scholarly journals An Expression of Fatigue Crack Propagation Rates under Wide Ranged Stress Ratios

1983 ◽  
Vol 1983 (153) ◽  
pp. 336-343 ◽  
Author(s):  
Akihiko Katoh ◽  
Masayoshi Kurihara ◽  
Masanori Kawahara
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Stress Ratios

Fatigue Crack Propagation Tests on 304 Stainless Steel in High Temperature Water: Accelerated Cracking Rates and Transition to Lower Rates

2004 ◽  
Author(s):  
G. L. Wire ◽  
W. M. Evans ◽  
W. J. Mills
Keyword(s):  
Stainless Steel ◽  
Fatigue Crack ◽  
High Temperature ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Hold Time ◽  
304 Stainless Steel ◽  
High Temperature Water ◽  
Stress Ratios ◽  
Temperature Water

Previous fatigue crack propagation (FCP) tests on a single heat of 304 stainless steel (304 SS) specimens showed a strong acceleration of rates in high temperature water with 40–60 cc H2/kg H2O at 288°C, with rates up to 20X the air rates. The accelerated rates were observed under fully reversed conditions (R = −1) (Wire and Mills, 2001) and high stress ratios (R = 0.7 and 0.83) (Evans and Wire, 2001). In this study, a second heat of 304 SS has been tested at 243°C and 288°C and lower positive stress ratios (R = 0.3, 0.5). The second heat showed the large acceleration of rates at 288°C observed previously. Rates were up to two times lower at 243°C, but were still 7–8X the air rates. A time-based correlation successfully correlates the accelerated rates observed, and is nearly identical to fits of literature data in hydrogen water chemistry (HWC), which has hydrogen added at a lower level of about 1 cc/kg H2O. The accelerated rates on the second heat were not stable under two different test conditions. In contrast to the first heat, the second heat showed a reduction in environmental enhancement at long rise times, accompanied by a change in fracture mode. Addition of a constant load hold time of 1200 s between cycles also caused a marked reduction in crack propagation rates in both heats, with reduction to nearly air rates in the second heat. The differing rise time effects between the two heats could be rationalized by time-dependent deformation. More hold time testing is required to define the material and loading conditions which lead to reduced rates.

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.

Influence of Stress Ratio on Fatigue Crack Propagation in TiAl Alloy

2013 ◽  
Vol 457-458 ◽  
pp. 7-10 ◽  
Author(s):  
Rui Cheng Feng ◽  
Zhi Yuan Rui ◽  
Yan Rui Zuo ◽  
Guo Tao Zhang ◽  
Chang Feng Yan
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Stress Ratio ◽  
Tial Alloy ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Fatigue Crack Propagation Rate ◽  
Stress Ratios ◽  
Region Ii

Based on the experiments did by B.K.Parida and T.Nicholas [1], the fatigue crack propagation rate of TiAl alloy under different stress ratios had been tested in order to find out the role of stress ratio and to derive an improved fatigue crack propagation formula for region II(the expansion region) according to Paris formula and to calculate the specific values of the constants in the formula. The experimental results reveal that stress ratio has a significant influence on fatigue crack growth rate.

Influence of Microstructure and Stress Ratio on Fatigue Crack Propagation in TiAl Alloy

2014 ◽  
Vol 881-883 ◽  
pp. 1330-1333 ◽  
Author(s):  
Yan Rui Zuo ◽  
Zhi Yuan Rui ◽  
Rui Cheng Feng ◽  
De Chun Luo ◽  
Chang Feng Yan
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Stress Ratio ◽  
Tial Alloy ◽  
Lamellar Microstructure ◽  
Propagation Resistance ◽  
Crack Propagation Resistance ◽  
Stress Ratios ◽  
Fully Lamellar

Based on the fatigue crack propagation experiments did by A.-L. Gloanec et al., the fatigue crack propagation rates of TiAl alloy of two processing routes, namely casting and PM, and stress ratios had been tested, in order to find out the effects of microstructure and stress ratio. An improved fatigue crack propagation formula for region Ⅱ (the expansion region) was derived according to Paris formula. The specific values of the constants in the formula were calculated. Fatigue crack propagation resistance of nearly fully lamellar microstructure is superior to that of equiaxed γ grain. The experimental results present that both microstructure and stress ratio has a significant influence on fatigue crack growth rate.

