Competition between plasticity-controlled and crack-growth controlled failure in static and cyclic fatigue of thermoplastic polymer systems

The structural integrity analysis of nuclear power plants (NPPs) is an essential procedure since the age of NPPs is increasing constantly while the number of new NPPs is still limited. Low-cyclic fatigue (LCF) and stress corrosion cracking (SSC) are the two main causes of failure in light-water reactors (LWRs). In the last few decades, many types of research studies have been conducted on these two phenomena separately, but the joint effect of these two mechanisms on the same crack has not been discussed yet though these two loads exist simultaneously in the LWRs. SCC is mainly a combination of the loading, the corrosive medium, and the susceptibility of materials while the LCF depends upon the elements such as compression, moisture, contact, and weld. As it is an attempt to combine SCC and LCF, this research focuses on the joint effect of SCC and LCF loading on crack propagation. The simulations are carried out using extended finite element method (XFEM) separately, for the SCC and LCF, on an identical crack. In the case of SCC, da/dt(mm/sec) is converted into da/dNScc (mm/cycle), and results are combined at the end. It has been observed that the separately calculated results for SCC da/dNScc and LCF da/dNm of crack growth rate are different from those of joint/overall effect, da/dNom. By applying different SCC loads, the overall crack growth is measured as SCC load becomes the main cause of failure in LWRs in some cases particularly in the presence of residual stresses.

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Measuring effect of the blooming of chemical curatives on the rate of cyclic fatigue crack growth in natural rubber filled with a silanized silica nanofiller

Journal of Applied Polymer Science ◽

10.1002/app.34913 ◽

2011 ◽

Vol 124 (2) ◽

pp. 1372-1383 ◽

Cited By ~ 5

Author(s):

Farhan Saeed ◽

Ali Ansarifar ◽

Robert J. Ellis ◽

Yared Haile-Meskel

Keyword(s):

Fatigue Crack ◽

Fatigue Crack Growth ◽

Natural Rubber ◽

Crack Growth ◽

Cyclic Fatigue ◽

Silanized Silica

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Cyclical fatigue of annealed and of thermally tempered soda-lime-silica glass

MATEC Web of Conferences ◽

10.1051/matecconf/201816518003 ◽

2018 ◽

Vol 165 ◽

pp. 18003

Author(s):

Jens Schneider ◽

Jonas Hilcken

Keyword(s):

Crack Growth ◽

Silica Glass ◽

Subcritical Crack Growth ◽

Soda Lime ◽

Cyclic Fatigue ◽

Growth Exponent ◽

Static Fatigue ◽

Strength Increase ◽

Soda Lime Silica Glass ◽

Number Of Cycles

We present experimental and theoretical investigations on the cyclic fatigue of annealed and of thermally tempered soda-lime-silica glass. Static fatigue due to subcritical crack growth at micro cracks significantly decreases the macroscopic strength of soda-lime-silica glass and causes a time-dependent strength reduction. A subsequent thermal tempering process is typically used to induce residual surface compression stresses, which inhibit the crack growth of surface cracks, and corresponding bulk tension stresses. From the experimental results we show that the existing models for static fatigue used in linear elastic fracture mechanics can be used for the lifetime prediction of cyclically loaded annealed glass and thermally tempered glass, although the (static) crack growth exponent slightly decreases in cyclic loading. The equivalent duration of tensile stress at the crack tip of a micro crack governs the crack growths and not the number of cycles. The threshold for subcritical crack growth determined from the cyclic experiments was found to be in good agreement with data from literature. But unlike in strength tests with singular and quasi-static re-loading, it could be found that periodic loading with load free intervals does not lead to a strength increase by crack healing effects. Based on the results, an engineering design concept for cyclically loaded glass is presented.

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