A Comparison of Direct Calculation Approaches Applied on the Fatigue Strength Assessment of a Panamax Container Ship

2012 ◽  
Author(s):  
Zhiyuan Li ◽  
Wengang Mao ◽  
Jonas W. Ringsberg
Keyword(s):  
Stress Response ◽  
Fatigue Strength ◽  
Fatigue Damage ◽  
Measurement Data ◽  
Direct Calculation ◽  
Container Ship ◽  
Calculation Methods ◽  
Strength Assessment ◽  
Strip Theory ◽  
Calculation Procedures

Today, it is common practice to carry out fatigue assessments of ship structures using direct calculation procedures. A direct calculation analysis of a ship’s fatigue strength involves hydrodynamic analysis, stress response evaluation followed by fatigue damage calculation. Many numerical codes are available for these types of analyses. They could yield different values in a fatigue life prediction because of the different degrees of complexity in the computation of the ship’s response. For example, hydrodynamic loads can be calculated using the strip theory or the panel method. The stress response to these loads can be computed using a beam theory or more advanced analyses, such as global and/or local finite element analyses. In a direct fatigue analysis for ship design, spectral methods have been dominating but there is a growing interest in time-domain fatigue damage calculation procedures. The objective of the current investigation is to compare four commonly used direct calculation methods against measurement data. The comparison is carried out by making a case study on a Panamax container ship on which full-scale measurements have been performed. The computational efforts involved in the application of the current direct calculation methods are compared and their applicability in ship fatigue design is discussed.

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.

A Method for Fatigue Evaluation of Trimaran Cross Structure With the Influence of Slamming

2017 ◽  
Author(s):  
Zhe Li ◽  
Huilong Ren ◽  
Kai Jin
Keyword(s):  
Stress Response ◽  
Fatigue Strength ◽  
Fatigue Damage ◽  
Linear Response ◽  
Operating Conditions ◽  
Wave Load ◽  
Hull Structure ◽  
Non Linear ◽  
Slamming Load ◽  
Cross Structure

Slamming is a highly non-linear phenomenon between hull structure and wave. Due to the special structure of trimaran, the slamming mode is extremely different from that of traditional vessel. Besides bow emergence and enter, the slamming phenomenon of the out shell at the cross structure is also obvious. In conventional hull structure fatigue strength evaluation, the slamming load is usually not considered. However, the slamming problem is unavoidable at danger load cases, and the stress concentration of the trimaran cross structure is serious. So it is dangerous to ignore the existence of slamming in serious load cases when evaluating the structural fatigue strength. Therefore, it is necessary to study the contribution of slamming load to fatigue damage. In this paper, a practical method for calculating and analyzing is presented to consider the effect of slamming on the fatigue strength of the trimaran cross structure to ensure that the fatigue life of the structure is closer to the true value. According to the linear theory, the relative motion and relative speed of the hull in wave and the stress response of the wave load on the structure are calculated firstly. Then, the stress response of the non-linear out shell slamming force is calculated. The linear response and non-linear response are combined. And the stress response time history under the combined action of slamming and wave load are obtained. Finally, the fatigue damage of the structure under dangerous operating conditions is calculated by the rain flow counting method. And the contribution value of the slamming load to the structural damage degree is calculated. The paper will put forward some reference suggestions for fatigue study calculation and evaluation of Trimaran cross structure with the influence of slamming.

Fatigue Assessment of Trimaran Structure Based on Simplified Procedure

2012 ◽  
Vol 525-526 ◽  
pp. 333-336
Author(s):  
Hui Long Ren ◽  
Shehzad Khurram ◽  
Chun Bo Zhen ◽  
Khurram Asifa
Keyword(s):  
Fatigue Damage ◽  
High Speed ◽  
Hot Spot ◽  
Mathematical Formulation ◽  
Direct Calculation ◽  
Assessment Procedure ◽  
Hot Spot Stress ◽  
Fatigue Assessment ◽  
Strength Assessment ◽  
Simplified Procedure

