scholarly journals Effect of Periodic Overloads on Short Fatigue Crack Behavior in CuNi2Si Alloy under Rotating Bending Load

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1267
Author(s):  
Yahang Qin ◽  
Bing Yang ◽  
Bo Feng ◽  
Yifan Li ◽  
Shoune Xiao ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Cracks ◽  
Fatigue Crack Initiation ◽  
Constant Load ◽  
Multiple Cracks ◽  
Short Fatigue Crack ◽  
Crack Behavior ◽  
Bending Load ◽  
Rotating Bending

In this study, the short fatigue crack behavior in a precipitation-strengthened CuNi2Si alloy was investigated using a replica technique under rotating bending loads with periodic overloads, an overload ratio of 1.5, and the stress ratio of both was R = −1. The results show that all the fatigue cracks originated from the surface of the specimen and displayed a trend of slow initiation and then rapid propagation. The introduction of overloads significantly reduced the fatigue crack initiation time and the fatigue life of the sample. The average life of the overloaded samples was only 31% that of the constant load samples. For overload specimens, multiple cracks grew at the same time and merged at different stages, causing the crack length to increase instantaneously after they merged, thereby considerably reducing the fatigue life. Fractographical analysis and observation of the surface-etched sample replica film showed that cracks in samples with and without overload both propagated along the grain boundaries.

scholarly journals Short Fatigue Crack Behavior of LZ50 Axle Steel Under Rotating-Bending Cyclic Loading

2018 ◽  
Vol 50 (1) ◽  
pp. 193-202 ◽  
Author(s):  
B. Yang ◽  
S. Dai ◽  
Y. Y. Wu ◽  
Z. Liao ◽  
S. Liang ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Cyclic Loading ◽  
Short Fatigue Crack ◽  
Crack Behavior ◽  
Rotating Bending

Fatigue Crack Initiation and Propagation Life of Welded Joints

2005 ◽  
Vol 297-300 ◽  
pp. 781-787 ◽  
Author(s):  
Jeong Woo Han ◽  
Seung Ho Han ◽  
Byung Chun Shin ◽  
Jae Hoon Kim
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Initiation ◽  
Welded Joints ◽  
Fatigue Crack Initiation ◽  
Welding Residual Stress ◽  
Multiple Cracks ◽  
Weld Toes ◽  
Crack Initiation And Propagation ◽  
Initiation And Propagation

The fatigue life of welded joints is associated with crack initiation and propagation life. Theses cannot be easily separated, since the definition of crack initiation is vague due to the initiation of multiple cracks that are distributed randomly along the weld toes. In this paper a method involving a notch strain and fracture mechanical approach, which considers the characteristics of welded joints, e.g. welding residual stress and statistical characteristics of multiple cracks, is proposed, in an attempt to reasonably estimate these fatigue lives. The fatigue crack initiation life was evaluated statistically, e.g. the probability of occurrence in 2.3, 50 and 97.7%, in which the cyclic response of the local stress/strain in the vicinity of the weld toes and notch factors derived by the irregular shape of the weld bead are taken into account. The fatigue crack propagation life was simulated in consideration of the Mk-factor and the mechanical behavior of mutual interaction/coalescence between two adjacent cracks. The estimated total fatigue life as a sum of crack initiation and propagation life was found to be in good agreement with the experimental results.

Effects of Hub Contact Shape on Contact Pressure and Fatigue Life in a Press-Fitted Shaft

2010 ◽  
Vol 654-656 ◽  
pp. 1638-1641 ◽  
Author(s):  
Dong Hyung Lee ◽  
Seok Jin Kwon ◽  
Jung Won Seo ◽  
Won Hee You
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Initiation ◽  
Contact Pressure ◽  
Fatigue Crack Initiation ◽  
Press Fit ◽  
Bending Load ◽  
Contact Surfaces ◽  
Crack Initiation Life ◽  
Contact Shape

The objective of this study is to clarify the effect of hub contact shape on contact pressure and fatigue life with regard to the selection of a suitable taper design near the end of the fit. A numerical asymmetric-axisymmetric finite element model was developed in order to determine the contact stress state of press-fitted shaft by using four types of tapered contact surfaces on the hub. The variations of fatigue crack initiation life according to the change of tapered contact surfaces on the hub were evaluated by using the Smith-Watson-Topper (SWT) multiaxial fatigue criterion. As the result, comparing with the contact pressure and the fatigue crack initiation life, maximum decrease of contact pressure and maximum increase of fatigue crack initiation life were obtained for the 1/400 m/m tapered hub subjected to a bending load near the fretting fatigue limit. Furthermore, as the change of bending load, the optimal amout of taper in hub which fatigue life gets into maximum is varied. Therefore, we suggest that the best performance, in terms of pressure distribution and fatigue life of press fit, can be obtained by using a proper taper values for the hub element.

