Corrosion Fatigue Tests on Welded Tubular Joints

1985 ◽  
Vol 107 (1) ◽  
pp. 68-73
Author(s):  
T. Iwasaki ◽  
J. G. Wylde
Keyword(s):  
Corrosion Fatigue ◽  
Welded Joints ◽  
Sea Water ◽  
Water Environment ◽  
Offshore Structures ◽  
Fatigue Tests ◽  
Tubular Joints ◽  
Fatigue Design ◽  
Out Of Plane ◽  
The Cost

The corrosion fatigue performance of welded tubular joints is recognized as one of the most important factors in the design of offshore structures. Because of the cost of such tests it has been practice to carry out tests on tubular joints in air and to perform corrosion fatigue tests on simple welded joints. Thus very few corrosion fatigue tests have been carried out on tubular joints. The present paper describes the results of fatigue tests which have been carried out on welded tubular joints both in air and in a sea water environment. The specimens were tubular K and KT-joints with chord dimensions of 168 mm diameter and 6 mm wall thickness. The tests were carried out under out-of-plane bending. The corrosion fatigue tests were carried in sea water at 10° C at a frequency of 10 cycles per min, which is typical of wave periods. The specimens were not cathodically protected. The fatigue results in air and sea water are compared, and discussed in connection with the current fatigue design S-N curves for tubular joints contained in various standards.

Efficient Fatigue Testing of Tubular Joints

2015 ◽  
Author(s):  
P. Thibaux ◽  
J. Van Wittenberghe ◽  
E. Van Pottelberg ◽  
M. Van Poucke ◽  
P. De Baets ◽  
...  
Keyword(s):  
Finite Element ◽  
Fatigue Testing ◽  
Fatigue Loading ◽  
Tubular Joints ◽  
Testing Method ◽  
Out Of Plane ◽  
Resonance Principle ◽  
Tubular Joint ◽  
The Cost ◽  
Good Agreement

Tubular joints are intensively used in off-shore structures for shallow waters. Depending on the sea conditions and the type of structure, the design can be fatigue driven. This is particularly the case for off-shore wind turbines, where turbulences are generating a fatigue loading. Any improvement of the fatigue performance of the tubular joint would be beneficial to reduce the weight and the cost of the structure. To assess efficiently the fatigue resistance of the tubular joint, a testing method has been developed based on the resonance principle. The complete circumference of the welded joint can be loaded, successively in the in-plane and out-of-plane modes at a frequency close to 20Hz. Finite element computations were used to investigate the feasibility of the concept. Then, an X-node was made and successfully tested to investigate the stress distribution along the weld. The experimental results were compared with finite element computations, giving a good agreement.

Corrosion fatigue strength of ship structural steel butt welded joints in synthetic sea-water

1999 ◽  
Vol 13 (5) ◽  
pp. 385-391
Author(s):  
Y Kobayashi ◽  
Y Tanaka ◽  
H Goto ◽  
K Matsuoka ◽  
Y Motohashi
Keyword(s):  
Fatigue Strength ◽  
Structural Steel ◽  
Corrosion Fatigue ◽  
Welded Joints ◽  
Sea Water ◽  
Corrosion Fatigue Strength

Differences in Fatigue Strength Between Arc and Laser Hybrid Welded Joints

2008 ◽  
Vol 24 (03) ◽  
pp. 139-146
Author(s):  
H. Remes ◽  
P. Varsta
Keyword(s):  
Fatigue Strength ◽  
Welded Joints ◽  
Fatigue Tests ◽  
Notch Depth ◽  
Butt Joints ◽  
Fatigue Design ◽  
Notch Stress ◽  
Notch Geometry ◽  
Laser Hybrid ◽  
Fatigue Endurance

This paper presents the results of fatigue tests, including tests of laser hybrid and arc welded butt joints, for two plate thicknesses, 6 and 12 mm. Pure laser welded joints were also tested. The S-N curves based on nominal stresses for the different welded joints are presented. The results were further analyzed using the notch stress approach, where the fatigue notch factors were determined from the measured geometries of the welded joints. Unexpected differences in the S-N curves based on the notch stresses were found between the laser hybrid and arc welded joints and between the laser hybrid and pure laser welded joints. The reasons for this difference were studied with the help of extensive measurements of weld notch geometries. Significant differences in the geometries were observed. Taking into account the notch geometry and the notch depth, the notch stress approach partially explains the differences between the fatigue endurance limits of the laser hybrid and arc welded joints. The applicability of the notch stress approach to the fatigue design of laser hybrid welded joints is also discussed.

Evaluation of Low-Cycle Fatigue in Simulated PWR Environment

2006 ◽  
Vol 326-328 ◽  
pp. 1011-1014 ◽  
Author(s):  
Ill Seok Jeong ◽  
Sang Jai Kim ◽  
Taek Ho Song ◽  
Sung Yull Hong
Keyword(s):  
Fatigue Life ◽  
Nuclear Power ◽  
Power Plants ◽  
Low Cycle Fatigue ◽  
Water Environment ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Fatigue Design ◽  
Number Of Cycles ◽  
Measured Length

For developing fatigue design curve of cast stainless steel that is used in piping material of nuclear power plants, a low-cycle fatigue test rig was built. It is capable of performing tests in pressurized high temperature water environment of PWR. Cylindrical solid fatigue specimens of CF8M were used for the strain-controlled environmental fatigue tests. Fatigue life was measured in terms of the number of cycles with the variation of strain amplitude at 0.04%/s strain rates. The disparity between target length and measured length of specimens was corrected by using finite element method. The corrected test results showed similar fatigue life trend with other previous results.

