scholarly journals Improvement of the Ship Emergency Response Procedure in Case of Collision Accident Considering Crack Propagation during Salvage Period

2021 ◽  
Vol 9 (7) ◽  
pp. 737
Author(s):  
Ivana Gledić ◽  
Antonio Mikulić ◽  
Joško Parunov
Keyword(s):  
Crack Propagation ◽  
Emergency Response ◽  
Software Tool ◽  
Fatigue Loading ◽  
Rayleigh Distribution ◽  
Crack Size ◽  
Initial Crack ◽  
Stiffened Panel ◽  
Wave Loads ◽  
Hull Girder

Specialized procedures to help in the emergency response situations following ship accidents have been under development by the Classification Societies. Such procedures consider the hull-girder collapse as the most important failure mode, without the possibility of crack propagation caused by fluctuating wave loads. In the present study, the fatigue crack propagation in the main deck of the oil tanker damaged in collision during salvage is investigated. The shape and size of the damage are modelled using the realistic bow shape of the striking ship and historical data of ship accidents. The stress intensity factor (SIF) across the main deck of the struck ship is calculated numerically and by the method based on the available experimental results of the crack propagation in the stiffened panel. Fluctuating wave–induced stresses in short-term sea conditions during salvage are obtained by Monte Carlo simulation (MC) based on Rayleigh distribution. Cycle-by-cycle crack propagation is calculated using Paris law. Many salvage simulations are performed to cover different possible time-histories of the fatigue loading. Results of the analysis are presented as histogram of the crack increase during salvage. Parametric analysis is performed to investigate the influence of the sea state severity, initial crack size, and towing duration on the final crack size. The proposed procedure can be considered as a part of a software tool for emergency response action during salvage of damaged ship.

Method of Construction for High Cycle Fatigue Resistant Pressure Vessels in Hydrogen Service

2018 ◽  
Author(s):  
Pooya Mahmoudian
Keyword(s):  
Fatigue Crack ◽  
Fracture Mechanics ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Applied Pressure ◽  
Design Procedure ◽  
Fatigue Loading ◽  
Crack Size ◽  
Initial Crack ◽  
Pressure Vessels

Currently, pressure vessels that operate in hydrogen service and subjected to fatigue must be designed using a defect tolerant design procedure. This means that first the fracture mechanics properties of the material being considered must be measured in hydrogen at the maximum service pressure. The properties are fatigue crack propagation properties and threshold stress intensity factor for hydrogen embrittlement (KIHE). With these properties, a fatigue crack propagation life can be estimated assuming an initial crack size and geometry and growing this defect to failure. The property measurements are costly and can only be performed at a few laboratories. Furthermore, the resulting lives are usually very short because of the assumed initial crack size. These things limit the application of this design method to lower cycle or static loading applications. This work introduces a cost-effective method of design and construction of pressure vessels for high cycle use in hydrogen service at pressures below 40,000 psi that eliminates the need for determining fracture mechanics properties in hydrogen environment. The method uses shrink fit construction of a liner inside a jacket. The method requires that when the pressure is applied, the magnitude of the resultant stress at the pressure boundary of the liner is more compressive than the magnitude of the applied pressure and the maximum allowed size of defect in the jacket at the interface between the jacket and the liner is such that when the cyclic stress is applied the resultant fatigue loading of that defect at that location to be less than the threshold value for growth of that defect.

scholarly journals Fatigue Life Assessment and Reliability Analysis of Cope-Hole Details in Steel Bridges

2020 ◽  
Vol 15 (1) ◽  
pp. 26-46 ◽  
Author(s):  
Ping Liao ◽  
Yongbao Wang ◽  
Xiucheng Zhang ◽  
Renda Zhao ◽  
Yi Jia ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Crack Propagation ◽  
Reliability Index ◽  
Crack Size ◽  
Initial Crack ◽  
Steel Bridges ◽  
Fatigue Reliability ◽  
Intensity Factors ◽  
Cope Hole

Cope-hole details are widely applied to steel bridges. However, the safety of steel bridges is influenced by the fatigue performance of welded details. So, cope-hole details with flange and web subjected to axial loads were selected as the research object. Based on the basic theory of linear elastic fracture mechanics and the Finite Element Method, the stress intensity factors of cope-holes details were calculated. The influences of geometry size and crack size of the detail on the stress intensity factors were then investigated. The Paris model of fatigue crack propagation predicted the crack propagation life of cope-hole details. Besides, the fatigue limit-state equation was also established to analyse the effect of random variables (such as initial crack size, critical crack size, crack propagation parameter) on the fatigue reliability index. Finally, the recommended value of the detection period was present. The results show that the stress intensity factor gradually increases with the increase of the cope-hole radius, the weld size, the flange plate thickness, the crack length and the web thickness. However, it gradually decreases with the increase of the ratio of the long and short axle to the crack. The predicted number of fatigue cyclic loading required by the fatigue crack depth propagating from 0.5 mm to 16 mm under nominal stress amplitude of 63 MPa is 122.22 million times. The fatigue reliability index decreases with the fatigue growth parameter, the crack shape ratio and the mean of initial crack size increasing, which is relatively sensitive. However, the variation coefficient of the initial crack size has little effect on it. The detection period of cope-hole details is the service time corresponding to the fatigue accumulated cyclic loading of 198.3 million times.

