Fatigue Threshold Considerations During Crack Propagation

2002 ◽  
Author(s):  
Lichun Bian ◽  
Jae-Kyoo Lim
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Effective Strain ◽  
Crack Problem ◽  
Potential Drop ◽  
Fatigue Tests ◽  
Fatigue Threshold ◽  
Stress Intensity Factor Range ◽  
Engineering Structures

The angled crack problem has been given special attention in the recent years by fracture mechanics investigators due to its close proximity to realistic conditions in engineering structures. In this paper, an investigation of fatigue crack propagation in steel pipes containing an inclined surface crack is presented. The inclined angle of the crack with respect to the axis of loading varied between 0° and 90°. During the fatigue tests, the growth of the fatigue crack was monitored using the AC potential drop technique. Based on the concept of the effective stress intensity factor range, Δkeff, the rate of fatigue crack propagation, db/dN, is postulated to be a function of the effective strain energy density factor range, ΔSeff. Subsequently, this concept is applied to predict crack growth due to fatigue loads.

Investigation of Fatigue Crack Propagation in Line Pipes Containing an Angled Surface Flaw

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Lichun Bian ◽  
Farid Taheri
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Surface Crack ◽  
Effective Strain ◽  
Crack Problem ◽  
Fatigue Crack Initiation ◽  
Stress Intensity Factor Range ◽  
Threshold Condition ◽  
Engineering Structures

The angled crack problem has been given special attention in the recent years by fracture mechanics investigators due to its close proximity to realistic conditions in engineering structures. In the present paper, an investigation of fatigue crack initiation and propagation in line pipes containing an inclined surface crack is presented. The inclined angle of the surface crack with respect to the axis of loading varies between 0deg and 90deg. Based on the concept of the effective stress intensity factor range Δkeff, the rate of fatigue crack propagation db∕dN is postulated to be a function of the effective strain energy density factor range ΔSeff. This concept is applied to predict the crack growth due to fatigue loading. Furthermore, the threshold condition for nongrowth of the initial crack was established and assessed based on the experimental data.

Heterogeneous Microstructure Effect on Residual Stress and Fatigue Crack Resistance in Dual-Phase Materials

2009 ◽  
Author(s):  
Masahito Mochizuki ◽  
Yoshiki Mikami
Keyword(s):  
Residual Stress ◽  
Fatigue Crack ◽  
Stress Distribution ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Compressive Residual Stress ◽  
Fatigue Tests ◽  
Residual Stress Distribution ◽  
Experimental Result ◽  
Microstructure Effect

The effect of transformation-induced microscopic residual stress on fatigue crack propagation behaviour of ferrite-martensite lamellar steel was discussed. Fatigue tests of prestrained and non-prestrained specimens were performed. Inflections and branches at ferrite-martensite boundaries were observed in the non-prestrained specimens. On the other hand, less inflections and branches were found in the prestrained specimens. The experimental results showed that the transformation induced microscopic residual stress has influence on the fatigue crack propagation behaviour. To estimate the microscopic residual stress distribution, a numerical simulation of microscopic residual stress induced by martensitic transformation was performed. The simulation showed that compressive residual stress was generated in martensite layer, and the result agree with the experimental result that inflections and branches were observed at ferrite-martensite boundaries. In addition, the change in the microscopic residual stress distribution by prestraining was also calculated to show the compressive residual stress changed to tensile by prestraining. This also agree with the experimental result of the observation of fatigue crack path.

Corrosion-Fatigue Crack Propagation Studies of Some New High-Strength Structural Steels

1969 ◽  
Vol 91 (4) ◽  
pp. 570-574 ◽  
Author(s):  
T. W. Crooker ◽  
E. A. Lange
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Salt Water ◽  
High Strength ◽  
Structural Steels ◽  
Stress Intensity Factor Range ◽  
Corrosion Fatigue Crack ◽  
Crack Growth Rates

Fatigue crack propagation studies were conducted on three new high-strength structural steels: 9Ni–4Co–0.20C quenched-and-tempered, 10Ni–2Cr–1Mo–8Co dual-strengthened, and 13Cr–8Ni–2Mo precipitation-hardened stainless. The yield strengths of these steels ranged from 176 to 193 ksi. Notched cantilever-bend specimens of each steel were cycled zero-to-tension in two environments, room air and 3.5 percent NaCl salt water. Fatigue crack growth rates were measured experimentally and correlated with the crack tip stress-intensity factor range. The results indicate that these new steels possess greater resistance to fatigue crack propagation and less sensitivity to environment than previously studied steels of comparable strength.

scholarly journals Comparison of fatigue crack propagation behaviour in two steel grades S235, S355 and a steel from old crane way

2020 ◽  
Vol 310 ◽  
pp. 00034 ◽  
Author(s):  
Stanislav Seitl ◽  
Pavel Pokorný ◽  
Petr Miarka ◽  
Jan Klusák ◽  
Zdeněk Kala ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Experimental Tests ◽  
Fatigue Behaviour ◽  
Fatigue Properties ◽  
Stress Intensity Factor Range ◽  
Fracture Properties ◽  
Long Time ◽  
Steel Grades

Utilization of various steel grades in civil engineering allows designing bridges, bridge elements or simple structures according to their fracture mechanical properties. The service intervals of structures, which are going to be in use for a long time, cannot be calculated only on the basis of tensile and brittle fracture properties but also on the knowledge of the resistance to the fatigue crack growth. This contribution presents a comparison of the fatigue behaviour of two modern steel grades S235 J2, S355 J2 and a steel extracted from an old crane way. The comparison of these steel grades is done by fatigue crack propagation tests (the results of the experimental tests are described using concept of the stress intensity factor range ΔK). The fatigue properties are discussed and recommendations for the use of the steels are stated.

Fatigue and Corrosion-Fatigue Crack Propagation in Intermediate-Strength Aluminum Alloys

1973 ◽  
Vol 95 (3) ◽  
pp. 150-156 ◽  
Author(s):  
T. W. Crooker
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Aluminum Alloys ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
High Stress ◽  
Stress Intensity Factor Range ◽  
Stress Intensity Range ◽  
Corrosion Fatigue Crack

Fatigue crack propagation studies were conducted on a variety of intermediate-strength aluminum alloys under high stress-intensity range cycling (ΔK > 10 ksiin.). Tests were conducted in ambient room air and in 3.5-percent NaCl saltwater environments. Data are presented on log-log coordinates in terms of fatigue crack growth rate (da/dN) as a function of the stress-intensity factor range (ΔK). Comparisons are made among similar crack propagation data for steel and titanium alloys.

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.

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