scholarly journals Effect of Laser Peening with a Microchip Laser on Fatigue Life in Butt-Welded High-Strength Steel

2021 ◽  
Vol 2 (4) ◽  
pp. 878-890
Author(s):  
Tomoharu Kato ◽  
Yoshihiro Sakino ◽  
Yuji Sano
Keyword(s):  
Fatigue Life ◽  
Residual Stresses ◽  
High Strength Steel ◽  
Welded Joint ◽  
Base Material ◽  
High Strength ◽  
Microchip Laser ◽  
Laser Peening ◽  
Near Surface ◽  
Compressive Residual Stresses

Laser peening introduces compressive residual stresses on the surfaces of various materials and is effective in enhancing fatigue strength. Using a small microchip laser, with energies of 5, 10, and 15 mJ, the authors applied laser peening to the base material of an HT780 high-strength steel, and confirmed compressive residual stresses in the near-surface layer. Laser peening with a pulse energy of 15 mJ was then applied to fatigue samples of an HT780 butt-welded joint. It was confirmed that laser peening with the microchip laser prolonged the fatigue life of the welded joint samples to the same level as in previous studies with a conventional laser.

The Study of Fatigue Life of the Crack of Weld Bead

2006 ◽  
Vol 324-325 ◽  
pp. 467-470 ◽  
Author(s):  
Dong Xia Li ◽  
Ying Mei ◽  
Fang Jia ◽  
Bao Chun Jia
Keyword(s):  
Fatigue Life ◽  
High Strength Steel ◽  
Welded Joint ◽  
Fatigue Property ◽  
High Strength ◽  
Fatigue Tests ◽  
Weld Bead ◽  
Steel Weld ◽  
Weld Joints ◽  
Important Basis

The effects of multiple repairing-weld and TIG-dressing on the fatigue property of high strength steel weld joints used in platform have been investigated. Through the fatigue tests on high strength steel welded joint samples, the life estimating formula is obtained after each time of repairing weld and TIG-dressing. The S-N curve and the equation after repairing weld and TIG-dressing are given. The work in this paper offers an important basis for the multiple repairing-weld of platforms.

Enhanced Surface Residual Compression of Carburized Steel Parts Using Laser Peening Process With Preload

2014 ◽  
Author(s):  
Zhichao (Charlie) Li ◽  
B. Lynn Ferguson
Keyword(s):  
Residual Stresses ◽  
High Strength ◽  
Laser Peening ◽  
X Ray Diffraction ◽  
Carburized Steel ◽  
Initiation And Propagation ◽  
Quench Hardening ◽  
Enhanced Surface ◽  
Compressive Residual Stresses ◽  
Residual Compression

Residual stresses are critical to the fatigue performance of parts. In general, compressive residual stress in the surface is beneficial, and residual tension is detrimental because of the effect of stress on crack initiation and propagation. Carburization and quench hardening create compressive residual stresses in the surface of steel parts. The laser peening process has been successfully used to introduce residual compression to the surface of nonferrous alloy parts. However, the application on carburized steel parts has not been successful so far. The application of laser peening on carburized steel parts is limited due to two main reasons: 1) the high strength and low ductility of carburized case, and 2) the compressive residual stresses in the surface of the part prior to laser peening. In this paper, the carburization, quench hardening, and laser peening processes are integrated using finite element modeling. The predicted residual stresses from quench hardening and laser peening are validated against residual stresses determined from X-ray diffraction measurements. An innovative concept of laser peening with preload has been invented to enhance the residual compression in a specific region of laser peened parts. This concept is proved by FEA models using DANTE-LP.

Fracture Mechanics Analysis of a High Strength Steel for Offshore Application

2002 ◽  
Author(s):  
Arild Lundberg ◽  
Ba˚rd Nyhus ◽  
Oddvin O̸rjasæter
Keyword(s):  
Fatigue Life ◽  
Fracture Mechanics ◽  
High Strength Steel ◽  
Fatigue Testing ◽  
Base Material ◽  
High Strength ◽  
Contact Forces ◽  
Coarse Grained ◽  
Circumferential Welds ◽  
Mechanics Analysis

One of the main bearing elements of the Siri jack-up is three tubular legs; outside diameter 3.5m and an overall length of 104m. The main material grade is high strength steel with SMYS≥690MPa. This strength was required due to contact forces during the jacking phase. One of the major issues concerning integrity of the platform was associated with the fatigue life of the legs. The fatigue life of the legs WAS to be 60 years for inaccessible locations, 40 years for accessible submerged locations and 20 years for accessible dry locations. To achieve the required fatigue lives, wall thickness of 65mm, 75mm and 90mm were utilized for the 690 steel. Furthermore, to meet the 40-year requirement, lives for the lower circumferential welds were designed to Class C, i.e. they needed to be improved by grinding. Based on performed research, it was aimed at minimum CTOD values of 0.20mm and 0.25mm in the PWHT and AW conditions respectively. Although the aim was achieved for the base material and sub critical HAZ, the weld metal and the coarse grained HAZ values were significantly below these values, i.e. 0.12mm and 0.02mm respectively. In order to verify the integrity of the platform a fracture mechanics analysis was performed. The assessment comprised evaluation of critical defect sizes and fatigue life calculations using PD6493. Wide plate testing, residual stress measurements and fatigue testing have been performed. The assessment showed that the integrity of the platform was maintained. In order to obtain additional safety an inspection program for the critical welds has been implemented in the operational phase.

