针对近地圆轨道卫星编队维持问题,开展了脉冲控制方案与维持控制策略研究,并搭建了仿真环境进行验证。根据相对轨道根数(relative orbital elements,ROEs)的状态转移方程,推导了各ROEs元素在J 2摄动下的漂移速率,并针对编队构型受到空...针对近地圆轨道卫星编队维持问题,开展了脉冲控制方案与维持控制策略研究,并搭建了仿真环境进行验证。根据相对轨道根数(relative orbital elements,ROEs)的状态转移方程,推导了各ROEs元素在J 2摄动下的漂移速率,并针对编队构型受到空间摄动的破坏问题,提出了两种不同的编队脉冲控制方案和维持策略。基于空间圆编队长期维持需求,建立了包括高精度轨道递推算法的任务仿真环境,从脉冲消耗与控制误差对提出的方案策略进行了分析讨论,验证了脉冲方案与维持策略的可行性。仿真结果表明,所提出的脉冲控制方案与维持策略具有较高的有效性及可靠性,可用于未来空间编队飞行任务。展开更多
Practical experiences gained in the past several years show that the thermal residual stress(TRS)is a main cause leading polycrystalline diamond compacts(PDC)to premature failure.It is the very important to measure th...Practical experiences gained in the past several years show that the thermal residual stress(TRS)is a main cause leading polycrystalline diamond compacts(PDC)to premature failure.It is the very important to measure the TRS accurately for optimizing the interface and improving the service performance of PDC.In this paper,the TRS in 1913 flat-interface PDC was measured using improved stress-release method(ISRM).The TRS on the surface of polycrystalline diamond(PCD)table was obtained,which can be used to calculate the radial thermal residual stress(RTRS)at the interface of PCD table via a refutation process.The obtained results show that there are compressive residual stress at the PCD table interface and in the most region of PCD table surface.The exception occurs near the outer diameter of the PCD table,where the PDC begins to bend and put the PCD table surface into a tension state,an undesirable state for a brittle material.The ISRM has covered the shortage existing in traditional stress-release method,in which only finite points on the surface of PCD table can be tested for one specimen and one time.Simple as the experimental procedures are,the test results are also very accurate and reliable.This method provides the theoretical and experimental basis for testing TRS of PDC accurately.展开更多
The differential thermal expansion of the polycrystalline diamond layer and the tungsten carbide substrate results in large residual stresses as PDC cutters cooling after sintering.The residual stresses on the top sur...The differential thermal expansion of the polycrystalline diamond layer and the tungsten carbide substrate results in large residual stresses as PDC cutters cooling after sintering.The residual stresses on the top surface of the diamond layer of PDC were measured at five points along the radial direction of PDC using X-ray Diffraction Residual Stress Instrument,thus the stresses and their radial distribution were obtained.The results show that the stresses on the diamond surface are compressive,the biggest stress appears at the central point(about 1200 MPa),and that from the center to the edge of PDC,the magnitude of the stress decreases.A finite element analysis(FEA)was made to check the validity of the testing results.The FEA modeling results were found to correlate well with the measured values.Factors leading to the deviation between XRD experimental measurements and the calculations of residual stress by FEA were also analyzed.展开更多
文摘针对近地圆轨道卫星编队维持问题,开展了脉冲控制方案与维持控制策略研究,并搭建了仿真环境进行验证。根据相对轨道根数(relative orbital elements,ROEs)的状态转移方程,推导了各ROEs元素在J 2摄动下的漂移速率,并针对编队构型受到空间摄动的破坏问题,提出了两种不同的编队脉冲控制方案和维持策略。基于空间圆编队长期维持需求,建立了包括高精度轨道递推算法的任务仿真环境,从脉冲消耗与控制误差对提出的方案策略进行了分析讨论,验证了脉冲方案与维持策略的可行性。仿真结果表明,所提出的脉冲控制方案与维持策略具有较高的有效性及可靠性,可用于未来空间编队飞行任务。
基金supported by the Natural Science of Hunan(06JJ4062)
文摘Practical experiences gained in the past several years show that the thermal residual stress(TRS)is a main cause leading polycrystalline diamond compacts(PDC)to premature failure.It is the very important to measure the TRS accurately for optimizing the interface and improving the service performance of PDC.In this paper,the TRS in 1913 flat-interface PDC was measured using improved stress-release method(ISRM).The TRS on the surface of polycrystalline diamond(PCD)table was obtained,which can be used to calculate the radial thermal residual stress(RTRS)at the interface of PCD table via a refutation process.The obtained results show that there are compressive residual stress at the PCD table interface and in the most region of PCD table surface.The exception occurs near the outer diameter of the PCD table,where the PDC begins to bend and put the PCD table surface into a tension state,an undesirable state for a brittle material.The ISRM has covered the shortage existing in traditional stress-release method,in which only finite points on the surface of PCD table can be tested for one specimen and one time.Simple as the experimental procedures are,the test results are also very accurate and reliable.This method provides the theoretical and experimental basis for testing TRS of PDC accurately.
文摘The differential thermal expansion of the polycrystalline diamond layer and the tungsten carbide substrate results in large residual stresses as PDC cutters cooling after sintering.The residual stresses on the top surface of the diamond layer of PDC were measured at five points along the radial direction of PDC using X-ray Diffraction Residual Stress Instrument,thus the stresses and their radial distribution were obtained.The results show that the stresses on the diamond surface are compressive,the biggest stress appears at the central point(about 1200 MPa),and that from the center to the edge of PDC,the magnitude of the stress decreases.A finite element analysis(FEA)was made to check the validity of the testing results.The FEA modeling results were found to correlate well with the measured values.Factors leading to the deviation between XRD experimental measurements and the calculations of residual stress by FEA were also analyzed.
