Effect of laser remelting of weld toe on fatigue strength of aluminum alloy A5083P-O welded joint.

One general method for improving the fatigue strength of welded joints is introduction of compressive residual stress by peening. However, there is concern that the fatigue strength of the welded joint may decrease if excessive preloading is applied after peening. It has been found that fatigue strength decreased after applying compressive preloading to a welded joint due to cancellation of the compressive stress at the weld toe. In the present research, the influence of excessive preloading on the fatigue strength of welded joints with compressive residual stress at the weld toe was clarified by experiments using hammer peening with an improved pin. When hammer peening was applied to welded joints, increasing the radius of the weld toe reduced the decrease of compressive residual stress due to excessive preloading. As a result, the decrease of the fatigue strength of the welded joint was also reduced.

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Fatigue Strength Evaluation of Welded Structure on Aluminum Alloy Car Body Based on Multi-Axial Stress

10.21203/rs.3.rs-1115402/v1 ◽

2021 ◽

Author(s):

Yiming Shangguan ◽

Wenjing Wang ◽

Chao Yang ◽

Anrui He

Keyword(s):

Shear Stress ◽

Aluminum Alloy ◽

Fatigue Strength ◽

Normal Stress ◽

Welded Joint ◽

Axial Stress ◽

Stress Component ◽

Local Coordinate System ◽

Strength Evaluation ◽

Welded Structure

Abstract With the continuous development of the subway, the demand for its safety and stability is getting higher and higher. It is of great significance to accurately evaluate the fatigue life of the carbody to ensure the subway's safe operation. In this paper, the finite element model of a subway head carbody was established, and the fatigue strength of the welded structure on the carbody was evaluated based on Multi-axial stress. The local coordinate system was defined according to the geometrical characteristics of the welds. Local stresses perpendicular and parallel to the weld seam were obtained to calculate the stress ratio, stress range, and allowable stress value corresponding to the stress component. According to the joint fatigue resistance, the components of the degree of utilization and comprehensive degree of utilization are calculated to evaluate the structural fatigue strength under the survival rate of 97.5% and load cycles of 10 7 . The evaluation of the fatigue strength of the pivotal weld joints shows that the fatigue strength of the aluminum alloy carbody meets the design requirements, the weld of the carbody has a strong ability to resist fatigue damage. The fatigue strength of the weld is mainly affected by the normal stress component, while the shear stress has little effect on the fatigue strength of the structure. In addition, compared with the filleted weld joint and the butt-welded joint, the normal stress parallels to and perpendicular to the weld direction and shear stress have the greatest effect on the lap-welded joint. Meanwhile, the comprehensive degree of utilization of the lap-welded joint is the largest at 0.49. The introduction of multi-axial stress for the fatigue strength evaluation is beneficial when considering the material utilization degree in multiple structural directions. This research results provide a reference for fatigue strength evaluation of subway carbody's welded structure.

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Improvement of Fatigue Strength of Aluminum Alloy Welded Joint by High Hardness and Large Specific Gravity Shot Peening

QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY ◽

10.2207/qjjws.22.524 ◽

2004 ◽

Vol 22 (4) ◽

pp. 524-530 ◽

Cited By ~ 3

Author(s):

Masayoshi HASEGAWA ◽

Hiroaki SUZUKI

Keyword(s):

Aluminum Alloy ◽

Fatigue Strength ◽

Specific Gravity ◽

Shot Peening ◽

Welded Joint ◽

High Hardness

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Effect of Weld Toe Burr Grinding on Fatigue Strength of Transverse Welded Specimens Made From DH36 Steel

Volume 6: Materials Technology; C.C. Mei Symposium on Wave Mechanics and Hydrodynamics; Offshore Measurement and Data Interpretation ◽

10.1115/omae2009-79331 ◽

2009 ◽

Cited By ~ 3

Author(s):

Helena Polezhayeva ◽

Joong-Kyoo Kang ◽

Joo-Ho Heo ◽

Kwang-Seok Kim

Keyword(s):

