scholarly journals Fatigue Strength and Angular Distortion of the Full-Penetration Tee Type Joint Fabricated by One-Side Single-Pass Laser-Arc Hybrid Welding

2016 ◽  
Author(s):  
Koji Gotoh ◽  
Shuichi Tsumura
Keyword(s):  
Fatigue Strength ◽  
Welded Joints ◽  
Offshore Structures ◽  
Fatigue Performance ◽  
Angular Distortion ◽  
Hybrid Welding ◽  
High Quality ◽  
Full Penetration ◽  
Welding Technology ◽  
Tee Joints

Laser-arc hybrid welding is a high-quality welding technology and is expected to improve the productivity of manufacturing hull and offshore structures. Application of this technology allows the replacement of fillet-welded joints in structures with full-penetration welded joints. The fatigue performance and deformation caused by welding will be improved by this replacement. The present study experimentally investigates the fatigue performance and deformation due to welding. Two types of tee joints, which penetrate from one side and both sides, were applied. The investigations confirm the superiority of full-penetration tee joints fabricated by laser-arc hybrid welding over conventional fillet-welded joints.

Ultrasonic Fatigue Performance of Welded Joints in 16Mn Steel

2012 ◽  
Vol 251 ◽  
pp. 392-396
Author(s):  
Liang Chen Wu ◽  
Dong Po Wang
Keyword(s):  
Fatigue Strength ◽  
Welded Joints ◽  
Performance Test ◽  
Test System ◽  
Fatigue Performance ◽  
Traditional Concept ◽  
Welded Structure ◽  
Ultrasonic Fatigue ◽  
Long Life ◽  
16Mn Steel

Ultrasonic fatigue performance test of 16Mn steel and welded joints are carried out by using ultrasonic fatigue test system devices developed by Tianjin University to research its fatigue behavior in the super long life regime. The results show that: regardless of the base mental or welded joints, the S-N curve is a continuous decline curve; Welded joints does not exist the traditional concept of fatigue limit within the range of 106~107, when the number of load cycles exceeds 107 even 109, fatigue fracture still occurs. Within the super long life range, the fatigue strength of welded joint is much lower than the fatigue strength of base mental. It is dangerous to use the existing fatigue data to design the welded structure within the super long life regime.

CREATION OF JOINTS FROM INTERMETALLIC TITANIUM ALLOYS (review)

2021 ◽  
pp. 31-38
Author(s):  
A.A. Skupov ◽  
◽  
A.V. Sviridov ◽  
E.A. Khodakova ◽  
A.N. Afanasev-Khodykin ◽  
...  
Keyword(s):  
Electron Beam ◽  
Titanium Alloys ◽  
Welded Joints ◽  
Electron Beam Welding ◽  
Common Method ◽  
Filler Materials ◽  
High Quality ◽  
Welding Technology

An review of studies on the development of technologies for creating joints of intermetallic titanium alloys is presented. Today, electron beam welding is most common method for producing welded joints of this class of alloys. Brands of filler materials and solders used for intermetallic titanium alloys, as well as the properties that can be obtained when using them, are given. Approaches to the choice of welding technology that ensure the production of high-quality joints with the required characteristics are described.

Fatigue Performance of Friction Welds Manufactured Both in Air and Underwater

2017 ◽  
Author(s):  
Siak Manteghi ◽  
Dave Gibson ◽  
Carol Johnston
Keyword(s):  
Residual Stress ◽  
Fatigue Strength ◽  
Experimental Work ◽  
Welded Joints ◽  
Friction Welding ◽  
Arc Welding ◽  
Fatigue Performance ◽  
Cost Component ◽  
High Fatigue ◽  
Fatigue Endurance

Friction welding is being performed offshore in environments where arc welding may be difficult and where fatigue performance is critical. Friction welding underwater with Remotely Operated Vehicles (ROVs) can greatly reduce the cost of a project compared with using divers and arc welding because the support vessel, which is the major cost component in such an operation, is smaller. This paper describes two different programs of experimental work in which the fatigue endurance of friction welds were found to be better than that which could be expected from arc welded joints of similar geometry. The first program involved experimental work done with 25mm diameter steel bars. It found that, in the as-welded condition, friction welds have high fatigue strength. Residual stress measurements showed that this was due to a beneficial residual stress distribution in which compressive stresses are present at the surface adjacent to the failure site. Further evidence of this was obtained by subjecting some specimens to thermal stress relief. The fatigue strength of the stress relieved specimens was reduced compared with the as-welded joints but nevertheless the fatigue strength of these specimens was still high. The second program involved fatigue tests on friction stud welds in which the friction welding equipment was deployed offshore by divers or ROVs. The test specimens were made up of 19mm diameter studs friction welded onto structural steel plate. As with the first program, the specimens showed high fatigue endurance with results approximating to a DNV Class C1 curve. In some of the tests, the studs were preloaded in tension and results from specimens that were preloaded to the correct value specified for the joint were all stopped as run-outs, with specimens remaining unbroken.

scholarly journals Statistical analysis of sub-zero temperature effects on fatigue strength of welded joints

2021 ◽  
Author(s):  
Moritz Braun
Keyword(s):  
Fatigue Strength ◽  
Welded Joints ◽  
Temperature Effects ◽  
Offshore Structures ◽  
Design Guidelines ◽  
International Standards ◽  
Material Behavior ◽  
The Arctic ◽  
Test Results ◽  
Zero Temperature

