波激振动和砰击颤振对大型油船疲劳强度影响研究

文章给出线性波激振动和砰击颤振引起的大型油船结构疲劳贡献度的计算方法。基于三维线性水弹性理论可计算得到包括刚体和2节点的振动模态下的垂向弯矩的传递函数,采用谱分析法对某30万吨油船进行结构疲劳强度计算,分析波激振动对船体结构疲劳损伤影响;基于二维非线性波浪载荷程序（含砰击颤振的波浪载荷）,采用时域方法对该油船进行船体梁弯矩计算,分析砰击颤振对船体梁弯矩及疲劳载荷的影响;结果表明对于该类大型油船波激振动和砰击颤振对船体的结构疲劳损伤的影响不可忽略。     

考虑波激振动的超大型船舶疲劳损伤计算

超大型船舶由于相对刚度较低,导致波激振动现象明显。常规的准静态谱分析法未考虑船体的弹性特征及与水动力载荷的耦合效应,无法求解考虑波激振动下的船舶疲劳损伤问题。针对上述问题,以应力模态叠加法为基础,来解决考虑波激振动影响时的船体疲劳强度评估问题,并以某超大型矿砂船为例进行疲劳计算,将结果与准静态谱分析法的结果进行对比分析。结果表明：计及波激振动效应,疲劳应力响应在高频段出现双峰甚至多峰现象,峰值点出现在遭遇频率接近船体固有频率时。波激振动效应使船体结构疲劳寿命大大降低,对于北大西洋海况,船舶在压载工况下的波激振动效应相较满载工况更明显。此方法对解决考虑波激振动下的船舶疲劳评估问题具有一定的参考意义。     

考虑水弹性效应的船体监测疲劳损伤评估方法

船舶结构应力监测系统作为智能船体的主要技术手段之一,近年来已逐步应用于高性能船和大型运输船,但考虑波激振动、砰击颤振水弹性效应的船体结构监测技术,目前还少有应用实例。超大型集装箱船船体梁刚度较小、大外飘船艏结构等特点使得波浪中更容易发生共振与颤振,这些波浪诱导的高频成分对船体结构的疲劳影响需要进一步研究。本文考虑波激振动等水弹性效应影响,对风浪中航行的超大型船舶进行了结构疲劳损伤评估分析方法的研究,并对一艘21 000 TEU集装箱船实船监测数据进行了数据分析,量化研究了波激弹振对监测结构疲劳寿命的影响。     

基于三维水弹性方法散货船运动与波浪载荷分析

采用三维有限元方法分析船体干结构在真空中的振动模态,结合模态叠加法和边界元法计算船体在流场中的水弹性主坐标响应,给出船体剖面载荷。讨论波激振动对船体结构疲劳损伤的影响,分析表明,大型船舶的弹性效应较为明显,在高频处容易发生波激振动现象,而波激振动加大了船体结构的疲劳损伤。     

基于雨流计数法的高低频复合疲劳试验研究

船体固有频率与遭遇波浪频率及其倍频相接近时,波浪载荷极易引起船体结构产生持续的波激振动现象,对大型船舶结构疲劳损伤的影响达到40 %以上。因此,有必要针对波激振动引起的非线性垂向弯矩载荷特点,开展高低频复合工况下典型切口试件疲劳试验及累计损伤分析研究。基于非线性随机载荷的分析方法,采用闭合雨流计数法提取叠加应力历程中的多级循环载荷,并结合平均应力修正方法和疲劳极限以下SN曲线局部修正法,对叠加应力历程中小载荷的损伤效应展开研究。分析结果表明,高低频载荷叠加产生的附加损伤效应对疲劳寿命的影响显著,在恒定应力比下随平均应力的变化近似成二次函数关系。考虑高频小载荷的叠加应力历程疲劳寿命明显降低,可以通过修正累计损伤临界值或引入应力放大因子,近似的利用线性累积损伤理论预测实际叠加应力历程的寿命范围。     

