摘要
疲劳强度是起重机金属结构设计的重要内容之一,移动载荷是引发起重机金属结构承受循环应力的主要因素。现有的起重机金属结构疲劳评定中通常忽略了移动载荷的影响,导致寿命预测结果误差很大。为此,文中首先分析了移动载荷在典型起重机工作循环过程中的作用,发现一个起重机工作循环常常包含多个应力循环,致使实际计算点的寿命预测值成倍减小。其次,提出了一种脉冲载荷叠加的移动载荷处理方法,针对某通用桥式起重机主梁结构中的主要焊缝,基于等效结构应力法计算并获得了主梁结构的整体疲劳寿命场。研究表明:脉冲载荷叠加法和等效结构应力法相结合,能够有效反映移动载荷对焊接结构疲劳寿命的影响,获得较准确的整体疲劳寿命场;主腹板下方的连接焊缝对应跨中区段和端部变截面区段的大隔板位置是起重机主梁结构的疲劳薄弱点,且裂纹更易萌生于腹板侧焊趾,在实际检测时应予以足够重视。
Fatigue strength is one of the important contents to be considered in the design of the metal structure of cranes,and moving load is the main factor causing the metal structure of cranes to bear cyclic stress.In the current fatigue assessment of the metal structure of cranes,the influence of moving load is usually ignored,which leads to a large error in life prediction results.Firstly,the role of moving load in typical crane working cycle was analyzed,and it was found that a crane working cycle often contains multiple stress cycles,which leads to the life prediction of actual calculation points being reduced by times.Then,a treatment method by superimposing pulse loads is put forward.For the main welds in the main beam structure of a common bridge crane,the whole fatigue life field of the main beam structure was calculated and obtained by using the equivalent structural stress method.Results show that the combination of pulse superimposed load method and equivalent structural stress method can better reflect the influence of moving load on the fatigue life of welded structures and obtain a more accurate whole fatigue life field;The location of the large partition corresponding to the mid-span section and the variable cross-section section at the end of the connecting weld under the main web is the most prone to fatigue in the main beam structure of cranes,and the weld toe on the side of the web is more prone to cracks,so attention should be paid to this kind of areas in actual inspection.
作者
魏国前
胡珂
余震
党章
Wei Guoqian;Hu Ke;Yu Zhen;Dang Zhang
出处
《起重运输机械》
2021年第9期47-53,共7页
Hoisting and Conveying Machinery
基金
国家自然科学基金资助项目(51575408)。
关键词
桥式起重机
移动载荷
主梁
疲劳寿命场
脉冲载荷叠加法
bridge crane
moving load
main beam
fatigue life field
pulse superimposed load method
