The magnetic flux leakage (MFL) method is commonly used in the nondestructive evaluation (NDE) of gun barrels. The key point of MFL testing is to estimate the crack geometry parameters based on the measured signal. Th...The magnetic flux leakage (MFL) method is commonly used in the nondestructive evaluation (NDE) of gun barrels. The key point of MFL testing is to estimate the crack geometry parameters based on the measured signal. The analysis of magnetic leakage fields can be obtained by solving Maxwell’s equations using finite element method (FEM). The radial component of magnetic flux density is measured in MFL testing. The peak-peak value, the separation distance between positive and negative peaks of signal and the lift-off value of Hall-sensor are used as the main features of every sample. This paper establishes the multi-regression equations related to the width (the depth) of crack and the main characteristic values. The regression model is tested by use of the magnetic leakage data. The experimental results indicate that the regression equations can accurately predict the 2-D defect geometry parameters and the MFL quantitative testing can be achieved.展开更多
In this paper,the influences of bore damage on the bullet-barrel interaction process and the mechanism of how bore damage results in the end of a machine gun barrel’s service life were studied,which had seldom been p...In this paper,the influences of bore damage on the bullet-barrel interaction process and the mechanism of how bore damage results in the end of a machine gun barrel’s service life were studied,which had seldom been paid attention to in the past several decades.A novel finite element mesh generation method for the damaged barrel and a new transient coupled thermo-mechanical finite element(FE)model,which were based on the damage data obtained through barrel life tests,were developed to simulate the interior ballistics process of a coupled bullet-barrel system.Additionally,user subroutine VUAMP was developed in the FE model in order to take the bullet base pressure brought by propellant gas into account.Good consistency between the simulation results and the experimental results verified the preciseness of the proposed mesh generation method and the FE model.The simulation results show that the increase of bullet’s initial disturbance at the muzzle and the variation of its surface morphology caused by bore damage are primarily responsible for the life end of this 12.7 mm machine gun barrel.展开更多
为探究主轴式滚磨光整加工中齿轮与颗粒接触界面处的作用行为,基于离散元法(discrete element method,DEM)对主轴式滚磨光整加工进行模拟仿真。首先阐述齿轮附近及齿面接触颗粒的运动形式,然后探究齿轮埋入深度、齿轮和滚筒的转速对齿...为探究主轴式滚磨光整加工中齿轮与颗粒接触界面处的作用行为,基于离散元法(discrete element method,DEM)对主轴式滚磨光整加工进行模拟仿真。首先阐述齿轮附近及齿面接触颗粒的运动形式,然后探究齿轮埋入深度、齿轮和滚筒的转速对齿面接触颗粒相对运动速度及齿面接触力的影响,最后通过实验进行验证。结果表明:主轴式滚磨光整加工对齿轮齿面的作用具有周期性;齿轮上下齿面受力不均匀,上齿面所受接触力是下齿面的1.5~1.8倍。增加齿轮埋入深度主要影响颗粒与齿面的接触力,埋入深度增大75%,齿面接触力增大76%;提升齿轮与滚筒转速则主要影响颗粒与齿面的相对运动速度,齿轮与滚筒转速增大150%,齿面接触颗粒相对运动速度增大148%。且增加齿轮埋入深度可减小齿轮齿面沿轴向的加工差异性,埋入深度由80 mm增大到140 mm后,上下齿面沿轴向的粗糙度下降率由17%和36%变为62%和55%,而改变转速和埋入深度对沿齿廓方向的加工差异性改变不明显。展开更多
基金National Nature Science Found of China(50175109)Science Fund of Ordnance Engineering College in China
文摘The magnetic flux leakage (MFL) method is commonly used in the nondestructive evaluation (NDE) of gun barrels. The key point of MFL testing is to estimate the crack geometry parameters based on the measured signal. The analysis of magnetic leakage fields can be obtained by solving Maxwell’s equations using finite element method (FEM). The radial component of magnetic flux density is measured in MFL testing. The peak-peak value, the separation distance between positive and negative peaks of signal and the lift-off value of Hall-sensor are used as the main features of every sample. This paper establishes the multi-regression equations related to the width (the depth) of crack and the main characteristic values. The regression model is tested by use of the magnetic leakage data. The experimental results indicate that the regression equations can accurately predict the 2-D defect geometry parameters and the MFL quantitative testing can be achieved.
基金supported by the National Natural Science Foundation of China(grant number 11802138)the China Postdoctoral Science Foundation(grant number 2018T110503)the Fundamental Research Funds for the Central Universities(grant number 30918011302)
文摘In this paper,the influences of bore damage on the bullet-barrel interaction process and the mechanism of how bore damage results in the end of a machine gun barrel’s service life were studied,which had seldom been paid attention to in the past several decades.A novel finite element mesh generation method for the damaged barrel and a new transient coupled thermo-mechanical finite element(FE)model,which were based on the damage data obtained through barrel life tests,were developed to simulate the interior ballistics process of a coupled bullet-barrel system.Additionally,user subroutine VUAMP was developed in the FE model in order to take the bullet base pressure brought by propellant gas into account.Good consistency between the simulation results and the experimental results verified the preciseness of the proposed mesh generation method and the FE model.The simulation results show that the increase of bullet’s initial disturbance at the muzzle and the variation of its surface morphology caused by bore damage are primarily responsible for the life end of this 12.7 mm machine gun barrel.
文摘为探究主轴式滚磨光整加工中齿轮与颗粒接触界面处的作用行为,基于离散元法(discrete element method,DEM)对主轴式滚磨光整加工进行模拟仿真。首先阐述齿轮附近及齿面接触颗粒的运动形式,然后探究齿轮埋入深度、齿轮和滚筒的转速对齿面接触颗粒相对运动速度及齿面接触力的影响,最后通过实验进行验证。结果表明:主轴式滚磨光整加工对齿轮齿面的作用具有周期性;齿轮上下齿面受力不均匀,上齿面所受接触力是下齿面的1.5~1.8倍。增加齿轮埋入深度主要影响颗粒与齿面的接触力,埋入深度增大75%,齿面接触力增大76%;提升齿轮与滚筒转速则主要影响颗粒与齿面的相对运动速度,齿轮与滚筒转速增大150%,齿面接触颗粒相对运动速度增大148%。且增加齿轮埋入深度可减小齿轮齿面沿轴向的加工差异性,埋入深度由80 mm增大到140 mm后,上下齿面沿轴向的粗糙度下降率由17%和36%变为62%和55%,而改变转速和埋入深度对沿齿廓方向的加工差异性改变不明显。
