scholarly journals Fatigue Strength Assessment of Trimaran Cross-Deck Structure Based on Spectral and Simplified Fatigue Method

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Chunbo Zhen ◽  
Tianlin Wang ◽  
Pengyao Yu ◽  
Liang Feng
Keyword(s):  
Transfer Functions ◽  
Three Dimensional ◽  
Stress Transfer ◽  
Direct Calculation ◽  
Fatigue Behaviour ◽  
Fatigue Analysis ◽  
Fe Analysis ◽  
Linear Potential ◽  
Wave Loads ◽  
Strength Assessment

In order to investigate the fatigue behaviour of trimaran cross-deck structural details, the spectral and simplified fatigue analysis approaches are proposed. In spectral fatigue approach, three-dimensional (3D) linear potential flow theory and global FE analysis are used for wave loads and stress transfer functions calculation; the stochastic spectral fatigue analysis is carried out considering the weighted wave headings factors. In simplified fatigue approach, based on the direct calculation procedure of LR rules, the evaluation of simplified fatigue loads and loading conditions are presented, and the stress ranges are obtained by global finite element (FE) analysis. Then the fatigue lives of a few hot spots are computed to demonstrate the application of the proposed method. The result shows that the method given in this paper has a good applicability. This study offers methodology for the fatigue analysis of trimaran cross-deck structure, which may be regarded as helpful references for structural design of these types of ships.

The Research of Statistic Prediction for Wave Loads Based on Three Dimensional Method

2013 ◽  
Author(s):  
Yihan Zhang ◽  
Huilong Ren ◽  
Hui Li ◽  
Xiaoyu Li
Keyword(s):  
Structural Strength ◽  
Wave Spectrum ◽  
Three Dimensional ◽  
Frequency Interval ◽  
Wave Loads ◽  
Short Term ◽  
Empirical Formulas ◽  
Strength Assessment ◽  
Term Prediction

The exact prediction of wave loads for ship or other marine structure is the key to its design and the assessment of structural strength, reliability and security. The short-term and long-term prediction of wave loads are always used in direct calculation for structural strength, fatigue strength assessment and so on based on spectral analysis method. In this paper, the numerical calculation method for statistic prediction is discussed firstly, including the Weibull distribution fitted method and the stack method. Further more, it is necessary to find a quick solution in order to improve the efficiency to compute the nonlinear equation in the second method. Then, some main factors that may influence the long-term or short-term prediction are discussed, such as wave spectrum, wave scatter diagram, incident wave angle interval and frequency interval. Finally, the wave loads prediction for a series of typical bulk carriers and oil tankers are calculated by the uniform predict method discussed above base on three dimensional wave loads calculation theory. The results showed that the method used in this paper can predict the statistic value of wave loads induced by irregular incident waves conveniently and efficiently. A rule to choose a series of uniform factors is confirmed for statistic prediction and some empirical formulas for long-term value of wave bending moment are concluded which are very useful in marine engineering.

scholarly journals Predictions of Ship Extreme Hydroelastic Load Responses in Harsh Irregular Waves and Hull Girder Ultimate Strength Assessment

2019 ◽  
Vol 9 (2) ◽  
pp. 240 ◽  
Author(s):  
Jialong Jiao ◽  
Yong Jiang ◽  
Hao Zhang ◽  
Chengjun Li ◽  
Chaohe Chen
Keyword(s):  
Ultimate Strength ◽  
Time Domain ◽  
Three Dimensional ◽  
Direct Calculation ◽  
Wave Force ◽  
Irregular Waves ◽  
Restoring Force ◽  
Strength Assessment ◽  
Hull Girder ◽  
Rule Approach

In this paper, the hydroelastic motion and load responses of a large flexible ship sailing in irregular seaways are predicted and the hull girder ultimate strength is subsequently evaluated. A three-dimensional time-domain nonlinear hydroelasticity theory is developed where the included nonlinearities are those arising from incident wave force, hydrostatic restoring force and slamming loads. The hull girder structure is simplified as a slender Timoshenko beam and fully coupled with the hydrodynamic model in a time domain. Segmented model towing-tank tests are then conducted to validate the proposed hydroelasticity theory. In addition, short-term and long-term predictions of ship responses in irregular seaways are conducted with the help of the developed hydroelastic code in order to determine the extreme design loads. Finally, a simplified strength-check equation is proposed, which will provide significant reference and convenience for ship design and evaluation. The hull girder ultimate strength is assessed by both the improved Rule approach and direct calculation.