Abstract Ships and offshore structures in Arctic environments are exposed to severe environmental actions and sub-zero temperatures. Thus, the design of such structures has to account for the Arctic environment and must be cost-efficient at the same time. A vital part of the design process is to ensure that fatigue-induced failure does not occur in the lifetime of the structure. While effects of high temperatures on material behavior are well covered in international standards and guidelines, there is no comprehensive guidance for sub-zero temperature fatigue strength assessment. Additionally, stress-life (S–N) test data of welded joints at sub-zero temperatures is particularly scarce. Hence, this study presents an extensive review of recent test results of various weld details tested in the range of − 50 to 20 °C. This data could build the basis for future considerations of temperature effects in fatigue design guidelines and recommendations. For this purpose, the fatigue test results are submitted to a rigorous statistically assessment—including a summary of the limitations of current design guidelines with respect to sub-zero temperature effects.

Improve the Fatigue Performance of Welded Joints with Undercuts by TIG Dressing Treatment

2012 ◽  
Vol 472-475 ◽  
pp. 1300-1304 ◽  
Author(s):  
Liang Chen Wu ◽  
Dong Po Wang
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Adverse Effects ◽  
Dynamic Loading ◽  
Weld Joint ◽  
Welded Joints ◽  
Fatigue Cracks ◽  
Fatigue Property ◽  
Fatigue Performance ◽  
Weld Toe

Undercuts often exists in the surface at weld toe. Undercuts affects the capability of weld subjected to dynamic loading greatly and fatigue cracks usually initiate from these zones with undercuts. Combining with low-alloy middle strength steel 16Mn，study of increasing the fatigue strength and the fatigue life was carried out. Compared with specimen without defects, the fatigue strength of specimen with undercuts has been increased by 10~20%. Study also shows that comparing with as-welded specimen with defects, with TIG dressing treatment, fatigue strength of cruciform weld joint of steel 16Mn has been increased by 70%, fatigue life by 5~8 times. Compared with as-welded specimen without defects, fatigue strength has been increased by 34%, fatigue life by 3~4 times. Undercuts have no adverse effects on fatigue property of welded joints under TIG dressing.

Sub-Zero Temperature Fatigue Strength of Butt-Welded Normal and High-Strength Steel Joints for Ships and Offshore Structures in Arctic Regions

2020 ◽  
Author(s):  
Moritz Braun ◽  
Aleksandar-Saša Milaković ◽  
Sören Ehlers ◽  
Adrian Kahl ◽  
Tom Willems ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Fatigue Strength ◽  
Welded Joints ◽  
High Strength Steel ◽  
Material Selection ◽  
High Strength ◽  
Offshore Structures ◽  
International Standards ◽  
Effect Of Temperature ◽  
Selection For

Abstract Ships and offshore structures operating in Artic regions face specific challenges such as ice loads and seasonal low temperatures. In order to meet these extreme environmental requirements, the effect of temperature on material behaviour needs to be considered. It is well known that static material properties (yield strength, fracture toughness etc.) undergo significant changes with temperature. In recent studies, significantly higher fatigue strength was observed in welded joints in comparison to estimates based on international standards. Fatigue strength increased even for temperatures far below the allowed service temperature based on fracture toughness results; however, studies on fatigue strength of structural steel at sub-zero temperatures are scarce. Moreover, material selection for ships and offshore structures is usually based on empirical Charpy and fracture toughness relations at the design temperature, minus a safety margin. This study aims at introducing an S-N curve database for welded joints that can be used to verify the fatigue design approaches for ships and offshore structures subject to sub-zero temperatures. Therefore, the effect of temperature on the fatigue strength of butt-welded normal and high strength steel structures is analysed experimentally for sub-zero temperatures. For this purpose, fatigue test results of SAW and MAG welded joints for temperatures down to −50 °C are analysed and the potential for changes regarding material selection for ships and offshore structures are discussed.

Guidance for material selection based on static and dynamic mechanical properties at sub-zero temperatures

2020 ◽  
pp. 1-45
Author(s):  
Moritz Braun ◽  
Adrian Kahl ◽  
Tom Willems ◽  
Marc Seidel ◽  
Claas Fischer ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Fatigue Strength ◽  
Welded Joints ◽  
Material Selection ◽  
Safety Margin ◽  
Offshore Structures ◽  
Material Behavior ◽  
Arctic Regions ◽  
Steel Strength ◽  
Selection For

Abstract It is well known that material properties undergo significant changes with temperature. In order to meet extreme environmental requirements for ships and offshore structures operating in Arctic regions, the effect of temperature on material behavior needs to be considered. In recent studies, significantly higher fatigue strength was observed for base materials and welded joints in comparison to room temperature. Fatigue strength increased even for temperatures far below the allowed service temperature based on fracture toughness results; however, sub-zero temperatures fatigue data is scarce and effects of steel strength and welding type on fatigue strength changes are unknown. Material selection for ships and offshore structures is typically based on empirical Charpy and fracture toughness relations at the design temperature, minus a safety margin. Thus, this study presents material test results including fatigue tests of butt-welded joints, tensile test, and Charpy impact toughness tests at room and sub-zero temperatures of different structural steel types. Additionally, the effect of welding techniques and steel strength are discussed. The results can be used to extend design approaches for ships and offshore structures subject to sub-zero temperatures and to improve material selection for ships and offshore structures operating in Arctic regions.

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