起重机桁架臂疲劳寿命与可靠性研究

发布时间：2018-05-26 19:04

本文选题：起重机 + 桁架臂　；参考：《大连理工大学》2014年博士论文

【摘要】：桁架臂起重机是广泛应用于国民经济各领域的一种起重设备,桁架臂是起重机关键承载部件。如何有效地对臂架寿命和可靠性进行预测,是起重机疲劳研究领域备受关注的一个重要课题。目前国内的研究缺乏专门针对起重机典型工况下的桁架臂疲劳寿命S-N曲线；采用比较常用的线性累积损伤理论对疲劳寿命进行计算所得到的结果精度不高,其他非线性累积损伤理论由于需要大量试验数据拟合,公式复杂,工程适用性不强。针对上述问题,本文主要开展了如下研究工作： (1)利用双曲正弦函数与断裂力学裂纹扩展曲线相似性理论,提出在常幅应变-寿命公式Basquin-Manson-Coffin(BMC)公式的基础上,提出了累积损伤比例因子概念,建立了单位裂纹扩展速率与寿命的归一化约束关系。根据起重机应力特性,提出了基于模糊损伤的改进型非线性累积损伤模型和概率模型,通过比较疲劳寿命影响的各个因素,得到了各个参数的基本敏感度趋势。 (2)针对起重机获取实际应力谱比较困难的现状,提出了基于虚拟样机技术的“实测+仿真+比对+统计”组合策略的危险点确定和应力谱获取方法。通过建立起重机整体和局部危险区域细化的耦合有限元虚拟样机,实现了用动力学仿真手段获取了应力谱,为起重机的应力谱获取提供了新的途径。 (3)对影响起重机桁架臂可靠性的七个体系单因素及其评价指标进行了分析,建立了多层次构权与动态构权相结合的臂架整体可靠性评估体系框架,并基于此提出了疲劳剩余寿命可靠度与臂架整体可靠度的安全决策措施。设计了基于Elman神经网络的臂架整体可靠度预测模型,可根据大量专家数据的训练,自动计算可靠度,方便工程应用。 (4)基于热点应力法,对起重机桁架臂K节点的疲劳试验方法进行了研究,确定了起重机典型工况下的较优工装设计,获取了起重机典型载荷下的桁架臂K节点S-N曲线,对影响疲劳寿命的应变历程、平均应力和初始损伤三个主要因素进行了试验,通过数据拟合得到了概率BMC公式的材料参数,为起重机抗疲劳设计的工程应用提供了数据参考。 (5)开发了面向起重机桁架臂的疲劳寿命与可靠性评估系统,能够实现起重机载荷记录、寿命计算、安全决策等功能。通过案例分析,探讨了起重机理论计算结果与实际检测的符合性。
[Abstract]:Truss jib crane is a kind of lifting equipment which is widely used in various fields of national economy. Truss jib is the key bearing part of crane. How to effectively predict the life and reliability of boom is an important subject in the field of crane fatigue research. At present, there is a lack of S-N curve for the fatigue life of truss arm under typical conditions of crane, and the accuracy of fatigue life calculated by linear cumulative damage theory is not high. Other nonlinear cumulative damage theories require a large number of experimental data to fit, the formulas are complex, and the engineering applicability is not strong. In view of the above problems, this paper mainly carried out the following research work: 1) based on the similarity theory of hyperbolic sinusoidal function and crack growth curve in fracture mechanics, the concept of cumulative damage proportional factor is proposed based on the constant amplitude strain-life formula Basquin-Manson-Coffin BMCs. The normalized constraint relationship between unit crack growth rate and life is established. According to the stress characteristics of crane, an improved nonlinear cumulative damage model and a probabilistic model based on fuzzy damage are proposed. By comparing various factors affecting fatigue life, the basic sensitivity trend of each parameter is obtained. 2) aiming at the difficult situation of obtaining actual stress spectrum of crane, a method of determining the dangerous point and obtaining stress spectrum of the combination strategy of "measured simulation comparison and statistics" based on virtual prototyping technology is put forward. By establishing the coupled finite element virtual prototype of the whole and local dangerous areas of crane, the dynamic simulation method is used to obtain the stress spectrum, which provides a new way to obtain the stress spectrum of the crane. In this paper, the single factor of seven system and its evaluation index which affect the reliability of crane truss arm are analyzed, and the frame of the whole reliability evaluation system of jib is established, which combines multi-level construction weight and dynamic construction weight. Based on this, the safety decision measures of fatigue residual life reliability and overall reliability of boom are put forward. An integral reliability prediction model based on Elman neural network is designed, which can automatically calculate reliability according to a large number of expert data, and is convenient for engineering application. 4) based on the hot spot stress method, the fatigue test method of K-joint of crane truss arm is studied, and the optimum tooling design under typical condition of crane is determined, and the S-N curve of K-node of truss arm under typical load of crane is obtained. Three main factors affecting the fatigue life, such as strain history, average stress and initial damage, are tested. The material parameters of the probabilistic BMC formula are obtained by fitting the data, which provides a data reference for the engineering application of anti-fatigue design of cranes. The fatigue life and reliability evaluation system for crane truss arm is developed, which can realize the functions of crane load record, life calculation, safety decision and so on. Through the case analysis, the conformance between the calculation results of crane theory and the actual inspection is discussed.
【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TH21

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