scholarly journals Fatigue Limit Improvement and Rendering Defects Harmless by Needle Peening for High Tensile Steel Welded Joint

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 143 ◽  
Author(s):  
Ryutaro Fueki ◽  
Koji Takahashi ◽  
Mitsuru Handa
Keyword(s):  
Fatigue Limit ◽  
Welded Joints ◽  
Surface Defects ◽  
Welded Joint ◽  
Fatigue Tests ◽  
Dominant Factor ◽  
Bending Fatigue ◽  
Industrial Utilization ◽  
High Fatigue ◽  
Weld Toe

The effects of needle peening (NP) on the bending fatigue limit of a high tensile steel (HTS) HT780 (JIS-SHY685)-welded joint containing an artificial semicircular slit on the weld toe were investigated. Three-point bending fatigue tests were conducted at a stress ratio of R = 0.05 for NP-treated welded specimens with and without a slit. The fatigue limits of all specimens increased by 9–200% due to the NP treatment. Furthermore, NP-treated specimens with slit depths of a = 1.0 mm exhibited high fatigue limits that were equal to those of NP-treated specimens without a slit. Therefore, a semicircular slit of less than a = 1.0 mm could be rendered harmless through NP treatment. This result indicates that the reliability of HTS-welded joints can be significantly improved via NP for surface defects with depths that are less than 1 mm, which are not detected through non-destructive inspection (NDI). Therefore, the problem regarding the reliability of HTS-welded joints that restricts the industrial utilization of HTS can be solved by performing both NDI and NP. The dominant factor that contributed to the improvement of the fatigue limit and increase in the acceptable defect size was the introduction of large and deep compressive residual stress with non-propagating cracks.

Fatigue Limit Improvement by Needle-Peening for Stainless Steel Welded Joint Containing a Crack-Like Defect

2016 ◽  
Author(s):  
Ryutaro Fueki ◽  
Koji Takahashi
Keyword(s):  
Stainless Steel ◽  
Fatigue Limit ◽  
Stress Ratio ◽  
Welded Joint ◽  
Circular Crack ◽  
Fatigue Tests ◽  
Bending Fatigue ◽  
Circular Slit ◽  
High Fatigue ◽  
Weld Toe

The effects of needle-peening on the bending fatigue limit of an austenitic stainless steel JIS-SUS316 welded joint containing an artificial semi-circular slit on the weld toe were investigated. Peening was applied to specimens with a semi-circular slit at depths of a = 1.0 mm and 1.5 mm. Then, plane bending fatigue tests were carried out at a stress ratio of R = 0. The fatigue limits of welded specimens containing a semi-circular slit were increased for the peened specimens. Peened specimens with slit sizes of a = 1.0 mm had high fatigue limits that were nearly equal to those of non-slit, peened specimens. We observed that a semicircular slit with a depth of less than a = 1.0 mm could be rendered harmless by peening. Additionally, the values of fatigue limit and the maximum depth of a semi-circular slit that can be rendered harmless by peening were predicted based on fracture mechanics, where we assume that a semi-circular slit is equivalent to a semi-circular crack. The prediction results were consistent with experimental results.

Effect of peening on the fatigue limit of welded structural steel with surface crack, and rendering the crack harmless

2014 ◽  
Vol 5 (4) ◽  
pp. 279-289 ◽  
Author(s):  
Keiji Houjou ◽  
Koji Takahashi ◽  
Kotoji Ando ◽  
Hisanori Abe
Keyword(s):  
Fatigue Limit ◽  
Design Methodology ◽  
Systematic Investigation ◽  
Fatigue Tests ◽  
Residual Stress Distribution ◽  
Content Type ◽  
Bending Fatigue ◽  
Circular Slit ◽  
Welded Structure ◽  
Weld Toe

Purpose – The purpose of this paper is to investigate the effect of peening on the fatigue limit of steels for welded structure with a crack in the weld toe zone. Design/methodology/approach – An artificial semi-circular slit was created in the weld toe, and peening was conducted. Then, bending fatigue tests were carried out. Findings – First, owing to the shot peening, the maximum slit depths that can be rendered harmless were 1.0 and 1.2 mm in SUS316 and SM490, respectively. Second, during the fatigue test, the fracture of a peened specimen originated outside the slit, which indicated that peening eliminated the effect of the slit on the fatigue limit. Third, the fatigue limit of a slit specimen was improved by the enhanced residual stress distribution and the decreased stress concentration due to plastic deformation at the weld toe. Originality/value – There are very few studies about which a fatigue crack is rendered harmless by residual compressive stress, as a result the structures could be continued to use. Moreover, the study defining the concept about rendering crack harmless and systematic investigation was not able to be found.