Fatigue Strength Evaluation for Gas Welded Joint of Similar and Dissimilar Materials

2007 ◽  
Vol 345-346 ◽  
pp. 359-362
Author(s):  
Dong Ho Bae ◽  
Yeong Sin Kim ◽  
Gyu Young Lee ◽  
Kwang Jin Park
Keyword(s):  
Welded Joints ◽  
Welded Joint ◽  
Hot Spot ◽  
Tensile Load ◽  
Dissimilar Materials ◽  
Fatigue Tests ◽  
Design Criterion ◽  
Hot Spot Stress ◽  
Fatigue Design ◽  
Fatigue Design Criterion

In order to establish a reasonable and integrated fatigue design criterion for the long life design of the gas welded body structure, stress distribution around the gas welded joints subjected to tensile load was numerically analyzed. And also, the P-Nf curves were obtained by fatigue tests. By using these results, P-Nf curves were rearranged in the σ-Nf relation with the hot spot stress at the welded joint. And a guideline for fatigue design of gas welded joints was proposed.

scholarly journals Influence of Friction Stir Welding (FSW) on Mechanical and Corrosion Properties of AW-7020M and Aw-7020 Alloys

2016 ◽  
Vol 23 (3) ◽  
pp. 86-90
Author(s):  
Krzysztof Dudzik ◽  
Wojciech Jurczak
Keyword(s):  
Friction Stir Welding ◽  
Impedance Spectroscopy ◽  
Welded Joints ◽  
Sea Water ◽  
Electrochemical Impedance ◽  
Water Environment ◽  
Al Alloys ◽  
Basic Material ◽  
Transfer Resistance ◽  
Friction Stir

Abstract Friction welding associated with mixing the weld material (FSW - Friction Stir Welding ) is an alternative to MIG and TIG welding techniques for Al-alloys. This paper presents experimental results obtained from static tension tests on specimens made of AW-7020M and AW-7020 alloys and their joints welded by using FSW method carried out on flat specimens, according to Polish standards : PN-EN ISO 4136:2011 and PN-EN ISO 6892-1:2010. Results of corrosion resistance tests are also presented. The tests were performed by using the electrochemical impedance spectroscopy (EIS). EIS measurement was conducted with the use of three-electrode system in a substitute sea water environment (3,5% NaCl - water solution). The impedance tests were carried out under corrosion potential. Voltage signal amplitude was equal to 10mV, and its frequency range - 100 kHz ÷ 0,1 Hz. Atlas 0531 EU&IA potentiostat was used for the tests. For the tested object an equivalent model was selected in the form of a substitute electric circuit. Results of the impedance spectroscopy tests are presented in the form of parameters which characterize corrosion process, as well as on Nyquist’s graphs together with the best-fit theoretical curve. Analysis of the test results showed that the value of charge transfer resistance through double layer , Rct , for the FSW-welded specimen , was lower than that for the basic material, and that much greater difference was found in the case of AW-7020M alloy. The impedance spectroscopy tests showed that both the FSW-welded joints and basic material of AW-7020M and AW-7020 alloys were characterized by a good resistance against electrochemical corrosion in sea water environment , and that FSW-welded joints revealed a greater corrosion rate.. The performed tests and subject-matter literature research indicate that application of FSW method to joining Al-alloys in shipbuilding is rational.

Development of a Welding Sequence Optimized for the Fatigue Resistance of Tubular Joints With a Novel Representative Welded Sample

2018 ◽  
Author(s):  
Philippe Thibaux ◽  
Eric Van Pottelberg
Keyword(s):  
Fatigue Resistance ◽  
Fatigue Testing ◽  
Welding Process ◽  
Offshore Structures ◽  
Fatigue Tests ◽  
Complex Geometries ◽  
Tubular Joints ◽  
Welding Sequence ◽  
Welding Procedure ◽  
Welding Position

Tubular joints are complex geometries present in many offshore structures. Fatigue testing of tubular joints requires either downsizing of the dimensions of the joints or the use of a simplified geometry, to avoid prohibitive costs. For the development of a welding process optimized for the fatigue performance of tubular joints, one needs to use a representative sample: same material, same thickness, use of similar welding positions, same level of restraint as in a real structure, combined with the supplementary requirement of ease of manufacturing and testing. A novel geometry was developed to fulfil all these requirements. Then, different welds were produced using robot and manual welding in different positions. The fatigue tests proved to be very reproducible, and indicate a strong influence of the welding position on the fatigue resistance. For that reason, an optimized welding procedure and sequence was developed, in which the welds in the most fatigue sensitive locations are produced first in optimum condition, while the less sensitive parts are produced by subsequent welding in position.

Formulas for Variation of Stress Concentration Around Intersection in Tubular Joints

1988 ◽  
Vol 110 (4) ◽  
pp. 237-245 ◽  
Author(s):  
R. Sundaravadivelu ◽  
M. Hariharan ◽  
C. Ganapathy
Keyword(s):  
Fatigue Life ◽  
Stress Concentration ◽  
Current Practice ◽  
Saddle Points ◽  
Offshore Structures ◽  
Exploration And Exploitation ◽  
Empirical Formulas ◽  
Tubular Joints ◽  
Fatigue Design ◽  
Semi Empirical

Many of the offshore structures used for oil exploration and exploitation are built of tubular members. The repeated damages in tubular joints have clearly shown that the safety of these structures depends on the safe fatigue design of the joints. The fatigue life of the joint depends very much on the Stress Concentration Factor, SCF. The current practice is to use semi-empirical formulas proposed by various investigators to determine SCF. While some of the formulas give the maximum SCF, others give the SCFs at both the crown and saddle points. The design of fatigue life using the value of maximum SCF is conservative, while using SCFs at crown and saddle is unsafe. The main aim of this paper is to propose a set of formulas for T and Y-joints, which gives not only the magnitude of maximum SCF as in the presently available formulas, but also the variation of SCF around intersection.

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