Methods for Fatigue Assessment of Critical Ship Details

2004 ◽  
Author(s):  
Xiaozhi Wang ◽  
Haihong Sun ◽  
Zhan Cheng
Keyword(s):  
Hot Spot ◽  
Mesh Size ◽  
High Strength ◽  
Ship Design ◽  
Hot Spot Stress ◽  
Fatigue Assessment ◽  
Strength Assessment ◽  
Type Selection ◽  
Element Type ◽  
Steel Weight

Fatigue assessment, as part of ship design, was not required until about 10 years ago, due to the increasing use of high strength steel and demand for minimizing structure weight. As early as 1993, ABS (American Bureau of Shipping) published Guidance on fatigue strength assessment of tankers (the latest version of the Guide can be found in [1]). Since then, ship design has been developed with more optimization involved, as a balance of cost, steel weight and safety. Consequently, fatigue assessment has become a more and more important factor in ship design. There are various methods, design codes and recommended practices on fatigue design and assessment of welded structures. Industries have tried to organize Joint Industry Projects (JIPs) to further develop the method or see the possibility of harmonizing the codes or practices. Individuals have also made their efforts to provide information from view points of designers, operators or regulators. This paper addresses some of the available methods applicable for critical ship details through the case studies of bilge knuckle joint of an oil tanker and a side longitudinal/frame connection of an FPSO. Various methods of hot spot stress calculation including mesh size schemes and element type selection will be evaluated and comparison of fatigue lives from the hot spot stress methods with associated S-N curves will be made with the experimental data.

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).

A Comparative Study on the Fatigue Evaluation for Weldments under Out-of Plane Bending Load Using Structural Stress and Hot Spot Stress

2006 ◽  
Vol 326-328 ◽  
pp. 995-998
Author(s):  
Myung Hyun Kim ◽  
Chung In Ha ◽  
Sung Won Kang ◽  
Jeong Hwan Kim ◽  
Jae Myung Lee
Keyword(s):  
Fatigue Strength ◽  
Hot Spot ◽  
Mesh Size ◽  
Structural Stress ◽  
Hot Spot Stress ◽  
Strength Assessment ◽  
Bending Load ◽  
Load Carrying ◽  
Out Of Plane ◽  
Plane Bending

Fatigue strength assessments with two types of load carrying fillet weldment under out-of-plane bending load have been carried out by using both hot spot stress and structural stress methods. Basis for the derivation of structural stress method is discussed in detail. Finite element analyses using shell elements models have been performed for the fatigue strength assessment of weldments. As a result of the fatigue strength evaluation for load carrying transverse fillet weldment, hot spot stress method is found to be consistent with structural stress method as well as measurement. Hot spot stress, however, estimated for the load carrying longitudinal fillet weldment exhibit large variation with respect to mesh size and element type while the calculated structural stress for the longitudinal fillet weldment is relatively independent of mesh size. The fatigue life estimation according to structural stress has been introduced with the master S-N curve.

Fatigue Strength Assessment of the Cruciform Fillet Welded Joint Using Hot-spot Stress Approach

2005 ◽  
Vol 29 (11) ◽  
pp. 1488-1493 ◽  
Author(s):  
Chang-Sung Seok ◽  
Dae-Jin Kim ◽  
Jae-Mean Koo ◽  
Jung-Won Seo ◽  
Byeong-Choon Goo
Keyword(s):  
Fatigue Strength ◽  
Welded Joint ◽  
Hot Spot ◽  
Hot Spot Stress ◽  
Strength Assessment ◽  
Fatigue Strength Assessment

Qualification of the Notch Stress Approach for the Fatigue Assessment of Welded Pressure Equipment and Power Plant Components

2017 ◽  
Author(s):  
Jürgen Rudolph ◽  
Ralf Trieglaff ◽  
René Stößlein ◽  
Fabian Hauser
Keyword(s):  
Test Data ◽  
Welded Joints ◽  
Low Cycle Fatigue ◽  
Hot Spot ◽  
Pressure Vessels ◽  
Assessment Procedure ◽  
Element Analysis ◽  
Hot Spot Stress ◽  
Fatigue Assessment ◽  
Notch Stress

