Brittle failure caused by lamellar splitting in a large-scale tubular joint with fatigue cracks

This paper reports a new incidence of brittle failure by lamellar splitting in a large-scale tubular X-joint and examines the possible causes of this failure. The X-joint, with multiple pre-existing fatigue cracks at the weld toe along the brace-to-chord intersection, experiences brittle failure during a monotonic in-plane bending test. Post-test sectioning of the material around the brace-to-chord intersection reveals lamellar splitting in the mid-thickness of the chord wall instead of rapid extensions of the fatigue cracks in the through-thickness direction. The lamellar splitting observed in this test differs from the conventional lamellar tearing both in its appearance and in its causes. The elongated nonmetallic inclusions concentrated at the mid-thickness, as revealed by the microscopic scanning, leads to delamination cracking near the mid-thickness and subsequently to the brittle failure of the joint. The material requirements in prevailing engineering codes do not suffice to prohibit the lamellar splitting failure observed in this study, which may cause catastrophic failures in engineering structures designed with insufficient redundancy.     

32万吨原油船挂舵臂铸造检验

32万吨挂舵臂是目前中国船级社检验的最大船用铸钢件,具有产品结构复杂、体积庞大、检验标准高、生产工艺难度大的特点。目前该挂舵臂已经完工,符合产品检验要求,在这里通过建造过程,对其检验的要点进行总结。     

残余应力对船舶建造质量的影响及控制

摘船舶设计阶段,主要是按照外载荷对船体结构进行强度校核,未充分考虑到建造过程中构件所产生的残余应力的影响。从船厂生产实际出发,分析船舶建造的过程中容易产生残余应力的部位以及产生原因,并对典型部位的残余应力进行分析。结合船体建造过程及船舶航运期间出现的若干质量问题,提出了一系列的优化改进工艺,从实际生产反馈的效果来看,具有较好的适用性和可行性。     

长兴潜堤后方滩涂圈围工程疏浚土利用研究*

疏浚土正逐渐成为长江口滩涂造地泥沙资源供给的有效补充。长兴潜堤后方滩涂圈围工程紧邻长江口12.5 m深 水航道南港圆圆沙段,航道疏浚土利用的区位优势显著。在调查掌握南港圆圆沙段航道疏浚土产量、分布、土质及稳定性 的基础上,针对圈围工程特点,比选适合的疏浚吹填工艺,并提出可行的吹泥上滩技术方案。结果表明：南港圆圆沙段航 道疏浚土产量丰富稳定、运距短且土质条件较好,可满足圈围工程吹填用砂的要求。各类疏浚吹填工艺中,艏吹和耙吸装 驳工艺的技术适用性较好,现阶段可采用技术成熟的艏吹方案进行疏浚吹填,而耙吸装驳方案可作为备选,待2013年底正 式投入运营时可应用于圈围工程。研究成果为圈围工程吹填开辟了砂源,实现了航道疏浚与圈围造地的双赢。     

考虑荷载作用下抗力时变特性的沿海钢筋混凝土结构可靠度分析

针对海洋环境下钢筋混凝土结构破坏影响因素复杂的特点,建立了荷载作用下的氯离子侵蚀模型和钢筋锈蚀率模型;将钢筋混凝土构件的抗力和作用荷载均视为随机过程,并离散为设计基准期内服从某种分布的随机变量,通过改进的一次二阶矩法计算结构的可靠度指标,建立了荷载作用下考虑构件抗力时变特性的海洋环境下钢筋混凝土结构可靠度分析方法。通过高桩码头的算例说明了该方法的可行性,研究了荷载作用对结构耐久性和承载力寿命的影响。     

Evaluating competitiveness using fuzzy analytic hierarchy process—A case study of Chinese airlines

With the development of a national market economy, the Chinese aviation industry is now confronted with international competition. Therefore, it is necessary to research the competitive status of Chinese national aviation, as well as advice on how to enhance the competitiveness of the Chinese aviation industry. The main objective of this paper is to propose FAHP as an effective solution for resolving the uncertainty and imprecision in the evaluation of airlines' competitiveness. In this paper, we review the research of industrial international aviation competitiveness at both home and abroad, discuss a theoretical framework for the study of aviation competitiveness, establish an index system with five first‐order indicators and 17 second‐order indicators, set up a Chinese aviation competitiveness model based on simple fuzzy numbers from the fuzzy analytic hierarchy process, and evaluate the competitiveness of five major Chinese airlines. The results showed that this model and these indicators are scientific and practical, with a wide range of application prospects for the purpose of improving and increasing Chinese airline competitiveness in the international market. The effective approach presented in this paper is especially applicable when subjective judgments on performance ratings and attribute weights are not accessible or reliable, or when suitable decision makers are not available. Copyright © 2011 John Wiley & Sons, Ltd.     

基于AHP的舰船器材仓库选址方法研究

分析了目前舰船器材仓库的现状和存在问题,提出了将AHP法运用于仓库选址的决策方法,结合实例肯定了AHP法能够为舰船器材仓库选址方案的优选提供一个客观、科学的定量与定性分析相结合的方法和决策手段。     

气垫船复合材料导管支臂制备工艺与性能试验

分析气垫船(Air-Cushion Vessel,ACV)复合材料导管支臂制备工艺的可行性,对导管支臂样件材料的组合设计方案进行优化,确定混合纤维环氧树脂复合材料-泡沫夹芯作为导管支臂材料.考虑导管支臂结构制造的经济性和可操作性,选择整体成型模式,采用真空导入模塑工艺(Vacuum Infusion Molding P...     

票价优惠政策下的 BRT系统绩效评价

出于对我国政府在城市公共交通财政投入项目绩效评价工作的需要,利用网络分析原理,提出票价优惠政策下的BRT系统绩效评价指标体系。对政府公共交通票价优惠政策和快速公交绩效影响因素进行分析;结合公共交通政策和绩效影响因素分析结果构建基于网络分析的综合评价模型;采用超级决策软件对评价模型进行计算;结合广州市2011年度公交票价优惠政策绩效评价实例结果表明:计算结论与市民满意度调查的分析结果一致,从而验证了网络分析方法的可行性。      

基于纯电动公交车的场站设施体系规划研究

纯电动公交车推广已成为城市低碳交通方式重要引擎,结合盐田纯电动汽车场站设施概念规划,分析充电流程及场站规模发展诉求,可为制定地区纯电动汽车场站体系构建模式提供参考。