Fatigue Crack Propagation at Negative Stress Ratio in 2A12 Aluminum Alloy

2010 ◽  
Vol 146-147 ◽  
pp. 185-188 ◽  
Author(s):  
Yu Sha ◽  
Shi Gang Bai ◽  
Jia Zhen Zhang
Keyword(s):  
Growth Rate ◽  
Aluminum Alloy ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Stress Ratio ◽  
Compressive Loading ◽  
Loading Effect

Fatigue crack propagation tests in the Paris region were performed in order to get compressive loading effect on fatigue crack growth at negative stress ratio (R) in 2A12 aluminum alloy. The results of the tests showed that the effect of the compressive loading part of the applied stress cycle on fatigue crack growth rate da/dN in 2A12 aluminum alloy at negative stress ratio can not be omitted. The fatigue crack growth rate at R<0 was more than that at R>0 under the same range of stress intensity factor Kmax. The da/dN is the function of Kmax and stress ratio R. The promoting effect has an increase trend with the increase of the absolute value of the negative stress ratio R. Then a model involved compressive loading effect on fatigue crack propagation at negative stress was obtained. The model has been obtained good agreements with the experimental data.

Study on Fatigue Crack Propagation at Negative Stress Ratio in 2A12 Aluminum Alloy

2011 ◽  
Vol 335-336 ◽  
pp. 809-812
Author(s):  
Shi Gang Bai ◽  
Jia Zhen Zhang ◽  
Yu Sha
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Stress Ratio ◽  
Compressive Loading ◽  
Stress Cycle ◽  
Made In

This paper intends to get compressive loading effect on fatigue crack growth of 2A12 aluminum alloy. The fatigue crack propagation tests at negative stress ratio R=-0.5, -1and -2 were made in different applied compressive loading. The result showed that the effect of the compressive loading part of the applied stress cycle on fatigue crack growth rate in 2A12 aluminum alloy at negative stress ratio can not be omitted.

Effect of Environment on Fatigue Crack Propagation Behavior of an Al-Cu-Mg Aluminum Alloy

2014 ◽  
Vol 1004-1005 ◽  
pp. 142-147
Author(s):  
Ming Liu ◽  
Kun Zhang ◽  
Sheng Long Dai ◽  
Guo Ai Li ◽  
Min Hao ◽  
...  
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Fatigue Crack Growth Rate ◽  
Fatigue Crack Propagation Behavior ◽  
Stress Ratios

The fatigue crack propagation behaviors of an Al-Cu-Mg alloy are investigated in different environments and with varying stress ratios. Fatigue experiments are carried out via a fatigue crack growth rate test in laboratory air, a 3.5% (mass fraction) NaCl solution and a tank seeper. The results show that a corrosion environment has an obvious influence on the fatigue crack growth rate, and the degrees of influence of the two different corrosive environments are basically identical. When the stress ratio is R = 0.5 and 0.06 with a decrease of the stress intensity factor, the difference in the crack propagation rates for the corrosion and air environments gradually increases. However, the corrosion acceleration in each stage of crack propagation is obvious while R=−1.

Experimental Study on Fatigue Crack Propagation of Glare3-3/2 with Mechanics Properties

2012 ◽  
Vol 600 ◽  
pp. 273-278
Author(s):  
Zong Hong Xie ◽  
Tian Jiao Zhao ◽  
Rui Wu
Keyword(s):  
Growth Rate ◽  
Aluminum Alloy ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Stress Level ◽  
Maximum Stress ◽  
Fatigue Tests

This study is to investigate the fatigue crack growth behavior of Glare3-3/2 under various stress levels. The Glare3-3/2 specimen consists of three 2024-T3 aluminum alloy sheets and two layers of glass/epoxy composite lamina. Tensile-tensile cyclic fatigue tests were conducted on centrally notched specimen at four stress levels with various maximum values. A digital camera system was used to take photos of the propagating cracks on both sides of the specimen. Image processing software was adopted to accurately measure the length of the cracks on each photo. The test results show that 1) Compared to 2024-T3 aluminum alloy, the fatigue properties of Glare3-3/2 are much better: under the same loading condition with maximum stress level of 120MPa, the crack growth rate of Glare3-3/2 is roughly 5% of the corresponding value of 2024-T3 aluminum alloy, while the fatigue life is 4 times higher than that of 2024-T3 aluminum alloy. 2) The maximum stress level shows strong influence on fatigue crack propagation behavior of Glare3-3/2. The value of steady state crack growth rate increases linearly, while the number of load cycles decreases exponentially, with respect to the maximum stress values used in the fatigue tests.