Simulation on the Short Fatigue Crack Initiation of LZ50 Axle Steel for Railway Vehicles

2007 ◽  
Vol 353-358 ◽  
pp. 989-992
Author(s):  
Yan Hai Xu ◽  
Yong Xiang Zhao
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Fatigue Cracks ◽  
Voronoi Tessellation ◽  
Fatigue Crack Initiation ◽  
Stress And Strain ◽  
Railway Vehicles ◽  
Short Fatigue Crack ◽  
Lz50 Steel ◽  
The Given

The short fatigue crack initiation of LZ50 axle steel for railway vehicles was investigated by numerical simulation in this paper. The microstructure of LZ50 steel was constructed with the application of 2D Voronoi tessellation. The stress and strain distributions in the microstructure were obtained by FEM under the boundary condition shifted from loading level applied in fatigue specimen of this steel. Finally, the probability of short fatigue crack initiation was given with different loading cycles to illustrate the process of crack initiation of LZ50 steel under the given loading cycles based on the S-N curve of the material. The further work on the research of crack growth and collective evolution of short fatigue cracks can be conducted with the simulated results of crack initiation in the microstructure of LZ50 steel.

scholarly journals Influence of Strain Ratio on Bending Fatigue Life in TiNi Shape Memory Thin Wire

2007 ◽  
Vol 340-341 ◽  
pp. 1193-1198 ◽  
Author(s):  
Ryosuke Matsui ◽  
Hisaaki Tobushi ◽  
Yoshiyasu Makino
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Shape Memory ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Strain Ratio ◽  
Thin Wire ◽  
Bending Fatigue ◽  
Rotating Bending ◽  
Plane Bending

In this study, we performed the bending fatigue test and investigated the influence of strain ratio on fatigue life in TiNi shape memory thin wire. The pulsating plane bending, alternating plane bending and rotating bending fatigue tests were carried. Additionally, we carried out the observation of the fatigue fracture surface by a scanning electron microscope. The behavior of fatigue crack was investigated. The results obtained are summarized as follows. (1) The martensitic transformation (MT) stress of the superelastic thin wire (SE-NT) is higher than that of the SMA thin wire (SME-NT) and the fatigue life of SE-NT is shorter than that of SME-NT. Maximum bending strain at the fatigue limit is the MT starting strain. (2) The low-cycle fatigue life curve in plane bending for SE-NT is expressed by a power function of maximum strain εmax and the number of cycles to failure Nf. The smaller the strain ratio for the same εmax, the shorter the fatigue life. (3) In both the rotating bending and the plane bending, fatigue cracks nucleate on the surface of the wire and one fatigue crack grows preferentially. The region in which fatigue crack propagated is fan-shaped.

Plastic Slip and Early Stage of Fatigue Damage in Polycrystals: Comparison between Experiments and Crystal Plasticity Finite Elements Simulations

2014 ◽  
Vol 891-892 ◽  
pp. 1711-1716 ◽  
Author(s):  
Loic Signor ◽  
Emmanuel Lacoste ◽  
Patrick Villechaise ◽  
Thomas Ghidossi ◽  
Stephan Courtin
Keyword(s):  
Fatigue Crack ◽  
Finite Elements ◽  
Crack Initiation ◽  
Fatigue Damage ◽  
Crystal Plasticity ◽  
Early Stage ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Fatigue Crack Initiation ◽  
Plastic Slip

For conventional materials with solid solution, fatigue damage is often related to microplasticity and is largely sensitive to microstructure at different scales concerning dislocations, grains and textures. The present study focuses on slip bands activity and fatigue crack initiation with special attention on the influence of the size, the morphology and the crystal orientation of grains and their neighbours. The local configurations which favour - or prevent - crack initiation are not completely identified. In this work, the identification and the analysis of several crack initiation sites are performed using Scanning Electron Microscopy and Electron Back-Scattered Diffraction. Crystal plasticity finite elements simulation is employed to evaluate local microplasticity at the scale of the grains. One of the originality of this work is the creation of 3D meshes of polycrystalline aggregates corresponding to zones where fatigue cracks have been observed. 3D data obtained by serial-sectioning are used to reconstruct actual microstructure. The role of the plastic slip activity as a driving force for fatigue crack initiation is discussed according to the comparison between experimental observations and simulations. The approach is applied to 316L type austenitic stainless steels under low-cycle fatigue loading.

