Remaining fatigue life assessment of corroded mooring chains using crack growth modelling

Failures caused by the combined actions of fatigue, corrosion and wear are important safety concerns for mooring chains used on floating structures in the oil and gas industry. Prediction of remaining corrosion fatigue life based on surface condition could therefore be a useful tool for the continued safe operation of corroded chains. This paper investigates the use of crack growth modelling for estimating the remaining corrosion fatigue life of mooring chains that exhibit significant pitting corrosion damage. A crack growth modelling approach is used to produce remaining fatigue life estimates for a selection of severely pitted mooring chains. Using fatigue crack growth rate test results for grade R4 high strength mooring chain steel, empirical crack growth laws are presented for free corrosion and cathodic protection conditions at load ratio R = 0.1. Two different methods for establishing equivalent cracks from surface scans of corrosion damage are presented. The mooring chains are proof loaded as part of their manufacturing process. Residual stresses introduced during this process have therefore been determined by finite element analysis and accounted for in the fatigue crack growth predictions. One of the equivalent crack models, accounting for the single dominant corrosion pit, provided quite accurate fatigue life predictions when compared with full scale test results.     

船舶成品管尺寸偏差自动测量系统

针对使用传统量具对船舶成品管尺寸偏差进行检验存在效率低、误差大等问题，设计一种基于多相机摄影测量系统的船舶成品管尺寸偏差自动测量系统。该系统由近景工业摄影测量双相机系统、扫码枪软件集成系统、实时数字化分析软件和编码定位工装组成，实现不同种类成品管的实时在线检测工作，并出具检测结果报告。该系统可提高船舶成品管的检测精度和检测效率。     

Analysis of S–N data for new and corroded mooring chains at varying mean load levels using a hierarchical linear model

Results from full scale fatigue tests of offshore mooring chains are analyzed. The data set includes new and used chains, tested at a variety of mean load levels. The used chains have been retrieved after operation offshore and include samples with varying surface conditions, ranging from as-new to heavily corroded. Based on a parameterized S–N curve intercept parameter, the effects of mean load and chain condition are estimated empirically by regression analysis. A hierarchical linear model is used, to account for and quantify correlations within subsets of the data. The choice of grouping criterion for the hierarchical model is discussed, and assessed based on the current data. Results show that the mean load and corrosion effects are both significant. Differences in the fatigue performance of new versus used chains are quantified and discussed.     

布置方案对近海小型无人监测船波浪运动的影响

以一艘近海小型双体无人监测船为例,建立该双体无人监测船模型,通过使用基于平面势流理论的二维切片法,对无人监测船在不同布置方案下的运动响应情况进行计算分析,得出布置方案与无人监测船运动响应间的关系。研究结果表明:吃水深度、惯性矩对小型无人监测船在波浪中的运动性能影响明显,应在一定范围内酌情进行选取;重心高度对小型无人监测船在波浪中的运动性能影响不大,设计时应主要从稳性方面进行考虑。     

锚链多体系统最优化求解方法及其对比分析

为了在不添加额外方程或判断条件的情况下，求解锚链多体系统悬链和卧链共存的状态，提出利用最优化原理描述静态锚链多体系统的状态方程，即最小势能方程，并与传统的悬链线方程和多体系统一般力学方程进行对比分析。结果表明，该方法不需要进行复杂的受力分析，形式简单且物理意义明确。数值计算结果与传统方法在计算悬链时是一致的，且可在统一的框架下计算悬链和卧链同时存在的状态。     

车路协同网络中服务功能链可行时长优化映射算法

以车路协同网络为研究对象，针对物理链路间连通时长的差异性，本文提出优化可行时长的服务功能链映射算法。首先，建立车路协同的物理传输网络模型，并分别分析车车链路和车路链路的连通时长；其次，以映射可行时长为优化目标，以服务功能链的映射规则为约束，建立整数规划问题；最后，为求解该NP-hard问题，提出基于改进子图同构的映射算法，联合考虑车路协同环境中的节点属性、链路属性及链路间关联关系，设计剪枝策略，从而实现服务链路在物理链路上的组合优化映射。实验结果表明，通过考虑物理链路连通时长的差异性，并对其进行优化选择，提出算法在车间通信距离150m和最大车速60km·h-1 条件下，可将可行时长提升34.4%；同时，在车车通信范围、车辆数以及最大车辆速度这3项主要参数设置中均可验证发现，所提算法可有效提升映射可行时长。