Study on Crack Propagation of a Bearing Inner-Ring under Cyclic Loading

2016 ◽  
Vol 851 ◽  
pp. 317-321
Author(s):  
Jie Zheng ◽  
Ya Xiong Hu
Keyword(s):  
Fatigue Crack ◽  
Cyclic Loading ◽  
Crack Propagation ◽  
Failure Modes ◽  
Great Influence ◽  
Crack Size ◽  
Initial Crack ◽  
Fe Model ◽  
Analysis Method ◽  
Propagation Characteristics

The performance of bearing has great influence on mechanical components and fatigue is one of the most important failure modes. However, the occurrence of crack is inevitable in the process of manufacture and usage. Research on characteristics of crack propagation is an important supplement and development to the traditional fatigue analysis method and test. The FE model of a bearing inner ring with a semielliptical crack is established in ABAQUS to carry out further analysis of crack propagation. The crack propagation characteristics with different initial crack size are analyzed and the energy changing law during crack propagation has been investigated under cyclic loading though FE calculation. The results provide valuable guidance for further study on fatigue crack propagation of bearings.

scholarly journals Fatigue Reliability Analysis of Tunnelling Boring Machine Cutterhead with Cracks

2020 ◽  
Author(s):  
jie li ◽  
bin zhang ◽  
chuang liu ◽  
jingbo guo
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Stress Amplitude ◽  
Crack Size ◽  
Initial Crack ◽  
Load Spectrum ◽  
Factors Affecting ◽  
Main Factors ◽  
Fatigue Crack Propagation Life

The cutterhead of tunnel boring machine is a large-scale metal welding structure, which is prone to problems such as wear and cracking during the tunnelling process. For the issue, the fatigue crack propagation rate model of cutterhead under different reliability was established, based on the damage tolerance of cutterhead. Its dangerous position of cutterhead failure was determined by using finite element method. According to the fatigue load spectrum, the fatigue propagation life of cutterhead under different reliability was calculated, the main factors affecting the reliability of cutterhead were analyzed and the engineering experiment is carried out. The results show that three dangerous positions of the cutterhead failure are the junction of the split plane, the maximum deformation of the block and the central cutter seat. The load stress amplitude and initial crack size are the main factors affecting the crack propagation life and the reliability of cutterhead. With the increase of load stress amplitude and initial crack size of cutterhead, the fatigue crack propagation life of cutterhead decreases and the reliability is worse. When the initial crack size of cutterhead is greater than 0.5mm, the fatigue crack propagation life of cutterhead decreases obviously. The research results provide a scientific basis for crack detection, life prediction and reliability evaluation of cutterhead structure.

Prediction of Ship Response Statistics in Severe Sea Conditions Using RANS

2012 ◽  
Author(s):  
Jan Oberhagemann ◽  
Jens Ley ◽  
Bettar Ould el Moctar
Keyword(s):  
Structural Design ◽  
International Association ◽  
Rayleigh Distribution ◽  
Ship Motions ◽  
Wave Loads ◽  
Large Wave ◽  
Hull Girder ◽  
New Methods ◽  
Design Loads ◽  
Wave Induced

The International Association of Classification Societies (IACS) promotes the paradigm shift in structural design rules for ships towards risk based approaches. This requires improvements in the assessment of structural design loads and new methods for estimation of wave loads and responses, amongst others with respect to extreme value distributions. In this paper we present a numerical method based on the solution of RANS equations to deal with large wave-induced ship motions and corresponding loads for different ship types. Nonlinearities of wave excitation and ship response are included. Short-term ship response distributions from time domain simulations are compared with model test data. Significant deviations from Rayleigh distribution of amplitudes are observed, especially for hull girder loads including effects of structural elasticity.

scholarly journals Mode I Crack Propagation Experimental Analysis of Adhesive Bonded Joints Comprising Glass Fibre Composite Material under Impact and Constant Amplitude Fatigue Loading

