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.

Effect of Ultrasonic Impact Treatment on Fatigue Life in Butt Welded Joints of Austenitic Stainless Steel

2010 ◽  
Author(s):  
Yu Togasaki ◽  
Takashi Honda ◽  
Tetsuya Sasaki ◽  
Atsushi Yamaguchi ◽  
Hirokazu Tsuji
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Fatigue Life ◽  
Stress Concentration ◽  
Austenitic Stainless Steel ◽  
Welded Joints ◽  
Diffraction Method ◽  
Weld Toes ◽  
Ultrasonic Impact Treatment ◽  
Weld Joints

Ultrasonic impact treatment (UIT), which is a type of peening method, is usually used as a post-weld treatment for mild steel in order to improve the fatigue strength of its welded joints. As there is insufficient fatigue data available on welded joints of austenitic stainless steel treated by UIT, the authors decide to conduct fatigue tests on butt welded joints of austenitic stainless steel treated by UIT. The results were compared with the fatigue lives of as-weld joints to investigate the effect of UIT on the fatigue lives of welded joints of austenitic stainless steel. The fatigue lives of butt welded joints treated by UIT were more than 1.5 times longer than those of as-weld joints. The following were considered as possible reasons for this improvement in fatigue life: change in residual stress near the weld toes, relaxation of stress concentration at the weld toes, and refinement of grains under the weld toes. The residual stress measured near the weld toes by using the X-ray diffraction method was transformed from tension to compression by the application of UIT. The stress concentration factors at the welded toes were reduced about 10% by the application of UIT.

Investigation of mechanical and corrosion behavior of laser hybrid weld joint of 2205 duplex stainless steel

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Chuanbo Zheng ◽  
Cheng Zhang ◽  
Xiao Yong Wang ◽  
Jie Gu
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Duplex Stainless Steel ◽  
Base Metal ◽  
Corrosion Behavior ◽  
Welded Joints ◽  
Two Phase ◽  
Content Type ◽  
2205 Duplex Stainless Steel ◽  
Laser Hybrid

Purpose Duplex stainless steel is composed of equal amounts of austenite and ferrite, which has excellent corrosion resistance and strength. However, after the metal was welded, the ratio of austenite and ferrite in the joint is unbalanced, and secondary phase precipitates are produced, which is also an important cause of pitting corrosion in the joint. Design/methodology/approach This paper aims to study the mechanical and corrosion behavior of welded joints, by adjusting the welding parameters of laser hybrid welding, dual heat sources are used to weld 2205 duplex stainless steel. The two-phase content of different parts of the welded joint is measured to study the influence of the ratio of the two-phase on the mechanical and corrosion properties of the joint. Findings The ratio of austenite and ferrite in different welded joints has an obvious difference, and from top to bottom, the austenite content decreased gradually, and the ferrite content increased gradually. The harmful phases are precipitated in the middle and lower part of the joint. The strength of welded joints is slightly lower than that of base metal. At the same time, the fracture analysis shows that some ferrite phases are affected by the precipitate in the grain and produce quasi-cleavage fracture. The corrosion results show that the corrosion resistance of the welded joints is lower than that of the base metal, and the concentration of chloride ions affects the corrosion resistance. Originality/value In this paper, the authors use the influence of different welding processes on the two-phase ratio of the joint to further study the influence of the microstructure on the corrosion resistance and mechanical properties of the weld.

Additive manufacturing of 316L stainless-steel structures using fused filament fabrication technology: mechanical and geometric properties

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Miguel Ángel Caminero ◽  
Ana Romero ◽  
Jesús Miguel Chacón ◽  
Pedro José Núñez ◽  
Eustaquio García-Plaza ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Additive Manufacturing ◽  
Austenitic Stainless Steel ◽  
Material Properties ◽  
Steel Structures ◽  
Fused Filament Fabrication ◽  
Geometric Properties ◽  
Content Type ◽  
Build Orientation ◽  
Manufacturing Alternatives

