Prediction of Fatigue Lifetime under Multilevel Cyclic Loading Based on a Short Crack Growth Model in a Low Carbon Steel SAE 1017

Abstract Underwater wet welding (UWW) is widely used in repair of offshore constructions and underwater pipelines by the shielded metal arc welding (SMAW) method. They are subjected the dynamic load due to sea water flow. In this condition, they can experience the fatigue failure. This study was aimed to determine the effect of water flow speed (0 m/s, 1 m/s, and 2 m/s) and water depth (2.5 m and 5 m) on the crack growth rate of underwater wet welded low carbon steel SS400. Underwater wet welding processes were conducted using E6013 electrode (RB26) with a diameter of 4 mm, type of negative electrode polarity and constant electric current and welding speed of 90 A and 1.5 mm/s respectively. In air welding process was also conducted for comparison. Compared to in air welded joint, underwater wet welded joints have more weld defects including porosity, incomplete penetration and irregular surface. Fatigue crack growth rate of underwater wet welded joints will decrease as water depth increases and water flow rate decreases. It is represented by Paris's constant, where specimens in air welding, 2.5 m and 5 m water depth have average Paris's constant of 8.16, 7.54 and 5.56 respectively. The increasing water depth will cause the formation of Acicular Ferrite structure which has high fatigue crack resistance. The higher the water flow rate, the higher the welding defects, thereby reducing the fatigue crack resistance.

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SMALL FATIGUE CRACK GROWTH IN A LOW CARBON STEEL UNDER TENSION?COMPRESSION AND PULSATING-TENSION LOADING

Fatigue & Fracture of Engineering Materials & Structures ◽

10.1111/j.1460-2695.1990.tb00574.x ◽

1990 ◽

Vol 13 (1) ◽

pp. 31-39 ◽

Cited By ~ 11

Author(s):

Keiro Tokaji ◽

Takeshi Ogawa ◽

Tetsuya Aoki

Keyword(s):

Fatigue Crack ◽

Carbon Steel ◽

Fatigue Crack Growth ◽

Crack Growth ◽

Low Carbon Steel ◽

Low Carbon ◽

Small Fatigue Crack ◽

Tension Loading

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The Initial Life and Short Crack Propagation Life for Low Carbon Steel Based on Dislocation Method

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1145.1 ◽

2018 ◽

Vol 1145 ◽

pp. 1-7

Author(s):

Yuan Long Yang ◽

Qing Chun Meng ◽

Wei Ping Hu

Keyword(s):

Fatigue Life ◽

Carbon Steel ◽

Crack Propagation ◽

Low Carbon Steel ◽

Short Crack ◽

Low Carbon ◽

Grain Sizes ◽

Steel Material ◽

The Relationship ◽

Good Agreement

In the paper, the relationship between the grain size and fatigue life are studied. To specify the initial and short crack propagation life of low carbon steel material, three methods are used in the simulation. At first, the K. Tanaka’s model is introduced to calculate the fatigue life of a grain. Then, the Voronoi Diagram is used to generate the microstructure of grains. At last, a criteria to specify the short crack is proposed. Based on these methods, the numerical simulation is conducted. With the help of the process, the grain sizes are generated randomly in order to specify how grain sizes effect fatigue life. The computational results are in good agreement with the experimental data. The results show that the randomness of fatigue life is closely related to the randomness of grain sizes.

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