【作者】 刘士明；

【导师】 陆念力；

【作者基本信息】 哈尔滨工业大学 ， 机械设计及理论， 2008， 硕士

【摘要】 伸缩臂是轮式起重机最重要的工作部件,其稳定性计算是设计分析的关键。目前,伸缩臂的稳定性计算主要依据中国起重机设计规范《GB3811-83》,其伸缩臂的计算长度是以未考虑油缸影响的变截面梯形柱模型采用能量方法推导而得,理论上既不严密也不够精确。新修订的起重机设计规范的计算模型采用的仍是变截面阶梯柱,但求解采用精确的微分方程得到阶梯柱递推公式形式的精确解析解,在理论上更严密一些,但也没有考虑油缸和伸缩臂搭接处摩擦的影响,与伸缩臂实际工作状态不完全相符。因此,求解考虑油缸和摩擦影响的伸缩臂的稳定性是十分必要。本文通过对臂间搭接与摩擦影响的箱形伸缩臂稳定性分析研究,可知在伸缩吊臂的搭接处产生摩擦力,从而使伸缩吊臂的轴向力由箱形臂与油缸共同成承受,箱形臂自身在承受一定的轴向力的同时承受全部的弯矩。由此受力关系推导出由单个多级油缸支承至顶部的箱形伸缩臂欧拉临界力的递推公式,定性并定量地分析变截面梯形柱、考虑油缸和计及摩擦影响时吊臂整体失稳欧拉临界力的差异。本文采用微分方程法和精确有限元法两种方法求解伸缩吊臂在计及臂间搭接与摩擦影响时起升平面外的欧拉临界力的精确解,同时辅以弹性支座法验证其理论的准确性。本文给出单个油缸支承在顶部时伸缩臂欧拉临界力精确解的递推公式;通过比较用微分方程法、弹性支座法、有限元法三种方法确定伸缩臂的临界力;并求出了伸缩臂在不同支承情况下的失稳特征方程,同时给出了伸缩臂的计算长度系数;并详细的阐述了采用精确有限元法求解伸缩臂的欧拉临界力的求解过程。根据《GB3811-83》规范的有关计算参数和图表,用本研究结果同原起重机设计规范、变截面梯形柱模型和考虑油缸支承作用的伸缩臂模型进行比较,分析结果表明,计及臂间搭接与摩擦影响的伸缩臂欧拉临界力介于变截面梯形柱模型欧拉临界力与考虑油缸作用的多节伸缩臂模型的欧拉临界力之间,与伸缩吊臂的实际工作情况相符合。更多还原

【Abstract】 Telescopic boom is the most important component of wheel crane, whose stability calculation is the key of design and analysis. At present, stability calculation of telescopic boom mainly according to Chinese crane design specifications《GB3811-83》, and calculation length of telescopic arm is derived by energy method according to the variable cross-section ladder model without considering the impact of fuel tank, therefore, it is theoretically neither rigor nor precision. The revised crane design specifications still uses variable cross-section ladder model; although it got precise analytical solutions in the form of ladder recurrence formula, which is more rigor theoretically, it did not consider the friction impact of fuel tank and telescopic boom’s lap so that it is completely not consistent with the actual working conditions. Therefore, it is very necessary to work out the stability of telescopic boom with considering fuel tank and friction.Crane’s telescopic boom is usually composed of a number of variable cross-section box-arms that are connected by sliders, which allows axial expansion. Its fuel tank generally lies inside of the telescopic boom, and bears axial force together with box-arms, while the latter at the same time bear all the bearing moment. Therefore, telescopic boom’s Euler critical force is different from that of both the variable cross-section ladder model and the multi-telescopic boom model only considering fuel tank. It depends on the moment of inertia of lazy arm’s section and the axial force, friction, box-arm bears. Meanwhile, with different support forms of fuel tanks, Euler critical force would also be different. The issue mentioned above is that this paper will focus on.In this paper, two methods, differential equation method and precision FEM, are introduced to get Euler critical force’s precision solution of telescopic boom with considering the effects of arm lap and friction outside the lifting plane. Then, elastic support method is applied to verify the accuracy of theory. In this paper, the recurrence formula of Euler critical force’s precision solution of telescopic boom with a single fuel tank at its top is proposed; critical force of telescopic boom is determined by three methods: differential equations method, elastic support method and FEM; work out the instability characteristic equation of telescopic boom in different support; and describe in detail the solution process of telescopic boom’s Euler critical force using precision FEM.According to the relevant parameters and charts in standard《GB3811-83》, comparison of results between this paper and both the variable cross-section ladder model and the telescopic boom model with considering fuel tank support in the standard shows that Euler critical force of telescopic boom with considering arm lap and friction is between that of those two models mentioned above, which is consistent with the real work of telescopic boom.更多还原