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Influence of the residual stresses on the contact failure of ceramic laminates
German, Roman ; Majer, Zdeněk (referee) ; Ševeček, Oldřich (advisor)
The presence of the compressive or tensile thermal residual stresses in layers of a ceramic laminate induced due to different volume change of each layer´s material during the cooling from the sintering temperature can considerably affect resistivity of ceramics against contact damage. Within this work 2D parametric FEM models were created, in order to study the effect of the surface layer thickness, residual stress values and indenting body dimension on the initiation and propagation of the cone crack in the surface layer of the laminate. For the analysis of the critical conditions for the crack initiation, the coupled stress-energy criterion was used and for the determination of the direction of crack propagation we used the maximum tangential stress criterion. The results show that compressive thermal stresses in the surface layer increase the critical force for the crack initiation, shorten the crack distance from the contact area and shorten the occurred crack itself. Moreover, the compressive stresses enlarge the angle of the crack declination during the propagation process which cause an earlier crack arrest. The tensile thermal stresses have exactly the opposite effect. Results of simulations were compared to experimental results but due to lack of available measurements, the verification is partially limited.
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Design of experimental device for durability testing of bearings
Frejlich, Tomáš ; Dvořák, Antonín (referee) ; Svoboda, Petr (advisor)
Diploma thesis deals with the structural design and subsequent implementation of a functional prototype of an experimental device for durability testing of bearings. The first part of the thesis deals with an overview of the current state of knowledge and summarizes information about testing the durability of bearings. In the next part follows the design, selection and analysis of the optimal design variants. The last part deals with the verification of the functionality of the prototype bearing life testing and evaluation of data measured during testing.
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Influence of the residual stresses on the contact failure of ceramic laminates
German, Roman ; Majer, Zdeněk (referee) ; Ševeček, Oldřich (advisor)
The presence of the compressive or tensile thermal residual stresses in layers of a ceramic laminate induced due to different volume change of each layer´s material during the cooling from the sintering temperature can considerably affect resistivity of ceramics against contact damage. Within this work 2D parametric FEM models were created, in order to study the effect of the surface layer thickness, residual stress values and indenting body dimension on the initiation and propagation of the cone crack in the surface layer of the laminate. For the analysis of the critical conditions for the crack initiation, the coupled stress-energy criterion was used and for the determination of the direction of crack propagation we used the maximum tangential stress criterion. The results show that compressive thermal stresses in the surface layer increase the critical force for the crack initiation, shorten the crack distance from the contact area and shorten the occurred crack itself. Moreover, the compressive stresses enlarge the angle of the crack declination during the propagation process which cause an earlier crack arrest. The tensile thermal stresses have exactly the opposite effect. Results of simulations were compared to experimental results but due to lack of available measurements, the verification is partially limited.
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Design of experimental device for durability testing of bearings
Frejlich, Tomáš ; Dvořák, Antonín (referee) ; Svoboda, Petr (advisor)
Diploma thesis deals with the structural design and subsequent implementation of a functional prototype of an experimental device for durability testing of bearings. The first part of the thesis deals with an overview of the current state of knowledge and summarizes information about testing the durability of bearings. In the next part follows the design, selection and analysis of the optimal design variants. The last part deals with the verification of the functionality of the prototype bearing life testing and evaluation of data measured during testing.
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