桥式起重机主梁变幅疲劳寿命试验载荷谱

通过对实测的桥式起重机主梁应力—时间历程的统计分析处理,得到了主梁的应力幅谱。并说明了主梁变幅疲劳试验八级程序加载应力幅图的编制。     

单梁门式起重机主梁加固设计

2004年石家庄铁道学院对某单梁起重机进行了检测,检测结果表明主梁存在跨中及悬臂根部应力幅偏大、2悬臂弹性下挠超出标准值的问题,要继续使用,应对主梁加固。本设计对主梁提出了加固方案,对加固前后的主梁危险截面进行了应力计算。     

电动单梁起重机主梁应力测试分析

通过对LD5T电动单梁起重机主梁应力测试数据分析,提取出主梁额定载荷下静态应力稳定值,各吊载动作动态冲击振动固有频率和幅值,各吊载动作动载系数和冲击振动阻尼比系数等评价主梁性能的特征值。为起重机械主梁金属结构性能综合评价提供重要的数据依据。     

桥式起重机主梁危险截面应力幅的分布规律及计算方法

探讨了桥式起重机主梁跨中应力幅值Sr的分布规律及计算方法，并用实例验算了计算方法的可行性。为起重机金属构件的疲劳概率设计做了一些基础性工作。     

造船龙门起重机主梁结构的疲劳强度计算方法对比

造船龙门起重机是由各类金属结构件焊接而成,在随机载荷和动载荷作用下疲劳破坏是钢结构主要失效形式之一。为预防疲劳事故发生,以580t级在役造船龙门起重机主梁结构为研究对象,对实际结构进行模拟,分别采用应力比法和应力幅法进行疲劳强度分析,并从计算原则和过程比较异同,对比两种方法计算结果,表明对于焊接结构应力幅法普遍严于应力比法,这对实际疲劳设计与计算具有较好的指导意义。     

基于许用应力法和极限状态法的架桥机主梁校核

目前起重机金属结构设计采用许用应力法和极限状态法两种方法并行。文中在阐述许用应力法和极限状态法的原理和特点的基础上,针对某型桁架式架桥机主梁,应用许用应力法和极限状态法分别对主梁结构进行强度校核,之后现场实测主梁应力值,分析结果表明相比许用应力法,架桥机桁架式主梁使用极限状态设计方法校核时,富余量较大。     

大跨度龙门起重机变截面主梁优化设计

目前,大跨度龙门起重机主梁设计为减轻主梁自重,主要考虑箱形截面的翼缘板及腹板在长度和高度方向上采用不同厚度的板材,而使主梁沿长度方向分为多种截面形式,并以跨度中心向2侧对称分布。采用有限单元法和优化设计方法,以龙门起重机为研究对象,通过计算机仿真分析起重机主梁的强度、刚度,找出最大应力和最大变形处,然后在此基础上,完成以结构轻量化为主要目标的优化计算。     

抓斗装卸桥主梁疲劳寿命的估算

利用常幅疲劳 S-N 曲线和 Miner 线性累积损伤理论,在对实测抓斗装卸桥时间应力历程所进行的雨流计数结果和八级载荷谱分析的基础上,得出其符合威希尔分布的结论,并提出了计算主梁结构疲劳寿命的简易方法。     

基于Pro/MECHANICA桥式起重机箱形主梁的结构分析

应用Pro/MECHANICA有限元分析软件,对箱形桥式起重机主梁进行有限元分析。得到了主梁的承载应力大小及分布状况,其结果与传统力学计算方法一致。分析表明:这种分析方法是科学了解起重机主梁在复杂载荷下的应力大小及分布状况的一种有效手段。     

大型门机在自然风场中的脉动特性研究

大型门式起重机结构轻柔,其固有频率处于低频段,风的脉动效应不容忽视。利用顺风向的Davenport谱与Shinozuka谐波叠加法来模拟脉动风的随机过程,利用FEA方法来分析门机在自然风场中的脉动特性,将其与静载处理结果对照研究:风的脉动效应对结构的最大应力值影响主要体现在非工作状态下,此时支反力大幅波动,整机稳定性受到威胁,而工作状态下由于主梁承受较大工作载荷,风的脉动效应会对主梁结构有较大的振动激励作用,主梁的位移幅值增大较多。     

桥门式起重机疲劳裂纹扩展寿命的模拟估算

根据前人的试验和研究成果,总结推荐了桥门式起重机焊接箱形梁的各项疲劳参数取值,同时以等辐载荷疲劳裂纹稳定扩展阶段的计算公式为基础,针对起重机承受随机载荷的特点,根据时间循环法,用计算机模拟估算出桥门式起重机焊接箱形梁的疲劳裂纹扩展寿命。     

Large-eddy simulation of fluid flow and heat transfer in a mixing tee junction

The temperature fluctuation caused by thermal striping phenomena of hot and cold fluids mixing results in cyclical thermal stress fatigue failure of the pipe wall. Mean temperature difference between hot and cold fluids was often used as thermal load in previous analysis of thermal fatigue failure, thereby the influences of the amplitude and frequency of temperature fluctuation on thermal fatigue failure were neglected. Based on the mechanism of flow and heat transfer which induces thermal fatigue, the turbulent mixing of hot and cold water in a tee junction is simulated with FLUENT platform by using the Large-eddy simulation(LES) turbulent flow model with the sub-grid scale(SGS) model of Smagorinsky-Lilly(SL) to capture the amplitude and frequency of temperature fluctuation. In a simulation case, hot water with temperature of 343.48 K and velocity of 0.15 m/s enters the horizontal main duct with the side length of 100 mm, while cold water with temperature of 296.78 K and velocity of 0.3 m/s enters the vertical branch duct with the side length of 50 mm. The numerical results show that the mean and fluctuating temperatures are in good agreement with the previous experimental data, which describes numerical simulation with high reliability and accuracy; the power spectrum density(PSD) on top wall is higher than that on bottom wall(as the frequency less than 1 Hz), while the PSD on bottom wall is relatively higher than that on top wall (as the frequency of 1-10Hz). The temperature fluctuations in full mixing region of the tee junction can be accurately captured by LES and can provide the theoretical basis for the thermal stress and thermal fatigue analyses.     