In recent years, Trimaran platform design has got the attention of naval architects owing to its superior seagoing performance. Trimaran structure experiences severe loads due to its unique configuration and high speed, causing stress concentration, especially in cross deck region and accelerate fatigue damage. This paper presents fatigue strength assessment of Trimaran structure by simplified procedure. A methodology is proposed to evaluate fatigue loads and loading conditions by load combinations of direct calculation procedure of Lloyds Register Rules for Classification of Trimaran (LR Rules). Global FE analysis, in ANSYS, is performed to investigate the stress response. The stress range is computed by hot-spot stress approach, and its long term distribution is specified by Weibull distribution. Fatigue damage of selected critical details is calculated using mathematical formulation of simplified fatigue assessment procedure of Common Structure Rules (CSR).

Fatigue Yield of Ship Structures

2009 ◽  
Author(s):  
Kalman Zˇiha ◽  
Branko Blagojevic´
Keyword(s):  
Fatigue Strength ◽  
Fatigue Damage ◽  
Fatigue Analysis ◽  
Assessment Method ◽  
Rule Based ◽  
Strength Assessment ◽  
Variable Amplitude ◽  
Damage Progression ◽  
Double Hull ◽  
Fatigue Endurance

The paper on the first place summarizes the fatigue yield approach as a cause-effect interaction between fatigue damage progression and fatigue endurance. Secondly it investigates the fatigue strength worsening on experimental S-N data and the load variability effects in shipbuilding. Next it applies the Classification Society’s rule-based procedure for fatigue analysis of ship’s structure that uses a simplified fatigue strength assessment method. The example elaborates fatigue yield effect on the seagoing operation of a double hull 47400 tdw tanker. At the end the paper recommends the procedure for assessment of ship lifetime shortening due to the fatigue yielding under constant and variable amplitude block loadings.

Study on Wave Load Prediction and Fatigue Damage Analysis of River-Sea-Going Ship

2018 ◽  
Author(s):  
Guohu Guo ◽  
Yiwen Wang ◽  
Jin Gan ◽  
Weiguo Wu ◽  
Yunling Ye
Keyword(s):  
Finite Element ◽  
Stress Response ◽  
Fatigue Damage ◽  
Response Spectrum ◽  
Container Ship ◽  
Stress Range ◽  
Wave Load ◽  
Fatigue Assessment ◽  
Cumulative Fatigue Damage ◽  
Distribution Of Stress

With the consideration of shipping efficiency and the limited conditions of the Yangtze River, flat and wide ship become the preferred type for River-Sea-Going ship. This kind of structure is adverse to the ship’s stiffness under longitudinal bending, transverse bending. And two-stage repeated loading brings to the fatigue assessment of the ship structure new uncertainties, so accurate cumulative fatigue damage is a matter of necessary. Based on the theory of three-dimensional potential flow, the hydrodynamic analysis of River-Sea-Going container ship under specific route is carried out. The hull motion and the load transfer function of each section are obtained. The finite element model is used to calculate the amplitude-frequency response Operator RAOs. The influence of special routes and speed factors are also considered. Based on the frequency domain spectral analysis method combined with the scatter diagram of E1 sea area, the characteristics of wave-induced load are analyzed under 10−7.5 probability level. The stress response spectrum and the short-term distribution of stress range are obtained by combining the structural stress response calculation with the whole ship finite element structure model. The long-term distribution of stress response spectrum and stress range is also obtained. The cumulative fatigue damage of River-Sea-Going container ship under the special route is evaluated by using the S-N curve recommended by the criterion. It can provide the basis for the fatigue assessment of the new type of River-Sea-Going container ship.

