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.

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.

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 behavior of precipitation strengthened Cu–Ni–Si alloy modified by Cr and Zr addition

2020 ◽  
Vol 11 (6) ◽  
pp. 861-873
Author(s):  
Ş. Hakan Atapek ◽  
Spiros Pantelakis ◽  
Şeyda Polat ◽  
Apostolos Chamos ◽  
Gülşah Aktaş Çelik
Keyword(s):  
Design Methodology ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Lower Stress ◽  
Content Type ◽  
Hardened Alloy ◽  
Zr Addition ◽  
Nucleation Sites ◽  
The Matrix ◽  
Lower Stress Level

Purpose The purpose of this paper is to investigate the fatigue behavior of precipitation-strengthened Cu‒2.55Ni‒0.55Si alloy, modified by the addition of 0.25 Cr and 0.25 Zr (wt%), using mechanical and fractographical studies to reveal the effect of microstructural features on the fracture. Design/methodology/approach For strengthening, cast and hot forged alloy was subjected to solution annealing at 900°C for 60 min, followed by quenching in water and then aging at 490°C for 180 min. Precipitation-hardened alloy was exposed to fatigue tests at R=−1 and different stress levels. All fracture surfaces were examined within the frame of fractographical analysis. Findings Fine Ni-rich silicides responsible for the precipitation strengthening were observed within the matrix and their interactions with the dislocations at lower stress level resulted in localized shearing and fine striations. Although, by the addition of Cr and Zr, the matrix consisted of hard Ni, Zr-rich and Cr-rich silicides, these precipitates adversely affected the fatigue behavior acting as nucleation sites for cracks. Originality/value These findings contribute to the present knowledge by revealing the effect of microstructural features on the mechanical behavior of precipitation-hardened Cu‒Ni‒Si alloy modified by Cr and Zr addition.

Fatigue limit prediction of A356-T6 cast aluminum alloys with different defect sizes sampled from an actual large-scale component

2017 ◽  
Vol 8 (6) ◽  
pp. 617-631 ◽  
Author(s):  
Yoshihiko Uematsu ◽  
Toshifumi Kakiuchi ◽  
Akiko Tajiri ◽  
Masaki Nakajima
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Limit ◽  
Large Scale ◽  
Prediction Method ◽  
Fatigue Tests ◽  
Extreme Value Statistics ◽  
Cast Aluminum Alloy ◽  
Cast Aluminum ◽  
Content Type ◽  
Modified Method

Purpose The purpose of this paper is the proposal of fatigue-life-prediction curve for cast aluminum alloy A356-T6 with different casting defect sizes. Design/methodology/approach Four kinds of A356-T6 fatigue specimens were sampled from the actual large-scale cast component, where the cooling rates were different. In addition, three kinds of A356 were casted under different casting conditions to simulate different defect sizes in the actual component. Subsequently, rotating bending fatigue tests were conducted using those samples. The maximum sizes of casting defects were quantitatively evaluated through microstructural observation and extreme value statistics. The fatigue limits of all samples were predicted using hardness and defect sizes based on modified Murakami’s equation. Findings The modified equation for fatigue limit prediction in A356-T6 was proposed. Fatigue limits were successfully predicted using the proposed equation. Originality/value Fatigue limit prediction method using hardness and maximum defect size was limited to steels. This paper proposed the modified method for A356-T6 aluminum alloy with lower elastic modulus. The method was valid for A356-T6 with different defect sizes.

Tribological problems in shaft hoist ropes wear process

2015 ◽  
Vol 67 (1) ◽  
pp. 47-51 ◽  
Author(s):  
Michal Styp-Rekowski ◽  
Eugeniusz Manka ◽  
Maciej Matuszewski ◽  
Monika Madej ◽  
Dariusz Ozimina
Keyword(s):  
Design Methodology ◽  
Fatigue Tests ◽  
Significant Excess ◽  
Fatigue Wear ◽  
Content Type ◽  
Wear Process ◽  
Current State ◽  
Strength Tests ◽  
Qualitative Index ◽  
Practical Implications