起重机箱型梁疲劳裂纹与寿命预估

起重机疲劳裂纹是起重机破坏的主要形式之一,根据断裂力学与损伤力学,给出了单一裂纹的线弹性与弹塑性的应力强度因子和恒幅载荷与无级变幅载荷下的疲劳裂纹扩展公式,推导出了在无级变幅载荷下多裂纹的应力强度因子公式.运用起重机数据记录仪测得的数据,结合峰值计数法,得出起重机箱形梁的应力谱.结合实例对1台在役起重机箱型梁疲劳裂纹进行分析,实例表明,推导出的疲劳裂纹公式能够正确快捷地求出箱型梁的疲劳寿命;对特种设备检验以及减少起重机疲劳事故的发生具有重要的工程价值.     

Finite element analysis of shot-peening effect on fretting fatigue parameters

Shot peening is widely used to improve the fretting fatigue strength of critical surfaces. Fretting fatigue occurs in contacting parts that are subjected to fluctuating loads and sliding movements at the same time. This paper presents a sequential finite element simulation to investigate the shot peening effects on normal stress, shear stress, bulk stress and slip amplitude, which are considered to be the controlling parameters of fretting damage. The results demonstrated that among the modifications related to shot peening, compressive residual stress has a dominant effect on the fretting parameters.     

Assessment of fatigue life of remanufactured impeller based on FEA

Predicting the fatigue life of remanufactured centrifugal compressor impellers is a critical problem. In this paper, the S-N curve data were obtained by combining experimentation and theory deduction. The load spectrum was compiled by the rain-flow counting method based on the comprehensive consideration of the centrifugal force, residual stress, and aerodynamic loads in the repair region. A fatigue life simulation model was built, and fatigue life was analyzed based on the fatigue cumulative damage rule. Although incapable of providing a high-precision prediction, the simulation results were useful for the analysis of fatigue life impact factors and fatigue fracture areas. Results showed that the load amplitude greatly affected fatigue life, the impeller was protected from running at over-speed, and the predicted fatigue life was satisfied within the next service cycle safely at the rated speed.     

应力与腐蚀因素对连接件腐蚀疲劳寿命交互作用的研究

在应力控制下分别研究了不同应力,预腐蚀时间对3．5％NaCl溶液中有涂层的LY12CZ铝合金铆接连接件的腐蚀疲劳性能影响的规律。试样结构是根据飞机蒙皮的真实结构设计制成的单剪切连接件,按实际工艺过程进行表面处理。试验结果表明,提高应力和延长预腐蚀时间均会缩短连接件的腐蚀疲劳寿命。应力与环境腐蚀因素对连接件的腐蚀疲劳寿命的影响作用不是简单的叠加关系,而是相互影响的,结果还表明,在无预腐蚀的条件下有涂层连接件在pH值为6的NaCl溶液中的腐蚀疲劳寿命比空气中的寿命要高,并且在高低应力范围内均有此现象,在30MPa下预腐蚀对连接件的疲劳寿命的影响作用比50MPa下预腐蚀对连接件疲劳寿命的作用要明显。     

关于微动磨损与微动疲劳的研究

微动磨损与微动疲劳是２种主要的微动模式,造成的损伤在工业中相当普遍,并可能引发灾难性的后果。主要研究了们移幅度、压力和疲劳应力３个基本微动参数,并以获得的微动区域、微动图为基础,分析了微动磨损与微动疲劳的运行机制和破坏规律。为更好地了解微动磨损与微动疲劳之间的内在联系,进一步探讨了接触磨损与局部疲劳、局部疲劳与整体疲劳之间的竞争机制。     

Methodology to Evaluate Fatigue Damage of High-Speed Train Welded Bogie Frames Based on On-Track Dynamic Stress Test Data

The current method of estimating the fatigue life of railway structures is to calculating the equivalent stress amplitude based on the measured stress data. However, the random of the measured data is not considered. In this paper, a new method was established to compute the equivalent stress amplitude to evaluate the fatigue damage based on the measurable randomness, since the equivalent stress is the key parameter for assessment of structure fatigue life and load derivation. The equivalent stress amplitude of a high-speed train welded bogie frame was found to obey normal distribution under uniform operation route that verified by on-track dynamic stress data, and the proposed model is,in e ect, an improved version of the mathematical model used to calculate the equivalent stress amplitude. The data of a long-term, on-track dynamic stress test program was analyzed to find that the normal distribution parameters of equivalent stress amplitude values di er across di erent operation route. Thus, the fatigue damage of the high-speed train welded bogie frame can be evaluated by the proposed method if the running schedule of the train is known a priori. The results also showed that the equivalent stress amplitude of the region connected to the power system is more random than in other regions of the bogie frame.     

基于有限元子模型法的架桥机主梁螺栓强度分析

介绍了节段拼装一体化架桥机的主体结构,特别是主梁结构.为了得到架桥机桁架主梁中节段连接构件螺栓的受力情况,选取全悬挂工况对主梁的强度和刚度进行分析,通过有限元子模型法建立螺栓计算的子模型,施加边界条件,对螺栓进行受力分析.计算结果表明,采用有限元子模型法可以较准确地获得螺栓的受力情况,且该方式对计算机性能要求较低,为架...