基于模型试验与三维水弹性理论的船舶波激振动响应研究

船体波激振动使得船体结构中产生高频、持续和具有一定幅值的振动应力,可能引起结构发生严重的疲劳损伤,因而对船舶结构的安全性带来严峻的挑战。文章以一艘大型LNG船为研究对象,采用三维线性水弹性理论与水池模型试验方法对船舶波激振动响应进行了比较分析,研究了规则波与不规则波中的波激振动特性。改变该LNG船的刚度,并保持船型、重量分布等其它主船体特征不变,在模型试验和理论计算中探讨了刚度对波激振动的影响。通过两种刚度船体梁的模型试验与理论计算结果的比较分析,给出了波浪周期和船体刚度的变化对波激振动影响的几点结论。     

船舶波激振动研究进展

随着船舶大型化的发展,高强度钢的大量使用,对于船舶长度超过300m以上的大型船舶来说,波激振动现象逐渐突出。波激振动是一种高频谐振,它对船体结构的疲劳寿命产生重大影响。文章从理论预报、模型试验和实船测试三个方面对船舶的波激振动现象进行综合性的阐述,并提出当今船舶波激振动领域的研究展望。     

基于谱分析法的FPSO剩余疲劳寿命研究

疲劳破坏是船舶与海洋工程结构破坏的主要模式之一。多年来,船舶结构的疲劳断裂问题一直是造船界广泛关注的问题[1]。对于由大型油船改装而成的FPSO而言,预测并延长其服役寿命是很关键的。本文通过谱分析法对船体疲劳损伤度进行计算,分别对油船和FPSO阶段进行计算从而得到FPSO剩余疲劳寿命。通过建立3D有限元模型,采用热点应力方法来确定评估处应力传递函数,分别计算各个短期海况损伤度并通过线性叠加来计算总的损伤度以及剩余疲劳寿命。根据疲劳评估结果,更加高效地实施船体结构的检测及维修。     

超大型油船波激振动研究

本文论述了超大型油船发生波激振动的机理、波激振动的实船测量及船模试验，波激振动理论预报方法，探讨了它对超大型油船总纵强度及疲劳寿命的影响。     

基于HCSR和CSR—OT的油船疲劳有限元法对比分析

为了对比新的散货船、油船协调共同规范和旧的双壳油船结构共同规范,选取两艘具有水平桁结构和两艘具有槽型舱壁油船作为研究对象,对这两种不同结构形式的油船,分别按HCSR和CSR规范的要求,进行加载分析计算疲劳寿命,并基于CSR规定,比较底边舱下折角位置处的疲劳寿命。认为HCSR疲劳载荷选取更加合理,评估体系更加严格。     

HCSR规范疲劳筛选方法研究

分别对1型散货船和1型油船的有限元模型进行t×t和50 mm×50 mm的网格细化分析,总结出散货船油船协调共同规范(HCSR规范)中疲劳筛选方法的应力放大因子,并验证该方法应力放大因子的合理性。     

Extensive study on the design loads used for strength assessment of tanker and bulk carrier structures

ClassNK has undertaken wide-ranging basic research covering many aspects related to the safety of ship structures, including design loads, structural analysis, strength assessment of buckling, collapse, and fatigue, and rational corrosion margins to develop new design standards which have transparency and consistency. Among the wide-ranging basic research, this article summarizes the results of extensive work on the design loads used for strength assessments of tanker and bulk carrier structures. The main aim of the research was to develop practical estimation methods of design loads with rational technical backgrounds relating to the actual loads acting on the primary structural members of tankers and bulk carriers. During this study, we proposed the following methodology. Design sea states that closely resemble the actual sea states which are considered to be the most severe for hull structures. Find practical estimation methods for the design sea states by parametric studies using the results of series calculations on representative tankers and bulk carriers. Find practical estimation methods for design regular waves which will result in the same level of stresses as those induced in irregular waves under the design sea states. We also briefly introduced some practical estimation methods for the design loads, such as ship motions, accelerations, hull-girder bending moments, and hydrodynamic pressures that are induced under design regular waves. The findings in this study have been summarized and implemented in the new design standards for tanker and bulk carrier structures.Updated from the Japanese original which won the 2003 SNAJ prize (J Soc Nav Archit Jpn 2002; 191:195–207; 2002; 191:208–220; and 2002; 192:723–733)     

大型集装箱船弹振和颤振研究简

随着集装箱船尺度的迅猛增大,弹振和颤振已成为大型集装箱船设计中需要重点关注的问题。从船舶运动和波浪砰击的角度出发,对大型集装箱船弹振和颤振的计算方法和模型试验进行了研究。研究表明,弹振和颤振对大型集装箱船体的结构强度和极限强度都有重要影响,在恶劣海况下,弹振和颤振对船体的影响甚至已经超过波浪对船体的影响。     

