scholarly journals Effects of Stress Concentration Factor and Welding Residual Stress. Fatigue Strength of Welded Joint of High Strength Steel and Its Controlling Factor.

1995 ◽  
Vol 13 (3) ◽  
pp. 438-443 ◽  
Author(s):  
Osamu Watanabe ◽  
Shigeto Matsumoto ◽  
Yoshifumi Nakano ◽  
Yoshiyuki Saito
Keyword(s):  
Residual Stress ◽  
Fatigue Strength ◽  
Stress Concentration ◽  
Stress Concentration Factor ◽  
High Strength Steel ◽  
Concentration Factor ◽  
Welded Joint ◽  
High Strength ◽  
Welding Residual Stress ◽  
Stress Fatigue

Pipe Joint Management for Risers and Pipelines

2021 ◽  
Author(s):  
Ghiath (Guy) Mansour
Keyword(s):  
Fatigue Strength ◽  
Stress Concentration ◽  
Software Development ◽  
Wall Thickness ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Joint Management ◽  
Pipe Joints ◽  
Best Fit ◽  
Pipe Joint

Abstract Minimizing the stress concentration factor (SCF) in pipe joint welding subjected to fatigue is a major concern. Machining the joint ends is one way to achieve this. However, this adds cost, time, risk of potential crack starters, and loss of wall thickness which is detrimental for fatigue, strength, and engineering criticality assessment (ECA) in particular. Pipe joint sorting (certain joints in sequence) and end matching (rotating the pipe joints for best fit) are other ways. However, this adds time, costly logistics, risk of errors, and does not guarantee the minimum possible SCF is achieved. In a typical project, more pipe joints are procured than required in order to mitigate contingencies. For pipelines, this overage is typically a percentage of the required number of joints or pipeline length. For risers, typically double the required number of joints is procured where half of the joints is sent offshore for installation and the remaining half is kept onshore for a spare riser. Then, it becomes very important to send for installation the best pipe joints that produce the best (lowest) SCFs out of the entire batch of pipe joints. This requires calculating the SCF for every potential match of any random joints to be welded together, and then choosing the best joints. Performing such calculations by spreadsheet is not feasible considering the tremendous number of required iterations and calculations. A pipe joint management software development is presented herein which accomplishes this task and examples provided to illustrate the benefits. Note: Selecting pipe joints with the best end measurements, whether ID, OD, OOR, or thickness does not guarantee that the minimum possible SCFs will be achieved since the SCF is a function of all those measurements.

Capability of martensitic low transformation temperature welding consumables for increasing the fatigue strength of high strength steel joints

2020 ◽  
Vol 62 (9) ◽  
pp. 891-900
Author(s):  
Jonas Hensel ◽  
Arne Kromm ◽  
Thomas Nitschke-Pagel ◽  
Jonny Dixneit ◽  
Klaus Dilger
Keyword(s):  
Residual Stress ◽  
Phase Transformation ◽  
Fatigue Strength ◽  
High Strength Steel ◽  
Transformation Temperature ◽  
Fatigue Cracks ◽  
High Strength ◽  
Filler Material ◽  
Phase Transformation Temperature ◽  
Filler Materials

Abstract The use of low transformation temperature (LTT) filler materials represents a smart approach for increasing the fatigue strength of welded high strength steel structures apart from the usual procedures of post weld treatment. The main mechanism is based on the effect of the low start temperature of martensite formation on the stress already present during welding. Thus, compressive residual stress formed due to constrained volume expansion in connection with phase transformation become highly effective. Furthermore, the weld metal has a high hardness that can delay the formation of fatigue cracks but also leads to low toughness. Fundamental investigations on the weldability of an LTT filler material are presented in this work, including the characterization of the weld microstructure, its hardness, phase transformation temperature and mechanical properties. Special attention was applied to avoid imperfections in order to ensure a high weld quality for subsequent fatigue testing. Fatigue tests were conducted on the welded joints of the base materials S355J2 and S960QL using conventional filler materials as a comparison to the LTT filler. Butt joints were used with a variation in the weld type (DY-weld and V-weld). In addition, a component-like specimen (longitudinal stiffener) was investigated where the LTT filler material was applied as an additional layer. The joints were characterized with respect to residual stress, its stability during cyclic loading and microstructure. The results show that the application of LTT consumables leads to a significant increase in fatigue strength when basic design guidelines are followed. This enables a benefit from the lightweight design potential of high-strength steel grades.

