The Effect on Large Container Ships’ Fatigue due to Springing Loads Coupling Horizontal and Torsional Vibrations

2018 ◽  
Author(s):  
Hui Li ◽  
Huifen Xu ◽  
Huilong Ren ◽  
Xiaoxi Shen ◽  
Yubo Wang
Keyword(s):  
Fatigue Damage ◽  
Torsional Vibration ◽  
Calculation Method ◽  
Wave Loads ◽  
Analysis Method ◽  
Element Analysis ◽  
Hull Structure ◽  
Torsional Loads ◽  
Large Container ◽  
Simplified Calculation

The issue of hydroelasticity caused by hull vibration has become an unavoidable problem in the design and verification of large ships. Driven by environmental protection and economical efficiency, the size of ships are increasingly larger, and the resulting springing and whipping response and their effects on fatigue damage has been paid more and more attention especially for ultra large container ships (ULCS). Many classification societies typically check fatigue damage caused by vertical bending when considering springing, while it needs to be emphasized that large container ships can suffer severe torsional loads compared to other large ships due to wide breath and big hatch openings. In the existing stress calculation method, the finite element analysis method obviously has a high calculation accuracy. However, there are so much work to do with FEM model established, and partially refined, operated at all sea states etc., which not only requires much time, but also higher computing equipment. Therefore, in this paper, a simplified calculation method of fatigue damage considering the effect of bending and torsion is proposed, and a 21000TEU will be calculated by this method. The wave loads on the hull structure will be estimated based on the 3D linear hydroelastic theory coupling horizontal and torsional vibration, and the stress caused by bending and torsion will be obtained respectively. Finally, the fatigue damage is calculated by spectral analysis method considering high frequency springing loads. Then the effect on large container ships’ fatigue due to bending and torsional vibration is discussed.

The Underwater Vehicle Cabins Wave Loads Linear-Simplified Calculation Method

2013 ◽  
Vol 712-715 ◽  
pp. 1448-1454
Author(s):  
Xue Hong He ◽  
Yue Yang ◽  
Xin Meng Liu ◽  
Xiu Feng Tan ◽  
Yan Yan Li
Keyword(s):  
Calculation Method ◽  
Water Surface ◽  
Underwater Vehicle ◽  
Underwater Vehicles ◽  
Wave Loads ◽  
Calculation Methods ◽  
Strip Theory ◽  
Simplified Calculation ◽  
Simplified Calculation Method

Based on the research of wave loads calculation methods for the submarine and ship, compared the date of wave loads obtained by strip theory with that obtained by linear-simplified calculation method, we proved the engineering feasibility of linear-simplified calculation method of wave loads on underwater vehicles cabin when sailing on the water surface and near the water surface, the linear-simplified calculation method shorten the calculation cycle and guarantee the engineering accuracy.

Large Containerships’ Fatigue Analysis due to Springing and Whipping

2016 ◽  
Author(s):  
Huilong Ren ◽  
Kaihong Zhang ◽  
Hui Li ◽  
Di Wang
Keyword(s):  
Statistical Analysis ◽  
Fatigue Damage ◽  
Time Domain ◽  
High Frequency ◽  
Influence Factor ◽  
Irregular Waves ◽  
Wave Loads ◽  
Analysis Method ◽  
Load Case ◽  
Factor Modification

As the sea transport demand increases constantly, marine corporations around the world are pursuing solutions with large scale and low cost, which makes ultra large containerships’ construction consequentially. Ultra large containerships are more flexible relatively, and the 2-node natural frequency can easily fall into the encountered spectrum frequency range of normal sea state. Meanwhile, as the speed of containerships is high and its large bow flare, when sailing with high speed, the bow structures may suffer severe slamming forces which can increase the design wave loads’ level and the fatigue damage. The importance of hydroelastic analysis of large and flexible containerships of today has been pointed out for structure design. Rules of Many Classification Society have made changes on design wave loads’ value and fatigue influence factor modification. The paper firstly introduced 3-D linear hydroelasticity theory to calculate the Response Amplitude Operator (RAO) in frequency domain, and then described 3-D nonlinear hydroelasticity theory to obtain the nonlinear wave loads time history in irregular waves in time domain, considering large amplitude motion and slamming force due to severe relative motion between ship hull and wave. Based on the theories, computer programs are made to conduct the calculations under specified load case, and some calculation and statistical results are compared with experimental results to verify the accuracy and stability of the programs secondly. The paper focused on the influence of springing and whipping on fatigue damages of 8500TEU and 10000TEU containerships in different loading cases, using spectrum analysis method and time domain statistical analysis method. The spectrum analysis method can calculate fatigue damage due to low-frequency wave loads and high-frequency springing separately, while the time domain statistical analysis can calculate fatigue damage due to the high-frequency damping whipping additionally, based on 3-D time domain nonlinear hydroelasticity wave loads’ time series simulation in irregular waves and rain flow counting method. Finally, discussions on influence factor of springing and whipping with different loading cases are made. Based on these two containerships in example, the fatigue damage due to whipping can be the same as the fatigue damage due to springing and even sometimes can be larger than the springing damage. According to the wave loads influence factor, the fatigue assessment of different position on midship section is done on the basis of nominal stress. Besides, some suggestions on calculating load case selection are made to minimize the quantity of work in frequency and time domain. Thus the tools for fatigue influence factor modification are provided to meet the demand of IACS’ UR[1].

