Hot-Spot Stress Approach for Fatigue Assessment of Welded Joints

2010 ◽  
Author(s):  
Nur Syahroni ◽  
◽  
Stig Berge ◽  
Keyword(s):  
Welded Joints ◽  
Hot Spot ◽  
Hot Spot Stress ◽  
Fatigue 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.

Probabilistic S-N Fatigue Assessment Methods for Welded Joints in Offshore Structures

2008 ◽  
Author(s):  
A. Muhammed ◽  
A. Stacey
Keyword(s):  
Welded Joints ◽  
Hot Spot ◽  
Offshore Structures ◽  
Assessment Methods ◽  
Nominal Stress ◽  
Stress Range ◽  
Hot Spot Stress ◽  
Fatigue Assessment ◽  
Jacket Structures ◽  
Stress Estimation

A study of probabilistic fatigue assessment methods for offshore structures confirmed that fatigue life predictions for offshore welded joints is dominated by uncertainties in hot spot stress estimation, arising from uncertainties in nominal stress and stress concentration factors. Analysis of data from previous fatigue studies on North Sea jacket structures conducted in the late 1980s suggests that nominal stresses are, in general, overestimated by about 30% and the COV of the bias is about 0.35. The study demonstrated that in-service fatigue failure probability is not only dependent on the COV but also on the median bias of the nominal stress range. A number of nominal stress COVs are recommended with associated median values for general offshore application. Distributions are also suggested for other variables such as Miner’s damage sum and the S-N design curve coefficients. Methods based on long-term stress range distribution with random parameters to cater for uncertainties in stress estimation are described and example calculations are given.

scholarly journals Use of 3D Scan of Weld Joint in Finite Element Analysis and Stochastic Analysis of Hot-Spot Stresses in Tubular Joint for Fatigue Life Estimation

2019 ◽  
Author(s):  
Mikkel L. Larsen ◽  
Vikas Arora ◽  
Marie Lützen ◽  
Ronnie R. Pedersen ◽  
Eric Putnam
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Welded Joints ◽  
Hot Spot ◽  
Strain Range ◽  
Fe Model ◽  
Design Codes ◽  
Element Analysis ◽  
Hot Spot Stress ◽  
Weld Toe

Abstract Several methods for modelling and finite element analysis of tubular welded joints are described in various design codes. These codes provide specific recommendations for modelling of the welded joints, using simple weld geometries. In this paper, experimental hot-spot strain range results from a full-scale automatically welded K-node test are compared to corresponding finite element models. As part of investigating the automatically welded K-joint, 3D scans of the weld surfaces have been made. These scans are included in the FE models to determine the accuracy of the FE models. The results are compared to an FE model with a simple weld geometry based on common offshore design codes and a model without any modelled weld. The results show that the FE model with 3D scanned welds is more accurate than the two simple FE models. As the weld toe location of the 3D scanned weld is difficult to locate precisely in the FE model and as misplacement of strain gauges are possible, stochastic finite element modelling is performed to analyse the resulting probabilistic hot-spot stresses. The results show large standard deviations, showing the necessity to evaluate the hot-spot stress method when using 3D scanned welds.

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).

scholarly journals Research on Fatigue Properties of Typical Welded Joints of DH36 Steel at −60 °C

2020 ◽  
Vol 10 (11) ◽  
pp. 3742
Author(s):  
Weidong Zhao ◽  
Guoqing Feng ◽  
Wenchao Liu ◽  
Huilong Ren
Keyword(s):  
Stress Concentration ◽  
Welded Joints ◽  
Room Temperature ◽  
Polar Region ◽  
Hot Spot ◽  
Fatigue Properties ◽  
Test Results ◽  
Hot Spot Stress ◽  
Confidence Levels ◽  
Better Than

As the development of the polar region continues to increase, the fatigue properties of structures at low temperature are increasingly receiving researcher attention. This study aimed to investigate the fatigue properties of T-welded and cruciform welded joints at −60 °C. Logarithmic S–N curves based on the hot-spot stress of the T-welded and cruciform welded joints at 50% and 95% confidence levels were obtained at −60 °C. The test results showed that the fatigue properties of T-welded joints were almost 2–7% better than those of the cruciform welded joints at −60 °C. Factors that affected the fatigue properties of welded joints, such as the stress concentration factor, microstructure, Vickers hardness profiles, and fractography, were also studied and the test results showed that the fatigue properties of cruciform welded joints at −60 °C were 57.215% better than at room temperature.

Fatigue Strength Evaluation for Gas Welded Joint of Similar and Dissimilar Materials

2007 ◽  
Vol 345-346 ◽  
pp. 359-362
Author(s):  
Dong Ho Bae ◽  
Yeong Sin Kim ◽  
Gyu Young Lee ◽  
Kwang Jin Park
Keyword(s):  
Welded Joints ◽  
Welded Joint ◽  
Hot Spot ◽  
Tensile Load ◽  
Dissimilar Materials ◽  
Fatigue Tests ◽  
Design Criterion ◽  
Hot Spot Stress ◽  
Fatigue Design ◽  
Fatigue Design Criterion

In order to establish a reasonable and integrated fatigue design criterion for the long life design of the gas welded body structure, stress distribution around the gas welded joints subjected to tensile load was numerically analyzed. And also, the P-Nf curves were obtained by fatigue tests. By using these results, P-Nf curves were rearranged in the σ-Nf relation with the hot spot stress at the welded joint. And a guideline for fatigue design of gas welded joints was proposed.

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
Sign in / Sign up

Export Citation Format

Share Document