Re-evaluation of weld root fatigue strength for load-carrying fillet welded joints using the notch stress concept

The purpose of this study is to investigate the fatigue strength of butt-welded joints with special attention paid to employing different kinds of backing plates. The effect of the under-matched weld was also considered. Four different cases of backing scenarios for butt-welded specimens such as steel backing, ceramic backing, CMT (no backing by cold metal transfer) and UM (under-matched welded specimen) were investigated. A series of fatigue tests was performed to compare the fatigue strength of butt-welded joints with respect to different backing scenarios. Effective notch stress was used for the interpretation of fatigue strength of butt-welded specimens with backing plates based on finite element analyses for calculating fatigue notch factors. When results were presented from the effective notch stress, all backing scenarios considered in this study exhibited the fatigue strengths corresponding to the FAT 225 curve. From the experimental results of this study, it was determined that the fatigue strengths of butt-welded joints were found to be in the order of CMT, ceramic backing, UM, and steel backing. No significant decrease in fatigue strength, however, was observed when backing plates were steel backing and ceramic backing types.

Download Full-text

Structural stress, notch stress and stress intensity approach for assessment of fatigue strength of spot welded joints

Design and Analysis of Fatigue Resistant Welded Structures ◽

10.1533/9781845698751.299 ◽

1990 ◽

pp. 299-342 ◽

Cited By ~ 5

Author(s):

Dieter Radaj

Keyword(s):

Stress Intensity ◽

Fatigue Strength ◽

Welded Joints ◽

Structural Stress ◽

Notch Stress ◽

Spot Welded

Download Full-text

Differences in Fatigue Strength Between Arc and Laser Hybrid Welded Joints

Journal of Ship Production ◽

10.5957/jsp.2008.24.3.139 ◽

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.

Download Full-text