80米甲板运输船结构设计与有限元计算外文翻译资料

 2022-09-20 10:32:36

Numerical study onensp;fatigueensp;crack growth at a web-stiffener of ship structural details by an objected-oriented approach in conjunction with ABAQUS

It is necessary to manage the fatigue crack growth (FCG) once those cracks are detected during in-service inspections. This is particular critical as high strength steels are being used increasingly in ship and offshore structures. In this paper, a simulation program (FCG-System) is developed utilizing the commercial software ABAQUS with its object-oriented programming interface to simulate the fatigue crack path and to compute the corresponding fatigue life. In order to apply FCG-System in large-scale marine structures, the substructure modeling technique is integrated in the system under the consideration of structural details and load shedding during crack growth. Based on the nodal forces and nodal displacements obtained from finite element analysis, a formula for shell elements to compute stress intensity factors is proposed in the view of virtual crack closure technique. Neither special singular elements nor the collapsed element technique is used at the crack tip. The established FCG-System cannot only treat problems with a single crack, but also handle problems with multiple cracks in case of simultaneous but uneven growth. The accuracy and the robustness of FCG-System are demonstrated by two illustrative examples. No stability and convergence difficulties have been encountered in these cases and meanwhile, insensitivity to the mesh size is confirmed. Therefore, the FCG-System developed by authors could be an efficient tool to perform fatigue crack growth analysis on marine structures.

Probabilistic methods for planning of inspection forensp;fatigueensp;cracks in offshore structures

Due to the nature of the fatigue phenomena it is well known that small changes in basic assumptions for fatigue analysis can have significant influence on the predicted crack growth lives. Calculated fatigue lives based on the S–N approach are sensitive to input parameters. Fracture mechanics analysis is required for prediction of crack sizes during service life in order to account for probability of detection after an inspection event. Analysis based on fracture mechanics needs to be calibrated to that of fatigue test data or S–N data. Calculated probabilities of fatigue failure using probabilistic methods are even more sensitive to the analysis methodology and to input parameters used in the analyses. Thus, use of these methods for planning inspection requires considerable knowledge and engineering skill. Therefore the industry has asked for guidelines that can be used to establish reliable inspection results using these methods. During the last years DNV GL has performed a joint industry project on establishing probabilistic methods for planning in-service inspection for fatigue cracks in offshore structures. The recommendations from this project are now included in a Recommended Practice. The essential features of the probabilistic methods developed for this kind of inspection planning are described in this paper.

Time-variant bulk carrier reliability analysis in pure bending intact and damage conditions

Time-variant reliability analysis of a corroded bulk carrier in intact and damage conditions is performed by First-Order (FORM), Second-Order (SORM) Reliability Methods and Importance Sampling simulation. Annual failure probabilities are determined up to 25-year ship lifetime, accounting for time-variant corrosion wastage of structural members contributing to hull girder strength. Statistical properties of hull girder capacity are determined by Monte Carlo simulation, applying three correlation models among corrosion wastages of structural members contributing to hull girder strength, namely no correlation, full correlation and full correlation among wastages of structural members belonging to the same category of compartments. A modified incremental-iterative method is applied, to account for instantaneous neutral axis rotation, in case of asymmetrical damage conditions, as for collision and grounding events. Incidence of intact/damage condition, as well as correlation among corrosion wastages, on annual sagging/hogging time-variant failure probability is investigated and discussed. Time-variant sensitivity analyses for intact and damage conditions are also performed, to investigate the incidence of random variables uncertainties on the attained failure probability. Finally, the bulk carrier section scheme, benchmarked in the last ISSC Report, is applied as test case.

A simple parametric formulation for the seabed trench profile beneath a steel catenary riser

Seabed trench has a profound influence on the fatigue performance of a steel catenary riser (SCR) at the touchdown zone. At present, the most well-regarded approach for simulating the complex trench development process is by applying a nonlinear hysteresis seabed contact model, which is time consuming. Field observations have indicated that the trench depth almost stabilizes after a few months following installation. Hence, for practical fatigue design, it is expedient to specify an initial static trench profile to perform the dynamic simulations. This paper presents a new simple parametric formulation for delineating an initial trench profile, as there appears to be no such approach in the literature. The formulation entails two unknown trench parameters (trench length and global trench position), which can be determined usi

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Numerical study onensp;fatigueensp;crack growth at a web-stiffener of ship structural details by an objected-oriented approach in conjunction with ABAQUS

It is necessary to manage the fatigue crack growth (FCG) once those cracks are detected during in-service inspections. This is particular critical as high strength steels are being used increasingly in ship and offshore structures. In this paper, a simulation program (FCG-System) is developed utilizing the commercial software ABAQUS with its object-oriented programming interface to simulate the fatigue crack path and to compute the corresponding fatigue life. In order to apply FCG-System in large-scale marine structures, the substructure modeling technique is integrated in the system under the consideration of structural details and load shedding during crack growth. Based on the nodal forces and nodal displacements obtained from finite element analysis, a formula for shell elements to compute stress intensity factors is proposed in the view of virtual crack closure technique. Neither special singular elements nor the collapsed element technique is used at the crack tip. The established FCG-System cannot only treat problems with a single crack, but also handle problems with multiple cracks in case of simultaneous but uneven growth. The accuracy and the robustness of FCG-System are demonstrated by two illustrative examples. No stability and convergence difficulties have been encountered in these cases and meanwhile, insensitivity to the mesh size is confirmed. Therefore, the FCG-System developed by authors could be an efficient tool to perform fatigue crack growth analysis on marine structures.

