National Repository of Grey Literature 16 records found  previous11 - 16  jump to record: Search took 0.01 seconds. 
13th Conference Applied Mechanics 2011 - conference proceedings
Náhlík, Luboš ; Majer, Z. ; Seitl, Stanislav ; Ševčík, Martin ; Zouhar, Michal
Contributions from the field of fatigue of materials, dynamics, biomechanics and structural mechanics were presented on the traditional doctoral conference Applied Mechanics.
The influence of residual stresses on the polymer pipe lifetime
Luky, R. ; Zouhar, Michal ; Hutař, Pavel
The aim of this article is study the influence of residual stresses on the pipe lifetime. The two dimensional numerical model of the pipe with inner crack was created and the creep crack growth in the pipe with and without residual stress is modelled. The results of K-kalibration curves are presented. After that the Paris law is used for solving the lifetime. The results of time to failure in dependency on the hoop stress for pipe with and without residual stress were compared. The existence of residual stresses decrease the lifetime of the pipe. Combination of the creep crack growth tests and numerical simulations can be a very powerful tool for lifetime estimation of plastic pipes under different loading conditions.
Crack stability condition at the interface between two polymer materials
Zouhar, Michal ; Hutař, Pavel ; Náhlík, Luboš ; Ševčík, Martin ; Knésl, Zdeněk
The aim of this work is to study the behaviour of crack with its tip at the interface of two polymer materials. The numerical model of cracked bi-material tension specimen is investigated and a stability criterion was tested. Usually a stability criterion based on general stress concentrator needs the relation between critical value of the generalized stress intensity factor and critical value of the stress intensity factor (fracture toughness). This relation is a function of elastic mismatch between particular materials, fracture toughness of the main material and critical distance d. Estimation of d is usually not straightforward and different authors use different approaches for its determination. Therefore main aim of this study is mutual comparison of published approaches for d estimation and to quantify their effect on the critical loading value. The results of this study can lead to better lifetime prediction and design of layered structures.
Two-layer pipe - the influence of materials interface on creep crack behaviour
Zouhar, Michal ; Hutař, Pavel ; Náhlík, Luboš
Nowadays the using of layered structures is increasing. The aim of this article is study the influence of material interface of two layer pipe with inner crack on the crack behaviour. The numerical model of two layer pipe was created and the creep crack growth was modelled (taking into account realistic crack shape evolution). The results of two layer pipe were compared with homogenous approximation and accuracy of the lifetime prediction was discussed.
Fracture description of two- layer pipe with polypropylene protective layer
Zouhar, Michal ; Hutař, Pavel ; Náhlík, Luboš ; Vallet, L.
Nowadays, using of layered polymer pipes is increase. Protective layer can contribute to the better mechanical resistance of basic material. In this paper the three-dimensional numerical model of pipe consisting of main pipe material and outer protective layer material is modeled. The creep crack propagation in main material is simulated and the influence of protective layer is observed. Presented description of the crack in two-layer pipe can help for more accurate estimation of pipe-system residual life time.
Dimensioning of thick-walled pipe in creep
Zouhar, Michal ; Hutař, Pavel ; Náhlík, Luboš ; Hlavoň, P.
The numerical simulations of the creep in the case of X10CrMoVNb91 steel were performed. Geometry of the objects studied well-fit usual parts of the pipe system. The discrepancies between numerical simulations and usual standard Design By Formula (DBF) used for the pipe system lifetime prediction were found. Therefore, accurate numerical simulations based on creep description of the material behaviour is necessary for the accurate estimation of the service conditions.

National Repository of Grey Literature : 16 records found   previous11 - 16  jump to record:
See also: similar author names
2 Zouhar, Marek
6 Zouhar, Martin
1 Zouhar, Matěj
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