Whole Ship and Fatigue Analyses for Development of Ice Class LNGC

2009 ◽  
Author(s):  
Min-Jung Jun ◽  
Jae-Hyung Park ◽  
Je-Hyouk Woo
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Fatigue Damage ◽  
Design Stage ◽  
Wave Load ◽  
Unit Load ◽  
Direct Wave ◽  
Load Analysis ◽  
Global Strength ◽  
Stress Rao

This paper describes the whole ship and fatigue analyses of a 170 k Ice class LNGC, first ice class vessel of DSME. This paper includes determination of design load, global strength and fatigue strength. This subject vessel was designed to have more than 40 years’ fatigue life against given environmental conditions and fatigue damage was assessed based on stochastic method. Whole ship FE analysis was also carried out to verify the structural adequacy of global strength based on direct wave load analysis. In stochastic fatigue analysis, fatigue damage was calculated based on direct wave load analysis. D-SAFS, developed by DSME, was used in stress RAO generation and fatigue damage assessment. Stress RAOs were made based on ‘Component Based Method’. In this method, structural analyses were carried out for each unit load case and then resultant stress was combined with wave load analysis results to generate stress RAOs. D-SFAS defines unit load cases automatically and generated stress RAO from motion analysis results. Whole ship FE models having fine mesh in fatigue sensitive area were used in structural analysis. Different steel density was also assigned along ship length for mass adjustment within hull structure. Some hot spots were found not to satisfy the design fatigue life of 40 years in initial design stage. Through geometry modification, structural reinforcement or improving fabrication method such as grinding, all structural details could satisfy design fatigue life of 40 years. According to the results of whole ship analysis, there were some high stresses at local area. Conclusively, additional strengthening of the hull was required compared to standard class rule requirements, with respect to yield and buckling and fatigue strength, leading to a more robust vessel.

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.

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.

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 Life Assessment of Offshore Patrol Vessel

2009 ◽  
Author(s):  
Asokendu Samanta ◽  
P. Kurinjivelan
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Fatigue Damage ◽  
Hot Spot ◽  
Design Guidelines ◽  
Life Assessment ◽  
Strength Analysis ◽  
Hot Spot Stress ◽  
Critical Locations

Fatigue is a phenomenon, which needs to be considered in the present day’s vessel design. The welded joints are particularly affected by the fatigue damage due to high stress concentrations caused by the metallurgical discontinuities present in the weld. For oil tankers and bulk carriers adequate guidelines for the fatigue strength assessment have been established by the classification societies. But for navy vessel, like offshore patrol vessel, the design guidelines for the fatigue strength analysis are not widely available. In the present paper, an attempt has been made to calculate the fatigue life of offshore patrol vessel (OPV). In general five stages of work is involved in calculating fatigue life of any ship structure. These are, load calculation, nominal and hot spot stress computation, long-term stress distribution, selection of S-N curve and the fatigue damage calculation. In the present study, the wave loads are obtained by the rule based estimation. The finite element analysis with the submodeling approach has been used to get the hot spot stress at critical locations. The two-parameter Weibull curve has been used to get the long-term distribution of stress. And at the end, the fatigue damage and the fatigue life have been computed using the Palmgren-Miner linear cumulative damage theory at the critical locations of the vessel.

Study on the Fracture Energy and Fracture Toughness of the Polypropylene Fiber Reinforced Concrete

2007 ◽  
Vol 353-358 ◽  
pp. 1251-1254 ◽  
Author(s):  
Yuan Hua ◽  
Tai Quan Zhou ◽  
Jun Ying Lian
Keyword(s):  
Experimental Data ◽  
Fracture Toughness ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Fracture Energy ◽  
Fatigue Damage ◽  
Cyclic Load ◽  
Polypropylene Fiber ◽  
Fiber Reinforced Concrete ◽  
Polypropylene Fiber Reinforced Concrete