Application of Direct Hydrodynamic Loads in Spectral Fatigue Analysis

2017 ◽  
Author(s):  
Yogendra Parihar ◽  
Saikat Dan ◽  
Karan Doshi ◽  
Shivaji Ganesan Thirunaavukarasu
Keyword(s):  
Transfer Function ◽  
Stress Transfer ◽  
Bending Moment ◽  
Direct Calculation ◽  
Fatigue Analysis ◽  
Direct Application ◽  
Fe Model ◽  
Bending Moments ◽  
Hydrodynamic Loads ◽  
Fatigue Assessment

It is common practice to employ direct calculation procedures for spectral based fatigue assessment. Numerical codes are used to compute direct hydrodynamic loads. There are several complexities and nuances associated with application of loads on finite element (FE) model. It is a computationally expensive task especially when a large number of cases need to be analyzed (for e.g. spectral fatigue analysis). The present paper outlines an approach to evaluate the stress transfer function based on the direct application of moments (vertical bending, horizontal bending and torsional moments) computed using a frequency-domain based sea-keeping code. Multi-point constraint (MPC) method is utilized for application of bending moment. The structural responses computed using direct application of the bending moments (Method 1) and the panel pressures (Method 2) are compared. The evaluated stress transfer function is used for spectral fatigue analysis. Overall, the present study provides a methodology for spectral fatigue assessment using direct application of bending moments.

Global Strength Assessment of Trimaran Structure

2012 ◽  
Vol 538-541 ◽  
pp. 2860-2863 ◽  
Author(s):  
Khurram Shehzad ◽  
Hui Long Ren ◽  
Chun Bo Zhen ◽  
Asifa Khurram
Keyword(s):  
Structural Strength ◽  
Direct Calculation ◽  
Fe Analysis ◽  
Strength Analysis ◽  
Stress Concentrations ◽  
Strength Assessment ◽  
Analysis Technique ◽  
Current Design ◽  
Design Loads ◽  
Global Strength

This paper presents structural strength assessment of trimaran by global FE-analysis. Global strength analysis using the finite-element method is a powerful tool extensively used to design well-balanced and reliable sea going vessels. This analysis technique is particularly recommended in unconventional and new ship designs. Lloyd’s Register rules (LR Rules) for classification of trimaran are used to compute design loads and load cases. Global FE analysis is performed as per direct calculation procedure of LR Rules. Maximum stress concentration locations or hot spots corresponding to each load case are identified. The stresses induced in trimaran structure for all load cases are less than the maximum allowable stress. Furthermore, some modifications in current design are suggested to reduce the stress concentrations and hence to improve the structural strength.

Study on Effect of Cycle Counting Correction Factors in Spectral Based Fatigue Computation

2013 ◽  
Vol 275-277 ◽  
pp. 193-197
Author(s):  
Khurram Shehzad ◽  
Ren Huilong ◽  
Rehan Khan ◽  
Asifa Khurram
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Transfer Functions ◽  
Stress Transfer ◽  
Direct Calculation ◽  
Wide Band ◽  
Complex Stress ◽  
Response Analysis ◽  
Correction Factors ◽  
Wave Load

This paper investigates the effect of various cycle counting correction factors in spectral fatigue damage calculations. Spectral fatigue calculations are based on complex stress transfer functions established through direct wave load analysis combined with stress response analysis. Cycle counting correction factors are introduced in the computation process to cater swell’s effect and to reduce the conservatism in the results due to narrow band approximation for a wide band random process. In this study, fatigue life of a ship structural detail is predicted by spectral method utilizing ANSYS software along with 3D liner sea-keeping code AQWA. Cumulative fatigue damage is calculated by a MATLAB program based on direct calculation procedure of spectral fatigue using cycle counting correction factors proposed by Wirsching, Rice and Dirlik. The results show an overall decrease in the computed fatigue damage and a corresponding increase in the expected fatigue life of the structure.

Fatigue Strength Assessment Analysis of Large Container Ship

2014 ◽  
Vol 602-605 ◽  
pp. 385-389 ◽  
Author(s):  
Feng Lei Han ◽  
Chun Hui Wang ◽  
An Kang Hu ◽  
Ya Chong Liu
Keyword(s):  
Fatigue Strength ◽  
Hot Spot ◽  
Direct Calculation ◽  
Linear Wave ◽  
Container Ship ◽  
Wave Loads ◽  
Wave Load ◽  
Strength Assessment ◽  
Fatigue Strength Assessment ◽  
Large Container

Fatigue assessments of container ship structures can be processed using various direct calculation approaches or various approaches of classification societies [1,2]. In this investigation, the fatigue strength assessment to the key positions of a 9200TEU container ship has been performed ,subjected to the rules of BV about fatigue strength specification of large container ships, based on design wave method and Miner fatigue cumulative damage theory analysis method. Wave loads have been computed using linear wave load calculation method based on three-dimensional potential flow theory. And the fatigue strength assessment of the typical hot spot structures has also been conducted based on a series of critical single design wave.

scholarly journals Application of Fatigue Damage Evaluation Considering Linear Hydroelastic Effects of Very Large Container Ships Using 1D and 3D Structural Models