Effects of Negative Stress Ratios on Crack Propagation Behavior After an Overload

2003 ◽  
Vol 17 (08n09) ◽  
pp. 1580-1586 ◽  
Author(s):  
C. Makabe ◽  
A. J. McEvily ◽  
A. Purnowidodo ◽  
A. Yamauchi
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Stress Intensity Factor Range ◽  
Fatigue Crack Propagation Behavior ◽  
Propagation Behavior ◽  
Stress Ratios ◽  
Crack Propagation Behavior

A study of the effect of an overload on fatigue crack propagation behavior has been carried out at baseline R-values of 0, -1, and -1.5. The usual delayed retardation event was observed at R = 0. At R = -1 the degree of retardation was reduced. At R = -1.5 the fatigue crack growth rate was observed to accelerate after the overload. These behaviors were related to the extent of crack closure, which existed following the overload. The rate of fatigue crack propagation for all loading conditions was correlated with the parameter Δ K eff - Δ K effth , where Δ K effth is the effective value of the stress intensity factor range at threshold.

Correspondence Between Notched and Unnotched Specimen’s Fatigue Data: Fundamental Concept and Formulation of Equivalent Stress Ratio REQ

2005 ◽  
Author(s):  
Hiroshi Matsuno
Keyword(s):  
Fatigue Crack ◽  
Fatigue Strength ◽  
Cyclic Loading ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Equivalent Stress ◽  
Cyclic Stress ◽  
Fatigue Data ◽  
Mechanical Models ◽  
Stress Ratios

In the present study, a creative consideration is developed for the problem of the correspondence between notched and unnotched specimen’s fatigue data. The proposed concept is essentially different from that of volumetric damage, and it has the great advantage of being avoidable to encounter the fatally invalid point of the volumetric approach, such as determination of damage-volume sizes. Moreover, the fatigue criteria derived are very easy to be applied to practical notch problems. The approach is developed as follows; (1) A hypothesis of plastic adaptation in a surface layer is proposed and mechanical models reflecting the hypothesis are constructed. (2) From these models, equivalent stress ratios REQ are derived as the new parameter for the correspondence between the cyclic stress conditions of the notched and unnotched specimens. REQ is generalized for proportional multiaxial cyclic loading through the consideration for the case of torsional cyclic loading. Moreover, REQ is derived from the mechanical model for the stress field of the mode I fatigue crack tip. (3) Experimental data on fatigue strength and fatigue crack propagation rates are rearranged on the basis of REQ and are formulated. (4) Practical criteria are proposed for the fatigue strength and the fatigue crack propagation rates.

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.

Fatigue Properties for Micro-Sized Ni-P Amorphous Alloy Specimens

1999 ◽  
Vol 605 ◽  
Author(s):  
S. Maekawa ◽  
K. Takashima ◽  
M. Shimojo ◽  
Y Higo ◽  
M. V Swain
Keyword(s):  
Fatigue Crack ◽  
Amorphous Alloy ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Stress Ratio ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Stress Intensity Factor Range ◽  
Fatigue Crack Propagation Rate ◽  
Stress Ratios

AbstractFatigue crack propagation tests at different stress ratios of 0.1 and 0.5 have been performed on microsized Ni-P amorphous alloy specimens to investigate the influence of stress ratio in the crack growth properties of microsized materials. The specimens tested were cantileverbeam-type with dimensions of 10 × 12 × 50 νm3 prepared by focused ion beam machining. Notches with a depth of 3 [m were introduced in all specimens. The entire set of fatigue tests as performed using a newly developed fatigue testing machine in air at room temperature. Fine stripes deduced to be striations were observed on the fatigue fracture surface. Careful measurements of the striation spacings were made. Fatigue crack propagation rate, that is striation spacing, is plotted as a function stress intensity factor range. Fatigue crack propagation rate at stress-ratios of 0.1 and 0.5 in microsized Ni-P amorphous alloy specimens are given by da/dN ∼ 1.3 × 10−8 ΔK;1.16 and da/dN ∼ 3.7 × 10−8 ΔK0.5, respectively. At a given ΔK, crack propagation rate at a stress ratio of 0.5 was higher than that at 0.1. It is considered that a decrease in crack propagation rate at stress ratio of 0.1 is due to adecrease in effective stress intensity factor range ΔKeff, by the effect of crack closure.

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