To investigate the progressive fracture processes around a tunnel triggered by static stress and dynamic disturbance,experiments and numerical simulations were performed.The results show that the spatial distributions...To investigate the progressive fracture processes around a tunnel triggered by static stress and dynamic disturbance,experiments and numerical simulations were performed.The results show that the spatial distributions of acoustic emission(AE)events become very different as lateral pressure coefficients change.The combined effect of static stress and dynamic disturbance causes the damage around the tunnel,and initial stress conditions control the damage morphology.The blast disturbance cannot fundamentally change the damaged area but will deepen the extent of damage and accelerate the failure speed.The more significant the difference between the vertical and horizontal stresses is,the higher the impact on the tunnel by the dynamic disturbance is.The AE activity recovers to a relatively stable state within a short time after the blast and conforms to power-law characteristics.展开更多
由于我国导线制造工艺、试验条件和电力运行环境的不同,在使用美国邦纳维尔电力公司(BPA)推荐的公式对我国特高压交流(UHVAC)输电线路可听噪声(AN)进行预测时,准确性仍有待提高。为此,利用电晕笼分别对分裂数为6、8、9、10和12的17种不...由于我国导线制造工艺、试验条件和电力运行环境的不同,在使用美国邦纳维尔电力公司(BPA)推荐的公式对我国特高压交流(UHVAC)输电线路可听噪声(AN)进行预测时,准确性仍有待提高。为此,利用电晕笼分别对分裂数为6、8、9、10和12的17种不同型式导线束的可听噪声水平进行了测量,并采用多元回归分析法分析获得了导线声功率计算方法。针对1 000 k V特高压交流示范工程河南焦作与湖北钟祥电磁环境长期观测站的可听噪声,分别采用BPA推荐公式与所提公式对它们进行了计算,并与实测值进行了对比。结果显示,所提公式得到的计算值与河南、湖北两地实测L50值偏差分别为0.66 d B和0.32 d B,小于BPA推荐公式偏差3.07 d B和2.14 d B。由此可见,针对我国特高压交流输电线路可听噪声问题,所提计算式比BPA推荐计算式的运算准确性更高。研究结果可为我国特高压交流输电线路可听噪声预测提供技术支撑。展开更多
The multibody system transfer matrix method(MSTMM),a novel dynamics approach developed during the past three decades,has several advantages compared to conventional dynamics methods.Some of these advantages include av...The multibody system transfer matrix method(MSTMM),a novel dynamics approach developed during the past three decades,has several advantages compared to conventional dynamics methods.Some of these advantages include avoiding global dynamics equations with a system inertia matrix,utilizing low‐order matrices independent of system degree of freedom,high computational speed,and simplicity of computer implementation.MSTMM has been widely used in computer modeling,simulations,and performance evaluation of approximately 150 different complex mechanical systems.In this paper,the following aspects regarding MSTMM are reviewed:basic theory,algorithms,simulation and design software,and applications.Future research directions and generalization to more applications in various fields of science,technology,and engineering are discussed.展开更多
基金Project(2017YFC0602904)supported by the National Key Research and Development Program of ChinaProject(51974059)supported by the National Natural Science Foundation of ChinaProject(N180115010)supported by the Fundamental Research Funds for the Central Universities,China。
文摘To investigate the progressive fracture processes around a tunnel triggered by static stress and dynamic disturbance,experiments and numerical simulations were performed.The results show that the spatial distributions of acoustic emission(AE)events become very different as lateral pressure coefficients change.The combined effect of static stress and dynamic disturbance causes the damage around the tunnel,and initial stress conditions control the damage morphology.The blast disturbance cannot fundamentally change the damaged area but will deepen the extent of damage and accelerate the failure speed.The more significant the difference between the vertical and horizontal stresses is,the higher the impact on the tunnel by the dynamic disturbance is.The AE activity recovers to a relatively stable state within a short time after the blast and conforms to power-law characteristics.
文摘由于我国导线制造工艺、试验条件和电力运行环境的不同,在使用美国邦纳维尔电力公司(BPA)推荐的公式对我国特高压交流(UHVAC)输电线路可听噪声(AN)进行预测时,准确性仍有待提高。为此,利用电晕笼分别对分裂数为6、8、9、10和12的17种不同型式导线束的可听噪声水平进行了测量,并采用多元回归分析法分析获得了导线声功率计算方法。针对1 000 k V特高压交流示范工程河南焦作与湖北钟祥电磁环境长期观测站的可听噪声,分别采用BPA推荐公式与所提公式对它们进行了计算,并与实测值进行了对比。结果显示,所提公式得到的计算值与河南、湖北两地实测L50值偏差分别为0.66 d B和0.32 d B,小于BPA推荐公式偏差3.07 d B和2.14 d B。由此可见,针对我国特高压交流输电线路可听噪声问题,所提计算式比BPA推荐计算式的运算准确性更高。研究结果可为我国特高压交流输电线路可听噪声预测提供技术支撑。
基金National Program on Key Basic Research Project of China,Grant/Award Number:613308Science Challenge Project,Grant/Award Number:TZ2016006‐0104+3 种基金Natural Science Foundation of China Government,Grant/Award Number:11472135supported by the National Program on Key Basic Research Project of China(973 Program,No.613308)the Science Challenge Project(No.TZ2016006‐0104)the Natural Science Foundation of China Government(No.11472135).
文摘The multibody system transfer matrix method(MSTMM),a novel dynamics approach developed during the past three decades,has several advantages compared to conventional dynamics methods.Some of these advantages include avoiding global dynamics equations with a system inertia matrix,utilizing low‐order matrices independent of system degree of freedom,high computational speed,and simplicity of computer implementation.MSTMM has been widely used in computer modeling,simulations,and performance evaluation of approximately 150 different complex mechanical systems.In this paper,the following aspects regarding MSTMM are reviewed:basic theory,algorithms,simulation and design software,and applications.Future research directions and generalization to more applications in various fields of science,technology,and engineering are discussed.
