Fatigue crack curvature under the weld toe in a tubular joint

2021 ◽  
pp. 543-550
Author(s):  
D. Bowness ◽  
M.M.K. Lee
Keyword(s):  
Fatigue Crack ◽  
Weld Toe ◽  
Tubular Joint

Fatigue Crack Growth Analyses of Offshore Structural Tubular Joint

1989 ◽  
Vol 111 (1) ◽  
pp. 49-55 ◽  
Author(s):  
H. C. Rhee
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Three Dimensional ◽  
Diagram Method ◽  
The North ◽  
Weld Toe ◽  
Tubular Joint

Fracture mechanics fatigue life estimation procedures have been developed for offshore structural tubular joints through analyzing a K-joint under the North Sea environment. The objective of this study was to establish reliable procedures for estimating the remaining fatigue life of a tubular joint with cracklike defects. The analysis approach was the utilization of fracture mechanics methods for fatigue crack growth and failure analyses. In this study, the fully mixed mode stress intensity factors of weld toe surface flaws of the K-joint, which were calculated through detailed three-dimensional finite element analyses, were used for fatigue crack growth simulation. For the failure analyses, the failure assessment diagram method was used to predict the conditions for brittle fracture during fatigue crack propagation. The loading conditions considered in the analyses are the brace axial force, in and out-of-plane bending, and torsion.

Fatigue crack propagation analysis for multiple weld toe cracks in cut-out fatigue test specimens from a girth welded pipe

2017 ◽  
Vol 94 ◽  
pp. 158-165 ◽  
Author(s):  
John H.L. Pang ◽  
Hsin Jen Hoh ◽  
Kin Shun Tsang ◽  
Jason Low ◽  
Shawn Caleb Kong ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Test ◽  
Fatigue Crack Propagation ◽  
Propagation Analysis ◽  
Weld Toe ◽  
Welded Pipe

scholarly journals Analysis of the Fatigue Crack Evolution of Corrugated Web Girders

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 869
Author(s):  
Guoqian Wei ◽  
Fan Ye ◽  
Shanshan Li ◽  
Siwen Chen
Keyword(s):  
Fatigue Crack ◽  
Crack Front ◽  
Small Region ◽  
Initial Crack ◽  
Evolution Process ◽  
Crack Evolution ◽  
Element Analysis ◽  
Bending Load ◽  
Corrugated Web ◽  
Weld Toe

Based on linear elastic fracture mechanics (LEFM), the fatigue crack evolution process and behavior of corrugated web girders were studied. The global finite element analysis (FEA) model of corrugated web girders was first developed and the equivalent structural stress method was used to reveal the dangerous locations along the weld under the bending load. The weld toe between the tension flange and the web weld, which is near the intersection of the inclined fold and the parallel fold, was determined as the fatigue crack easy-initiating location. Then a small region containing the crack-prone site was extracted as the sub-model for a crack propagating simulation. A semi-circle initial crack with 0.1 mm radius was inserted at the crack easy-initiating location. The stress intensity factors (SIFs; KI, KII, and KIII) of some discrete points along the crack front were calculated by the M-integral method. Based on Nasgro law, the geometry of the new crack front with a given extension length was obtained. Finally, the complete evolution process of the crack propagation was simulated. Results showed that the dominant crack propagating mode is open type (Mode I) and KI is the most important propagating driving force. According to the crack front shape evolution, the whole propagating process was divided into 6 stages. An obvious kink of the crack was found in stage 1, which covered only a very short time. The stages 3, 4 and 5 accounted for the majority of life, among which the stage 3 accounted for as high as 81% of the total life. Therefore, the cycles of the weld toe crack propagating from 0.1 mm to the thickness of the flange can be defined as the prediction life of this kind of structures.

Three-dimensional stress analysis of tubular joint using rezone technique

1986 ◽  
Vol 13 (3) ◽  
pp. 382-385
Author(s):  
G. S. Bhuyan ◽  
M. Arockiasamy ◽  
K. Munaswamy
Keyword(s):  
Stress Analysis ◽  
Transition Zone ◽  
Degrees Of Freedom ◽  
Hot Spot ◽  
Three Dimensional ◽  
Axial Loading ◽  
Boundary Displacement ◽  
Solid Element ◽  
Weld Toe ◽  
Tubular Joint

