A statistical investigation of time-variant hull girder strength of aging ships and coating life

Risk- and reliability-based approaches are increasingly being applied in assisting inspection and maintenance planning. One of the keys to such approaches is properly predicting the hull girder strength (HG) of gradually degradated hull structures. The development has been limited by the lack of data on aging ships—validation of the developed methods has not been possible. To fill the gap of knowledge on hull strength of ships in service, this paper presents a database of as-gauged hull structures and a statistical study of the time-variant HG of tankers. The expanded data set was collected from 2195 as-gauged girth belts (transverse sections) of 211 single-hull tankers that were 12–32 years old. It was intended to (1) provide actual data on hull girder section modulus (HGSM) of tankers, (2) investigate the general trends of the change in the HG over ships’ service life, and (3) propose formulations for presenting time-variant HGSM and coating life.

The data set demonstrated a high variation of HGSM that changed over time. The mean value and standard deviation of HGSM loss were derived as functions of time. The probability density function (pdf) of coating life was also derived. Comparisons were made between previous studies on HG and the current data set. It was found that almost all previous studies showed much greater HG loss than what this database revealed. The refinement of existing calculations appears to be needed. The data set and statistical study were expected to form the basis for validating formulations of HG that are key components in risk- and reliability-based approaches.     

浅论中学思想政治课教学环节的提高和优化

中学思想政治教育在素质教育中占有重要地位,加强中学生思想政治教育,已成为素质教育的当务之急。本文针对素质教育对中学思想政治教育提出的要求,从教学过程和"施教者"这两个方面加以论述,提出了优化中学思想政治课的方法和途径。     

石太客运专线GSM-R无线网络优化案例分析

对石太客运专线GSM-R无线网络优化的典型案例进行分析,采用调整无线资源参数、小区天线工程参数,以及整治直放站设备等手段,解决石太客专GSM-R无线网络质量问题。     

水下船体表面清刷机器人方案研究

介绍一种新型的用于船体表面清刷、涂装等作业的水下船体表面清刷机器人总体组成、基本功能和工作原理，并提出了机械本体、清刷作业装置和控制系统三部分的设计方案。该机器人具有工作效率高，安全性好等优点。     

VLGC全船结构有限元分析研究

超大型全冷式液化气船（VLGC）由于其结构的复杂特性,需进行全船结构有限元分析以准确评估结构强度。本文对VLGC全船有限元分析方法、流程进行了研究,对一系列技术关键点进行了讨论,并结合目标船进行FEA建模和计算分析工作。对计算结果进行了分析和讨论,得出相关结论,对该类复杂船型的主船体结构、支承系统以及A型独立液货舱的设计具有重要参考意义和指导作用。     

竞赛帆船龙骨盒结构优化设计

龙骨盒是竞赛帆船特有的结构,其功能是维持压载龙骨竖直升降,因其为帆船主要受力构件之一,实际使用中易损坏,提高龙骨盒强度是企业和艇主亟须解决的问题。通过水动力分析获得龙骨盒结构响应,运用多级优化对龙骨盒帽型材和桅杆作用区域进行形状、尺寸优化和铺层顺序优化。优化结果显示,基于响应面法和遗传算法的多级优化降低75.92%的龙骨盒整体应变能和提高29.40%的铺层强度比,该方法对提升龙骨盒强度和承载能力具有实用和借鉴意义。     

超大型全回转浮吊轮压分析及优化研究

在全回转浮吊中,滚轮在提供回转能力的同时,起着支撑压力和平衡倾覆力矩的作用。研究轮压的形成及优化对回转浮吊的设计有着重要的意义。文章解析了轮压分布的物理要素,并通过有限元模型进行了验证,所得到的思路及分析成果解决了回转浮吊轮压分布规律的原理性问题,必然会对设计有一定的借鉴作用。     

Effect of pitting corrosion on the ultimate strength of steel plates subjected to in-plane compression and bending

Corrosion pits with a circular cone shape are typically observed on coated hold frames of aged bulk carriers which carry exclusively coal and iron ore. In order to ensure the safety of these types of bulk carrier, it is necessary to understand the effect of pitting corrosion on the local strength of hold frames. In order to investigate this effect, a series of nonlinear finite-element (FE) analyses has been performed with pitted plates subjected to in-plane compressive loads and bending moments. It has been shown that the ultimate compression load or bending moment of pitted plates is smaller than that of uniformly corroded plates in terms of average thickness loss, and that predictions of the ultimate strength using the average thickness loss at the minimum cross section would be conservative. In order to establish a method of evaluating strength reduction due to pitting corrosion, it is important to identify the failure mode that would be most detrimentally affected by pitting corrosion. It was found that the reduction of the ultimate compressive load or bending moment due to pitting corrosion is smaller than that of the tensile strength in terms of equivalent thickness.     

编组站驼峰空压动力站的优化设计

本文通过对以往设计或调研的编组站驼峰空压动力站进行回顾和分析，在确保编组站运营安全的前提下进行优化，得出合理的配置，为设计或使用单位提供一些参考，同时也是对国家节能减排政策的积极响应。