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Influence of a Free Surface and Gradient Change of Material Properties on a Crack Behaviour
Ševčík, Martin ; Kohout, Jan (referee) ; Klusák, Jan (referee) ; Náhlík, Luboš (advisor)
This thesis was written under the supervision of Assoc. Prof. Luboš Náhlík, Ph.D. and Assoc. Prof. Pavel Hutař, Ph.D. The topic of this thesis is the study of a free surface effect and gradient change of material properties on a crack behavior. The common theme of the work is a fracture mechanics description of a crack behavior near a material nonhomogeneity. Here, the material nonhomogeneity can be understood either as a boundary of a body (interface between body and surrounding) or as a continuous change of material properties. The thesis is introduced by a review part where the state-of-the-art of the concerned topic is described. This part presents several stress state descriptions in the vicinity of some general singular stress concentrators, particularly a crack and a V-notch. The influence of the free surface on a fatigue crack front shape is discussed here. The review part follows with the fracture mechanics description of the graded materials. The problem formulation and the main aims of the thesis are stated in the following chapter. The core of this work is the fracture mechanical description of a crack propagating near the material nonhomogeneity. The thesis focuses on a stress field description near the free surface of the body where a change in a type of the singular stress field occurs. Methods used in generalized fracture mechanics are applied here to describe the stress field near the free surface. The difference between crack behavior in thin-walled and thick-walled structures is shown and supplied by relevant examples. Methods and procedures used are later utilized for estimation of a crack behavior in graded structures. The thesis is concluded by the discussion of obtained results in appropriate context.
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Influence of a Free Surface and Gradient Change of Material Properties on a Crack Behaviour
Ševčík, Martin ; Kohout, Jan (referee) ; Klusák, Jan (referee) ; Náhlík, Luboš (advisor)
This thesis was written under the supervision of Assoc. Prof. Luboš Náhlík, Ph.D. and Assoc. Prof. Pavel Hutař, Ph.D. The topic of this thesis is the study of a free surface effect and gradient change of material properties on a crack behavior. The common theme of the work is a fracture mechanics description of a crack behavior near a material nonhomogeneity. Here, the material nonhomogeneity can be understood either as a boundary of a body (interface between body and surrounding) or as a continuous change of material properties. The thesis is introduced by a review part where the state-of-the-art of the concerned topic is described. This part presents several stress state descriptions in the vicinity of some general singular stress concentrators, particularly a crack and a V-notch. The influence of the free surface on a fatigue crack front shape is discussed here. The review part follows with the fracture mechanics description of the graded materials. The problem formulation and the main aims of the thesis are stated in the following chapter. The core of this work is the fracture mechanical description of a crack propagating near the material nonhomogeneity. The thesis focuses on a stress field description near the free surface of the body where a change in a type of the singular stress field occurs. Methods used in generalized fracture mechanics are applied here to describe the stress field near the free surface. The difference between crack behavior in thin-walled and thick-walled structures is shown and supplied by relevant examples. Methods and procedures used are later utilized for estimation of a crack behavior in graded structures. The thesis is concluded by the discussion of obtained results in appropriate context.
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