Static mode fatigue crack propagation and generalized stress intensity correlation for fatigue–brittle polymers

In the present study, the fatigue crack propagation tests of Zr-based metallic glass were conducted in laboratory air, and the fracture surface was observed to clarify the effects of loading frequency and the stress ratio. In spite of being brittle material, the metallic glass showed stable fatigue crack propagation behaviour, and the relationship between the crack propagation rate, da/dN, and the stress intensity range, K, can be divided into three regions as well as conventional crystalline metals. The crack propagation rate can be expressed as a function of the stress intensity range by Paris law in the middle region. The power in Paris law was 1.4, and it is considerably smaller than the value for conventional crystalline metals. The threshold stress intensity range, Kth, was 1.8 MPam1/2. The effects of the stress ratio and the loading frequency were not observed on the relationships, da/dN-K and da/dN-Keff. Then, the fatigue crack propagation of the metallic glass is cycle dependent in laboratory air.

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System for Determining the Critical Range of Stress-Intensity Factor Necessary for Fatigue-Crack Propagation

Journal of Mechanical Engineering Science ◽

10.1243/jmes_jour_1973_015_048_02 ◽

1973 ◽

Vol 15 (4) ◽

pp. 271-273 ◽

Cited By ~ 23

Author(s):

K. Jerram ◽

E. K. Priddle

Keyword(s):

Stress Intensity Factor ◽

Fatigue Crack ◽

Stress Intensity ◽

Intensity Factor ◽

Crack Propagation ◽

Fatigue Crack Propagation ◽

Critical Stress Intensity Factor ◽

Published Data ◽

Critical Range ◽

A New Technique

A new technique is described for determining the critical stress intensity factor required for fatigue crack propagation to occur. It enables data to be obtained more rapidly and with fewer testpieces than existing techniques. Initial results obtained for En 3A mild steel are in excellent agreement with published data.

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Experimental Investigations of Fatigue Crack Propagation for Pipe Under Torsional Loading

ASME 2010 Pressure Vessels and Piping Conference: Volume 1 ◽

10.1115/pvp2010-25831 ◽

2010 ◽

Author(s):

Motoki Nakane ◽

Satoshi Kanno ◽

Shota Hashimoto ◽

Takayuki Watanabe ◽

Yukio Takahashi

Keyword(s):

Stress Intensity Factor ◽

Fatigue Crack ◽

Stress Intensity ◽

Intensity Factor ◽

Crack Propagation ◽

Crack Growth ◽

Fatigue Crack Propagation ◽

Growth Rates ◽

Torsional Loading ◽

Crack Growth Rates

This study discusses methods for evaluating fatigue crack propagation under torsional loading for pipes. To achieve this objective, fatigue crack propagation tests were carried out on both stainless steel and carbon steel used in piping systems of nuclear power plants. Two different kinds of pipes were tested in this study. These pipes had the same shape but the diameter and thickness of the larger pipe were twice those of the smaller pipe. The nominal shear stress amplitudes applied to the specimen were set between 50 and 100 MPa depending on the dimension of the specimen and desired crack growth rates. All fatigue tests were conducted under pure torsional loading with stress ratio R = −1 and at room temperature. The geometrical correction factors for the specimen were derived from elastic J-integral calculated by the FEM. The fatigue crack propagation tests results show that the crack growth rates estimated by the elastic stress intensity factor with the geometrical correction factor were much faster than curves prescribed in The Japan Society of Mechanical Engineers (JSME) codes. These results suggest that elastic plastic fracture parameters should be considered into the stress intensity factor because yield stresses for torsional loading would be smaller than those of uniaxial loading. The plastic zone correction method and modified reference stress method were examined as alternative methods. The crack growth rates estimated by the proposed methods almost totally correspond to the JSME curves. The two proposed methods were found to be quite effective at correctly evaluating the crack growth rates under torsional loading.

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