Multiaxial Fatigue in Drill Pipes Under Non-Proportional Loading

2017 ◽  
Author(s):  
Nahla A. Helmy ◽  
Maher Y. A. Younan
Keyword(s):  
Fatigue Life ◽  
Crack Initiation ◽  
High Cycle Fatigue ◽  
Drill Pipe ◽  
Real Life ◽  
Design Guidelines ◽  
Multiaxial Fatigue ◽  
Data Sets ◽  
Cycle Fatigue ◽  
Proportional Loading

The scope of this research is to estimate the fatigue life and crack initiation direction in components subjected to multiaxial, nonproportional loading. Two critical plane approaches — Fatemi-Socie and McDiarmid — were used to estimate low cycle and high cycle fatigue lives, respectively. A software program (Elrond) was constructed to estimate the fatigue life and crack initiation plane. The code was validated using experimental fatigue data sets from previous research, then was applied to a real-life drilling problem. Drill pipe operating in the “Build and Hold” drilling job condition was analyzed using the developed software. Results were compared with the API RP7G fatigue design guidelines. Fatigue life charts were prepared using fatigue lives estimated by Elrond at several axial loadings, dogleg severities and torque amplitudes. Also, maximum allowable torque under high cycle fatigue conditions was estimated.

The Influence of Multiaxial Superimposed Static Mean Stress on High-Cycle Fatigue Life of Cu-ETP Copper

2016 ◽  
Vol 250 ◽  
pp. 157-162
Author(s):  
Lukasz Pejkowski ◽  
Dariusz Skibicki ◽  
Mateusz Wirwicki
Keyword(s):  
Fatigue Life ◽  
High Cycle Fatigue ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Mean Stress ◽  
Loading Conditions ◽  
Cycle Fatigue ◽  
Proportional Loading ◽  
Mean Stresses

High–cycle multiaxial fatigue tests under proportional and non-proportional loading conditions with various combinations of superimposed static mean stresses was carried out on Cu-ETP copper. The results show differences in fatigue life between various ratios of mean stresses. These results are similar to others described in the literature.

Enhancing Fatigue Properties of Nanostructured Metals and Alloys

2007 ◽  
Vol 29-30 ◽  
pp. 117-122 ◽  
Author(s):  
Terry C. Lowe
Keyword(s):  
Fatigue Life ◽  
Crack Initiation ◽  
Computational Methods ◽  
High Cycle Fatigue ◽  
Low Cycle Fatigue ◽  
Metals And Alloys ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Nanostructured Metals ◽  
Improve Fatigue

Recent research on the fatigue properties of nanostructured metals and alloys has shown that they generally possess superior high cycle fatigue performance due largely to improved resistance to crack initiation. However, this advantage is not consistent for all nanostructured metals, nor does it extend to low cycle fatigue. Since nanostructures are designed and controlled at the approximately the same size scale as the defects that influence crack initiation attention to preexisting nanoscale defects is critical for enhancing fatigue life. This paper builds on the state of knowledge of fatigue in nanostructured metals and proposes an approach to understand and improve fatigue life using existing experimental and computational methods for nanostructure design.

The Improvement of High Cycle Fatigue Properties of AC4CH Alloy with Shot Peening Treatment

2005 ◽  
Vol 297-300 ◽  
pp. 1919-1924
Author(s):  
Kiyotaka Masaki ◽  
Yasuo Ochi ◽  
Takashi Matsumura
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Initiation ◽  
Shot Peening ◽  
High Cycle Fatigue ◽  
Fatigue Crack Initiation ◽  
Crack Propagation Rate ◽  
Fatigue Properties ◽  
Fatigue Crack Propagation Rate ◽  
Cycle Fatigue

In order to investigate the effect of SP treatment on the high cycle fatigue properties such as fatigue strength, crack initiation and propagation behaviors, rotating bending fatigue tests on shot-peening (SP) treated AC4CH aluminum alloy were carried out. The fatigue properties of the SP-treated material were compared with fatigue properties of the non-peened material, the hot isostatic pressure (HIP) treated material and the semi-liquid (SL) die casting material. the main conclusions obtained were, (1) The fatigue properties of SP-treated material is most excellent in all materials. (2) The fatigue life property of AC4CH alloys is significantly affected by fatigue crack initiation behavior. The reason why the SP-treated material has longer fatigue life than those of other material is that it has no cast defects near the surface by the effect of SP treatment. (3) The reason of fatigue life improvement by SP treatment is decrease of fatigue crack propagation rate.

The Top 10 Influential Articles in Very High Cycle Fatigue

2015 ◽  
Vol 664 ◽  
pp. 22-30
Author(s):  
Yong Jie Liu ◽  
Muhammad Kashif Khan ◽  
Qing Yuan Wang
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Initiation ◽  
High Cycle Fatigue ◽  
Web Of Science ◽  
Cycle Fatigue ◽  
Science Data ◽  
Specialty Area ◽  
Very High Cycle Fatigue ◽  
Very High

The top 10 most influential articles in Very high cycle fatigue (VHCF) have been indentified from web of science data. The attributes of the top 10 papers have been discussed. It was found that specialty area of fatigue called as “VHCF” is an emerging field. The most cited papers discussed the two the fatigue crack mechanism in fatigue. It was found that crack initiation shifts from surface to subsurface if the material beyond 107 cycles. There are some models which can predict the fatigue life of the material however the exact estimation is still challenging. Hence, it was found that still further efforts are required in the field to accurately understand the VHCF behavior.