Fatigue Crack Growth Rate in Laser-Welded Web Core Sandwich Panels - Fatigue Crack Propagation in Welded Base Metal

2014 ◽  
Vol 891-892 ◽  
pp. 1212-1216
Author(s):  
Anghel Cernescu ◽  
Heikki Remes ◽  
Pauli Lehto ◽  
Jani Romanoff
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Crack Closure ◽  
Fatigue Crack Growth Rate ◽  
Stress Ratio ◽  
Closure Effect

The all-metal web-core sandwich structure consists of two face plates stiffened by one-directional system of web plates. These web core sandwich structures are used in many structural applications such as ship hulls, offshore platforms, bridge decks, and industrial platforms. However, the stress variation caused by the service loadings can be a determinant factor for crack initiation and growth until early failure of the entire structure. This paper presents an experimental study on fatigue crack growth rate in base material from a face plate after rolling and welding. The study is focused on the analysis of the stress ratio and crack closure effect on the fatigue crack growth rate in two directions. There is a significant stress ratio effect on fatigue crack growth rate, much more pronounced in the case of crack propagation in the longitudinal direction than in the transverse propagation. For all tests, the crack closure effect is more pronounced at low stress intensity factor range (in the threshold domain).

Fatigue Performance of High-Pressure Waterjet-Peened Aluminum Alloy

2001 ◽  
Vol 124 (1) ◽  
pp. 118-123 ◽  
Author(s):  
M. Ramulu ◽  
S. Kunaporn ◽  
M. Jenkins ◽  
M. Hashish ◽  
J. Hopkins
Keyword(s):  
High Pressure ◽  
Aluminum Alloy ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
High Cycle Fatigue ◽  
Cycle Fatigue

An experimental study of high-pressure waterjet peening on 7075-T6 aluminum alloy was conducted to investigate the effects of waterjet on high-cycle fatigue life and fatigue crack growth. Unnotched hourglass-shaped circular cross section test specimens were fatigue tested in completely reversed rotating bending R=Smin/Smax=−1 to determine fatigue life behavior (S-N curves). Single-edge-notched flat tensile test specimens were tested in the tension-tension fatigue crack growth tests R=Smin/Smax=0.1 to determine fatigue crack propagation behavior (da/dN versus ΔK). Surface characteristics and fracture surfaces were evaluated by scanning electron microscopy (SEM). Results show that waterjet peening can increase high-cycle fatigue life, delay fatigue crack initiation, and decrease the rate of fatigue crack propagation.

Fatigue Crack Propagation of Deepwater Structures Under Cyclic Compression Based on Extended McEvily Model

2015 ◽  
Author(s):  
Guang-en Luo ◽  
Jia-huan Dong
Keyword(s):  
Numerical Simulation ◽  
Growth Rate ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Cyclic Compression

The extended McEvily model is adopted to predict the fatigue life of deepwater structures under cyclic compression. The three dimensional finite element analysis is performed to estimate the residual stress distribution along the crack surface during the crack propagation under cyclic compression. Then the stress intensity factors and crack growth rate are achieved based on extended McEvily model. The doubled edged specimen under cyclic compressive loading is taken for example to illustrate the analysis procedure, including fatigue crack growth rate prediction by Artificial Neural Networks (ANN), parameters estimation method of the extended McEvily model, calculation of the stress intensity factor and numerical simulation of fatigue crack propagation. By comparing the predicted results and the experimental results, it is found that the numerical simulation of fatigue crack growth under cyclic compression based on extended McEvily model is reasonable and feasible.