The fracture toughness and the fracture energy are obtained on the notched beams in three-point bending according to the RILEM draft recommendation. An experiment is designed to obtain the law on the alteration of the PPFRC’s (Polypropylene Fiber Reinforced Concrete) fatigue life and fatigue strength caused by the fibers. S-lgN curve is plotted according to the experimental data and fatigue is obtained through the Linear Regression. Theoretical analysis of the PPFRC’s bending fatigue characteristic is carried out. The fiber’s influence on the PPFRC’s fatigue behavior is stated and the fiber reinforcement mechanism is discussed. The result shows that the fiber can improve the PPFRC’s fatigue life and fatigue strength. The composition and development of the fatigue strain under the cyclic load are analyzed using experimental data. The law of the fatigue damage accumulation and evolution under cyclic load is studied. A fatigue damage mode, which can be used to predict the fatigue life of the PPFRC, is established.

scholarly journals Cumulative Fatigue damage of AA7075-T6 under Shot Peening and Ultrasonic Surface Treatments

2021 ◽  
Vol 14 (1) ◽  
pp. 1-10
Author(s):  
Marwa S. Mahammed ◽  
Hussain J. Alalkawi ◽  
Saad T. Faris
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Fatigue Damage ◽  
Shot Peening ◽  
Endurance Limit ◽  
Mechanical Design ◽  
Ultrasonic Impact Treatment ◽  
Sample Group ◽  
Cumulative Fatigue Damage ◽  
Fatigue Endurance

One of the important aspects of mechanical design is improving fatigue life.; In this work, the effect of Ultrasonic impact treatment (UIP) and shot peening (SP)on constant cumulative fatigue life and fatigue strength of AA7075-T6 were studied; The sample group was machined and primed, and some specimens were treated using ultrasonic impact therapy (UIT) with one line of peening. Fatigue experiments were conducted under constant and variable amplitude (R=-1) at ambient temperature to determine the fatigue life of the S-N curve and fatigue strength during treatment 3.46% and 8.57% at 107 cycles for (UIT) and (SP). Cumulative fatigue damage testing was carried out for two steps loading it is observed that the fatigue life for SP and UIP treated specimens was improved compared to the unpeeled results. The fatigue endurance limit was enhanced by 35% for UIT and 54% for SP. The fatigue life for both treatments was much improved compared to as-received metal. These results also show a strong tendency of increasing fatigue strength after application of (UIT) and (SP) with an increase in mechanical properties of the material used.

scholarly journals Investigation of Changes in Fatigue Damage Caused by Mean Load under Block Loading Conditions

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2738
Author(s):  
Roland Pawliczek ◽  
Tadeusz Lagoda
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Strain Curve ◽  
Mean Value ◽  
Fatigue Properties ◽  
Stress Strain ◽  
Reference Case ◽  
Block Loading ◽  
The Mean ◽  
Mean Strain

The literature in the area of material fatigue indicates that the fatigue properties may change with the number of cycles. Researchers recommend taking this into account in fatigue life calculation algorithms. The results of simulation research presented in this paper relate to an algorithm for estimating the fatigue life of specimens subjected to block loading with a nonzero mean value. The problem of block loads using a novel calculation model is presented in this paper. The model takes into account the change in stress–strain curve parameters caused by mean strain. Simulation tests were performed for generated triangular waveforms of strains, where load blocks with changed mean strain values were applied. During the analysis, the degree of fatigue damage was compared. The results of calculations obtained for standard values of stress–strain parameters (for symmetric loads) and those determined, taking into account changes in the curve parameters, are compared and presented in this paper. It is shown that by neglecting the effect of the mean strain value on the K′ and n′ parameters and by considering only the parameters of the cyclic deformation curve for εm = 0 (symmetric loads), the ratio of the total degree of fatigue damage varies from 10% for εa = 0.2% to 3.5% for εa = 0.6%. The largest differences in the calculation for ratios of the partial degrees of fatigue damage were observed in relation to the reference case for the sequence of block n3, where εm = 0.4%. The simulation results show that higher mean strains change the properties of the material, and in such cases, it is necessary to take into account the influence of the mean value on the material response under block loads.

scholarly journals Fatigue Modeling and Numerical Analysis of Re-Filling Probe Hole of Friction Stir Spot Welded Joints in Aluminum Alloys

