梁柱齐平端板半刚性节点力学性能研究

为研究对齐平端板半刚性节点的力学性能,在试验的基础上,运用有限元软件ANSYS对典型截面半刚性节点进行静力及循环荷载加载分析,并通过改变柱翼缘、连接端板厚度和螺栓排列方式,以及增加节点域加劲肋,研究其对节点所受弯矩与梁柱相对转角曲线(M-θ曲线)的影响。有限元计算结果表明:在静力荷载作用下,M-θ曲线初期以线性关系变化,柱翼缘发生屈服后,节点表现明显的非线性特征;在循环荷载作用下,节点破坏时柱翼缘应力深入节点域发展,导致节点刚度逐渐退化,使得滞回曲线饱满,表明该节点具有较好的抗震特性。参数化分析结果表明:连接端板厚度对节点力学性能影响不大;增加柱翼缘厚度或者增设节点域加劲肋,均能显著提高节点的极限承载能力;适当减小螺栓边距能够有效提高节点的初始转动刚度和抗弯承载力。     

波磨与车轮扁疤耦合故障下车辆振动响应分析

钢轨波磨和车轮扁疤是车辆运行中经常同时存在的2种故障,为研究2种故障对行车安全产生的较大影响,建立了车辆动力学模型,讨论了车辆在通过曲线时2种故障的耦合作用,并利用统计学指标对振动响应特性进行分析。结果表明:钢轨波磨会引起扁疤冲击响应的幅值变大并引起小范围波动,且在钢轨波磨深度为0.01mm时,幅值响应相对车轮扁疤单一故障并不明显;当钢轨波磨深度为0.05mm与0.10mm时,幅值响应相对于车轮扁疤单一故障较为明显。     

浅谈短跑运动员基本技术训练的要求及方法

在培养短跑运动员训练过程中,有的教练员急于求成,不抠技术动作,一味地追求强度,成绩增长较快,但到一定水平,就停滞不前了。而有经验的教练员却恰恰相反,不急于上强度,而是先抠技术细节,等技术定型之后,再上强度。可想而知,后者训练水平是最高的,这就说明了一个道理：磨刀不误砍柴工呀。那么对于100米跑的技术来说,应该如果要求呢？     

纺车轮全攻略（七）

滚珠轴承（Ball Bearing） 钓友经常讨论的轴承,其实是滚珠轴承（Ball Bearing）,Bearing音译过来就是＂培林＂。 1.轴承的优劣鉴别 其实很简单,按价格来,一分钱一分货,如有钓友需要改装或者升级轴承的话,可以考虑进口轴承。但仅从商家的卖价来选择,还是存在一定风险,怎么更进一步买到物有所值的轴承呢？可以从以下两点考虑：①材料及制造工艺;     

穆雷正手击球赏析

1.穆雷的正手引拍环节有些与众不同。他的双手像是在身体侧面抱着一个球,正准备把这个球扔出去。此时球拍的高度几乎与整个右臂在同一水平面上。有不少人曾经质疑穆雷在侧身时髋关节转动的幅度不够,导致正手击球缺乏攻击性。如果仔细观察穆雷的右脚尖指向,或许就能发现问题所在——他的右脚脚尖指向斜前偏前的方向,而不是侧方,这个动作多少会限制右腿膝关节和髋关节向侧面的转动。     

“车轮”滚滚

一、游戏目的通过游戏提高学生的协调能力,培养学生积极参与、团结协作的集体主义精神。二、器材长绳一根(具体长度可以根据学主的高矮来定),挂钩两个。三、游戏方法1)将绳子用挂钩连成一个圆;2)5—6名学生站成一排纵队,双手抓绳上举,双脚站在长绳的两侧;3)游戏开始后,学生用手     

Research on the operating characteristics of parallel 4-DOF electric platform with 4TPS-PS structure

The 4TPS-PS parallel platform designed for a stabilization and automatic tracking system is a novel lower-mobility parallel mechanism. In the first part of this paper, the structure of the platform is described and the kinematics model is built. The workspace of the platform is defined as the full reachable rotation workspace when the Z coordinate dimension of the upper plate varies continuously. A fast searching method of the full reachable workspace is presented, after which the inverse kinematics of the platform is deduced. The forward and inverse solutions of the speed and force of the platform are deduced. According to the characteristic of the 4TPS-PS platform’s structure, a fast searching algorithm of the maximum generalized speed and maximum generalized force output by the upper plate is put forward based on the forward and inverse solutions of the platform’s speed and force. The 4TPS-PS platform prototype built by the State Key Laboratory of Fluid Power Transmission and Control of China is taken as the research subject. The full reachable rotation workspace of the prototype is computed out and analyzed. The curves of maximum generalized speed and maximum generalized force of the prototype are computed out and plotted. Finally, the com- puting and analyzing results of the operating characteristics are confirmed through the experiment.     

滚出什么图形来

如果将左边的物体涂上颜色后按照对应的箭头方向转动或滚动,请你想一想,会印出什么样的图形呢?从对应的右边一栏里找出正确的图形,并用笔把它圈画出来吧。     

无法分享的喜悦

几天前的一个余晖将尽的傍晚,我乘火车前往斯德哥尔摩。我坐的车厢里灯光暗淡,窗外一片黑沉沉,车上的乘客正在各自的座位上打着瞌睡,我静静地坐着,火车车轮撞击铁轨发出的哐哐声     

Novel high torque bearingless two-sided rotary ultrasonic motor

Applications are limited at present because the currently available ultrasonic motors (USMs) do not provide suffi-ciently high torque and power. The conventional travelling-wave USM needs the bearing to support, which required lubricant. To solve the above problem, a bearingless travelling-wave USM is designed. First, a novel structure of the two-sided USM consisting of a two-sided teeth stator and two disk-type rotors is designed. And the excitation principle of the two-sided travelling-wave USM is analyzed. Then, using ANSYS software, we set up the model of the stator to predict the excitation frequency and modal response of the stator. The shape of the vibration mode was obtained. Last, the load characteristics of the USM are measured using ex-perimental method. The maximum stall torque and the no-load speed were obtained. The results showed that the characteristics of the two-sided USM are better than those of the conventional one-sided USM.