进口原油运输船型经济性分析

石油是世界海上运量最大的货种之一,约占海上总运输量的三分之一。加入WTO后,中国石油海上运输量,特别是进口原油运输量将大幅度地增加。针对这一现实情况,本文对世界原油运输船队的技术经济作了概括性分析,对原油进口航线作了介绍。建立了单船运输经济性测算模型。基于实船经济指标测算结果,以必要运费率为主,通过比较选出了优良船型。并定量测算出不同类型船舶在同一航线上营运的必要运费率及其差异。研究结果指出,随着进口原油量的大幅度增加,中国应大力发展VLCC和Suezmax船队,重点建设大型深水油轮码头。     

Long-term correlation structure of wave loads using simulation

This paper proposes a new method for combining the lifetime wave-induced sectional forces and moments that are acting on the ship structure. The method is based on load simulation and can be used to determine the exceedance probabilities of any linear and nonlinear long-term load combination. It can also be used to determine the long-term correlation structure between these loads in the form of the long-term correlation coefficients. They are essential part of the load combination procedures in design and strength evaluations as well as in the fatigue and reliability analysis of ship structures.The simulation method treats the non-stationary wave elevations during the ship’s entire life (long-term) as a sequence of different stationary Gaussian stochastic processes. It uses the rejection sampling technique for the sea state generation, depending on the ship’s current position and the season. Ship’s operational profile is then determined conditional on the current sea state and the ship’s position along its route. The sampling technique significantly reduces the number of sea state-operational profile combinations required for achieving the convergence of the long-term statistical properties of the loads. This technique can even be used in combination with the existing long-term methods in order to reduce the number of required weightings of the short-term CDFs. The simulation method does, however, rely on the assumption that the ship is a linear system, but no assumptions are needed regarding the short-term CDF of the load peaks.The load time series are simulated from the load spectra in each sea state, taking into account the effects of loading condition, heading, speed, seasonality, voluntary as well as involuntary speed reduction in severe sea states and the short-crested nature of the ocean waves. During the simulation procedure, special care has been given to maintaining the correct phase relation between all the loads. Therefore, time series of various load combinations, including the nonlinear ones, can be obtained and their correlation structure examined. The simulation time can be significantly reduced (to the order of minutes rather than hours and days) by introducing the seasonal variations of the ocean waves into a single voyage simulation. The estimate of the long-term correlation coefficient, obtained by simulating only a single voyage with the correct representation of seasonality, approaches the true correlation coefficient in probability. This method can be applied to any ship and any route, or multiple routes as long as the percentage of the ship’s total lifetime spent in each of them is known.A study has been conducted to investigate the effects of ship type, route and the longitudinal position of the loads on the values of the correlation coefficients between six different sectional loads; vertical, horizontal and twisting moments, as well as shear, horizontal and axial forces. Three ocean-going ship types have been considered; bulk carrier, containership and tanker, all navigating on one of the three busy ship routes; North America-Europe, Asia-North America and Asia-Europe. Finally, the correlation coefficient estimates have been calculated for five different positions along the ship’s length to investigate the longitudinal variation of the correlation coefficient.     

5万吨级成品油船典型节点设计优化

随着油船共同结构规范(CSR)的推出,对油船的设计和开发影响很大,但业界讨论的大多是对规范实施中的变化、计算方法及计算工具等,如何详细分析评估油船结构节点的强度则较少提及。在此,基于CSR给出的油船结构节点细化分析的实施要求及衡准,以某5万吨级成品油船的槽形横舱壁顶凳底板与舷侧水平桁相交区域和槽形横、纵舱壁顶凳底板十字相交区域为例,对节点不同设计方案进行计算,经比较分析取得符合CSR的结构要求和衡准的设计方案。整个方案设计的过程及对油船典型节点的细化分析,可供同行在节点设计中参考。     

船舶结构疲劳评估简化方法对比研究

讨论船舶结构疲劳强度校核的简化方法的应用及计算步骤,基于CCS及CSR规范,以一艘40000t成品油船为实例,进行疲劳评估计算,并分析比较用两种方法计算的差异和相近之处.