【作者】 蔡福海；

【导师】 赵福令；

【作者基本信息】 大连理工大学 ， 机械电子工程， 2014， 博士

【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。更多还原

【Abstract】 Lattice boom cranes are widely used in various fields of national economy as lifting equipment. How to predict life and reliability of the boom effectively is a difficult area of research and focus. Fatigue Life research of lattice boom cranes in domestic is in relatively backward reflected in:the lack of fatigue life S-N curves under specialized crane typical conditions, low accuracy of the use of linear cumulative damage theory of fatigue life calculation. Because of other non-linear cumulative damage theories of complex formulas, engineering applicability is not populaer. The main research works are as follows:(1) Based using the curve similarity theory of hyperbolic sine function and fracture mechanics crack growth curve, a new simplified non-linear cumulative fatigue damage theory is built with the constant amplitude strain-life formula Basquin-Manson-Coffin (BMC). The concept of cumulative damage scale factor is described. Normalized constraint relations between the unit of crack growth rate and fatigue life is established. For the case of stress distribution on booms are in a fuzzy band, a improved non-linear cumulative damage model based on fuzzy damage and probability model is proposed. Comparison of the various factors that affect the fatigue life of lattice boom is expressed and a basic trend of the sensitivity of each parameter is described.(2) Actual stress spectrum is difficult to get under various working donditions for cranes. To obtain real crane stress spectra inexpensively and conveniently, a new stress spectra acquisition method based on the’measured&simulated&compared&statistics’integrated strategy is proposed based on virtual prototype technology.Through the establishment of global and local hazardous areas crane refinement coupled finite element model of virtual prototype, stress spectra can be abtained by dynamic simulation. It is a new way to get the stress spectra of cranes.(3) Seven system single-factors and evaluation indicators which will affect the reliability of the lattice boom crane are analyzed. Overall reliability of the boom system evaluation system framework is buit based on the multi Analytic Hierarchy Process conbined with dynamic weight built method. Through the process of assessing fatigue reliability analysis, security decisions are proposed. For the convenience of engineering applications, a self study evaluation model is buit based on Elman neural network which can calculate automaticly after a train of large number of expert training data. (4) Specially designed tooling is built for fatigue tests for lattice boom key nodes based on the hot spot method. A new S-N curve is obtained by fitting experimental under crane’s typical operating conditions which will fit for lattice boom crane fatigue life assessment. Three main factors which will have impact on fatigue life are compared in the test and the impact trend curve is derived. Material parameters of probability BMC formula are obtained by data fitting method.The fatigue test can provide design data for crane’s fatigue design.(5) A crane booms fatigue life assessment system is developed which can do crane load records, life expectancy calculations, security decisions and other functions. Through a case study, life calculation and safe reliability of crane lattice boom is described to verify the theoretical algorithm proposed by this project.更多还原