Purpose – The purpose of this paper was to create conditions for the correct decision concerning an exchange of the used rope for a new one. A cognitive goal was to indicate the causes of its wear and determining its mechanism reliability and durability. Design/methodology/approach – The magnetic, organoleptic and strength standard tests of lifting triangle-strand ropes of a mining hoist were carried out. This way the current state of the tested rope was defined. Findings – On the basis of an analysis of the results of the performed tests: magnetic, organoleptic and fatigue tests, it can be said that the magnetic one is accurate enough only to indicate the place of the rope’s biggest weakening, though the degree of weakening is not defined precisely – with significant excess. The accurate rope’s destruction degree is indicated by the strength tests. Practical implications – The results of described investigations can improve safety of the mining rope mechanisms operation, even for an increased resource. Originality/value – The elementary wear processes, which are the basic reason for the destruction of the rope, are indicated. Rope destruction is caused mainly by tribological factors: abrasion, corrosion and fatigue wear. Magnetic tests are accurate enough only to indicate the place of the rope’s biggest weakening (qualitative index). Most precisely, the rope’s destruction degree (quantitative index) can be found by the strength tests.

Improvement of fatigue limit by shot peening for high-strength steel containing a crack-like surface defect

2014 ◽  
Vol 5 (1) ◽  
pp. 45-59 ◽  
Author(s):  
Jun Yasuda ◽  
Koji Takahashi ◽  
Hideki Okada
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Fatigue Limit ◽  
High Strength Steel ◽  
Surface Defect ◽  
Stress Ratio ◽  
High Strength ◽  
Content Type ◽  
Circular Slit

Purpose – The purpose of this study is to clarify the influence of stress ratio (R) on the effects of shot peening (SP) on the fatigue limit of high-strength steel containing an artificial small defect. Design/methodology/approach – SP was subjected on the specimens with a semi-circular slit with a depth of a=0.1, 0.2 and 0.3 mm. Then, bending fatigue tests were carried out under R=0.4. Findings – The fatigue limits of specimens with a semi-circular slit were improved by SP under R=0.4. The fatigue limits of the SP specimens with a semi-circular slit under a=0.2 mm fractured outside the slit, and they had considerably high fatigue limits equal to specimens without a slit. Therefore, a semi-circular slit with a depth of under a=0.2 mm could be rendered harmless by SP under R=0.4. Compared to the results of R=0, the increasing ratios of fatigue limits under R=0.4 were lower than those under R=0. However, the size of semi-circular slit that could be rendered harmless by SP was same. In addition, it was found that whether the semi-circular slit is rendered harmless or not is decided by the relationship between the stress intensity factor range of semi-circular cracks and the threshold stress intensity factor regardless of stress ratio. Practical implications – The proposed method can be applied to mechanical parts used in vehicles, aircraft and trains. Originality/value – This is the first paper to investigate the fatigue limits after SP in materials containing a surface defect under positive stress ratio. In this study, the authors investigated the influence of stress ratio on the effects of SP on the fatigue limit containing a surface defects.

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.

Prediction of fatigue limit improvement in needle peened welded joints containing crack-like defects

2018 ◽  
Vol 9 (1) ◽  
pp. 50-64 ◽  
Author(s):  
Ryutaro Fueki ◽  
Koji Takahashi
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Stress Concentration ◽  
Yield Stress ◽  
Fatigue Limit ◽  
Welded Joints ◽  
Steel Structures ◽  
Content Type ◽  
Before And After ◽  
Weld Toe

Purpose The purpose of this paper is to estimate the acceptable defect size amax after needle peening (NP) and predict the fatigue limit improvement through the use of NP for an austenitic stainless steel welded joint containing an artificial semi-circular slit on a weld toe. Design/methodology/approach Residual stress and hardness distribution were measured. Microstructures around the weld toe were observed to clarify the cause for the change in hardness after NP. Finite element method analysis was used to analyze the change in the stress concentration following NP. Fracture mechanics was used to evaluate amax after NP. The fatigue limits before and after NP were predicted by determining amax for several levels of stress amplitude. Findings The tensile residual stress induced at the surface of the weld toe prior to NP changed to a compressive residual stress after NP. The residual stress near the surface layer after NP exceeded the yield stress prior to NP due to the increase in yield stress as a result of work hardening as well as the generation of a deformation-induced martensitic structure. The stress concentration was reduced due to the shape improvement caused by NP. The estimation value of amax after NP and the prediction results of fatigue limits were in good agreement with the fatigue test results. Practical implications The proposed method is useful in improving the reliability of welded joints used in large steel structures, transportation equipments and industrial machines. Originality/value From an engineering perspective, it is essential to estimate amax and the fatigue limit of welded joints with crack-like defects. However, it is unclear as to whether it is possible to predict amax and the effects of NP on the fatigue limit for stainless steel welded joints.

