FATIGUE STRENGTH IMPROVEMENT AT WELD TOE OF OUT-OF-PLANE GUSSET BY HAMMER PEENING TREATMENT

Mechanical post treatments for welded structures have been applied in various industrial fields and, in most cases, have been found to cause substantial increase in their fatigue strength. These methods, generally, consist of the modification of weld toe geometry and the introduction of compressive residual stresses. In hammer peening, the weld profile is modified due to removal or reduction of minute crack-like flaws; compressive residual stresses are also induced by repeated hammering of the weld toe region with blunt-nosed chisel. In this study, a hammer peening procedure, using commercial pneumatic chipping hammer, was developed; a quantitative measure of fatigue strength improvement was performed. The fatigue life of hammer-peened specimen was prolonged by approximately 10 times in S=240MPa, and was doubled for the as-welded specimen.

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Residual Stress Reduction and Fatigue Strength Improvement by Controlling Welding Pass Sequences

Journal of Engineering Materials and Technology ◽

10.1115/1.482779 ◽

1999 ◽

Vol 122 (1) ◽

pp. 108-112 ◽

Cited By ~ 29

Author(s):

Masahito Mochizuki ◽

Toshio Hattori ◽

Kimiaki Nakakado

Keyword(s):

Residual Stress ◽

Fatigue Strength ◽

Stress Reduction ◽

Stress Amplitude ◽

High Stress ◽

Initial Residual Stress ◽

Fatigue Strength Improvement ◽

Weld Toe ◽

Goodman Diagram ◽

Strength Improvement

The effects of residual stress on fatigue strength at a weld toe in a multi-pass fillet weld joint were evaluated. The residual stresses in the weld joints were varied by controlling the sequence of welding passes. The residual stress at the weld toe was 80 MPa in the specimen whose last welding pass was on the main plate side, but it was 170 MPa in the specimen whose last pass was on the attachment side. The fatigue strength was nearly the same at high stress amplitude for both specimens, but the fatigue strength of the specimen whose last weld pass on the main plate was higher than that of the other specimen at low stress amplitude. This difference is due to the magnitude of the initial residual stress and the relaxation of the residual stress under fatigue cycling. The effects of the residual stress were shown in a modified Goodman diagram, in which residual stress is treated as a mean stress. [S0094-4289(00)01701-1]

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Fatigue strength improvement of longitudinal fillet welded out-of-plane gusset joints using air blast cleaning treatment

International Journal of Fatigue ◽

10.1016/j.ijfatigue.2012.11.010 ◽

2013 ◽

Vol 48 ◽

pp. 289-299 ◽

Cited By ~ 7

Author(s):

In-Tae Kim

Keyword(s):

Fatigue Strength ◽

Air Blast ◽

Fatigue Strength Improvement ◽

Out Of Plane ◽

Cleaning Treatment ◽

Strength Improvement

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Evaluation of Fatigue Strength Improvement of Ship Structural Details by Weld Toe Grinding

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.324-325.1079 ◽

2006 ◽

Vol 324-325 ◽

pp. 1079-1082 ◽

Cited By ~ 2

Author(s):

Myung Hyun Kim ◽

Sung Won Kang ◽

Jae Myung Lee ◽

Wha Soo Kim

Keyword(s):

Fatigue Strength ◽

Surface Defects ◽

Quantitative Measure ◽

Fatigue Tests ◽

Weld Bead ◽

Fatigue Strength Improvement ◽

Structural Details ◽

Weld Toe ◽

Loading Modes ◽

Strength Improvement

In order to strengthen or repair the welded structural members or fatigue damaged areas, various surface treatment methods such as grinding, shot peening and/or hammer peening are commonly employed among other methods available. While the weld toe grinding method is known to give 3~4 times of fatigue strength improvement, this improvement may significantly vary according to weld bead shapes and loading modes. In this context, a series of fatigue tests is carried out for three types of test specimens that are typically found in ship structures. Weld burr grinding is carried out using an electric grinder in order to remove surface defects and improve weld bead profiles. The test results are compared with the same type of test specimen without applying the fatigue improvement technique in order to obtain a quantitative measure of the fatigue strength improvement. Moreover, structural stress method is employed to evaluate the effectiveness of the method in evaluating the fatigue strength improvement of welded structures.

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