Welding Residual Stresses in Tubular Joints

2013 ◽  
Vol 768-769 ◽  
pp. 605-612 ◽  
Author(s):  
Majid Farajian ◽  
Thomas Nitschke-Pagel ◽  
Klaus Dilger
Keyword(s):  
Residual Stress ◽  
Fatigue Crack ◽  
Crack Initiation ◽  
Residual Stresses ◽  
Structural Integrity ◽  
Fatigue Crack Initiation ◽  
Welding Residual Stress ◽  
Structural Safety ◽  
Welding Parameters

In spite of an increased awareness of welding residual stress threat to structural integrity, the extent of its influence on fatigue especially under multiaxial loading is still unclear and is a matter of debate. One important reason for this lack of clarities is that the determination of the initial welding residual stress field in welded structures even at the fatigue crack initiation sites is difficult and requires complementary instruments. Since the fatigue crack initiation in sound welds almost always occurs on the surface, the determination of surface residual stresses could increase the awareness of the extent of their threat to the structural safety. In this paper the development of residual stresses in different TIG-welded tubular specimens out of S355J2H and S690QL steel is studied and compared. The mechanisms of the development of residual stresses based on heat input and cooling rate are discussed. The welding parameters and thus heat inputs are varied and the mechanisms leading to different residual stress states are investigated. X-ray method was used for residual stress state characterization.

Assessment of Degrees of Cumulative Fatigue Crack Initiation Damage at Guyed Mast Earplate Joint

2011 ◽  
Vol 467-469 ◽  
pp. 776-781
Author(s):  
Wen Li Wang ◽  
Wei Lian Qu ◽  
Jie He
Keyword(s):  
Residual Stress ◽  
Fatigue Crack ◽  
Crack Initiation ◽  
Fatigue Crack Initiation ◽  
Welding Residual Stress ◽  
Critical Plane ◽  
Multi Scale ◽  
Cumulative Strain ◽  
Critical Plane Approach ◽  
Guyed Mast

This paper proposes a new method for assessing the degree of the cumulative fatigue crack initiation damage of the joint welds at the guyed mast earplate. Based on the multi-scale wind-induced stress analysis of the guyed mast earplate joint, and considering the welding residual stress in earplate joint, the critical plane approach is used for the calculation of cumulative strain fatigue damage due to the combined actions of the welding residual stress and the wind load.

A Statistical-Based Fatigue Crack Initiation Model for Axial Flaws in Zr-Nb Pressure Tubes

2014 ◽  
Author(s):  
Cheng Liu ◽  
Douglas Scarth ◽  
Alain Douchant
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Rise Time ◽  
Structural Integrity ◽  
Fatigue Crack Initiation ◽  
Mechanical Damage ◽  
Fuel Bundle ◽  
Test Parameters ◽  
Pressure Tubes ◽  
Criteria For Evaluation

Flaws found during in-service inspection of CANDU Zr-2.5Nb pressure tubes include fuel bundle scratches, debris fretting flaws, fuel bundle bearing pad fretting flaws, mechanical damage flaws and crevice corrosion marks. The CSA Standard N285.8 contains procedures and acceptance criteria for evaluation of the structural integrity of CANDU Zr-2.5Nb pressure tubes containing flaws. One of the requirements is to evaluate the flaws for fatigue crack initiation. There was a need to develop a statistical-based model of fatigue crack initiation at flaws for use in deterministic and probabilistic assessments of Zr-2.5Nb pressure tubes. A number of fatigue crack initiation experiments have been performed on notched specimens from irradiated and unirradiated Zr-2.5Nb pressure tube material with a range of hydrogen equivalent concentrations. These experiments were performed in an air environment and included temperature and load rise time as test parameters. The test data has been used to develop a statistical-based model of fatigue crack initiation at flaws that covers the effects of flaw root radius, load rise time and irradiation. This paper describes the development of the statistical-based model.

scholarly journals Influence of local residual stresses on fatigue crack initiation

2021 ◽  
Vol 31 ◽  
pp. 3-7
Author(s):  
M. Mlikota ◽  
S. Schmauder ◽  
K. Dogahe ◽  
Ž. Božić
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Residual Stresses ◽  
Fatigue Crack Initiation

A study on prognostic analysis of attachment lugs under off-axis loading

2019 ◽  
Vol 10 (6) ◽  
pp. 809-824
Author(s):  
Bharath Kenchappa ◽  
Lokamanya Chikmath ◽  
Bhagavatula Dattaguru
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Crack Growth ◽  
Structural Integrity ◽  
Fatigue Crack Initiation ◽  
Inequality Constraints ◽  
Computational Method ◽  
Engineering Structures ◽  
Content Type ◽  
Lug Joints