Purpose Fused filament fabrication (FFF) technique using metal filled filaments in combination with debinding and sintering steps can be a cost-effective alternative for laser-based powder bed fusion processes. The mechanical behaviour of FFF-metal materials is highly dependent on the processing parameters, filament quality and adjusted post-processing steps. In addition, the microstructural material properties and geometric characteristics are inherent to the manufacturing process. The purpose of this study is to characterize the mechanical and geometric performance of three-dimensional (3-D) printed FFF 316 L metal components manufactured by a low-cost desktop 3-D printer. The debinding and sintering processes are carried out using the BASF catalytic debinding process in combination with the BASF 316LX Ultrafuse filament. Special attention is paid on the effects of build orientation and printing strategy of the FFF-based technology on the tensile and geometric performance of the 3-D printed 316 L metal specimens. Design/methodology/approach This study uses a toolset of experimental analysis techniques [metallography and scanning electron microcope (SEM)] to characterize the effect of microstructure and defects on the material properties under tensile testing. Shrinkage and the resulting porosity of the 3-D printed 316 L stainless steel sintered samples are also analysed. The deformation behaviour is investigated for three different build orientations. The tensile test curves are further correlated with the damage surface using SEM images and metallographic sections to present grain deformation during the loading progress. Mechanical properties are directly compared to other works in the field and similar additive manufacturing (AM) and Metal Injection Moulding (MIM) manufacturing alternatives from the literature. Findings It has been shown that the effect of build orientation was of particular significance on the mechanical and geometric performance of FFF-metal 3-D printed samples. In particular, Flat and On-edge samples showed an average increase in tensile performance of 21.7% for the tensile strength, 65.1% for the tensile stiffness and 118.3% for maximum elongation at fracture compared to the Upright samples. Furthermore, it has been able to manufacture near-dense 316 L austenitic stainless steel components using FFF. These properties are comparable to those obtained by other metal conventional processes such as MIM process. Originality/value 316L austenitic stainless steel components using FFF technology with a porosity lower than 2% were successfully manufactured. The presented study provides more information regarding the dependence of the mechanical, microstructural and geometric properties of FFF 316 L components on the build orientation and printing strategy.

STUDY ON FATIGUE BEHAVIOR OF STRENGTHENED NON-LOAD-CARRYING CRUCIFORM WELDED JOINTS USING CARBON FIBER SHEETS

2012 ◽  
Vol 12 (01) ◽  
pp. 179-194 ◽  
Author(s):  
TAO CHEN ◽  
QIAN-QIAN YU ◽  
XIANG-LIN GU ◽  
XIAO-LING ZHAO
Keyword(s):  
Stress Concentration ◽  
Carbon Fiber ◽  
Welded Joints ◽  
Failure Modes ◽  
Fatigue Behavior ◽  
Local Stress ◽  
Fatigue Loading ◽  
Cfrp Sheets ◽  
Load Carrying ◽  
Weld Toe

This paper reports an experimental study on the use of carbon fiber-reinforced polymer (CFRP) sheets to strengthen non-load-carrying cruciform welded joints subjected to fatigue loading. Failure modes and corresponding fatigue lives were recorded during tests. Scatter of test results was observed. Thereafter, a series of numerical analyses were performed to study the effects of weld toe radius, the number of CFRP layers and Young's modulus of reinforced materials on local stress concentration at a weld toe. It was found that fatigue life of such welded connections can be enhanced because of the reduction of stress concentration caused by CFRP strengthening. Parametric study indicates that the weld toe radius and the amount of CFRP are the key parameters influencing the stress concentration factors and stress ranges of the joint. Enhancement of modulus for adhesive and CFRP sheets can also be beneficial to the fatigue performance to some extent.

Effect of Ultrasonic Impact Treatment on the Stress Corrosion Cracking of 304 Stainless Steel Welded Joints

2008 ◽  
Author(s):  
Gang Ma ◽  
Xiang Ling
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stainless Steel ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Welded Joints ◽  
Corrosion Cracking ◽  
Coarse Grained ◽  
304 Stainless Steel ◽  
Ultrasonic Impact Treatment

High tensile weld residual stress is an important factor contributing to stress corrosion cracking (SCC). Ultrasonic impact treatment (UIT) can produce compressive stresses on the surface of welded joints that negate the tensile stresses to enhance the SCC resistance of welded joints. In the present work, X-ray diffraction method was used to obtain the distribution of residual stress induced by UIT. The results showed that UIT could cause a large compressive residual stress up to 325.9MPa on the surface of the material. A 3D finite element model was established to simulate the UIT process by using a finite element software ABAQUS. The residual stress distribution of the AISI 304 stainless steel induced by UIT was predicted by finite element analysis. In order to demonstrate the improvement of the SCC resistance of the welded joints, the specimens were immersed in boiling 42% magnesium chloride solution during SCC testing, and untreated specimen cracked after immersion for 23 hours. In contrast, treated specimens with different coverage were tested for 1000 hours without visible stress corrosion cracks. The microstructure observation results revealed that a hardened layer was formed on the surface and the initial coarse-grained structure in the surface was refined into ultrafine grains. The above results indicate that UIT is an effective approach for protecting weldments against SCC.

