龙门起重机主梁的有限元分析及疲劳计算..doc

摘要
龙门起重机具有自重轻、迎风面积小、承载能力大的特点,在货物的起重,运输和安装等方面应用广泛。本文是以MH20-30单梁龙门起重机为研究对象,利用大型有限元软件ANSYS建立起重机的有限元模型。并对其进行静力学、模态分析、动力学的研究以及对本文起重机进行寿命疲劳估计,为以后的起重机设计与研制提供理论基础。
首先,本文从静力学的研究为基础入手,建立了龙门起重机的三维实体简化模型。选取了满载电动葫芦位于跨中和主梁悬臂端的位置对起重机主梁的静强度和静刚度进行校核,分析其承受载荷的能力,找出危险截面的位置,验证是否符合设计要求。
其次,对龙门起重机进行模态分析,选取前五阶固有频率进行主要分析。模态分析的目的是为了获取起重机的固有自振频率,通过查看各阶振型图,观察主梁的振动情况,以此来分析,可能会受到的外载激振对其影响。从而,避免此类振动而引起的过度振动,保证起重机的使用安全。
然后,对门机进行瞬态动力学分析。选取跨中货物起升离地的瞬间对起重机主梁的影响为分析点。分析了货物离地过程中经历的各个阶段,以预张紧阶段为切入点,利用ANSYS软件分析计算得出主梁的动力响应曲线,包括位移、速度和加速度曲线,验证其是否满足刚度设计要求。
最后,根据损伤容限设计方法和断裂力学理论,利用Paris公式,探讨了各参数的选择,然后对主梁的下腹板进行了疲劳寿命估算。并分析了各参数对主梁的疲劳寿命产生的影响,随着循环次数的增加疲劳裂痕的扩展规律,为起重机的安全使用提供理论依据。
关键词:龙门起重机;静力学;模态分析;动力学;疲劳寿命
Abstract
Gantry crane has many advantages such as light weight, small windward area, and large bearing capacity. It is widely used in the goods lifting, transportation and installation, etc. In this article, MH20-30 single-girder gantry crane is the research object. The finite element model of the crane is established by the large finite element software ANSYS and is researched with statics analysis, modal analysis, dynamics analysis and the fatigue life estimation in order to provide a theoretical basis for crane design and development in the future.
Firstly, begin with the statics research and establish the solid simplified model of the gantry crane. Select the middle position of the loaded electric hoist and the cantilever end of the main girder to check the static strength and static stiffness of the main girder. Analyze its load bearing capacity, find out the location of the dangerous section, verify whether the ply with the design requirements.
Secondly, select the top five order natural frequency of gantry crane as the main object for modal analysis. The purpose of mode analysis is to gain the inherent natural frequencies of crane, so that each order modal figure can be checked and the vibration of the main grider is observed. From that, the effect can be analyst by the outside vibration influence o