Purpose Lug joints with fasteners play a crucial role in connecting many major components of the aircraft. Most of the failures in the past were credited to the damages initiating and progressing from these types of joints. Ensuring the structural integrity of these fastener joints is a major issue in many engineering structures, especially in aerospace components, which would otherwise lead to fatal failure. The purpose of this paper is to adopting the prognostic approach for analysing these lug joints with fasteners subjected to off-axis loading by estimating the crack initiation and crack growth life of these joints. This data will be useful to estimate the remaining life of these joints at any given stage of operations, which is mandatory in structural health monitoring (SHM). Design/methodology/approach Straight and tapered lug joints are modelled using the finite element method in MSC PATRAN and analysed in MSC NASTRAN. These lug joints are analysed with a push fit fastener. The contact/separation regions at the pin–lug interface are carefully monitored throughout the analysis for various loading conditions. Critical locations in these lug joints are identified through stress analysis. Fatigue crack initiation and fatigue crack growth analysed is carried out at these locations for different load ratios. A computational method is proposed to estimate the cycles to reach crack initiation and cycles at which the crack in the lug joint become critical by integrating several known techniques. Findings Analysis carried out in this paper describes the importance of tapered lug joints, particularly when subjected to non-conventional way of loading, i.e. off-axis loading. There is a partial loss of contact between pin and lug upon pin loading, and this does not change further with monotonically increasing pin load. But during load reversals, there is a change in contact/separation regions which is effectively handled by inequality constraints in the boundary conditions. Crack growth in these lug joints pertains to mixed-mode cracking and is computed through the MVCCI technique. Originality/value Most of the earlier works were carried out on in-plane pin loading along the axis of symmetry of the lug. The current work considers the off-axis pin loading by loading the lug joints with transverse and oblique pin load. The significance of taper angle under such loading condition is brought in this paper. The results obtained in this paper through prognostic approach are of direct relevance to the SHM and damage tolerance design approach where the safety of the structural components is of foremost priority.

Influence of Residual Stress due to Prior Overloading on the Fatigue Life of a Notched Plate

2016 ◽  
Author(s):  
Kumarswamy Karpanan
Keyword(s):  
Residual Stress ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Initiation ◽  
Internal Pressure ◽  
Compressive Residual Stress ◽  
Fatigue Crack Initiation ◽  
Pressure Vessels ◽  
Stress And Strain ◽  
Maximum Shear Strain

During autofrettage, pressure vessels are subjected to high internal pressure, causing the internal wall to yield plastically. When the internal pressure is released, the inner wall of the vessel develops compressive residual stress. Similarly, when a subsea component is hydrotested, some of the highly stressed regions yield during hydrotesting and, when the pressure is released, these regions develop compressive residual stress. Fatigue life is greatly influenced by local stress on the component surface. Fatigue crack initiation primarily depends on the cyclic stress or strain and the residual stress state. Tensile residual stress decreases fatigue life and the compressive residual stress significantly increases fatigue life. This is true for both fatigue crack initiation and propagation. In this paper, effects of residual stress on a notched plate are studied by subjecting it to an initial overload cycle and subsequent low loading cycles. Tensile and compressive overloads on the notched plate induce compressive and tensile residual stresses, respectively. An elastic-plastic finite element analysis (FEA) was performed to simulate the overload and low loading cycles on the notched plate. The stress and strain from the FEA is used to perform strain-based fatigue analysis. ASME VIII-3, Brown-Miller (B-M), Maximum shear strain, Socie-Bannantine, and Fatemi-Socie methods are used for calculating the fatigue life of the notched plate. Fatigue life predicted by both stress and strain methods matches well with the test fatigue data.

scholarly journals Damage-Based Assessment of the Fatigue Crack Initiation Site in High-Strength Steel Welded Joints Treated by HFMI

Metals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 145
Author(s):  
Yuki Ono ◽  
Halid Can Yıldırım ◽  
Koji Kinoshita ◽  
Alain Nussbaumer
Keyword(s):  
Residual Stress ◽  
Fatigue Crack ◽  
Stress Relaxation ◽  
Crack Initiation ◽  
High Strength Steel ◽  
Fatigue Crack Initiation ◽  
High Strength ◽  
Initiation Site ◽  
High Peak ◽  
Crack Initiation Site

This study aimed to identify the fatigue crack initiation site of high-frequency mechanical impact (HFMI)-treated high-strength steel welded joints subjected to high peak stresses; the impact of HFMI treatment residual stress relaxation being of particular interest. First, the compressive residual stresses induced by HFMI treatment and their changes due to applied high peak stresses were quantified using advanced measurement techniques. Then, several features of crack initiation sites according to levels of applied peak stresses were identified through fracture surface observation of failed specimens. The relaxation behavior was simulated with finite element (FE) analyses incorporating the experimentally characterized residual stress field, load cycles including high peak load, improved weld geometry and non-linear material behavior. With local strain and local mean stress after relaxation, fatigue damage assessments along the surface of the HFMI groove were performed using the Smith–Watson–Topper (SWT) parameter to identify the critical location and compared with actual crack initiation sites. The obtained results demonstrate the shift of the crack initiation most prone position along the surface of the HFMI groove, resulting from a combination of stress concentration and residual stress relaxation effect.

Determination of the stress-strain state and conditions of fatigue crack initiation in a rectangular plate with a hole

1989 ◽  
Vol 24 (5) ◽  
pp. 500-506
Author(s):  
V. V. Panasyuk ◽  
G. S. Ivanitskaya ◽  
A. I. Zboromirskii ◽  
M. V. Iyanovich ◽  
O. P. Ostash ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Rectangular Plate ◽  
Strain State ◽  
Fatigue Crack Initiation ◽  
Stress Strain ◽  
Stress Strain State
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