Fatigue Properties of Casting TC4 Alloys Treated by Hot Isostatic Pressing

2011 ◽  
Vol 197-198 ◽  
pp. 1668-1673
Author(s):  
Yu Hong Yao ◽  
Xiao Feng Shangguan ◽  
Jiang Nan Liu ◽  
Zheng Pin Wang ◽  
Jian Feng Wei
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Growth Rates ◽  
Stress Ratio ◽  
Fatigue Properties ◽  
Stress Ratios ◽  
Crack Growth Rates

With the aircraft structure design criterion from traditional static strength design to damage tolerance design and with the independent research and development of new-type civil turbofan regional aircraft and the implement of the plan to develop the country's own large passenger jets in China, it is essential to do some researches on casting TC4 alloys for the lack of the data of fatigue properties. The detail fatigue rating cut-off (DFRcutoff) values of casting TC4 alloys are measured and calculated by double dots method, the thresholds in fatigue crack propagation and the fatigue crack growth rates at different stress ratios are studied and the fatigue fracture at different stress ratios are observed by scanning electron microscopy. The results show that DFRcutoff value by double-dot method is 375.83 Mpa. The thresholds of fatigue crack propagation decrease with the increase of the stress ratio, whereas the fatigue crack growth rates increase with the increment of the stress ratio and the relationship curves between fatigue crack propagation rates and the stress intensity factor range have been obtained. Moreover, SEM observations indicate that the fatigue trips become wide with the increasing of the stress ratio.

scholarly journals Effect of hydrogen on fatigue crack growth of quenched and tempered CrMo(V) steels

2018 ◽  
Vol 165 ◽  
pp. 03009
Author(s):  
Luis Borja Peral ◽  
Sergio Blasón ◽  
Alfredo Zafra ◽  
Cristina Rodríguez ◽  
Javier Belzunce
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Fatigue Crack Growth Rate ◽  
Desorption Kinetics ◽  
Vanadium Carbides

In order to select the most appropriate steel to deal with pressurized hydrogen during long times, the fatigue crack propagation rate of quenched and tempered 2.25Cr1Mo and 2.25Cr1Mo0.3V steel grades was evaluated by means of tests performed on thermally pre-charged specimens in a hydrogen reactor at 195 bar and 450°C during 21 hours. Cylindrical samples to measure the hydrogen content and their desorption kinetics at room temperature and compact tensile specimens to determine the fatigue crack growth rate were used. Finally, scanning electronic microscopy was used in the study of fracture surfaces. Using the aforementioned pre-charging conditions, significant amounts of hydrogen were introduced, being much larger in the 2.25Cr1Mo0.3V steel grade (vanadium carbides provide strong hydrogen tramps). Regarding fatigue tests, the fatigue crack growth rate was increased notably due to the presence of hydrogen in the 2.25Cr1Mo grades for frequencies lower than 10 Hz. On the other hand, the presence of vanadium carbides has significantly improved the fatigue crack propagation performance in the presence of internal hydrogen.

scholarly journals Effects of Shot-Peening and Stress Ratio on the Fatigue Crack Propagation of AL 7475-T7351 Specimens

2018 ◽  
Author(s):  
Natália Ferreira ◽  
Pedro Antunes ◽  
José A. M. Ferreira ◽  
José D. M. Costa ◽  
Carlos Capela
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Shot Peening ◽  
Stress Ratio ◽  
Stress Ratios ◽  
Crack Growth Rates ◽  
Hardness Values

Shot peening is an attractive technique for fatigue enhanced performance of metallic components, because it promotes crack initiation retardation and later crack growth. Engineering design based on fatigue crack propagation predictions applying the principles of fracture mechanics is commonly used in aluminum structures for aerospace engineering. The main purpose of present work was to analyze the effect of shot peening on the fatigue crack propagation of the 7475 aluminum alloy, under both constant amplitude loading and periodical overload blocks. The tests were performed on 4 and 8 mm thickness specimen's with stress ratios of 0.05 and 0.4. The analysis of the shot-peened surface showed a small increase of the micro-hardness values, due to the plastic deformations imposed by shot peening. The beneficial effect of surface peening on fatigue crack growth rates is quite limited to an increasing near the threshold. The specimens&rsquo; thickness has only marginal influence on the crack propagation, in opposite to the stress ratio. Periodic overload blocks of 300 cycles promotes a reduction of the fatigue crack growth rate for both intervals of 7,500 and 15,000 cycles.

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