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Fatigue Behaviour of AZ31 and AZ61 Magnesium Alloys
Gejdoš, Pavel ; Lukáč, Pavel (referee) ; Kohout, Jan (referee) ; Podrábský, Tomáš (advisor)
This doctoral thesis deals with the fatigue behaviour of AZ31 and AZ61 magnesium alloy casted by advanced methods of casting squeeze casting. Based on the regression functions and measured fatigue data were determined fatigue characteristics of these alloys. The work also extends into the area of fatigue cracks in the AZ31 alloy. Were measured fatigue crack propagation rate on modified cylindrical specimens. The paper also outlines the possibilities for describing the fatigue behaviour of AZ61 alloy in extremely low-cycle fatigue.
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Proceedings of the 16th International colloquium Mechanical Fatigue of Materials
Polák, Jaroslav ; Kruml, Tomáš ; Man, Jiří
The XVI International Colloquium on Mechanical Fatigue of Metals was organized by the Institute of Physics of Materials, Academy of Sciences of the Czech Republic in Brno, in September 24-26, 2012. The Colloquium has been opened to participants from all countries interested in the subject of fatigue of metallic materials. The proceedings contains 39 abstracts of 35 oral and of 4 poster contributions by 122 authors from 18 countries to be presented during the Colloquium.
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Fatigue crack growth and delamination in fiber metal laminate (GLARE) during loading with positive mean stress
Chlupová, Alice ; Kozák, Vladislav
The aim of the paper is to present the results of a study on the damage of fiber metal laminate (GLARE) subjected to the low cycle fatigue loading with positive mean stress. The fatigue crack initiation and growth was observed on the surface of notched specimens and then the individual layers of fatigued specimens were removed by chemical etching and polishing to obtain data about cracks length and delamination shape and area. Mechanism of initiation and crack growth in this type of materials differs from homogeneous monolithic materials. The fatigue life in term of number of cycles to crack initiation depending on amplitude of local plastic deformation and local stress in the notch root was evaluated.
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Numerical investigation of residual lifetime of the wheel during EN 13262 test
Matušek, P. ; Hutař, Pavel ; Náhlík, Luboš ; Knésl, Zdeněk ; Kunz, Ludvík
In this paper, the experimental set up corresponding to the test unit used for the full-scale fatigue test has been modelled. The numerical method for reliable estimation of residual fatigue lifetime of wheel web tested according to EN 13 262 Standard has been developed. Numerical calculations are based on finite element method utilizing the system ANSYS. The experimentally observed cracks in the wheel web have been taken as the initial crack configuration. Numerical calculations simulating the initial crack growth in the wheel web loaded by experimental set up have been performed. Under assumptions of linear elastic fracture mechanics the residual fatigue life of the cracked wheel has been predicted.
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Růst krátkých trhlin ve feriticko-perliticko-bainitické oceli
Polák, Jaroslav
The initiation and the growth of short cracks were studied in ferritic-pearlitic-bainitic steel. Short cracks initiate preferably in persistent slip markings in areas of proeutectoid ferrite. The kinetics of short crack growth is characterized by exponential growth. Crack growth coefficient was found to be a function of plastic strain amplitude. The comparison of the short crack growth kinetics with Coffin-Manson law allows determining the parameters of the short crack growth law from the low cycle fatigue experiments
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Výpočtová analýza růstu únavové trhliny v kole testovaném podle normy EN 13262
Hutař, Pavel ; Náhlík, Luboš ; Knésl, Zdeněk ; Kunz, Ludvík ; Matušek, P.
In this paper, the experimental set up corresponding to the test unit used for the full-scale fatigue test has been modeled and the numerical method for reliable estimation of residual fatigue lifetime of wheel web tested according to EN 13 262 Standard has been developed. Numerical calculations are based on finite element method utilizing the system ANSYS. The experimentally observed cracks in the wheel web have been taken as the initial crack configuration. Numerical calculations simulating the initial crack growth in the wheel web loaded by experimental set up have been performed. Under assumptions of linear elastic fracture mechanics the residual fatigue life of the cracked wheel has been predicted. The material properties necessary for numerical modeling were determined from the fatigue tests performed on small specimens taken from real wheel webs. The results obtained can be used for more reliable design of railway wheels.
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Crack stability analysis of the crack in surface protective layers based on crack mouth opening displacement
Bareš, Pavel
Paper deals with stability analysis of a crack in a coating on a substrate. It is considered that the crack is perpendicularly oriented to the interface between the coating and the substrate and the crack tip lies directly on the material interface. The simple method based on crack mouth opening displacement parameter CMOD is proposed here for a critical stress calculation in the case of through coating crack in very thin coatings. The method is then applied herein on the model example and the critical stresses for different material combinations of the coating and the substrate are calculated. Note that under these stresses the crack will start propagate across the interface to the substrate. All calculations are performed by a finite element method FEM in the system ANSYS.
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The Influence of T-stress on Mixed Mode Fracture Criterion
Seitl, Stanislav
In this paper, two-parameter constraint based linear elastic fracture mechanics is used to modify brittle fracture criterions under combination of normal and shear loading (Mode I and II). The value of constraint is characterized by T-stress. The results contribute to better description of influence of the geometry of a body on its fracture behaviour.
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