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.

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.

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.

Effect of the gear finishing process on bending fatigue crack initiation and propagation in spur gears

2001 ◽  
Vol 215 (7) ◽  
pp. 785-792 ◽  
Author(s):  
T. K. Hidayetoglu
Keyword(s):  
Residual Stress ◽  
Fatigue Crack ◽  
Crack Initiation ◽  
Fatigue Crack Initiation ◽  
Bending Fatigue ◽  
Gear Steel ◽  
Finishing Process ◽  
Single Tooth ◽  
Stress Profiles ◽  
Bench Testing

The depth and stress levels of residual stress profiles are a major concern in carburized components such as transmission gears. Residual stress profiles are, among other factors, a function of the gear steel composition, the carburizing process and the gear finishing process. One of the goals of the finishing process in gears is to obtain a certain level of toughness in the gear teeth to reduce and/or eliminate bending and contact fatigue failures. This article presents a comparison of the characteristics of bending fatigue crack initiation in cubic boron nitride (CBN)-ground only and CBN-ground and shot-peened gears during single-tooth bench testing, and also a comparison of the characteristics of bending fatigue crack initiation in shot-cleaned only and CBN-ground only gears during single-tooth bench testing. The gear steel used in this study was SAE 8620/22.

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