Research on the Wave Load Effect Based on Time History Analysis of Donghai Island Bridge

2014 ◽  
Vol 919-921 ◽  
pp. 587-589
Author(s):  
Wei Guo Yuan ◽  
Mu Yu Liu
Keyword(s):  
Time History ◽  
Wave Force ◽  
Wave Loads ◽  
Analysis Method ◽  
Sea Waves ◽  
Wave Load ◽  
Element Analysis ◽  
Load Effect ◽  
Structure Selection ◽  
Dynamic Time

The Dissertation, relying on the construction of Zhanjiang Donghai Island Sea-crossing Bridge and adopting the finite element analysis method to calculate the wave force of substructure, proposes the bridge structure analysis method based on dynamic time history of wave loads. Through emulation analysis, structural load effect under waves is attained, making it a theoretically rational foundation for the structure selection and reinforcement of substructure of Donghai Island Bridge and having important theoretical significance and practical value in guaranteeing the bridge security under any seismic sea waves.

Analysis of Fatigue Life of Ship Structure Under the Non-Linear Slamming Load

2019 ◽  
Author(s):  
Huilong Ren ◽  
He Ma
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Calculation Method ◽  
High Speed ◽  
Influence Coefficient ◽  
Wave Load ◽  
Ship Structures ◽  
Hull Structure ◽  
Non Linear ◽  
Slamming Load

Abstract As one of the hot topics in ship structures, hull structural fatigue has been widely studied by overseas and domestic scholars in recent years. And fatigue assessment methods can be divided into simplified calculation method and direct calculation method. However most of the calculation methods are based on liner wave load. Some high-speed ships, large external floats and larger ships may have frequent outflows and inflows during the voyage. These ships can be influenced by more serious wave attack. In this situation, the influence of nonlinear slamming load on ship structures cannot be ignored. In this paper, the author selected the deck longitudinal and the bottom longitudinal of the example ship midship section, then calculated the fatigue damage under the action of liner load and total fatigue damage under non-linear slamming load respectively. And the effect of non-linear slamming load on the fatigue life of hull structure can be obtained: it is 49% larger than that without attack fatigue damage in the deck longitudinal, and 35% larger in the bottom longitudinal. Based on the results, the author got the influence coefficient of non-linear slamming load on the fatigue life of the ship. Finally, a nonlinear correction method of fatigue damage is proposed.

Research on the Key Techniques of Zhanjiang Donghai Island Bridge

2014 ◽  
Vol 587-589 ◽  
pp. 1614-1617
Author(s):  
Wei Guo Yuan ◽  
Mu Yu Liu
Keyword(s):  
Time History ◽  
Wave Force ◽  
Wave Loads ◽  
Analysis Method ◽  
Sea Waves ◽  
Element Analysis ◽  
Load Effect ◽  
Structure Selection ◽  
History Of ◽  
Dynamic Time

The Dissertation, relying on the construction of Zhanjiang Donghai Island Sea-crossing Bridge and adopting the finite element analysis method to calculate the wave force of substructure, proposes the bridge structure analysis method based on dynamic time history of wave loads. Through emulation analysis, structural load effect under waves is attained, making it a theoretically rational foundation for the structure selection and reinforcement of substructure of Donghai Island Bridge and having important theoretical significance and practical value in guaranteeing the bridge security under any seismic sea waves.

