桥吊小车减速箱轴断裂原因分析及改进

小车减速箱是桥吊牵引机构的重要组成部份,保证减速箱在工作中的正常运行,对提高桥吊的工作效率和安全性能有着重要意义。对齿轮轴断口进行宏观分析,结合有限元和材料力学等方面,深入地分析减速箱齿轮轴断裂原因,同时提出合理化的处理方案和改进措施。     

机车抱轴箱随机应力谱下的疲劳寿命预估研究

针对机车铸钢抱轴箱在运行中产生疲劳裂纹的现象，笔者对机务段检修和返厂检修的抱轴箱进行了调研，认为裂纹长度服从正态分布。对抱轴箱及其改进结构进行了有限元分析，其应力最大部位与发生裂纹部位一致。通过动应力实测获取抱轴箱危险部位的应力谱，用局部应力一应变法结合断裂力学方法估算了抱轴箱的疲劳总寿命，并与名义应力法计算结果进行了比较。结果表明，2种方法所得的疲劳总寿命基本是一致的，用局部应力-应变法计算机车抱轴箱裂纹萌生寿命是一种合理的方法，而大的铸造缺陷是抱轴箱产生裂纹的最主要原因。最后采用统计方法得到了裂纹扩展破坏的累积失效概率函数。     

公路桥梁结构材质状况耐久性检测及综合评定方法研究

针对目前旧桥承载能力评定方法存在的不足,克服需大量借助昂贵荷载试验进行旧桥承载能力鉴定的缺点,主要介绍了混凝土旧桥表观损伤、强度、钢筋锈蚀电位、氯离子含量、钢筋分布及保护层厚度、混凝土碳化深度、电阻率、内部缺陷和表层损伤等的检测方法与评价指标及结构或构件的耐久性综合评定方法。     

一种基于冰载荷引起的船体结构疲劳损伤分析方法

目前对基于冰载荷引起的船体结构强度问题已经发展的较为成熟,但是基于冰载荷引起的结构疲劳强度的研究比较少。针对该问题,如果有一种简化方法来指导早期的结构设计,对船舶设计者来说是很有现实意义的。本文对英国劳氏船级社发布的ShipRight FDA ICE_^[1]作概括性的介绍,旨在向读者介绍这一简单而高效的评估方法以及技术背景和注意要点等。最后文章根据这一方法给出数条油船和LNG船的算例,并验证通过该方法改善疲劳节点的可行性。     

我国桥梁耐久性设计中存在的问题及对策

随着公路建设的增多,我国的桥梁设计技术也得到了快速发展,论述桥梁设计中存在的主要问题,对产生原因进行分析,提出桥梁全寿合设计理论的观点及解决策略,为桥梁耐久性设计提供借鉴。     

地铁车辆转向架天线梁模态与疲劳寿命分析

国内某地铁车辆转向架的ATP天线梁频繁出现断裂,为探寻天线梁断裂的原因,对其进行现场试验分析。依据实测的天线梁约束模态及有限元软件计算的整备状态下模态结果,分析天线梁实测动应力频谱的主频及振型,并利用IIW-1823《焊接接头与部件的疲劳设计标准》计算天线梁上测点的等效应力范围和疲劳寿命。结果表明,天线梁的1阶垂弯、1阶横弯及与构架八字变形的耦合振型(75 Hz)均对天线梁的疲劳寿命造成较大的影响;在随机振动疲劳分析下,天线梁上大部分测点的等效应力都已经超过焊缝的疲劳极限80 MPa,尤其是位于天线梁横梁中部支座上的T4测点,等效应力为214.4 MPa,已经极大地超过焊缝的疲劳极限,而且疲劳寿命也远远达不到设计要求。     

公路沥青路面的再思考和展望

路面早期病害依然存在，路面有效使用寿命远远低于设计寿命，针对此种现状，概述了路面3种主要病害的成因，并重点论述了半刚性基层材料组成设计中存在的几个问题。通过总结现有路面材料组成设计方法，从设计思想和设计方法两方面展望了基于半刚性基层耐久性路面的设计理念。     

道路常用透水砖的透水性能研究

城市道路中使用透水砖是城市可持续发展的趋势,也是保护水资源、维护生态平衡的重要举措。通过对常用透水砖的透水性能的研究,可为今后工程中透水砖的选择提供参考。     

Numerical simulation of fatigue crack propagation under superimposed stress histories containing different frequency components with several mean stress conditions

Fatigue crack propagation behavior under superimposed stress histories containing different frequency components with several mean stress conditions was investigated. Numerical simulation of fatigue crack propagation based on an advanced fracture mechanics approach using the RPG (Re-tensile Plastic zone Generating) stress criterion for fatigue crack propagation was improved to extract the effective part from the applied stress history for fatigue crack propagation. The parameter, which is based on the plastic hysteresis energy consumed in the vicinity of a crack tip, was applied and implemented into the numerical simulation code of fatigue crack propagation. Fatigue crack propagation tests under various superimposed stress conditions with several mean stress conditions were performed and compared with the fatigue crack propagation histories obtained from the improved numerical simulations. These comparisons show the validity of the proposed procedure for extracting the effective stress history from the superimposed stress histories with different frequency components and mean stresses. Additionally, practical fatigue strength evaluations based on the linear cumulative fatigue damage parameter were conducted to investigate the tendency of the fatigue damage value under these stress conditions.     

Numerical simulation of fatigue crack propagation under biaxial tensile loadings with phase differences

Fatigue crack propagation under the biaxial tensile loading, which loading directions are normal and parallel to the initial crack position, is highlighted in this study. Most of in-service structures and vessels are subjected to many types of loading. Generally, these loadings have different axial components with different phases. However, the structural integrities of structures and vessels are evaluated according to design codes based on theoretical and experimental investigations under a uniaxial loading condition. Most of these codes are based on the S–N curves approach. An approach that does not use S–N curves has been favored by researchers, with the fracture mechanics approach preferred for evaluating the fatigue life of structures. An advanced fracture mechanics approach was developed based on the Re-tensile Plastic zone Generating (RPG) stress criterion for fatigue crack propagation. In this study, fatigue crack propagation tests under biaxial loading with six different phase and loading conditions are performed and the effect of the phase difference under biaxial loading is evaluated. A numerical simulation method of fatigue crack propagation based on the RPG stress criterion under different biaxial loading phase conditions is presented and compared to measured data.