Papers by Keyword: Crack Opening Displacement (COD)

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Authors: Béla Palotás
Abstract: The testing of creep resistance (for example σ1%/100000 h) of metals has been required for a long time (about 10 years) and some methods have been worked out to decrease testing time. The application of these methods has some difficulties. Now we have worked out a new empirical method to reduce testing time, namely COD measuring at an elevated temperature. The paper presents this method, which makes it possible to determine creep properties by measuring the materials COD at an elevated temperature. To determine COD we use notched samples with different radii and we tear them at an elevated temperature. The determination of COD is based on the Czoboly Radon method. By opening three different radii notches we approximate to zero radius which gives the COD. Master Curves of COD and creep resistance connections were drawn at 500 °C, which is not dependent on materials and they can be used for determining Creep Properties from COD measured at 500 °C. This method can be used for the comparison of the creep resistance of materials and for that of the creep properties of different zones of welded joints. The method is found useful in technical practice.
Authors: Kenichi Shimizu, Tashiyuki Torii
Abstract: Using a fatigue testing method by which fatigue cracks can be initiated and propagated in a film adhered to cover a circular through-hole in a base plate subjected to cyclic loads, annealed copper films of 100m thickness with different crystal grain sizes were fatigued. The fatigue crack propagation in the film with large grains was often decelerated, so the crack propagation rate of the film with the large grain was lower than that of the film with the small grain. When the crack propagation was decelerated, the crack opening displacement obtained from the film with large grain size was smaller than that obtained from the film with small grain size. The relationship between the fatigue crack propagation rate and the stress intensity factor estimated from the crack opening displacement was identical for the cracks in the film with the large grain and the small grain.
Authors: Y. Sha, Hui Tang, Jia Zhen Zhang
Abstract: In this paper, a detailed elastic-plastic finite element analysis of the effect of the compressive loading on crack tip plasticity is studied based on the material’s kinematic hardening model. Five centre-cracked panel specimens with different crack lengths are analyzed. The analysis shows that in a tension-compression loading the maximum spread of the crack tip reverse plastic zone increases with the increase of the compressive stress and the near crack tip opening displacement decreases with the increase of the compressive stress at the same nominal stress intensity factor. The applied compressive stress is the main factor controlling the near crack tip parameters.
Authors: D.Y. Lyu, H.S. You, H.D. Jung, Jae Kyoo Lim, Se Hi Chung
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