Fatigue Life Improvement of Laser Clad 7075 Aluminium Alloy by Deep Surface Rolling Technique

2014 ◽  
Vol 891-892 ◽  
pp. 115-120
Author(s):  
Qian Chu Liu ◽  
Wyman Zhuang ◽  
Peter Khan Sharp
Keyword(s):  
Heat Treatment ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Aluminium Alloy ◽  
Laser Cladding ◽  
High Strength ◽  
Post Heat Treatment ◽  
Deep Surface ◽  
Life Improvement ◽  
Compressive Residual Stresses

The Deep Surface Rolling (DSR) technology can substantially increase the fatigue life of metallic materials due to the introduction of deep compressive residual stresses in the material surface. These beneficial compressive residual stresses can be achieved up to a depth of 1 mm. The DSR technology also produces a good surface finish unlike bead peening technology. In this study, the main objectives were: (1) to study the feasibility of DSR for fatigue life improvement of high strength aluminium alloy (7075-T651) repaired with laser cladding technology, and (2) to investigate the effect of thermal stressing on the fatigue life improvement of DSR. Previously published results have shown that post-heat treatment of laser clad high strength Al alloy coupons improved their fatigue life. The experimental results in this paper show that the fatigue life was substantially increased using the DSR technique on laser clad 7075-T6 aluminium alloy compared to laser cladding alone and laser cladding followed by post heat treatment.

The Effect of Several Finishing Processes on the Fatigue Resistance of Hole Surfaces

1989 ◽  
Vol 111 (1) ◽  
pp. 71-73 ◽  
Author(s):  
M. O. Lai ◽  
A. Y. C. Nee
Keyword(s):  
Surface Roughness ◽  
Plastic Deformation ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Fatigue Resistance ◽  
Radial Direction ◽  
Fatigue Loading ◽  
Steel Plates ◽  
Finishing Processes ◽  
Compressive Residual Stresses

This investigation examines the effects of different finishing processes on the fatigue life of premachined holes in Assab 760 steel plates. The finishing processes studied were reaming, ballizing, and emery polishing. A general decrease in fatigue life with increase in surface roughness is observed for all the processes employed. In comparing the different processes, for a constant surface roughness, polishing is generally found to give the longest fatigue life while ballizing, in spite of the greater compressive residual stresses induced on the surface of the finished hole, the shortest. The surprising phenomenon was found to be attributed to the amount of plastic deformation occurred before fatigue loading. For Assab 760 steel, a prestrain in the radial direction of less than about 2.5 percent appeared to reduce the fatigue resistance of the material.

scholarly journals Low-cycle fatigue behaviour of laser welded high-strength steel DOMEX 700 MC

2018 ◽  
Vol 157 ◽  
pp. 05013 ◽  
Author(s):  
Peter Kopas ◽  
Milan Sága ◽  
František Nový ◽  
Bohuš Leitner
Keyword(s):  
Fatigue Life ◽  
Welded Joints ◽  
High Strength Steel ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
High Strength ◽  
Fatigue Behaviour ◽  
Total Strain Amplitude ◽  
Cycle Fatigue ◽  
Fatigue Life Analysis

The article presents the results of research on low cycle fatigue strength of laser welded joints vs. non-welded material of high-strength steel DOMEX 700 MC. The tests were performed under load controlled using the total strain amplitude ɛac. The operating principle of the special electro-mechanic fatigue testing equipment with a suitable clamping system was working on 35 Hz frequency. Fatigue life analysis was conducted based on the Manson-Coffin-Basquin equation, which made it possible to determine fatigue parameters. Studies have shown differences in the fatigue life of original specimens and laser welded joints analysed, where laser welded joints showed lower fatigue resistance. In this article a numerical analysis of stresses generated in bending fatigue specimens has been performed employing the commercially available FEM-program ADINA.

Short Crack Propagation Model Applied to Shot Peened Aluminium Alloys

2009 ◽  
Vol 65 ◽  
pp. 53-61 ◽  
Author(s):  
J. Solis ◽  
J. Oseguera-Peña ◽  
I. Betancourt
Keyword(s):  
Surface Roughness ◽  
Residual Stresses ◽  
Crack Propagation ◽  
Aluminium Alloys ◽  
Micromechanical Model ◽  
High Strength ◽  
Crack Arrest ◽  
Propagation Model ◽  
Safe Load ◽  
Compressive Residual Stresses

The Navarro-Rios micromechanical model was used to assess the bounds of two different damage zones: crack arrest region and crack propagation region of controlled shot peening (CSP) of high strength aluminium alloys. Performance of CSP in terms of fatigue resistance was investigated. This comparison indicated that CSP in terms of fatigue depends on the competition between its beneficial and detrimental products, i.e. surface roughness and compressive residual stresses respectively. The gathered information can be used for safe load determinations in design.

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