Effect of Aluminized Coating on Combined Low and High Cycle Fatigue Life of Turbine Blade at Elevated Temperature

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Cao Chen ◽  
Xiaojun Yan ◽  
Xiaoyong Zhang ◽  
Yingsong Zhang ◽  
Min Gui ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Elevated Temperature ◽  
Crack Initiation ◽  
Turbine Blade ◽  
High Cycle Fatigue ◽  
Turbine Blades ◽  
Cycle Fatigue ◽  
Σ Phase ◽  
Initiation And Propagation ◽  
Crack Initiation Life

Some cracks were detected on the fir-tree root of turbine blade in an in-service aero-engine, and the aluminized coating was considered to be the main cause of these cracks. To study the effect of aluminized coating on fatigue life of turbine blade, the combined low and high cycle fatigue (CCF) tests are carried out at elevated temperature on both aluminized and untreated turbine blades. Probability analysis of test data is conducted and the result indicates that the median life is decreased by 62.2% due to the effect of the aluminized coating. Further study on the mechanism of crack initiation and propagation has been conducted based on fractography and cross section morphology analysis by using scanning electron microscope (SEM), and the results indicate: (1) The aluminized coating consists of two layers, of which the inner layer is considered to contain the σ phase and it reduces the resistance to fatigue of blade. (2) Many cavities are found in the inner layer of aluminized coating, which lead to the initiation of cracks and result in the reduction of crack initiation life. (3) The marker band widths of aluminized and untreated blade are very close, which indicated the aluminized coating may have no effect on the crack propagation life of the blade.

Fretting High-Cycle Fatigue Assessment through a Multiaxial Critical Plane-Based Criterion in Conjunction with the Taylor’s Point Method

2016 ◽  
Vol 258 ◽  
pp. 217-220 ◽  
Author(s):  
Camilla Ronchei ◽  
Andrea Carpinteri ◽  
Giovanni Fortese ◽  
Daniela Scorza ◽  
Sabrina Vantadori
Keyword(s):  
Fatigue Life ◽  
High Cycle Fatigue ◽  
Multiaxial Fatigue ◽  
Point Method ◽  
Cycle Fatigue ◽  
Structural Components ◽  
Severe Stress ◽  
Critical Plane ◽  
The Common ◽  
Crack Initiation Life

The critical plane-based multiaxial criterion originally proposed by the authors for plain fatigue is here applied to estimate the crack initiation life of fretting high-cycle fatigued structural components. Although fretting fatigue can be regarded as a case of multiaxial fatigue, the common multiaxial fatigue criteria have to be modified to account for the severe stress gradients in the contact zone. Therefore, the above criterion is used in conjunction with the Taylor’s point method to numerically estimate the fatigue life of Ti-6Al-4V and Al-4Cu specimens under cylindrical contacts.

scholarly journals Influence of Strain Gradient on Fatigue Life of Carbon Steel for Pressure Vessels in Low-Cycle and High-Cycle Fatigue Regimes

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 445
Author(s):  
Tomoyuki Fujii ◽  
Muhamad Safwan Bin Muhamad Azmi ◽  
Keiichiro Tohgo ◽  
Yoshinobu Shimamura
Keyword(s):  
Fatigue Life ◽  
Carbon Steel ◽  
Crack Initiation ◽  
Strain Gradient ◽  
High Cycle Fatigue ◽  
Pressure Vessels ◽  
Cycle Fatigue ◽  
Total Failure ◽  
Crack Initiation Life ◽  
Failure Life

This paper discusses how the strain gradient influences the fatigue life of carbon steel in the low-cycle and high-cycle fatigue regimes. To obtain fatigue data under different strain distributions, cyclic alternating bending tests using specimens with different thicknesses and cyclic tension–compression tests were conducted on carbon steel for pressure vessels (SPV235). The crack initiation life and total failure life were evaluated via the strain-based approach. The experimental results showed that the crack initiation life became short with decreasing strain gradient from 102 to 106 cycles in fatigue life. On the other hand, the influence of the strain gradient on the total failure life was different from that on the crack initiation life: although the total failure life of the specimen subjected to cyclic tension–compression was also the shortest, the strain gradient did not affect the total failure life of the specimen subjected to cyclic bending from 102 to 106 cycles in fatigue life. This was because the crack propagation life became longer in a thicker specimen. Hence, these experimental results implied that the fatigue crack initiation life could be characterized by not only strain but also the strain gradient in the low-cycle and high-cycle fatigue regimes.

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 Life ◽  
Fatigue Strength ◽  
Crack Initiation ◽  
Surface Defect ◽  
High Cycle Fatigue ◽  
Projection Area ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Artificial Surface ◽  
Very High

Additively manufactured (AM) alloy usually inevitably contains defects during manufacturing processor in service. 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. The fatigue life descends linearly with stress amplitude for interior defect induced failure. While for artificial surface defect induced failure, the fatigue life descends at first, and then exhibits a plateau region feature. We also observed competition of interior crack initiation with 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 defect on the fatigue crack initiation. Finally, the effect of artificial surface defect 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  N0 and  σ= CN ( area) for  N≥N , where  C,  a and  n are constants, N  is the number of cycles at the knee point.

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