Though the lengthened shrink-fit holder (LSFH) is widely applied in high speed milling of the parts characterized by deep cavities at present, its design and selection mainly depends on the experience and lacks a corr...Though the lengthened shrink-fit holder (LSFH) is widely applied in high speed milling of the parts characterized by deep cavities at present, its design and selection mainly depends on the experience and lacks a correct theoretical guidance. In this paper, attention is focus on the radial grip rigidity of the matching of LSFH and cutter in high speed milling. Based on the experiment modal analysis (EMA) technique, an accurate finite element model of the matching of LSFH and cutter is established firstly. Subsequently, the influence of different interference, grip length and spindle speed on the grip rigidity of LSFH are analyzed. The analysis results show that there is a reasonable interference and grip length between the LSFH and cutter so that to have a steepless grip and have a good radial grip rigidity and at the same time to avoid the strength of LSFH to exceed it’s yield limit which will reduce the precision and service life of LSFH, besides when spindle speed reach a extension the weakening influence of the centrifugal force on the radial grip rigidity of the matching of LSFH and cutter should been taken into account. Finally, the finite element analysis results are verified based on the construction of measurement method of the grip rigidity and the results fit very well. The studies provide a theoretical basis for the design, selection and the serialization and standardization of the matching of LSFH and cutter.展开更多
台风风场径向廓线模型对台风灾害的评估以及台风尺度的研究具有重要的价值.利用西北太平洋2001-2020年的台风最佳路径观测数据,评估了目前国际上应用比较广泛的六个分别基于经验参数和物理过程的台风风场径向廓线模型对台风尺度(台风大...台风风场径向廓线模型对台风灾害的评估以及台风尺度的研究具有重要的价值.利用西北太平洋2001-2020年的台风最佳路径观测数据,评估了目前国际上应用比较广泛的六个分别基于经验参数和物理过程的台风风场径向廓线模型对台风尺度(台风大风半径,R17)的估计精度,并探讨了台风结构、强度等内部因素以及垂直风切变和移动速度等环境因子对模型精度的影响.评估发现,所有模型均高估了R17较小的台风而低估了R17较大的台风,且R17越小,高估越明显,R17越大,低估越严重.总体而言,Willoughby et al发展的基于参数的模型具有最小的估计偏差且与观测记录之间最高的相关性.研究还发现,台风内核尺度(最大风速半径,RMW)和强度(最大地面风速,V_(max))对不同模型的影响具有显著的差异性.此外,在高环境风切变和高移速条件下,模型的估计偏差的量级会显著增加.以上研究为进一步完善适用于不同环境条件下,不同结构与强度台风的风场模型提供参考.展开更多
基金supported by National Hi-tech Research and Development Program of China (863 Program, Grant No. 2009AA44302)Scientific Research Fund of Hunan Provincial Education Department, China (Grant No. 10C1259)+2 种基金Hunan Provincial Planned Science and Technology Project of China (Grant No. 2011FJ3231)National Natural Science Foundation of China (Grant No. 51005194)Open Innovation Platform of Hunan College Fund, China (Grant No. 10K063)
文摘Though the lengthened shrink-fit holder (LSFH) is widely applied in high speed milling of the parts characterized by deep cavities at present, its design and selection mainly depends on the experience and lacks a correct theoretical guidance. In this paper, attention is focus on the radial grip rigidity of the matching of LSFH and cutter in high speed milling. Based on the experiment modal analysis (EMA) technique, an accurate finite element model of the matching of LSFH and cutter is established firstly. Subsequently, the influence of different interference, grip length and spindle speed on the grip rigidity of LSFH are analyzed. The analysis results show that there is a reasonable interference and grip length between the LSFH and cutter so that to have a steepless grip and have a good radial grip rigidity and at the same time to avoid the strength of LSFH to exceed it’s yield limit which will reduce the precision and service life of LSFH, besides when spindle speed reach a extension the weakening influence of the centrifugal force on the radial grip rigidity of the matching of LSFH and cutter should been taken into account. Finally, the finite element analysis results are verified based on the construction of measurement method of the grip rigidity and the results fit very well. The studies provide a theoretical basis for the design, selection and the serialization and standardization of the matching of LSFH and cutter.
文摘台风风场径向廓线模型对台风灾害的评估以及台风尺度的研究具有重要的价值.利用西北太平洋2001-2020年的台风最佳路径观测数据,评估了目前国际上应用比较广泛的六个分别基于经验参数和物理过程的台风风场径向廓线模型对台风尺度(台风大风半径,R17)的估计精度,并探讨了台风结构、强度等内部因素以及垂直风切变和移动速度等环境因子对模型精度的影响.评估发现,所有模型均高估了R17较小的台风而低估了R17较大的台风,且R17越小,高估越明显,R17越大,低估越严重.总体而言,Willoughby et al发展的基于参数的模型具有最小的估计偏差且与观测记录之间最高的相关性.研究还发现,台风内核尺度(最大风速半径,RMW)和强度(最大地面风速,V_(max))对不同模型的影响具有显著的差异性.此外,在高环境风切变和高移速条件下,模型的估计偏差的量级会显著增加.以上研究为进一步完善适用于不同环境条件下,不同结构与强度台风的风场模型提供参考.