船舶如果在服役期间检查出了裂纹，就有必要进行疲劳裂纹扩展（FCG）的监控。船舶与海洋结构物越来越多地使用高强度钢，因此进行疲劳裂纹扩展（FCG）的管理尤其重要。本文介绍了一个利用ABAQUS（一款商业软件，具有面向对象的编程接口）来模拟疲劳裂纹路径并计算相应的疲劳寿命的模拟程序（FCG-系统）。为了在大型海洋结构物中应用FCG-系统，在考虑结构节点和裂纹生长过程中的卸载情况下，本文将子模型技术集成到系统中。基于从有限元分析中得到的节点力和节点位移，从虚拟裂纹闭合技术的角度提出了一个公式来计算壳单元的应力强度因子。裂纹尖端既不需要使用特殊的奇异单元，也不需要崩塌单元技术。建立的FCG-系统不仅能处理单个裂纹的问题，而且还能处理同时但不均匀生长的多个裂纹的问题。由两个说明性的例子证明了FCG-系统的准确性和有效性。在这些例子中还没有遇到稳定性和收敛困难的情况，与此同时，这也证实了该方法对网格大小是不敏感的。因此，由作者开发的FCG -系统将会是进行海上结构疲劳裂纹增长分析的有效工具。

[1]He, W., Liu, J., amp; Xie, D. (2014). Numerical study on fatigue crack growth at a web-stiffener of ship structural details by an objected-oriented approach in conjunction with ABAQUS. Marine Structures, 35, 45-69.

Probabilistic methods for planning of inspection forensp;fatigueensp;cracks in offshore structures

Due to the nature of the fatigue phenomena it is well known that small changes in basic assumptions for fatigue analysis can have significant influence on the predicted crack growth lives. Calculated fatigue lives based on the S–N approach are sensitive to input parameters. Fracture mechanics analysis is required for prediction of crack sizes during service life in order to account for probability of detection after an inspection event. Analysis based on fracture mechanics needs to be calibrated to that of fatigue test data or S–N data. Calculated probabilities of fatigue failure using probabilistic methods are even more sensitive to the analysis methodology and to input parameters used in the analyses. Thus, use of these methods for planning inspection requires considerable knowledge and engineering skill. Therefore the industry has asked for guidelines that can be used to establish reliable inspection results using these methods. During the last years DNV GL has performed a joint industry project on establishing probabilistic methods for planning in-service inspection for fatigue cracks in offshore structures. The recommendations from this project are now included in a Recommended Practice. The essential features of the probabilistic methods developed for this kind of inspection planning are described in this paper.

众所周知，疲劳现象的本质决定了疲劳分析基本假设中的小变化可能对裂纹扩展寿命产生重大影响。基于S-N方法的疲劳寿命计算对输入参数是很敏感的。为了解释某次审查后的检测概率，需要用到断裂力学的分析方法来预报结构服务寿命期内的裂纹尺寸。基于断裂力学的分析也应该与疲劳实验数据或S-N数据保持统一标准。使用概率方法计算的疲劳失效概率对分析方法和分析中的输入参数更为敏感。因此,使用这些方法来制定检测方案需要相当的知识和工程技巧。因而工业界需要一个可以用来建立可靠检测方案的指导方针。去年，DNV GL集团开展了一个工业合作项目，旨在建立一套概率方法来制定在役海洋工程结构疲劳裂纹检测方案。现今，该项目的建议收录在操作规程建议中。本文描述了这种检查规划的概率方法的基本特征。

[2]Lotsberg, I., Sigurdsson, G., Fjeldstad, A., amp; Moan, T. (2016). Probabilistic methods for planning of inspection for fatigue cracks in offshore structures. Marine Structures, 46, 167-192.

Time-variant bulk carrier reliability analysis in pure bending intact and damage conditions

Time-variant reliability analysis of a corroded bulk carrier in intact and damage conditions is performed by First-Order (FORM), Second-Order (SORM) Reliability Methods and Importance Sampling simulation. Annual failure probabilities are determined up to 25-year ship lifetime, accounting for time-variant corrosion wastage of structural members contributing to hull girder strength. Statistical properties of hull girder capacity are determined by Monte Carlo simulation, applying three correlation models among corrosion wastages of structural members contributing to hull girder strength, namely no correlation, full correlation and full correlation among wastages of structural members belonging to the same category of compartments. A modified incremental-iterative method is applied, to account for instantaneous neutral axis rotation, in case of asymmetrical damage conditions, as for collision and grounding events. Incidence of intact/damage condition, as well as correlation among corrosion wastages, on annual sagging/hogging time-variant failure probability is investigated and discussed. Time-variant sensitivity analyses for intact and damage conditions are also performed, to investigate the incidence of random v

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