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CALIBRATION FUNCTIONS FOR EDGE CRACKS UNDER SELECTED BENDING LOADS.\n\n
Seitl, Stanislav ; Miarka, Petr
Fatigue cracks are found during the regular structural inspections. To precisely\ndescribe/suggest of fatigue cracks propagation throughout structure and for designed\nservice life, the knowledge of calibration functions is important. The cracks usually\npropagate from the edge or the surface of the structural element. The theoretical model\nof fatigue crack propagation is based on linear fracture mechanics (Paris law). Steel\nstructural elements are subjected to various bending load (three- and four-point bending,\npure bending etc.). The calibration functions for the edge cracks are calculated for\nvarious load and appropriate polynomial function independent on the distance are\nproposed for 3PB and 4PB load.
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PILOT ANALYSIS OF CHEVRON NOTCH LIGAMENT AREA FOR APPLICATION\nON QUASI-BRITTLE MATERIALS
Seitl, Stanislav ; Růžička, P. ; Miarka, P. ; Sobek, J.
Specimens for the bending tests with the chevron notch are standardized for the\nevaluation of the fracture toughness of various materials. The main advantage of this test\nset-up is that no sharp pre-crack has to be introduced, because a sharp crack is formed\nduring loading at the beginning of the test. Furthermore, no crack length measurement is\nrequired, and a stable crack growth can be reached due to geometry of the notch. In this\ncontribution a difference of the ligament area of the specimens with the straight through\nnotch and the chevron notch was investigated
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DISPLACEMENT FIELD ANALYSIS IN WEDGE SPLITTING TEST\nSPECIMEN BY ODM METHOD
Seitl, S. ; Miarka, P. ; Růžička, V. ; Malíková, Lucie ; Merta, I.
Multi-parameter fracture mechanics is nowadays quite extensively applied when cracked\nstructures/specimens are investigated. The reason is that it has been shown that it can be\nhelpful and bring more accurate results when fracture processes happen in a larger\nregion around the crack tip, what can be typical for material like concrete or other\nmaterials with quasi-brittle behaviour. Various relative crack length configurations have\nbeen chosen in order to investigate the importance of the higher-order terms of the\nWilliams power expansion on the crack-tip stress field distribution in Wedge splitting\ntest specimen. The higher-order terms are calculated by means of the over-deterministic\nmethod from displacements of nodes around the crack tip obtained by a finite element\nanalysis in different radial distances from the crack tip. The effect of the constraint level\nis investigated. Although the third and higher terms of the Williams series are very often\nneglected, their influence on the opening stress values is investigated.
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