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.     

基于智能船厂的三维电子地图开发技术

研究基于智能船厂的三维电子地图开发技术，开发三维电子地图相关组件并实现地图瓦片化、动态加载、位置校准、地图缓存等功能，通过直观的地理实景模拟表现方式快速搭建智能船厂三维电子地图服务，为管理者提供设备、人员和中间产品等信息检索服务，有效提升船厂数字化、智能化、信息化程度，可为构建船厂资源管理和工装管理智能化提供技术支撑，进一步挖掘生产和管理环节潜力，推进船舶行业信息化建设。     

基于有限元分析的桥墩钢模的结构优化分析

以某特大桥桥墩混凝土施工中钢模板设计为背景，结合Midas Civil有限元分析软件建模仿真分析该钢模板在混凝土侧压力作用下的各构件受力，通过改变对拉杆刚度、对拉杆位置来确定钢模板整体结构的最优受力，结果表明：在一定的对拉杆刚度情况下，合理的对拉杆位置对结构整体受力有着很大的提升；增加对拉杆刚度可以加强结构受力，但该过程不是无止境的增加，而是非线性的，增加到一定刚度情况下结构受力达到一个相对稳固状态；同时提出一些在钢模板设计和检算中的主要问题并提出改善建议。     

Sea trials of Sigma wave energy converter – slacking and snapping of TLP mooring lines

Sigma Energy has performed its foremost prototype tests of scaled wave energy converter in a real sea environment. The prototype was a point absorber with a cylindrical buoy, a mechanical power take-off system with a counterweight, moored to the seabed as a tension leg platform (TLP) with three equal tendons. In these extensive experiments, numerous device characteristics were measured and analysed. The present paper focuses on the dynamic forces in the mooring lines, and some unexpected and rare data obtained. It is well known that TLP tendons are prone to a brief loss of tension (the slacking) and that, after such events, high snapping forces of short duration can arise. Partly by intention, and partly due to underestimation of the dynamical forces, several such slacking-snapping incidents were recorded during the experiments. In some severe storms, the snapping forces were up to six times higher than the tendon pretension. The paper presents several recordings of dynamic forces and platform motion during these critical events. It analysis them, and gives a typical scenario under which they occur. It gives also some theoretical explanations, and numerical predictions of dynamical tendon forces, with their comparison to the experimental results.     

Uncertainty analysis of extreme mooring loads associated with environmental contours and peak tension distributions

This paper aims to assess the uncertainty on the extreme mooring loads of floating system considering short-term variability. Two environmental contour approaches based on the inverse First and Second Order Reliability Methods are employed to identify critical sea states that may give rise to extreme loads. The uncertainty related to the construction of environmental contours is addressed including significant differences due to marginal distribution fitting, parameter estimation methods and joint models. Three measured datasets are analysed using a known conditional joint distribution and proposed mixed copula model. 3-h time domain numerical simulation for each sea state is conducted and the characteristic extreme responses of mooring lines subjected to design loads are assessed. The uncertainties due to various statistical models including the average conditional exceedance rate method as well as global maxima, peak-over-threshold method combined with Gumbel distribution, Generalized Extreme Value distribution, Generalized Pareto distribution and 3-parameter Weibull distribution are investigated and quantified. It is observed that marginal distributions, joint models and parameters estimation methods have apparent effect on design loads estimation, and the extreme tensions of the semi-submersible platform shows significant difference using various probabilistic models. The results indicate that those epistemic uncertainties should be account for in the reliability analysis or safety factor calibration for mooring systems.     

面向“离位”儿童乘员的常开式安全气囊优化设计

儿童乘坐校车时常呈现多种"离位"坐姿,有必要开展多种儿童坐姿下,常开式安全气囊的优化设计研究,明确12岁儿童的损伤阈值。为此构建并验证校车的仿真模型,搭建校车和常开式安全气囊的耦合模型。选取躺卧坐姿、右倾坐姿作为12岁儿童乘员的典型"离位"坐姿,并针对正常坐姿、躺卧坐姿和右倾坐姿,以加权伤害指标为优化目标,基于响应面代理模型和改进型NSGA-Ⅱ算法,权衡确定常开式安全气囊的主要设计参数的最优配置为:泄气阀开度199.73%、泄气阀开启压力1.1628×105Pa、安装点高度0.362 8 m和中部拉带长度0.315 2 m。结果表明:3种儿童坐姿下,具备最优配置的常开式安全气囊能够最大限度地提升12岁儿童乘员的安全性。     

自动变速器电子换挡系统挡位位置自学习控制算法设计

电子换挡系统 （Electronic Transmission Range Select System，ETRS） 的控制精度受自动变速器、换挡执行机构的零件自身误差及装配误差的影响，驻车挡、倒车挡、空挡、前进挡各挡位的理论位置与实际装配结果不可能完全匹配，这不仅会影响电子换挡系统的控制精度，而且长期使用后可能存在换挡功能失效的潜在风险。针对上述问题，研究设计了电子换挡系统相关硬件架构、挡位位置识别方法及关键自学习控制算法。控制算法集成直流电机匀速控制、H桥驱动电流数据读取、槽底挡位位置识别、多轮次槽底扫描迭代及挡位位置校验。仿真及实车试验表明，设计的挡位位置识别方法能够实现误差不大于0.15°，自学习控制算法能够实现实车试验大数据下均值与理论角度位置差距不大于0.3°，同时保证100%成功率，满足电控换挡系统长期工作的准确性及耐久性要求。 .     

鸠江南路青弋江大桥设计简介

主要介绍青弋江大桥的设计过程，详细说明其桥址处的环境水文情况，依据其服役环境对主体桥梁和引桥进行了选线分析，整体选用S型线位布置。同时，利用自主开发的平面有限元软件SCDS对主桥箱梁横纵向承载力进行了计算分析，并利用Midas软件进行验算。该桥桥型新颖，结构复杂，具有一定的先进性。