现役散货船纵向构件蚀耗率的概率估算

该文以现役散货船测厚报告的数据料为基础,设船体纵向件的蚀耗率为服从威布尔分布的随顶变量,对其数字特征进行估算,并以其频率近似概率,给出了各构件蚀耗率的概率密度曲线、概率率分布曲线及超概率分布曲线。结合参考文献提供的数据,计算出了外板和内底板蚀耗率的均值随船龄变化曲线,从而为船体结构的强度评估和寿命预测提供了有益的参考依据。     

考虑腐蚀与疲劳损伤的船体总纵极限强度与可靠性分析

本文定量考虑了腐蚀与疲劳两类损伤对船体结构随时间变化的情况,并建立了船体总纵极限强度与时变可靠性的计算方法。对一条实船的分析说明,腐蚀和疲劳损伤虽然短时间内的破坏并不显著,但积累到一定程度,对船体结构的影响相当大。采用可靠性评估的方法,对船体总纵强度的安全水平可作出合理的评价。     

RD2轴卸荷槽部位腐蚀疲劳裂纹的失效分析

在现场调研的基础上,对典型失效样品进行失效分析。常规检验和对表面腐蚀坑、裂纹的宏微观分析表明,裂纹从腐蚀坑处萌生,沿着大体垂直于表面的方向向内穿晶扩展;扫描电镜能谱分析表明,腐蚀坑内的产物主要含Fe,Mn,Si,S等;X射线光电子谱分析得出,表面腐蚀产物主要有:Fe2O3,FeCl2,FeSO4,NH3,Si3N4等。由此综合分析推断,介质中主要含有H2O,Cl-,SO2-4等。结合卸荷槽部位的结构特点及受力情况,得出结论:引起RD2轴卸荷槽部位腐蚀疲劳裂纹的主要原因为大气腐蚀。为制定有效预防措施提供了可靠依据,对确保行车安全有重要意义。     

油气管道焊接接头的应力腐蚀及防护

焊接过程引起焊接接头组织和力学性能的不均匀性。通过研究焊接接头应力腐蚀的规律,发现焊缝比母材具有更高的应力腐蚀敏感性;焊缝硬化层越宽对应力腐蚀越敏感;工作温度越高应力腐蚀敏感电位区间越宽;适量的加入合金元素可提高焊接接头的抗应力腐蚀能力;改善介质条件也是很重要的方面。     

海底隧道注浆材料耐腐蚀性能研究及工程应用北大核心CSCD

海水具有较强的腐蚀性,极容易通过围岩薄弱区域侵蚀破坏隧道衬砌结构,为保证支护结构的耐久性,文章以普通硅酸盐水泥为基材,通过调节减水剂、速凝剂和高分子聚合物的掺量来设计耐腐蚀注浆材料的配合比,并对不同配合比注浆材料进行了耐腐蚀指标测试和现场注浆效果检验。室内试验结果表明,该注浆材料试块(水灰比为0.65~1.0)在海水浸泡360 d的强度腐蚀系数大于0.80,体积稳定性良好;为加快侵蚀速度,将试块浸泡在饱和MgSO;溶液中,注浆材料试块(水灰比为0.65)浸泡360 d的强度腐蚀系数大于0.80,体积稳定性仍良好。通过现场注浆试验对结石体强度进行测试,测试结果表明,在饱和MgSO4溶液中浸泡180 d的浆液结石体的点荷载强度均值为0.931 kN,比未浸泡试块的强度均值0.984 kN减少了5.5%,进一步验证了注浆材料的耐腐蚀性能。     

Experimental strength analysis of steel plates with a large circular opening accounting for corrosion degradation and cracks subjected to compressive load along the short edges

This work studies the combined effect of both geometrical characteristics (opening and initial imperfections) and age related damage (corrosion and cracks) on the local and global responses of thin rectangular steel plates. A series of experimental tests has been conducted for in-service steel plates with a circular opening and subjected to several damage actions and uni-axial compression. Different initial imperfection shapes and amplitudes, corrosion degradation levels and locked crack lengths are considered. Several collapse modes were observed and the reasons for their occurrence are discussed. The experimental results of force-displacement and stress––strain relationships are presented and the relevant dissipated energies, resilience and toughness are estimated. The experimental results are compared with published experimental results, confirming the complexity of the plate behaviour accounting for different damage scenarios.     

Statistical properties of bulk carrier longitudinal strength

The paper focuses on time-variant longitudinal strength of bulk carriers under corrosion wastage, applying both Taylor series expansion method and Monte Carlo simulation. Hull girder section modulus and ultimate bending moment capacity are determined, by classical beam theory and the commonly applied incremental-iterative approach, respectively. Two main aspects are fully discussed and investigated, according to the final recommendations of last ISSC Report. The former regards the covariance between annual corrosion rates of individual structural members, commonly assumed as uncorrelated. Really, as it is conceivable that a certain correlation exists, three different cases are investigated: uncorrelated variables, fully correlated variables, full correlation between structural members belonging to the same category of compartments. The latter investigates the probability density function of both hull girder section modulus and ultimate bending capacity, because the Central Limit Theorem cannot be applied when correlation among random variables exists. Finally, as a test example, the bulk carrier section, presented in the last ISSC benchmark study, is analysed.     

阴极保护在海洋工程中的应用研究

文章介绍了阴极保护基本工作原理,并阐述了其在海洋工程中对控制船体外壳防锈方面的应用。实例证明,在海洋工程中采用外加电流阴极保护更有优势。     

地下水对混凝土侵蚀性的热力学研究

采用化学热力学方法分析地下水对混凝土的碳酸型、硫酸盐型及硫氢酸型侵蚀。以新建渝怀线圆梁山隧道为实例,对隧道内地下水取样进行全分析,依据水质分析结果设计了五个化学反应方程式,利用德拜-休克尔极限公式及反应平衡常数与吉布斯自由能间的关系式进行活度和热力学计算,得到三组二氧化碳分压对数值和二组反应进行方向判据数值,继而依据创建的二氧化碳分压与反应进行方向的两组判据进行判别分析。分析结果表明,圆梁山隧道地下水对混凝土具有弱碳酸型侵蚀,不存在硫酸盐型侵蚀;由于逸出天然气中的H2S的溶解度较小,可不考虑H2S作用的硫氢酸侵蚀。     

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.