The fatigue assessment of welded joints in different engineering disciplines is usually based on nominal, structural or notch stresses on one hand (elastic concept using component fatigue curves of load controlled test data) and local strains on the other hand (elasto-plastic concept using material fatigue curves of strain-controlled push-pull test data of un-notched and polished standard specimens). The concepts of the first mentioned group are implemented in widespread standards and recommendations such as [1] to [3]. The fatigue assessment procedure of the European standard for unfired pressure vessels (EN 13445-3, Clause 17 & 18 and related annexes) [4] is currently under revision with one focus on the elaboration of user friendly fatigue assessment options for welded components [5]. The current state of the art focuses on the application of an adapted structural hot spot stress approach to the fatigue assessment of welded pressure equipment [5]. Although this is a significant step forward, the implementation of a notch stress approach can furtherly increase the fatigue assessment options by detailed weld seam analysis. The paper focuses on respective methodological proposals and application examples of typical welded joints. The finite element analysis as part of the procedure has to be harmonized with the requirements of the assessment procedure. Of course, the compatibility of the hot spot stress approach and a notch stress approach has to be guaranteed for individual examples. The direct comparison of the different approaches allows for a qualitative evaluation of methods. The application of an appropriate master fatigue curve FAT100 and the limitations with regard of stress/strain ranges in the low cycle fatigue (LCF) regime as well as the fatigue assessment of welded joints with mild weld toe notches is the subject of special considerations. The latest recommendations of German Welding Society (DVS) [6] constitute a reference for the last two subjects raised.

FATIGUE STRENGTH ASSESSMENT OF THE FILLET WELDED CRUCIFORM JOINTS

2006 ◽  
Vol 20 (25n27) ◽  
pp. 4225-4230
Author(s):  
DAE-JIN KIM ◽  
CHANG-SUNG SEOK ◽  
JAE-MEAN KOO
Keyword(s):  
Fatigue Strength ◽  
Stress Concentration ◽  
Hot Spot ◽  
Fatigue Tests ◽  
Structural Stress ◽  
Hot Spot Stress ◽  
Cruciform Joints ◽  
Strength Assessment ◽  
Load Carrying ◽  
Cruciform Joint

In this study, fatigue tests to obtain S - N curves and FE analyses to obtain structural stress concentration factors were conducted for two types of fillet welded cruciform joints, that is, load-carrying and non load-carrying types. The obtained S - N curve of the load-carrying joint was changed to that based on hot-spot stress. As a result, the S - N curve of the load-carrying joint based on hot-spot stress almost coincided with that of the non load-carrying joint based on nominal stress. The fatigue strength of a welded joint which has a different geometry from that of the non load-carrying cruciform joint but the same bead profile as that of the non load-carrying cruciform joint could be estimated by using both the structural stress concentration factor at the weld toe position obtained from FEM and the nominal S - N curve of the non load-carrying cruciform joint from experiment.

scholarly journals Definition of hot spot Stress in welded structure for fatigue assessment (2nd Report)

1991 ◽  
Vol 1991 (170) ◽  
pp. 705-721
Author(s):  
Susumu Machida ◽  
Masaaki Matoba ◽  
Hitoshi Yoshinari ◽  
Ryuichi Nishimura
Keyword(s):  
Hot Spot ◽  
Hot Spot Stress ◽  
Fatigue Assessment ◽  
Welded Structure ◽  
Definition Of

Fatigue Assessment of Ship Structures using Hot Spot Stress and Structural Stress Approaches with Experimental Validation

2008 ◽  
Author(s):  
Myung Hyunn Kim ◽  
Seong Minn Kim ◽  
Jae Myung Lee ◽  
Sung Wong Kang
Keyword(s):  
Experimental Investigation ◽  
Experimental Validation ◽  
Hot Spot ◽  
Initial Study ◽  
Systematic Investigation ◽  
Structural Stress ◽  
Ship Structures ◽  
Gusset Plates ◽  
Hot Spot Stress ◽  
Fatigue Assessment

The aim of this study is to investigate fatigue assessment of typical ship structures employing structural stress approach and to compare with hot spot stress approach. As an initial study of the systematic validation efforts on structural stress method, an experimental investigation is performed on a series of edge details with welded gusset plates. Extrapolation based hot spot stress using converged mesh were also calculated for each specimen types. Having validated the application of structural stress for small edge details, a systematic investigation is carried out for a fatigue assessment of typical ship structures employing structural stress approach. Fatigue strength of side shell connection of a 8,100 TEU container vessel is evaluated using hot spot stress and structural stress employing simplified fatigue analysis.

Fatigue assessment of a steel truss bridge based on multi-dimensional finite element modelling

2021 ◽  
Author(s):  
Kris Hectors ◽  
Hans De Backer ◽  
Lien Saelens ◽  
Wim De Waele
Keyword(s):  
Finite Element ◽  
Decision Support ◽  
Finite Element Modelling ◽  
Hot Spot ◽  
Hot Spot Stress ◽  
Fatigue Assessment ◽  
Railway Bridges ◽  
Element Modelling ◽  
Railway Traffic ◽  
Steel Truss Bridge

<p>This paper presents a multidimensional finite element modelling approach for the fatigue assessment of welded railway bridges based on a case study of a railway bridge in Belgium. The nominal stress approach of Eurocode 3 is compared to a hot spot stress based fatigue life calculation for the standardized fatigue load models for railway traffic. Hot spot stresses are calculated with an in-house developed framework that allows automated determination of hot spot stresses. It is discussed how this work can fit in a larger decision support system in the scope of structural health monitoring. The presented approach proves to be better for decision support compared to the conventional approach in the Eurocode.</p>

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