Fatigue Strength Assessment of Ship Structures Based on the Crack Propagation Theory

2009 ◽  
Author(s):  
Song Niu ◽  
Guoqing Feng ◽  
Huilong Ren ◽  
Jian Zhang
Keyword(s):  
Crack Propagation ◽  
Function Method ◽  
Failure Modes ◽  
Analysis Method ◽  
Propagation Theory ◽  
Ship Structures ◽  
Element Analysis ◽  
Fatigue Assessment ◽  
Strength Assessment ◽  
Simplified Procedures

Fatigue damage is one of the main failure modes of ship structures. At present, the fatigue assessment of ship structures is mainly based on S-N method, such as the simplified procedures by classification societies or the spectral fatigue analysis method, etc. Because the initial flaw or crack can not be taken into account in S-N method, the fatigue assessment of ship structures based on fracture mechanics or crack propagation theory is worth to be studied. In this paper, the crack propagation theory based fatigue assessment of ship structures is studied. First, the calculation of stress intensity factor based on finite element analysis and weight function method are given, then Paris model is used to predict the crack propagation life. Finally, a numerical example is given to show the procedure of fatigue assessment of ship structures.

Different Methods for Fatigue Assessment of T Welded Joints Used in Ship Structures

2007 ◽  
Vol 51 (02) ◽  
pp. 150-159 ◽  
Author(s):  
V. Crupi ◽  
E. Guglielmino ◽  
A. Risitano ◽  
D. Taylor
Keyword(s):  
Welded Joints ◽  
Fatigue Behavior ◽  
Experimental Tests ◽  
Ship Structures ◽  
Element Analysis ◽  
Fatigue Assessment ◽  
Endurance Limits ◽  
Thermographic Analysis ◽  
Using Data ◽  
Cycle Endurance

The aim of this work is the prediction of high-cycle fatigue behavior in welded joints, which represent regions of weakness in the ship structures. The traditional methods for fatigue assessment of welded joints have some limitations. Some new methods were recently developed by Taylor: the crack modeling method (CMM) and the theory of critical distances methods (TCD). Experimental tests were carried out to define the high-cycle endurance limits of aluminum T-shaped welded joints. Using data obtained from finite element analysis (FEA), the fatigue strength was evaluated according to the CMM and the TCD. Thermographic analysis was also carried out during the experimental tests to assess the high-cycle endurance limits of the welds by means of the Risitano method (RM). The previous methods were also applied to a specific case, fatigue in T joints containing a drilled hole at different angles, which allowed us to study a typical industrial design problem involving two different features. Good predictions were achieved using all the methods.

Buckling and Ultimate Strength Assessments of Ship Structures

2013 ◽  
Author(s):  
Shengming Zhang
Keyword(s):  
Ultimate Strength ◽  
Fe Analysis ◽  
Development Work ◽  
Ship Structures ◽  
Element Analysis ◽  
Strength Assessment ◽  
Stiffened Panels ◽  
Development History ◽  
Bulk Carriers ◽  
Oil Tankers

This paper presents buckling and ultimate strength assessment methods for ship structures. Buckling and collapsing analysis approaches for plates, stiffened panels and hull girders are described and their development history and employments in ship design assessments are reviewed and discussed. Examples using non-linear finite (FE) element analysis are given and comparisons between results obtained by formulae and FE analysis are carried out. Lloyd’s Register’s recent research and development work on ultimate strength and its applications to existing oil tankers and bulk carriers are also presented.

A Comparison of Two Wave Models and Their Influence on Fatigue Damage in Ship Structures

2013 ◽  
Author(s):  
Wengang Mao ◽  
Fredhi Agung Prasetyo ◽  
Jonas W. Ringsberg ◽  
Naoki Osawa
Keyword(s):  
Fatigue Damage ◽  
Failure Modes ◽  
Maritime Industry ◽  
Ship Structures ◽  
Fatigue Assessment ◽  
Practical Applications ◽  
The North ◽  
Fatigue Design ◽  
Wave Models ◽  
Different Sources

In the maritime industry, fatigue failure is one of the most significant failure modes for ship structures. The fatigue damage in ship structures is mainly caused by the variation of wave loadings applied on ships, leading to variable structural stresses. Therefore, a reliable description of wave environments encountered during a ship’s service life is essential for accurate fatigue assessment of ship structures. Besides the wave scatter diagram provided by classification society rules, different statistical wave models have also been built up to model wave environments along arbitrary ship routes. The wave models could provide more specific wave environment for any chosen sailing routes of an individual ship. They may have the potential to be used for some practical applications, such as conceptual ship fatigue design, remaining fatigue life prediction when a ship plans to change its original trade region, and crack maintenance planning etc. Since the development of these models may be based on different sources, e.g. satellite measurements, hindcast data, buoys, etc., the reliability and consistence of wave generations from various wave models must be validated by the measured wave environments in order to be used for those practical applications. In this paper, waves generated from two different wave models, one based on hindcast data and one mainly on satellite data, are compared with measured wave environments encountered by a 2800 TEU container vessel on the North Atlantic route. These wave models are used in the calculation of the fatigue damage in the vessel. The results obtained using waves generated from the two wave models are compared with the fatigue damage calculated based on strain measurements in the ship. Recommendations for future development of the wave models and further investigation to make the applications more realistic for ship fatigue assessment are also presented.

