基于非线性设计波的船体结构强度直接计算研究

针对规范公式不适用于小方形系数Cb<0.6的船舶以及线性设计波法不能反映波浪载荷非线性特征的情况,使用非线性设计波法研究了一艘小方形系数船的波浪载荷长期预报极值和波浪载荷与波高非线性变化规律,给出了非线性设计波参数的选取办法。根据参数,用非线性设计波法计算了船舶的波浪附加弯矩,并与线性设计波和规范公式两种方法得到的波浪附加弯矩进行了比较分析。分析结果表明,非线性设计波法能够反映出波浪幅值较大时波浪载荷随波高非线性变化的规律,以及中拱、中垂状态下舯剖面波浪附加弯矩的非对称特征,较线性方法更为合理。

腐蚀疲劳作用下的船舶极限强度可靠性分析

由于腐蚀和疲劳的综合作用,船舶舯横剖面模数随时间减少,造成船体结构承载能力降低。本文通过对腐蚀和疲劳作用的定量分析,提出一种船体结构可靠性的计算方法。建立随时间变化的腐蚀、疲劳及剖面模数的模型,并通过一阶二次矩法计算船体瞬时可靠性,得出了船舶全寿命期内舯横剖面的剖面模数、可靠性指标随时间的变化曲线。

再论货驳“843”的总体断裂破坏事故

从营运船舶总强度以及极限总强度的观点出发 ,重新对货驳“843”的总体断裂破坏事故进行了分析 ,认为引起该驳断裂破坏的主要原因是总强度储备不足 ,不合理的卸货方法 ,船体构件的严重腐蚀 ,制造中的焊接缺陷以及船底构件的损伤累积等诸多不利因素的综合 ,导致该驳的总体断裂破坏。

关于《花航拖八》号壳板产生裂缝原因分析及改进措施

《花航拖八》号内河钢质拖轮,在营运中船体机舱区域壳板出现严重裂缝,其原因究竟是主体材料问题,还是主机系统影响,亦或是船体结构布置问题,下面作一简要分析。 一、概况 随着珠江航运事业的蓬勃发展,航行于珠江水系的120马力至40马力内河拖轮为数不少,这类小型钢质拖轮有不少是由县属地方船厂建造的,这些船厂大部分是设备简陋,工人技术素质不高,加上有些地方验船部门专业人员不齐全,对送审的图纸没有进行严格的审查,因此往往造成不同程度的隐患。例如,“花航拖八”号钢质拖轮是由某县级船厂设计与制造,为单底、横骨架式、大开口隧道船,总长19.2米、型宽3.8米、型深1.0米,主机为上柴4135型柴油机一台,配杭州120A型齿轮箱,速比2∶1。该船船体结构按1973年《长江水系小型钢船建造规范》内河B级航区设计,船底板厚为5公厘,其它壳板厚4公厘,于一九八二年十一月竣工。该拖轮投入营运后,机舱壳板出现纵、横方向的裂缝,由于当时处理不妥,隐患继而发生,只能停航上排提交广州船检报验。为此,笔者首先全面查阅了船体设计图纸和结构计算书,并作现场分析。

The Effects of Stochastic Characteristics of Materials on the Reliability of a Composite Ship Hull

The effects of stochastic characteristics of materials on the reliability of ship hulls made of composite materials under longitudinal moment were extensively studied using reliability and sensitivity calculations of a composite ship hull which was sagging.The reliability indices and failure probabilities of the ship in three kinds of failure modes (buckling,material failure,and ultimate collapse) were calculated by the surface response method and JC method.The importance factors of random variables in stochastic models,such as the model errors in predicting the ultimate longitudinal strength of ship and the longitudinal bending moment that the ship withstands,as well as the stochastic characteristics of materials in the models used,were calculated.Then,the effects of these random variables,including the stochastic characteristics of materials on the reliability index and the failure probability of ships which were sagging,were discussed with their importance factors.The results show that the effects of stochastic characteristics of materials on the reliability of ship hulls made of composite materials should be considered during the reliability assessment of composite ships.Finally,some conclusions and recommendations were given for high-speed ship design and safety assessment.