Fatigue Strength Assessment of Crack Flaws in Thick High Tensile Steel Plates on Large Ships

2015 ◽  
Author(s):  
Yu Tian
Keyword(s):  
Fatigue Strength ◽  
Crack Growth ◽  
High Strength ◽  
Fatigue Performance ◽  
Container Ship ◽  
Near Surface ◽  
Strength Assessment ◽  
Deck Plate ◽  
Steel Grades ◽  
Fatigue Strength Assessment

The sizes of large container ship increased during the past years have accompanied by the use of thicker plate and higher steel grade. The fatigue performance of thick high strength steel plate is a problem which has to be investigated. As an example, the fatigue crack growth of the butt welds at the deck plate of a 8530 TEU container ship has been investigated. Crack growth life predication method in combination with failure assessment diagram (FAD) technology has been used to calculate the fatigue life and the critical crack length. It has been discussed the fatigue sensitivity of the steel grades, the plate thicknesses and the positions of initial defect in thickness direction. The FAD methodology used in this paper is a common approach which has been introduced in various standards, which is practical and useful in fatigue strength assessment of ship structures. Crack tip opening displacement (CTOD) tests of high tensile steel YP40 and YP 47 have been carried out to obtain the fracture toughness, which play an important role in FAD calculation. And the minimum value of the test results is used as the calculated value. It is concluded that the fatigue performance of high strength steels do not increase proportionally with the steel grades and plate thicknesses. The calculation results also have shown that there is significant decrease of fatigue performance along with the increase of plate thickness, and in the same initial conditions, the harmfulness of the near surface defects on structure detail is more serious compared to the embedded defects.

scholarly journals Modeling of German Low Voltage Cables with Ground Return Path

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1265 ◽  
Author(s):  
Johanna Geis-Schroer ◽  
Sebastian Hubschneider ◽  
Lukas Held ◽  
Frederik Gielnik ◽  
Michael Armbruster ◽  
...  
Keyword(s):  
Low Voltage ◽  
Measurement Data ◽  
Analytical Calculation ◽  
Laboratory Measurement ◽  
Model Parameters ◽  
Calculation Methods ◽  
Modeling Approach ◽  
Measurement Results ◽  
Simulation Results ◽  
Return Path

In this contribution, measurement data of phase, neutral, and ground currents from real low voltage (LV) feeders in Germany is presented and analyzed. The data obtained is used to review and evaluate common modeling approaches for LV systems. An alternative modeling approach for detailed cable and ground modeling, which allows for the consideration of typical German LV earthing conditions and asymmetrical cable design, is proposed. Further, analytical calculation methods for model parameters are described and compared to laboratory measurement results of real LV cables. The models are then evaluated in terms of parameter sensitivity and parameter relevance, focusing on the influence of conventionally performed simplifications, such as neglecting house junction cables, shunt admittances, or temperature dependencies. By comparing measurement data from a real LV feeder to simulation results, the proposed modeling approach is validated.

scholarly journals Fatigue Strength Analysis and Fatigue Damage Evaluation of Roller Chain

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 847 ◽  
Author(s):  
Ryoichi Saito ◽  
Nao-Aki Noda ◽  
Yoshikazu Sano ◽  
Jian Song ◽  
Takeru Minami ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Strength ◽  
Fatigue Damage ◽  
Fatigue Crack Initiation ◽  
Strength Analysis ◽  
The Finite Element Method ◽  
Roller Chain ◽  
Press Fitting ◽  
The Press ◽  
Static Tensile

This paper deals with the roller chain commonly used for transmission of mechanical power on many kinds of industrial machinery, including conveyors, cars, motorcycles, bicycles, and so forth. It consists of a series of four components called a pin, a bush, a plate, and a roller, which are driven by a sprocket. To clarify the fatigue damage, in this paper, the finite element method (FEM) is applied to those components under three different types of states, that is, the press-fitting state, the static tensile state, and the sprocket-engaging state. By comparing those states, the stress amplitude and the average stress of each component are calculated and plotted on the fatigue limit diagram. The effect of the plastic zone on the fatigue strength is also discussed. The results show that the fatigue crack initiation may start around the middle inner surface of the bush. As am example, the FEM results show that the fatigue crack of the inner plate may start from a certain point at the hole edge. The results agree with the actual fractured position in roller chains used in industry.

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