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.

Fatigue Crack Propagation Analysis of Nozzle Corner Using the Influence Function Method

2002 ◽  
Author(s):  
Mayumi Ochi ◽  
Kiminobu Hojo ◽  
Takeharu Nagasaki
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Influence Function ◽  
Function Method ◽  
Fatigue Cracks ◽  
Crack Depth ◽  
Element Analysis ◽  
Influence Function Method ◽  
Calculation System

A calculation system has been developed in order to evaluate the thermal fatigue crack propagation of a semi-elliptical crack on the corner of a nozzle. One fatigue crack was assumed on the inner surface of the nozzle corner of a representative PWR reactor vessel. The stress intensity factors K were calculated at the deepest and outermost surface points of the crack using the influence function method. A database was prepared for the cracks with a depth of 0.022 t − 0.5 t (t: pressure vessel thickness) and an aspect ratio of 0.1a/c – 1.0 a/c (a: crack depth and c: half surface width). Eight-noded solid elements and the finite element analysis code MARC were used. The calculation system enables the propagation of fatigue cracks at nozzle corners to be carried out in a very short time.

A Two-Stage Strength Assessment Methodology for Deep Concrete Cap Beams

2019 ◽  
Author(s):  
Rafael A. Salgado ◽  
Anish Sharma ◽  
Serhan Guner
Keyword(s):  
Finite Element ◽  
Failure Modes ◽  
Cost Savings ◽  
Assessment Methodology ◽  
Two Stage ◽  
Element Analysis ◽  
Strength Assessment ◽  
Traffic Loads ◽  
Existing Bridges

<p>A significant portion of the nation’s aging bridge inventory consists of bridges with deep cap beams which were not designed to carry modern traffic loads. A strength assessment of these bridges is required for accurately predicting their load and deformation capacities. This paper proposes a two-stage strength assessment methodology for deep cap beams based on a nonlinear finite element analysis. To validate the finite element modeling approach, five pier caps experimentally investigated in the literature were analyzed. Crack patterns, load-displacement response, failure modes, and governing critical members were investigated under near collapse conditions. The complete proposed methodology was employed on a case study involving five existing bridges located in Ohio and the predicted capacities were compared with the traditional sectional and strut-and-tie methods. The proposed methodology has the potential to reduce the number of bridges found overloaded using traditional methods, resulting in significant cost savings.</p>

Initial Crack Propagation Directions of Branched Crack under Tension with Finite Element Analysis

2010 ◽  
Vol 168-170 ◽  
pp. 2553-2557
Author(s):  
Yong Zhu ◽  
Ray K.L. Su ◽  
Qi Cai Yu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Elastic Stress ◽  
Initial Crack ◽  
Stress Fields ◽  
Analysis Method ◽  
Intensity Factors ◽  
Element Analysis

The initial crack propagation directions of branched cracks under tension are investigated. In this study, the material is assumed to be brittle and deformed linear elastically. The elastic stress fields and stress intensity factors are obtained by using finite element analysis method. Various parameters which including the lengths, the directions and the locations of branched cracks are investigated to study their effects on the crack initiation angles. Three kinds of crack propagation criteria are employed to obtain the crack initiation angles. The effects of crack propagation directions due to the use of different crack initiation criteria are studied and discussed in details.

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.

Use of the Finite Element Analysis Method in Pedodontics

2018 ◽  
Vol 55 (4) ◽  
pp. 666-675
Author(s):  
Mihaela Tanase ◽  
Dan Florin Nitoi ◽  
Marina Melescanu Imre ◽  
Dorin Ionescu ◽  
Laura Raducu ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Structural Model ◽  
Analysis Method ◽  
Ansys Software ◽  
Concentrated Force ◽  
Element Analysis ◽  
Finite Element Analysis Method ◽  
The Finite Element Analysis ◽  
Solid Type

The purpose of this study was to determinate , using the Finite Element Analysis Method, the mechanical stress in a solid body , temporary molar restored with the self-curing GC material. The originality of our study consisted in using an accurate structural model and applying a concentrated force and a uniformly distributed pressure. Molar structure was meshed in a Solid Type 45 and the output data were obtained using the ANSYS software. The practical predictions can be made about the behavior of different restorations materials.

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