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4380
Author(s):  
Alirio Andres Bautista Villamil ◽  
Juan Pablo Casas Rodriguez ◽  
Alicia Porras Holguin ◽  
Maribel Silva Barrera
Keyword(s):  
Crack Propagation ◽  
Structural Integrity ◽  
Crack Propagation Rate ◽  
Fatigue Loading ◽  
Propagation Rate ◽  
Operating Conditions ◽  
Impact Testing ◽  
Mode I ◽  
Mode I Crack ◽  
Constant Amplitude

The T-90 Calima is a low-wing monoplane aircraft. Its structure is mainly composed of different components of composite materials, which are mainly bonded by using adhesive joints of different thicknesses. The T-90 Calima is a trainer aircraft; thus, adverse operating conditions such as hard landings, which cause impact loads, may affect the structural integrity of aircrafts. As a result, in this study, the mode I crack propagation rate of a typical adhesive joint of the aircraft is estimated under impact and constant amplitude fatigue loading. To this end, effects of adhesive thickness on the mechanical performance of the joint under quasistatic loading conditions, impact and constant amplitude fatigue in double cantilever beam (DCB) specimens are experimentally investigated. Cyclic impact is induced using a drop-weight impact testing machine to obtain the crack propagation rate (da/dN) as a function of the maximum strain energy release rate (GImax) diagram; likewise, this diagram is also obtained under constant amplitude fatigue, and both diagrams are compared to determine the effect of each type of loading on the structural integrity of the joint. Results reveal that the crack propagation rate under impact fatigue is three orders of magnitude greater than that under constant amplitude fatigue.

Assessment of Residual Ultimate Strength of VLCC According to Damage Extents and Average Compressive Strength of Stiffened Panel

2014 ◽  
Author(s):  
Ji-Myung Nam ◽  
Joonmo Choung ◽  
Se-Yung Park ◽  
Sung-Won Yoon
Keyword(s):  
Compressive Strength ◽  
Ultimate Strength ◽  
Probabilistic Approach ◽  
Stiffened Panel ◽  
Moment Capacity ◽  
Hull Girder ◽  
Damage Area ◽  
Damage Indices ◽  
Smith Method ◽  
Average Compressive Strength

This paper presents the prediction of residual ultimate strength of a very large crude oil carrier considering damage extents due to collision and grounding accidents. In order to determine extents of damage, two types of probabilistic approaches are employed: deterministic approach based on regulations based on ABS [1], DNV [2], and MARPOL [3] and probabilistic approach based on IMO probability density functions (PDFs) (IMO guidelines [4]). Hull girder ultimate strength is calculated using Smith method which is dependent on how much average compressive strength of stiffened panel is accurate. For this reason, this paper uses two different methods to predict average compressive strength of stiffened panel composing hull girder section: CSR formulas and nonlinear FEA. Calculated average compressive strength curves using CSR formulas (IACS [5, 6]) and nonlinear FEA are imported by an in-house software UMADS. Residual ultimate moment capacities are presented for various heeling angles from 0° (sagging) to 180° (hogging) by 15° increments considering possible flooding scenarios. Three regulations and IMO guidelines yield minimum of reduction ratios of hull girder moment capacity (minimum of damage indices) approximately at heeling angles 90° (angle of horizontal moment) and 180° (angle of hogging moment), respectively, because damage area is located farthest from neutral axis.

The Behavior of Tiled Laminate GFRP Composites, a Class of Robust Materials for Civil Applications

2019 ◽  
Author(s):  
Wouter De Corte ◽  
Jordi Uyttersprot ◽  
Wim Van Paepegem
Keyword(s):  
Crack Propagation ◽  
Numerical Simulations ◽  
Bridge Deck ◽  
Fatigue Loading ◽  
Structural Behavior ◽  
Gfrp Composites ◽  
Civil Structures ◽  
Laminate Composites ◽  
Deck Panels ◽  
Highly Loaded

<p>This paper focuses on the structural behavior of tiled laminate composites. Such laminates, in which the plies are not parallel to the outer surfaces are found in GFRP bridge deck panels. The technology is developed for the construction of robust GFRP panels useful in highly loaded structures such as bridges or lock gates. In civil structures, the drawback in traditional FRP sandwich structures has always been debonding of skin and core. Such a debonding problem may occur after unintentional impact, followed by fatigue loading. Through the concept of using overlapping Z-shaped and two-flanged web laminates, alternating with polyurethane foam cores, debonding is no longer possible in vacuum infused GFRP bridge deck panels. In such panels, the fibers in the upper and lower skins as well as in the vertical webs run in all directions, rendering a resin-dominated crack propagation impossible. As a result of the integration of core and skin reinforcement, a skin material is created in which the reinforcement is not parallel to the outer surfaces, but tiled. Based on experimental results and numerical simulations the relevance of tiled laminates for civil applications is demonstrated.</p>

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