This note presents three-dimensional stress analysis results of a welded tubular T-joint under axial loading, using rezone technique. The rezone technique is used to reduce computer storage requirements, as well as solution costs, that result from the large number of degrees-of-freedom associated with three-dimensional analysis of the entire joint using solid elements. The hot-spot region around the weld toe and the weld reinforcement are modelled using three-dimensional incompatible 8-node brick and 6-node prism elements. The boundary nodal displacements for the rezoned model are obtained from plate analysis of the entire joint. The boundary values, at the plate-to-solid element transition zone, are distributed between two solid element nodes maintaining boundary displacement compatibility. The stresses at the critical lines, obtained from the rezoned analysis, are compared with those of the entire three-dimensional and plate model analyses. Key words: tubular joint, rezoned model, transition zone, boundary displacement compatibility, incompatible elements.

Fatigue Algorithm for Modeling Many Weld Toe Cracks Propagating at Welded Joints

2016 ◽  
Author(s):  
Kin Shun Tsang ◽  
John H. L. Pang ◽  
Hsin Jen Hoh
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Welded Joints ◽  
Multiple Cracks ◽  
Surface Cracks ◽  
Paris Law ◽  
Weld Toe

Fatigue crack growth at welded joints often propagates from as many as tens to hundreds of small weld toe cracks along the weld toe line in offshore welded structures. This paper will present a fatigue algorithm for modeling many small weld toe cracks propagating from a welded joint. Cracks usually initiate at the weld toe region of the structures and propagate as surface cracks at the stress concentration regions of the weld-toe line. The presence of such weld defects or crack-like flaws can have a severe detrimental effect on their fatigue life and fracture resistance. Currently, there is a lack of studies that considers the effects of multiple cracks and their distribution density in welded joints. This work focuses on the fatigue analysis and modeling of multiple weld toe cracks, specifically in T-butt joints. Fatigue crack growth prediction is usually determined by the stress intensity factor range and crack propagation rate through Paris law. To predict the Stress Intensity Factor (SIF) of a weld toe crack, the magnification (Mk) factor was used. The Mk factor is influenced by the size of the welded attachment, as well as the size and depth of the weld toe crack. Simplified solutions for practical prediction of Mk factors were determined from 3D extended finite element method (XFEM) by modelling a semi-elliptical weld toe crack in a T-butt weld for cracks of different dimensions. The accuracy of the Mk factor solutions was verified by comparison to HSE fatigue data on 16 mm thick tubular joints. The Mk factor solutions were used to predict the growth of fatigue cracks using a model based on Paris Law and SIF solutions by Newman and Raju with plastic zone size corrections. Fatigue life was predicted for plates with and without attachments. It could be seen that the predicted life of a weld toe crack was severely reduced with the addition of a welded attachment. The model was extended to the multiple surface cracks commonly observed at the weld toe, where each crack is treated as independent, following established code procedures. The multiple cracks will coalesce as they propagate, until a single dominant crack emerges and fracture occurs. In this paper, the relationship between the fatigue life and the number and density distribution of the initial cracks was investigated. Fatigue life was predicted for plates with attachments with 1, 2, 10 and 100 cracks initially. The results show that as the number of cracks increases, the predicted fatigue life decreases.

Experimental Study and Prediction of Fatigue Crack Growth in Girth Welded Pipes

2002 ◽  
Author(s):  
Yan H. Zhang ◽  
Stephen J. Maddox ◽  
G. Reza Razmjoo
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Large Diameter ◽  
Accurate Solution ◽  
Growth Data ◽  
3D Fea ◽  
Weld Toe ◽  
Stress Concentration Effect

Fracture mechanics fatigue crack growth analysis is widely used in the Engineering Critical Assessment of welded structures. An important requirement is an accurate solution for the stress intensity factor, K, for the particular type and geometry of crack under consideration. A case commonly encountered is the weld toe crack. A solution incorporating the stress intensity magnification factor, MK, to allow for the stress concentration effect of the welded joint, based on 2D FEA has been in use for many years. A new solution from 3D FEA has recently become available. However, in both cases, little has been done to validate the solutions against actual fatigue crack growth data. The results from a recent investigation of fatigue in large diameter (609mm OD × 20mm WT) girth-welded pipes provided an opportunity to do this. This paper presents a comparison of these crack growth data based on beachmarking information with predictions based on the 2D and 3D MK solutions. It was found that the 2D MK solution tended to over-estimate the crack growth rate, while the 3D solution provided better correlation between predicted and actual crack propagation behaviour. It is therefore recommended that the 3D MK solution should be used in the calculation of K for weld toe cracks.

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