Influence of Hydrogen on Tensile and Fatigue Life Properties of 304/308 Austenitic Stainless Steel Butt Welded Joints

2018 ◽  
Author(s):  
Saburo Okazaki ◽  
Hisao Matsunaga ◽  
Masami Nakamura ◽  
Shigeru Hamada ◽  
Saburo Matsuoka
Keyword(s):  
Fatigue Life ◽  
Martensitic Transformation ◽  
Fatigue Limit ◽  
Welded Joints ◽  
Welded Joint ◽  
Volume Fraction ◽  
Hydrogen Gas ◽  
Solution Treated ◽  
Internal Hydrogen ◽  
Weld Toe

To investigate the influence of hydrogen on the tensile and fatigue life properties of welded joints of 304/308 austenitic stainless steels, slow strain rate tensile (SSRT) tests and fatigue life tests were conducted in laboratory air using hydrogen exposed specimens. The specimens were fabricated from welded plates, and to elucidate the role of weld structure on hydrogen-induced degradation, the welded joint was solution-treated. In the SSRT tests of the as-welded (AW) joint, a non-exposed specimen failed at the base metal (BM), whereas a hydrogen-exposed specimen failed near the weld toe. In the case of the solution-treated-welded (STW) joint, the non-exposed specimen failed at the part of solution treated weld metal, whereas an H-exposed specimen failed near the weld toe. As a result, internal hydrogen significantly degraded the elongation of the AW joint. In the fatigue test, all the specimens failed near the weld toe. Internal hydrogen degraded the fatigue life considerably. However, the pre-charging led to little, if any, reduction in the fatigue limit. Similarly to the AW joint, hydrogen gas exposure notably degraded the fatigue life of the STW joint and led to little reduction in the fatigue limit. To investigate the relationship between the hydrogen-induced degradation and strain-induced martensitic transformation during fatigue testing, the volume fraction of ferrite in the broken specimens was measured by a ferrite scope. The volume fraction of martensitic transformation increased with an increase in the stress amplitude. These experimental results implied that the hydrogen-induced fatigue life degradation in the welded joint was closely related to the martensitic transformation during the fatigue process. The mechanisms of both the degradation in fatigue life and nondegradation in fatigue limit will be discussed further.

The Fatigue Property Research of Steel Q345 Butt Welded Joint

2014 ◽  
Vol 692 ◽  
pp. 424-427
Author(s):  
Wei Ping Ouyang ◽  
Liang Sheng Chen ◽  
Xiu Dong Xu
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Finite Element Modeling ◽  
Significant Influence ◽  
Welded Joints ◽  
Welded Joint ◽  
Fatigue Property ◽  
Fracture Analysis ◽  
Fatigue Tests ◽  
Fatigue Properties

The fatigue property of the butt welded joint has significant influence to hoisting equipment’s design, manufacture and using safety for its extensive application. This paper conducted a study on the fatigue properties of a series of the most commonly used thickness steel Q345 butt welded joints. Through fatigue tests and fracture analysis, the fatigue pattern and fracture law of the joints were revealed. Combining with the finite element modeling, the all field stress distribution situation was obtained. This has profound reference significance to hoisting machinery research.

scholarly journals Microstructure and Fatigue Behavior of 2205/316L Stainless Steel Dissimilar Welded Joints

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 93
Author(s):  
Saúl Leonardo Hernández-Trujillo ◽  
Victor Hugo Lopez-Morelos ◽  
Marco Arturo García-Rentería ◽  
Rafael García-Hernández ◽  
Alberto Ruiz ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Welded Joints ◽  
316L Stainless Steel ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Base Material ◽  
Fatigue Tests ◽  
Solidification Mode ◽  
Tension And Compression ◽  
Weld Toe

