510 Fatigue Strength and Fracture Mechanism on Spot Welded Joints of Ultra-High Strength Steel

2006 ◽  
Vol 2006.55 (0) ◽  
pp. 209-210
Author(s):  
Ryo ADOMI ◽  
Makoto OHSUKA ◽  
Keiichiro TOHGO ◽  
Hiroyasu ARAKI ◽  
Yoshinobu SHIMAMURA ◽  
...  
Keyword(s):  
Fatigue Strength ◽  
Welded Joints ◽  
Fracture Mechanism ◽  
High Strength Steel ◽  
High Strength ◽  
Ultra High Strength Steel ◽  
Spot Welded

Influence of Strength Level of Steels on Fatigue Strength and Fracture Morphology of Spot Welded Joints

2011 ◽  
Vol 462-463 ◽  
pp. 94-99
Author(s):  
Keiichiro Tohgo ◽  
Tomoya Ohguma ◽  
Yoshinobu Shimamura ◽  
Yoshifumi Ojima
Keyword(s):  
Finite Element ◽  
Fatigue Strength ◽  
Mild Steel ◽  
Welded Joints ◽  
High Strength ◽  
Fracture Morphology ◽  
Fatigue Tests ◽  
Finite Element Analyses ◽  
Ultra High Strength Steel ◽  
Spot Welded

In this paper, fatigue tests and finite element analyses are carried out on spot welded joints of mild steel (270MPa class) and ultra-high strength steel (980MPa class) in order to investigate the influence of strength level of base steels on fatigue strength and fracture morphology of spot welded joints. From the fatigue tests the following results are obtained: (1) Fatigue limit of spot welded joints is almost the same in both steels. (2) Fatigue fracture morphology of spot welded joints depends on the load level in the ultra-high strength steel, but not in the mild steel. From discussion based on the finite element analyses the following results are obtained: (3) The fatigue limit of spot welded joints can be predicted by stress intensity factors for a nugget edge, fracture criterion for a mixed mode crack and threshold value for fatigue crack growth in base steel. (4) Plastic deformation around a nugget in spot welded joints strongly affects the fatigue fracture morphology.

scholarly journals Crack Initiation and Propagation Fatigue Life of Ultra High-Strength Steel Butt Joints

2019 ◽  
Vol 9 (21) ◽  
pp. 4590 ◽  
Author(s):  
Markus J. Ottersböck ◽  
Martin Leitner ◽  
Michael Stoschka ◽  
Wilhelm Maurer
Keyword(s):  
Fatigue Life ◽  
Crack Initiation ◽  
Welded Joints ◽  
High Strength Steel ◽  
High Strength ◽  
Crack Initiation And Propagation ◽  
Butt Joints ◽  
Fatigue Assessment ◽  
Initiation And Propagation ◽  
Ultra High Strength Steel

The division of the total fatigue life into different stages such as crack initiation and propagation is an important issue in regard to an improved fatigue assessment especially for high-strength welded joints. The transition between these stages is fluent, whereas the threshold between the two phases is referred to as technical crack initiation. This work presents a procedure to track crack initiation and propagation during fatigue tests of ultra high-strength steel welded joints. The method utilizes digital image correlation to calculate a distortion field of the specimens’ surface enabling the identification and measurement of cracks along the weld toe arising during the fatigue test. Hence, technical crack initiation of each specimen can be derived. An evaluation for ten ultra high-strength steel butt joints reveals, that for this superior strength steel grade more than 50% of fatigue life is spent up to a crack depth of 0.5 mm, which can be defined as initial crack. Furthermore, a notch-stress based fatigue assessment of these specimens considering the actual weld topography and crack initiation and propagation phase is performed. The results point out that two phase models considering both phases enable an increased accuracy of service life assessment.

Fracture behaviour and numerical study of resistance spot welded joints in high-strength steel sheet

2016 ◽  
Vol 30 (8) ◽  
pp. 602-613 ◽  
Author(s):  
Teruki Sadasue ◽  
Satoshi Igi ◽  
Koichi Taniguchi ◽  
Rinsei Ikeda ◽  
Kenji Oi
Keyword(s):  
Welded Joints ◽  
High Strength Steel ◽  
Steel Sheet ◽  
Fracture Behaviour ◽  
Numerical Study ◽  
High Strength ◽  
Resistance Spot ◽  
Spot Welded

704 Spot Welded Tensile Strength Characteristics in Ultra High Strength Steel Sheets

2016 ◽  
Vol 2016.53 (0) ◽  
pp. _704-1_-_704-2_
Author(s):  
Yu KITAHARA ◽  
Junya NAITO ◽  
Shota CHINZEI ◽  
Akira IBANO ◽  
Yuki SHIMIZU ◽  
...  
Keyword(s):  
Tensile Strength ◽  
High Strength Steel ◽  
High Strength ◽  
Strength Characteristics ◽  
Steel Sheets ◽  
Ultra High Strength Steel ◽  
Spot Welded
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