Fatigue behaviour of laser-sintered PA12 specimens under four-point rotating bending

2014 ◽  
Vol 20 (4) ◽  
pp. 291-300 ◽  
Author(s):  
Javier Munguia ◽  
Kenny Dalgarno
Keyword(s):  
Endurance Limit ◽  
Dimensional Accuracy ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Uniaxial Tensile ◽  
Content Type ◽  
Bending Fatigue ◽  
Rotating Bending Fatigue ◽  
Rotating Bending ◽  
Part Orientation

Purpose – The purpose of this paper was twofold: first, to determine if rotating bending could be used as an effective way of determining the fatigue behaviour of laser-sintered nylon, and second, to examine whether the fatigue behaviour of laser-sintered PA12 showed any significant anisotropy. Design/methodology/approach – Specimens were measured to obtain dimensional accuracy, density and surface roughness levels. Then, uniaxial tensile and rotating-bending fatigue tests were performed. A purpose-built test-jig has been used to subject hourglass-shaped specimens to reversed bending at two frequencies: 50 and 30 Hz. Additionally, thermal and microstructural analyses were performed to understand the underlying mechanisms of failure. Findings – The experiments suggest PA12 specimens will fail in fatigue following the conventional fatigue mechanisms observed in previous research with ductile polymers. Although high-frequency loading caused a heat build-up in the specimen, temperatures stabilised between 20 and 30°C, suggesting that rotating-bending fatigue at frequencies of up to 50 Hz is a valid way of determining the fatigue behaviour of laser-sintered PA12 specimens. Stresses below 20 MPa led to fatigue lives above 1 million cycles. Some anisotropic behaviour was observed in the fatigue test results, with specimens made orientated with the Z axis showing the lowest fatigue lives on average, but an endurance limit of approximately 15 MPa seems to be common for all specimens regardless of their build orientation. Practical implications – The observed endurance limit of 15 MPa did not depend significantly on the orientation at which a part was built – meaning that it may be possible to guarantee a service life for a part which does not depend on part orientation within a build. Clearly, good-quality control will also be required to ensure performance, but this has important implications for the design of laser-sintered PA12 parts for realistic service conditions. Originality/value – To our knowledge, this is the first paper to present rotating-bending fatigue data for laser-sintered PA12 parts, and the first to identify an endurance limit which is independent of part orientation.

Correlation study on general and accelerated corrosion of the welded structure of aluminum alloy 2219 in N2O4

2015 ◽  
Vol 62 (3) ◽  
pp. 136-142
Author(s):  
Yuanbo Feng ◽  
Zhiyong Huang ◽  
Gan Tian ◽  
Guofeng Jin
Keyword(s):  
Aluminum Alloy ◽  
Water Content ◽  
Design Methodology ◽  
Comparison Method ◽  
Correlation Study ◽  
Accelerated Corrosion ◽  
Content Type ◽  
Dinitrogen Tetroxide ◽  
Welded Structure ◽  
Aluminum Alloy 2219

Purpose – This paper aims to present a correlation study on general and accelerated corrosion of the welded structure of aluminum alloy 2219 in N2O4. Design/methodology/approach – Corrosion experiments of the Tungsten Inert Gas (TIG)-welded aluminum alloy structure were conducted under both mild and accelerated corrosion conditions by changing the water content in N2O4. Findings – The experimental results indicated that both general and accelerated corrosion processes of the TIG-welded structure of aluminum alloy 2219 in N2O4 followed the linear equation ΔW = A + Bt, and the corrosion products were unchanged regardless of the water content in the N2O4 solution. Originality/value – The weight loss comparison method is used to identify the structure of the conventional aluminum welding and aluminum welding structure corrosion dinitrogen tetroxide in nitric acid accelerated corrosion relationship.

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