The relation among microstructure and fatigue behavior of 2205/316L stainless steel dissimilar welded joints was investigated. Plates of 6.35 mm in thickness with a single-V joint configuration were gas metal arc welded (GMAW) in a single pass by feeding at 6 m/min an ER2209 filler wire with a heat input of 1.2 kJ/mm. Grain growth in the high temperature-heat affected zone (HT-HAZ) occurred mostly at the mid-height of the plates, delimiting the width of this region up to ~1.28 and ~0.73 mm of the 2205 and 316L plates, respectively. Dilution of the 316L plate with the ER2209 filler altered the solidification mode in this side of the weld and led to a significant content of austenite along the fusion line. Fatigue tests were performed using sinusoidal waveform at room temperature applying uniaxial cyclic loading, between constant stress limits within the elastic deformation of tension and compression (Δσ) with stress ratio R = −0.3. With stress ranges of 98% and 95% the fatigue specimens rapidly failed in much less than 106 cycles. The failure crack initiated at the surface of the 316L in the HT-HAZ near the weld toe. Surface analyses of unbroken specimens before and after fatigue testing revealed a significant increment in roughness of the 316L base material owing to the formation of intrusions and extrusions.

Fatigue Strength Evaluation for Gas Welded Joint of Similar and Dissimilar Materials

2007 ◽  
Vol 345-346 ◽  
pp. 359-362
Author(s):  
Dong Ho Bae ◽  
Yeong Sin Kim ◽  
Gyu Young Lee ◽  
Kwang Jin Park
Keyword(s):  
Welded Joints ◽  
Welded Joint ◽  
Hot Spot ◽  
Tensile Load ◽  
Dissimilar Materials ◽  
Fatigue Tests ◽  
Design Criterion ◽  
Hot Spot Stress ◽  
Fatigue Design ◽  
Fatigue Design Criterion

In order to establish a reasonable and integrated fatigue design criterion for the long life design of the gas welded body structure, stress distribution around the gas welded joints subjected to tensile load was numerically analyzed. And also, the P-Nf curves were obtained by fatigue tests. By using these results, P-Nf curves were rearranged in the σ-Nf relation with the hot spot stress at the welded joint. And a guideline for fatigue design of gas welded joints was proposed.

Effect of Hammer Peening Processing on Fatigue Property of Welded Joints After Overload

2013 ◽  
Author(s):  
Yasushi Morikage ◽  
Satoshi Igi ◽  
Kenji Oi
Keyword(s):  
Residual Stress ◽  
Fatigue Strength ◽  
Compressive Stress ◽  
Welded Joints ◽  
Compressive Residual Stress ◽  
Welded Joint ◽  
Fatigue Property ◽  
Weld Toe ◽  
Hammer Peening ◽  
General Method

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.

Fatigue Properties of AF1410 Steel Welded Joint by Electron Beam Welding

2011 ◽  
Vol 287-290 ◽  
pp. 2181-2184
Author(s):  
Bing Wu ◽  
Zhi Yong Mao ◽  
Jian Xun Zhang
Keyword(s):  
Electron Beam ◽  
Fatigue Limit ◽  
Fatigue Test ◽  
Base Metal ◽  
Welded Joints ◽  
Electron Beam Welding ◽  
Welded Joint ◽  
Fracture Morphology ◽  
Fatigue Properties ◽  
Test Conditions

Fatigue test of AF1410 steel and two thickness of electron beam have been done, and fatigue properties of the base metal and EB-welded joints have been studied. The results showed that fatigue limit of electron beam welded joints was close to that of base metal under this test conditions, and the welded thickness has little effect on S-N curves of electron beam welded samples under this test conditions. From SEM fracture morphology, it can be seen that fracture morphology of the welded samples was not obvious different form base metal. In the instant-off area of electron beam welded sample, there was dimple-like morphology showing good ductility.

Sub-Surface Fatigue Strength of a Steel

1969 ◽  
Vol 11 (4) ◽  
pp. 432-443 ◽  
Author(s):  
P. F. Bray
Keyword(s):  
Fatigue Strength ◽  
Residual Stresses ◽  
Fatigue Limit ◽  
Fatigue Tests ◽  
Bending Fatigue ◽  
Surface Fatigue ◽  
Test Pieces ◽  
Surface Failure ◽  
Rotating Bending Fatigue ◽  
Rotating Bending

Rotating bending fatigue tests on En 40B steel gave a fatigue limit for surface failure of 30·5 tonf/in2. With nitrided test-pieces sub-surface failures were produced and, with no allowance being made for residual stresses, a fatigue limit of 34·5 tonf/in2 was obtained for sub-surface failure. In the absence of residual stresses this fatigue limit would probably have been higher.

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