scholarly journals Structural and mechanical defects of materials of offshore and onshore main gas pipelines after long-term operation

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Pavlo Maruschak ◽  
Sergey Panin ◽  
Iryna Danyliuk ◽  
Lyubomyr Poberezhnyi ◽  
Taras Pyrig ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Quantitative Analysis ◽  
Stress Concentration ◽  
Cyclic Loading ◽  
Fatigue Cracks ◽  
Preliminary Deformation ◽  
Term Operation ◽  
Steel Pipes

AbstractThe study has established the main regularities of a fatigue failure of offshore gas steel pipes installed using S-lay and J-lay methods.We have numerically analyzed the influence of preliminary deformation on the fatigue life of 09Mn2Si steel at different amplitudes of cyclic loading. The results have revealed the regularities of formation and development of a fatigue crack in 17Mn1Si steel after 40 years of underground operation. The quantitative analysis describes the regularities of occurrence and growth of fatigue cracks in the presence of a stress concentration.

Effect of Processing Layer on Fatigue Strength of Extruded AZ61 Magnesium Alloy

2013 ◽  
Vol 577-578 ◽  
pp. 429-432 ◽  
Author(s):  
Yukio Miyashita ◽  
Kyohei Kushihata ◽  
Toshifumi Kakiuchi ◽  
Mitsuhiro Kiyohara
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Magnesium Alloy ◽  
Crack Initiation ◽  
Crack Growth ◽  
Fatigue Crack Initiation ◽  
Fatigue Tests ◽  
Crack Growth Resistance ◽  
Az61 Magnesium Alloy

Fatigue Property of an Extruded AZ61 Magnesium Alloy with the Processing Layer Introduced by Machining was Investigated. Rotating Bending Fatigue Tests were Carried out with the Specimen with and without the Processing Layer. According to Results of the Fatigue Tests, Fatigue Life Significantly Increased by Introducing the Processing Layer to the Specimen Surface. Fatigue Crack Initiation and Propagation Behaviors were Observed by Replication Technique during the Fatigue Test. Fatigue Crack Initiation Life of the Specimen with the Processing Layer was Slightly Longer than that of the Specimen without the Processing Layer. Higher Fatigue Crack Growth Resistance was also Observed when the Fatigue Crack was Growing in the Processing Layer in the Specimen with the Processing Layer. the Longer Fatigue Life Observed in the Fatigue Test in the Specimen with the Processing Layer could be Mainly due to the Higher Crack Growth Resistance. it is Speculated that the Fatigue Strength can be Controlled by Change in Condition of Machining Process. it could be Effective way in Industry to Improved Fatigue Strength only by the Cutting Process without Additional Surface Treatment Process.

scholarly journals A fatigue crack initiation and growth life estimation method in single-bolted connections

2019 ◽  
Vol 54 (2) ◽  
pp. 79-94 ◽  
Author(s):  
Arash P Jirandehi ◽  
TN Chakherlou
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Initiation ◽  
Crack Growth ◽  
Fatigue Crack Initiation ◽  
Multiaxial Fatigue ◽  
Estimation Accuracy ◽  
Life Estimation ◽  
Lower Error ◽  
Fatigue Life Estimation

Fatigue life estimation accuracy of mechanical parts and assemblies has always been the source of concern in different industries. The main contribution of this article lies in a study on the accuracy of different multiaxial fatigue criteria, proposing and investigating the accuracy of four optimized fatigue crack initiation life estimation methods—volume, weighted volume, surface and point, thereby improving the multiaxial fatigue life estimation accuracy. In order to achieve the goal, the fatigue lives of bolt clamped specimens, previously tested under defined experimental conditions, were estimated during fatigue crack initiation and fatigue crack growth and then summed together. In the fatigue crack initiation part, a code was written and used in the MATLAB software environment based on critical plane approach and the different multiaxial fatigue criteria. Besides the AFGROW software was utilized to estimate the crack growth share of fatigue life. Experimental and numerical results showed to be in agreement. Furthermore, detailed study and comparison of the results with the available experimental data showed that a combination of Smith–Watson–Topper approach and volume method results in lower error values, while a combination of Fatemi–Socie criterion and surface or point method presents estimated lives with lower error values. In addition, the numerical proposed procedure resulted in a good prediction of the location of fatigue crack initiation.

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