【作者】 王华林；

【导师】 范勤；

【作者基本信息】 武汉科技大学 ， 机械设计及理论， 2005， 硕士

【摘要】 在实际生产中,机械设备重要零部件的故障往往造成生产停产和产出废品,严重的情况甚至造成人员的伤亡。板和梁是冶金桥式起重机金属结构的基本组成单元,而这些金属结构的损伤多以板、梁的疲劳裂纹表现其故障形式。随着大型金属结构的不断出现,由于裂纹未能及时发现而造成的疲劳裂纹扩展的结果往往造成整个结构的破坏,等到事故发生的时候一切已经不可挽回。因此,对结构和设备都需要及时准确的故障诊断,防范于未然。国内外学者在故障诊断方面做了大量的工作,提出了一系列结构损伤识别方法,但基于模态参数的损伤识别方法仍属于最普遍最基本的方法之一。在对结构疲劳裂纹的故障诊断中,本文主要对板裂纹的诊断研究,利用模态参数进行结构疲劳裂纹损伤识别。由于对裂纹的诊断是基于振动的宏观理论,故不考虑裂纹的尖端的应力情况。 本文对悬臂板模拟不同的位置、不同长度、不同角度的各种裂纹情况利用有限元分析软件ANSYS进行了数值仿真分析。在梁结构的振型斜率变化率基础上,得到了板结构两个方向的振型切角变化率。 冶金桥式起重机结构比较复杂,所受载荷和环境激励具有随机性,因此选择适当的诊断指标是很必要的。本文提出了固有频率变化率和振型切角变化率两个指标。分析了不同情况的裂纹对固有频率和振型切角变化率裂纹诊断指标的影响。得到结论是裂纹位置越靠近固定边,对诊断指标的影响越大;裂纹越长,对诊断指标的影响越大;裂纹角度越大,对诊断指标的影响越大。 本文进行了悬臂板完好板和有裂纹板的模态试验,得到了完好板和有裂纹板的试验模态数据,并与有限元数值仿真结果进行分析比较,对存在的误差进行了分析。更多还原

【Abstract】 The fault of mechanical main parts usually result in production breaking and waster, the sever fault even do harm to person. Plate and beam is the element of over head traveling crane. Crack damage of plates and beams is the main fault forms of structure. With more and more large structure appearing in our lives, if the crack were not diagnosis in time, the expanding crack would damage the whole structure in the end. Once the accidence occurred, it cannot be recovered. To avoid accident in advance, fault of both structure and equipment is necessary. In order to measure the position and degree of damage in time , the domestic and international scholar has done a large amount of work, presenting a series of method of discerning structure damage, but the law based on mode parameter damage discern is still the most generally most basic method. Crack diagnosis to beam is more perfect than of plate. Crack diagnosis to plate will be emphasized in this dissertation. The diagnosis to crack is based on vibration without considering the stress influence from the crack tip.FEM numerical simulation to cracks with different location, different length and different angle is taken with ANSYS. Mode tangent angle variance ration (Δtg a ) of the cantilever plate in two directions is gotten from the the beam the mode slope variance ratio.Over head traveling crane is a complex structure with random load and actuator. It is necessary to make a good choice with appropriate diagnosis index. Two diagnosis indexes are used in this dissertation. Influence both to natural frequency and Atga by different cracks is analyzed. Closer to the clasped edge, longer crack and lagle crack can all bring bigger influence to the dynamic features.Modal experiment of cracked cantileveer is carried out. A database of the relation between intact and cracked plate and mode and natural frequency is established. Compared the experiment with FEM numerical simulation, and evaluate errors in experiment data.更多还原