2021 ◽  
Vol 11 (7) ◽  
pp. 3001
Author(s):  
Sang-Ick Lee ◽  
Seung-Hwan Boo ◽  
Beom-Il Kim
Keyword(s):  
Fatigue Damage ◽  
Transfer Functions ◽  
Interaction Analysis ◽  
Hot Spot ◽  
Three Dimensional ◽  
Stress Transfer ◽  
Design Stage ◽  
Fe Model ◽  
Beam Model ◽  
Hull Girder

Owing to the increasing size and speed of ships to ensure economic efficiency, the hydroelastic phenomena of the hull have emerged as an important factor to be considered in the evaluation of strength during the design stage of current ship building procedures. In this study, we established a method to evaluate fatigue strength with linear spring effects using a 1D (one-dimensional) beam model and a 3D (three-dimensional) global Finite Element (FE) model. Firstly, FSI (fluid–structure interaction) analysis was carried out using the 1D beam model of a 15,000 twenty equivalent unit (TEU) container ship. In this step, the method proposed was to calculate the stress RAO (Response Amplitude Operator) of the hot spot points using only the hull girder load from the beam model. Next, a modal superposition analysis was carried out using the 3D global FE model that was directly calibrated to the fatigue damage of the hot spot points. Based on these stress transfer functions with hydroelastic effects, spectral fatigue analysis was carried out, and the portion of linear springing effects in the fatigue damage was analyzed, respectively. These results were compared with the rigid-body-based results in the final design stage. Finally, the applicability of the proposed method at the actual design stage is discussed.

Wellhead Fatigue Analysis Considering Global and Local Effects

2020 ◽  
Author(s):  
Filipe A. Rezende ◽  
Guilherme K. Lopes ◽  
Fernando J. M. Sousa ◽  
José R. M. Sousa ◽  
Carlos E. Fonseca ◽  
...  
Keyword(s):  
Fatigue Damage ◽  
Transfer Functions ◽  
Complex Geometry ◽  
Numerical Models ◽  
Stress Transfer ◽  
Fatigue Analysis ◽  
Global Model ◽  
Local Model ◽  
Critical Components ◽  
The Time Domain

Abstract During drilling operations, the wellhead system and top hole casings shall be designed to support dynamic loads from the connected riser through the BOP stack/LMRP. As dynamic motions are associated to stress variations, fatigue becomes a major concern for designers. The accumulation of damage at the wellhead and close regions is dependent on several aspects, such as the riser components, the interactions soil-conductor and conductor-surface casing, and of course the environmental conditions. Consequently, fatigue analysis involves complex numerical models and requires the simulation of a huge number of loading cases. The present paper aims to estimate the fatigue damage at critical components of the top hole casings and at the wellhead. Two different approaches were investigated. In the first, a global model is analyzed in the time domain (TD), and the Rainflow cycle counting method is used to calculate fatigue damage. The global model includes the drilling riser, wellhead, casings, and interactions between components and with soil. In the second, the same model is analyzed in the frequency domain (FD), and the Dirlik method is used to calculate fatigue damage. Additionally, to allow a better evaluation of stresses at complex geometry regions, forces and moments obtained using the TD methodology were combined with load-to-stress transfer functions, defined by means of a local model and symbolic regression (SR) analysis. The local model includes a detailed 3D model of the pressure housings, and soil-to-casing interaction. The obtained results indicate that the pressure housings are not sensitive to fatigue, and also that the analyses performed are feasible, contributing to reduce computational costs in wellhead fatigue assessments.

Pavement Damage Due to Conventional and New Generation of Wide-Base Super Single Tires

2005 ◽  
Vol 33 (4) ◽  
pp. 210-226 ◽  
Author(s):  
I. L. Al-Qadi ◽  
M. A. Elseifi ◽  
P. J. Yoo ◽  
I. Janajreh
Keyword(s):  
Carrying Capacity ◽  
Material Properties ◽  
Three Dimensional ◽  
Fe Analysis ◽  
Load Carrying Capacity ◽  
Inflation Pressure ◽  
3D Finite Element ◽  
Load Carrying ◽  
Pavement Damage ◽  
New Generation

Abstract The objective of this study was to quantify pavement damage due to a conventional (385/65R22.5) and a new generation of wide-base (445/50R22.5) tires using three-dimensional (3D) finite element (FE) analysis. The investigated new generation of wide-base tires has wider treads and greater load-carrying capacity than the conventional wide-base tire. In addition, the contact patch is less sensitive to loading and is especially designed to operate at 690kPa inflation pressure at 121km/hr speed for full load of 151kN tandem axle. The developed FE models simulated the tread sizes and applicable contact pressure for each tread and utilized laboratory-measured pavement material properties. In addition, the models were calibrated and properly validated using field-measured stresses and strains. Comparison was established between the two wide-base tire types and the dual-tire assembly. Results indicated that the 445/50R22.5 wide-base tire would cause more fatigue damage, approximately the same rutting damage and less surface-initiated top-down cracking than the conventional dual-tire assembly. On the other hand, the conventional 385/65R22.5 wide-base tire, which was introduced more than two decades ago, caused the most damage.

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