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2171
Author(s):  
Armin Yousefi ◽  
Ahmad Serjouei ◽  
Reza Hedayati ◽  
Mahdi Bodaghi
Keyword(s):  
Experimental Data ◽  
Tensile Strength ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Fatigue Behavior ◽  
Element Model ◽  
Plastic Strain Amplitude ◽  
Friction Stir ◽  
Probe Hole ◽  
Good Agreement

In the present study, the fatigue behavior and tensile strength of A6061-T4 aluminum alloy, joined by friction stir spot welding (FSSW), are numerically investigated. The 3D finite element model (FEM) is used to analyze the FSSW joint by means of Abaqus software. The tensile strength is determined for FSSW joints with both a probe hole and a refilled probe hole. In order to calculate the fatigue life of FSSW joints, the hysteresis loop is first determined, and then the plastic strain amplitude is calculated. Finally, by using the Coffin-Manson equation, fatigue life is predicted. The results were verified against available experimental data from other literature, and a good agreement was observed between the FEM results and experimental data. The results showed that the joint’s tensile strength without a probe hole (refilled hole) is higher than the joint with a probe hole. Therefore, re-filling the probe hole is an effective method for structures jointed by FSSW subjected to a static load. The fatigue strength of the joint with a re-filled probe hole was nearly the same as the structure with a probe hole at low applied loads. Additionally, at a high applied load, the fatigue strength of joints with a refilled probe hole was slightly lower than the joint with a probe hole.

A Multi-Level Low Cycle Fatigue Damage Model for Forging Die Material

2006 ◽  
Vol 514-516 ◽  
pp. 804-809
Author(s):  
S. Gao ◽  
Ewald Werner
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Low Cycle Fatigue ◽  
Damage Model ◽  
Fatigue Loading ◽  
Cycle Fatigue ◽  
Die Material ◽  
Multi Level ◽  
Loading Sequence ◽  
Forging Die

The forging die material, a high strength steel designated W513 is considered in this paper. A fatigue damage model, based on thermodynamics and continuum damage mechanics, is constructed in which both the previous damage and the loading sequence are considered. The unknown material parameters in the model are identified from low cycle fatigue tests. Damage evolution under multi-level fatigue loading is investigated. The results show that the fatigue life is closely related to the loading sequence. The fatigue life of the materials with low fatigue loading first followed by high fatigue loading is longer than that for the reversed loading sequence.

Hybrid Fatigue Analysis Method for Railway Carbody Structure

2008 ◽  
Vol 44-46 ◽  
pp. 733-738 ◽  
Author(s):  
Bing Rong Miao ◽  
Wei Hua Zhang ◽  
Shou Ne Xiao ◽  
Ding Chang Jin ◽  
Yong Xiang Zhao
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Hybrid Method ◽  
Dynamic Stress ◽  
Stress Test ◽  
Fatigue Analysis ◽  
Railway Vehicle ◽  
Analysis Method ◽  
Structure Dynamic ◽  
Multi Body

Railway vehicle structure fatigue life consumption monitoring can be used to determine fatigue damage by directly or indirectly monitoring the loads placed on critical vehicle components susceptible to failure from fatigue damage. The sample locomotive carbody structure was used for this study. Firstly, the hybrid fatigue analysis method was used with Multi-Body System (MBS) simulation and Finite Element Method (FEM) for evaluating the carbody structure dynamic stress histories. Secondly, the standard fatigue time domain method was used in fatigue analysis software FE-FATIGUE and MATLAB WAFO (Wave Analysis for Fatigue and Oceanography) tools. And carbody structure fatigue life and fatigue damage were predicted. Finally, and carbody structure dynamic stress experimental data was taken from this locomotive running between Kunming-Weishe for this analysis. The data was used to validate the simulation results based on hybrid method. The analysis results show that the hybrid method prediction error is approximately 30.7%. It also illustrates that the fatigue life and durability of the locomotive can be predicted with this hybrid method. The results of this study can be modified to be representative of the railway vehicle dynamic stress test.

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