入及何时介入,并根据驾驶员所需的滑行距离计算电机制动力的大小;然后,由台架试验获得前后电机外特性并建立前后电机最优利用效率模型;最后,利用Carsim和Simulink进行了联合仿真分析。仿真结果表明,在新欧洲驾驶循环(New European Driving Cycle,NEDC)工况下,与并联控制策略相比,能量回收率提升了13.64百分点;在滑行工况下可有效识别驾驶员需求滑行距离,提升了整车滑行经济性。