Fatigue Life ◽

Fatigue Strength ◽

High Cycle Fatigue ◽

Welded Joint ◽

Cycle Fatigue ◽

Constant Amplitude ◽

Joint Project ◽

Improvement Factor ◽

Weld Toe ◽

Marine Engineering

The effect of weld toe grinding on fatigue life of welded joint has been studied by a number of investigators who have established that improvement factor on fatigue life is greater for higher tensile steels as compared with mild steels [1]. To establish the effect of weld toe grinding on the fatigue strength of joints made from DH36 steel, transverse welded specimens were tested under constant amplitude loading. This work was carried out by DAEWOO Shipbuilding and Marine Engineering Co. within Lloyds Register/DSME Joint Project. It was shown that the improvement factor on fatigue strength due to weld toe burr grinding for DH36 steel is above 1.5 for high cycle fatigue range.

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Effect of ultrasonic impact treatment on surface microstructure and fatigue properties of 6082 aluminum alloy butt joint

Modern Physics Letters B ◽

10.1142/s0217984918502391 ◽

2018 ◽

Vol 32 (21) ◽

pp. 1850239 ◽

Cited By ~ 1

Author(s):

Bolin He ◽

Yaming Feng ◽

Li Li ◽

Zhaoxia Chen

Keyword(s):

Residual Stress ◽

Aluminum Alloy ◽

Crack Initiation ◽

Welded Joint ◽

Butt Joint ◽

Fatigue Properties ◽

Ultrasonic Impact Treatment ◽

Transmission Electron ◽

Weld Toe ◽

6082 Aluminum Alloy

Effect of ultrasonic impact treatment (UIT) on microstructure and fatigue properties of the aluminum alloy 6082 was studied at room temperature. The change of microstructure on the surface and the grain size after impact treatment was observed by metallographic microscope and transmission electron microscopy, respectively. The residual stress was measured by residual stress tester. The experimental results show that the UIT can lead to obvious plastic deformation layer in the treated surface, and nanocrystals were formed. Compressive residual stress of 50.4 MPa was maximum at the surface after the UIT. With an impact current of 1.0 A and impact time of 2 min, compared with untreated specimens, the fatigue strength of the 6082 aluminum alloy joint increases by about 11.18%. The fracture position for the treated specimen has been changed, the crack initiation is seen in the weld toe surface for the as-welded joint, and the crack initiation in the sub-surface for the treated specimen is comparable to the as-welded joint fatigue.

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Effect of ultrasonic impact time on Microstructure and properties of 7A52 aluminum alloy tandem MIG welded joint

10.21203/rs.3.rs-313541/v1 ◽

2021 ◽

Author(s):

Furong Chen ◽

Yihang Yang ◽

Nan Li

Keyword(s):

Mechanical Properties ◽

Aluminum Alloy ◽

Fatigue Strength ◽

Welded Joints ◽

Welded Joint ◽

Treatment Time ◽

High Strength ◽

Proper Treatment ◽

Welding Condition ◽

7A52 Aluminum Alloy

Abstract 7A52 (Al-Zn-Mg-Cu) alloy is a high-strength aluminum alloy, its welded joints are often accompanied by defects such as poor wear resistance and low fatigue strength. Herein, we try to optimize the welded joint of 7A52 aluminum alloy by using ultrasonic impact treatment (UIT). Generally, the mechanical properties such as microhardness and fatigue strength of the welded joint after UIT will be improved. 7A52 aluminum alloy tandem metal inert gas (MIG) welded joints with UIT time per unit area of 2.5 min, 5 min, 10 min, 15 min, 30 min, and 75 min were studied. Through the surface topography, microstructure observation, and mechanical properties test, the time parameters of excessive treatment, lack of treatment, and proper treatment were selected, and the effects of UIT, excessive treatment, lack of treatment, and proper treatment on fatigue strength were analyzed. Test results show that, the mechanical properties of welded joints after UIT are improved. The proper treatment time is 15min and its fatigue strength is 37.86MPa, respectively under the stress ratio of 0.1. Compared to the original welding condition with a fatigue strength of 28.61MPa, the fatigue strength of the welded joints of 7A52 aluminum alloy increased by 32.33%. The largest percentage of grain size reduction occurs when the UIT is 15 min. Moreover, excessive treatment and lack of treatment will not further refine the grains and optimize the mechanical properties.

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