Fatigue Behavior of the Low-Strength Steel Welded Joints Treated by TIG Dressing and Ultrasonic Peening Combined Method

2011 ◽  
Vol 295-297 ◽  
pp. 1885-1889
Author(s):  
Sen Li ◽  
Dong Po Wang ◽  
Hai Zhang ◽  
Bo Tan
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Stress Concentration ◽  
Compressive Stress ◽  
Stress Level ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Combined Method ◽  
Ultrasonic Peening ◽  
Weld Toe

Butt-joint specimens of Q235B low-strength steel were treated by TIG dressing and ultrasonic peening combined method. The paper presents comparative fatigue test for welded specimens in the as-welded condition and specimens treated by TIG dressing, ultrasonic peening treatment (UPT) and the combined method. When the ratio of stress R=0.1, contrasted with the specimens in as welded condition, the fatigue strength of the specimens treated by TIG dressing is increased by 36%. The fatigue strength of the specimens treated by the combined method and UPT are almost the same, which are increased by 57% and 56% respectively. In the high stress level, weld toe treated by the combined method has smaller stress concentration factor than that of UPT, resulting in less release of residual compressive stress. So it's more effective to improve the fatigue life by the combined method. While in the low stress level, the residual compressive stress of weld toe treated by the combined method and UPT are nearly the same. Besides, the effect of stress concentration factor is smaller, thus the fatigue life of the two methods have little difference.

The Thermal Fatigue Performance for Cast Iron Brake Drum of Large Trucks

2011 ◽  
Vol 117-119 ◽  
pp. 821-823
Author(s):  
Gao Lu ◽  
Wen Yan Wang ◽  
Jing Pei Xie
Keyword(s):  
Cast Iron ◽  
Stress Concentration ◽  
Crack Initiation ◽  
Thermal Fatigue ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Fatigue Crack Initiation ◽  
High Strength ◽  
Fatigue Properties ◽  
Brake Drum

This paper studies the application in different cast iron brake drum the thermal fatigue properties of materials. The results show that the stress concentration factor of grey cast iron, hot fatigue crack initiation, low intensity, and easy to expand, organization crack initiation poor stability, antioxidant ability is poor, thermal fatigue is poorer. 35% of vermicular cast iron and of ductile iron high strength, toughness, good stress concentration factor small, thermal fatigue is well.

Formation Mechanism of Hydrogen-Induced Delayed Cracking in Weld Center of High-Strength Steel

2012 ◽  
Vol 557-559 ◽  
pp. 1304-1307 ◽  
Author(s):  
Jing Qiang Zhang ◽  
Jian Guo Yang ◽  
Jia Jie Wang ◽  
Xue Song Liu ◽  
Zhi Bo Dong ◽  
...  
Keyword(s):  
Residual Stress ◽  
Formation Mechanism ◽  
Welded Joints ◽  
High Strength Steel ◽  
Hydrogen Pressure ◽  
High Strength ◽  
Welding Residual Stress ◽  
Cracking Behavior ◽  
Hydrogen Damage ◽  
Delayed Cracking

Based on the estimation of the critical hydrogen pressure and concentrations required for hydrogen-induced delayed cracking in high-strength steel, the conclusion that welded joints are hydrogen pressure microcracks body can be drawn under certain conditions. Through the analysis of the relationship between the microstructure evolution of welded joints, diffusion enrichment of hydrogen and cracking behavior, the formation mechanism of hydrogen-induced delayed cracking in weld center of high-strength steel joints is analyzed and the mechanism that stress induced the residual diffusion hydrogen gathered to promote the hydrogen pressure microcracks propagation is proposed. The research shows that the initation and propogation of hydrogen-induced delayed cracking in weld center can be divided into two stages, i.e. irreversible hydrogen damage stage and reversible hydrogen damage stage. In irreversible stage hydrogen pressure is the main causes of the initation of microcracks, while in reversible stage welding residual stress and residual diffusible hydrogen are necessary conditions for microcracks growth. The microcracks growth can be controlled by regulating welding residual stress.

Effect of Welding Residual Stress and Plastic Constraint on Brittle Fracture of a High Strength Steel

2009 ◽  
Author(s):  
Masaki Torigoe ◽  
Yoichi Yamashita ◽  
Takehisa Yamada
Keyword(s):  
Residual Stress ◽  
Brittle Fracture ◽  
High Strength Steel ◽  
Crack Tip ◽  
High Strength ◽  
Fracture Initiation ◽  
Parent Material ◽  
Welding Residual Stress ◽  
Cross Sectional ◽  
Plastic Constraint

This paper investigates the effect of welding residual stress and plastic constraint on brittle fracture of a 780 MPa class high-strength steel (HT780). In order to investigate the effect of welding residual stress, three point bend (3PB) fracture toughness tests were conducted using the parent-material specimens and groove-welded specimens which were prepared to have the same cross-sectional proportion; i.e., a ratio of thickness to width of 0.5. Crack length was determined so that the crack tip was located in the base-metal zone far from the heat-affected zone of the welded specimen to eliminate the effect of any degradation of the parent-material property on fracture resistance. Also, in order to investigate the effect of constraint, tensile loading tests in which the plastic constraint was expected to be less than 3PB were conducted using welded specimens as the same as employed in the 3PB test. Three dimensional finite element (FE) analyses were performed to evaluate the stress state near the crack tip at the point of brittle fracture initiation for each test condition. From the results of experiments and FE analyses, it is confirmed that the fracture test results can be evaluated using J or KJ – Q theory, by considering enhancement or reduction due to residual stress.

Sign in / Sign up

Export Citation Format

Share Document