scholarly journals Effect of Artificial Defects on the Very High Cycle Fatigue Behavior of 316L Stainless Steel

Metals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 412 ◽  
Author(s):  
Zhihong Xiong ◽  
Takashi Naoe ◽  
Masatoshi Futakawa
Keyword(s):  
Stainless Steel ◽  
Service Life ◽  
Empirical Formula ◽  
High Cycle Fatigue ◽  
Surface Defects ◽  
Critical Depth ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Indent Depth ◽  
Very High

Widely used for structural materials in nuclear engineering, 316L austenitic stainless steel undergoes very high cycle fatigue (VHCF) throughout its service life. Since defects caused by service conditions are unavoidable in many engineering components during service life, the effects should be properly understood. In the present study, the effect of surface defects on the VHCF behavior were investigated on solution annealed (SA) and cold-worked (CW) 316L. Surface defects were artificially created using indentation. The VHCF test was conducted using an ultrasonic fatigue testing system. The results showed that the fatigue crack initiation was independent of the indent with the applied range of depth in this research. Furthermore, the critical depth of the indent was evaluated based on an empirical formula (Murakami’s model). In the case of SA 316L, the VHCF strength was not affected when the indent depth was less than 40 μm, which is consistent with the value obtained from the empirical formula. In the case of 20% CW 316L, the VHCF strength was not affected when the indent depth was less than 80 μm. The experimental results, i.e., the critical depth of the indent, were much larger than the results obtained from the empirical formula, and might have been caused by the plastic deformation, residual stress, and probable deformation-induced martensite transition around the indent.

High-cycle and very-high-cycle fatigue behavior of a stainless steel for air-conditioning compressor valve plates

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xu Jia ◽  
Yang Ou Xiang ◽  
Hu Yuan Pei ◽  
Song Wei
Keyword(s):  
Stainless Steel ◽  
Cyclic Loading ◽  
Air Conditioning ◽  
High Cycle Fatigue ◽  
Loading Conditions ◽  
Cycle Fatigue ◽  
Content Type ◽  
Very High Cycle Fatigue ◽  
Load Characteristics ◽  
Very High

PurposeThe investigations could guide the structural design and fatigue life prediction of air-conditioning compressor valve plates.Design/methodology/approachThe High-Cycle Fatigue (HCF) and Very-High-Cycle Fatigue (VHCF) behaviors of stainless steel used for air-conditioning compressor valve plates were investigated. Monotonic and cyclic loading conditions were designed to explore the fatigue responses according to the load characteristics of the structure.FindingsThe crack initiation can be observed as the arc-shaped cracks at both sides of specimens and Y-shaped crack bifurcation in the specimens. Moreover, the middle section and the cracks at both ends are not connected to the surface of the specimen. The stress-life results of the materials under two directions (vertical and horizontal) were provided to examine the difference in fatigue strength.Originality/valueMonotonic and cyclic loading conditions were designed to explore the fatigue responses according to the load characteristics of the structure. Based on the experimental data, the results indicate that specimens under cyclic loading conditions could demonstrate better mechanical performance than static loadings.

scholarly journals Defect induced cracking and modeling of fatigue strength for an additively manufactured Ti-6Al-4V alloy in very high cycle fatigue regime

2021 ◽  
Author(s):  
Weiqian Chi ◽  
Wenjing Wang ◽  
Chengqi Sun
Keyword(s):  
Fatigue Strength ◽  
Crack Initiation ◽  
High Cycle Fatigue ◽  
Surface Defects ◽  
Fatigue Crack Initiation ◽  
Projection Area ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Artificial Surface ◽  
Very High

Additively manufactured (AM) alloy usually inevitably contains defects during the manufacturing processor or service process. Defects, as a harmful factor, could significantly reduce the fatigue performance of materials. This paper shows that the location and introduced form of defects play an important role in high cycle and very high cycle fatigue (VHCF) behavior of selective laser melting Ti-6Al-4V alloy. S-N curve descends linearly for internal defects induced failure. While for artificial surface defects induced failure, S-N curve descends at first and then exhibits a plateau region feature. We also observed competition of interior crack initiation with the fine granular area feature in VHCF regime. The paper indicates that only the size or the stress intensity factor range of the defect is not an appropriate parameter describing the effect of defects on the fatigue crack initiation. Finally, the effect of artificial surface defects on high cycle and VHCF strength is modeled, i.e. the fatigue strength   σ, fatigue life  N and defect size area (square root of projection area of defect perpendicular to principal stress direction) is expressed as  σ = CN ( area)  for  N and  σ = CN ( area)  for  N≥N, where  C,  a and  n are constants, N is the number of cycles at the knee point.

scholarly journals Bending Fatigue Behavior of 316L Stainless Steel up to Very High Cycle Fatigue Regime

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4820
Author(s):  
Yongtao Hu ◽  
Yao Chen ◽  
Chao He ◽  
Yongjie Liu ◽  
Qingyuan Wang ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Slip Band ◽  
316L Stainless Steel ◽  
High Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Propagation Mechanism ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Very High

Effect of microstructure on the crack initiation and early propagation mechanism in the very high cycle fatigue (VHCF) regime was studied in 316L stainless steel (316L SS) by atomic force microscope (AFM) and electron back scattered diffraction (EBSD). The results show that small fatigue cracks initiate from the slip band near the grain boundaries (GBs) or the twin boundaries (TBs). Early crack propagation along or cross the slip band is strongly influenced by the local microstructure such as grain size, orientation, and boundary. Besides, the gathered slip bands (SBs) are presented side by side with the damage grains of the run-out specimen. Finally, it is found that dislocations can either pass through the TBs, or be arrested at the TBs.

scholarly journals Very High Cycle Fatigue Behavior of Additively Manufactured 316L Stainless Steel

Materials ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3293
Author(s):  
Boris Voloskov ◽  
Stanislav Evlashin ◽  
Sarkis Dagesyan ◽  
Sergey Abaimov ◽  
Iskander Akhatov ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Fracture Surface ◽  
316L Stainless Steel ◽  
High Cycle Fatigue ◽  
Nonmetallic Inclusions ◽  
Cycle Fatigue ◽  
Fracture Surfaces ◽  
Lack Of Fusion ◽  
Very High Cycle Fatigue ◽  
Very High

The present paper is focused on an experimental study of the damage-to-failure mechanism of additively manufactured 316L stainless steel specimens subjected to very high cycle fatigue (VHCF) loading. Ultrasonic axial tension-compression tests were carried out on specimens for up to 109 cycles, and fracture surface analysis was performed. A fine granular area (FGA) surrounding internal defects was observed and formed a “fish-eye” fracture type. Nonmetallic inclusions and the lack of fusion within the fracture surfaces that were observed with SEM were assumed to be sources of damage initiation and growth of the FGAs. The characteristic diameter of the FGAs was ≈500 μm on the fracture surface and were induced by nonmetallic inclusions; this characteristic diameter was the same as that for the fracture surface induced by a lack of fusion. Fracture surfaces corresponding to the high cycle fatigue (HCF) regime were discussed as well to emphasize damage features related to the VHCF regime.

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