Long-Term Fatigue Damage of Ship Structures Under Nonlinear Wave Loads

2002 ◽  
Vol 39 (02) ◽  
pp. 95-104
Author(s):  
Xue KangGu ◽  
Torgeir Moan
Keyword(s):  
Fatigue Damage ◽  
Nonlinear Wave ◽  
Direct Analysis ◽  
Linear Wave ◽  
Wave Loads ◽  
Ship Structures ◽  
Hull Girder ◽  
Structural Fatigue ◽  
Large Container

Fatigue is a principal mode of failure in ship structures, especially when high tensile steels are applied. Although significant efforts have been made to predict fatigue damage, there are still uncertainties existing, e.g., in the stress histories that cause fatigue. This paper addresses estimation of fatigue damage in ships under wave loads, with an emphasis on containerships, which have large bow flare and low hull girder rigidity. Linear and nonlinear wave-induced loads as well as dynamic effects due to hull flexibility, i.e., whipping, are researched. With the direct analysis method of fatigue, the nature of the wave loading, hull rigidity, structural damping, stress range counting algorithm and SN curve on structural fatigue damage are investigated. In long-term fatigue damage estimates, the influence of different sea environments is numerically analyzed. The importance of nonlinearity of wave loads and especially the whipping on the structural fatigue damage is demonstrated by calculation for a large container vessel with large flare and lowest natural frequency of 0.749 Hz. Depending upon sea environments and SN curves used in long-term predictions, the fatigue damage based on nonlinear wave loads (excluding whipping) is 10–100% larger than that due to linear wave loads; the fatigue damage based on nonlinear combined loads (including whipping) may be 1–9 times larger than that of steady-state nonlinear wave loads.

Influence of Ship Speed and Heading Profiles on Fatigue Damage Accumulation for a Naval Vessel

2020 ◽  
Vol 64 (02) ◽  
pp. 127-138
Author(s):  
Ian Thompson ◽  
Bryan E. Ellis
Keyword(s):  
Fatigue Damage ◽  
Damage Accumulation ◽  
Wave Loads ◽  
Element Analysis ◽  
Naval Vessel ◽  
Linear Finite Element ◽  
Fatigue Damage Accumulation ◽  
Course Changes ◽  
Wave Conditions ◽  
Ship Speed

Ship speed and heading distributions are essential inputs for spectral fatigue analysis, and both may depend on wave conditions. Because rough-weather operational changes are rarely well defined, uncertainties in these distributions can introduce error in fatigue assessments. The influence of speed and relative heading distribution on fatigue estimates has not been thoroughly examined in the existing literature. This study investigates the influence of ship speed and relative heading distributions on fatigue damage accumulation of two sister naval ships. To represent uncertainties, 16 different operating profiles were used, including a baseline profile created from operator surveys and measurements. Fatigue damage estimates are calculated from a spectral analysis of four structural locations near midship. A linear frequency-domain seakeeping code provides the wave loads. The corresponding stresses are calculated using linear finite element analysis. Efforts to maintain seakeeping quality and crew readiness are reflected in the baseline profile with rough-weather speed and course changes. Ignoring these operational changes leads to reductions in estimated fatigue damage of up to 34% relative to the baseline estimate. This nonconservative result emphasizes the importance of understanding how operators manage rough wave conditions.

Application of Coupled Structural Acoustic Analysis and Sensitivity Calculations to a Tire Noise Problem

2012 ◽  
Vol 40 (1) ◽  
pp. 25-41 ◽  
Author(s):  
H. M. R. Aboutorabi ◽  
L. Kung
Keyword(s):  
Performance Improvement ◽  
Acoustic Analysis ◽  
Simulation Analysis ◽  
Analysis Method ◽  
Vehicle Manufacturer ◽  
Element Analysis ◽  
Equipment Manufacturer ◽  
Tire Noise ◽  
Fea Modeling ◽  
Testing Instruments

Abstract REFERENCE: H. M. R. Aboutorabi and L. Kung, “Application of Coupled Structural Acoustic Analysis and Sensitivity Calculations to a Tire Noise Problem,” Tire Science and Technology, TSTCA, Vol. 40, No. 1, January – March 2012, pp. 25–41. ABSTRACT: Tire qualification for an original equipment (OE) program consists of several rounds of submissions by the tire manufacturer for evaluation by the vehicle manufacturer. Tires are evaluated both subjectively, where the tire performance is rated by an expert driver, and objectively, where sensors and testing instruments are used to measure the tire performance. At the end of each round of testing the evaluation results are shared and requirements for performance improvement for the next round are communicated with the tire manufacturer. As building and testing is both expensive and time consuming predictive modeling and simulation analysis that can be applied to the performance of the tire is of great interest and value. This paper presents an application of finite element analysis (FEA) modeling along with experimental verification to solve tire noise objections at certain frequencies raised by an original equipment manufacturer (OEM) account. Coupled structural-acoustic analysis method was used to find modal characteristics of the tire at the objectionable frequencies. Sensitivity calculations were then carried out to evaluate the strength of contribution from each tire component to the identified modes. Based on these findings changes to the construction were proposed and implemented that addressed the noise issue.

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