Failure analysis and countermeasures of the SCM435 high-tension bolt of three-step injection mold

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ki-Woo Nam ◽  
Seo-Hyun Yun
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Failure Analysis ◽  
Crack Length ◽  
Fatigue Limit ◽  
Vickers Hardness ◽  
Injection Mold ◽  
Content Type ◽  
Damaged Material ◽  
High Tension

PurposeThe objective of this study was to perform damage analysis of SCM435 high-tension bolts connecting upper and lower parts of a three-stage injection molding machine.Design/methodology/approachDamage material used in this study was a SCM435 high-strength bolt connecting upper and lower molds of a three-stage injection mold. Causes of damage were determined by macroscopic observation. Microstructure observation was done using a metallic microscope, scanning electron microscope (SEM, S-2400, HiTachi, Japan), energy dispersive X-ray spectroscopy (EDS, Kevex Ltd., Sigma) and Vickers hardness tester (HV-114, Mitutoyo). Fatigue limit of the damaged material was evaluated using equivalent crack length.FindingsBolts were fractured by cyclic bending stress in the observation of ratchet marks and beach marks. The damaged specimen showed an acicular microstructure. Impurity was observed. Chromium carbide was observed near the crack origin. Both shape parameters of the Vickers hardness were similar. However, the scale parameter of the damaged specimen was about smaller than that of the as-received specimen. Much degradation occurred in the damaged specimen. Bolts should undergo accurate heat treatment to prevent the formation of chromium carbide. They must prevent the action of dynamic stresses. Bolts need accurate tightening and accuracy of heat treatment. Screws require compression residual stress due to peening.Originality/valueThis study conducted failure analysis of damaged SCM435 bolts connecting upper and lower parts of the three-stage injection mold. Fatigue limit of the damaged material was evaluated using equivalent crack length. In order to control this fracture, accurate tightening of bolts, accuracy of heat treatment and screws are required for compression residual stress due to peening.

Effect of Ultrasonic Impact Treatment on the Stress Corrosion Cracking of 304 Stainless Steel Welded Joints

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
Xiang Ling ◽  
Gang Ma
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stainless Steel ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Welded Joints ◽  
Corrosion Cracking ◽  
Coarse Grained ◽  
304 Stainless Steel ◽  
Ultrasonic Impact Treatment

High tensile weld residual stress is an important factor contributing to stress corrosion cracking (SCC). Ultrasonic impact treatment (UIT) can produce compressive stresses on the surface of welded joints that negate the tensile stresses to enhance the SCC resistance of welded joints. In the present work, X-ray diffraction method was used to obtain the distribution of residual stress induced by UIT. The results showed that UIT could cause a large compressive residual stress in access of 300 MPa on the surface of the material. A 3D finite element model was established to simulate the UIT process by using the finite element software ABAQUS. The residual stress distribution of the AISI 304 stainless steel induced by UIT was predicted by finite element analysis. In order to demonstrate the improvement of the SCC resistance of the welded joints, the specimens were immersed in boiling 42% magnesium chloride solution during SCC testing, and untreated specimen cracked after immersion for 23 h. In contrast, treated specimens with different impact duration were tested for 1000 h without visible stress corrosion cracks. The microstructure observation results revealed that a hardened layer was formed on the surface and the initial coarse-grained structure in the surface was refined into ultrafine grains. The above results indicate that UIT is an effective approach for protecting weldments against SCC.

Residual Stress and Strain Responses of Welded Piping Joints Under Low-Cycle Fatigue Loading

2009 ◽  
Author(s):  
Pei-Yuan Cheng ◽  
Tasnim Hassan
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Fatigue Failure ◽  
Welded Joints ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Stress And Strain ◽  
Weld Toe ◽  
Strain Responses

It is well known that residual stress of welded joints influence their fatigue lives. This influence of residual stress is manifested through strain ratcheting response at the weld toe. Among many other reasons, strain ratcheting at the weld toe is anticipated to be a reason of many premature fatigue failure of welded joints. Hence, accurate simulations of weld toe residual stress and strain responses are essential for fatigue life simulation of welded joints. This paper presents results form an ongoing study on fatigue failure of welded piping joints. A modeling scheme for simulating weld toe residual stress and strain response is developed. Uncoupled, thermo-mechanical, finite element analyses are employed for imitating the welding procedure, and thereby simulating the temperature history during welding and initial residual stresses. Simulated residual stresses are validated by comparing against the measured residual stresses. Finite element simulations indicate that both residual stress and resulting strain responses near the weld toe are the key factors in inducing fatigue cracks at the weld toe. Research needs in revealing the fatigue failure mechanisms at the weld toe are discussed.

The Simulation of Residual Stress for Stud Welding and Establishment of Strength Estimating Model

2008 ◽  
Vol 575-578 ◽  
pp. 816-820 ◽  
Author(s):  
Guang Tao Zhou ◽  
Xue Song Liu ◽  
Guo Li Liang ◽  
Pei Zhi Liu ◽  
De Jun Yan ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Tensile Stress ◽  
Welded Joints ◽  
Welding Residual Stress ◽  
Yield Limit ◽  
Stud Welding ◽  
Welding Joints ◽  
Simulation Results ◽  
Steel Stud

The distribution and value of welding residual stress for 1Cr18Ni9 stainless steel stud welding joints was systemically simulated by ANSYS FE software. The mathematical estimating models of strength of the welded joints were established. Simulation results showed that the welding residual stress was tensile at the edge of the stud, while it was compressive stress at the position near axis center. The largest tensile stress did not exceed yield limit of material. The residual stress had more influence on the strength of welded joints.

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