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Fatigue crack growth in 18g2a steel under mixed mode I+III loading
| Content Provider | Semantic Scholar |
|---|---|
| Author | Macha, Ewald Rozumek, Dariusz |
| Copyright Year | 2013 |
| Abstract | The paper presents the results of tests on fatigue crack growth under proportional bending with torsion in the low-alloy 18G2A steel. Specimens with square sections and stress concentrator in the form of external one-sided sharp notch were used. The tests were performed under the stress ratios R = -1, 0.5, 0. The test results were described by the ∆J integral range and compared with the ∆K stress intensity factor range. It has been found that there is a good agreement between the test results and the model of crack growth rate, which includes the ∆J integral range. Introduction Analysis of fatigue problems is usually focused on cases of loading causing cracks according to mode I [1, 2]. In practice, we can also observe fatigue crack growth in conditions involving two mixed mode I and II, I and III or II and III, which lead to the material failure. In paper [3], a model for mixed mode (I + III) of fatigue crack growth equivalent to mode I was proposed. Specimens bent in three points were tested, and the crack position was initiated at a certain angle β to the bending plane. Thus, a combination of bending with torsion was obtained. It was found that the crack growth beginning in mode I was dependent on the orientation (direction) and crack opening displacement in the specimen tested. The presented model was proposed by Yates and Miller [4, 5] for circumferential cracks. In [5], there was also shown a behaviour of cracks in the threshold period. Another approach to three-point bending of specimens with a crack for mixed mode I and III was proposed by Pook [6]. Mild steel was tested in the threshold crack range with an expected domination of mode I. In the initial discontinuous changes of mode I were observed, which were followed by a fluent rotation of the crack front up to the moment of an almost perpendicular location to the specimen side. Owing to the increase of the threshold crack in the specimen plane and the cracking stop in the same plane, there appeared some problems with the description of test results as there was no adequate stress intensity factor. The authors of [7] tested the fatigue crack growth in the elastic-plastic material under tension with torsion. The test results were described with the J-integral, using a simple method (force versus deflection) and the finite element method. It was found [7] that the J-integral was the most appropriate fracture mechanics parameter for modes I and III in elastic-plastic materials. A good correlation between the applied methods was obtained. The aim of this paper is to describe mixed mode I and III crack growth with the ∆J integral range and verify the proposed mathematical formula using as an example the test results for 18G2A construction steel. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://www.structuralintegrity.eu/pdf/esis/Documents/Conference/ECF/15/Macha%20E%20and%20Rozumek%20D.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
