Seminar
MECHANICS OF MACHINES AND MECHANISMS - MODELS AND MATHEMATICAL METHODS

 

PROGRAM

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Plan rada Seminara Mehanika mašina i mehanizama - modeli i matematičke metode za FEBRUAR 2019.

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UTORAK, 12.02.2019. u 12:00, Sala 301f, MI SANU, Kneza Mihaila 36
Jelena M. Djoković, Technical Faculty of Bor, University of Belgrade, Serbia
ANALYSIS OF DYNAMICALLY GROWING CRACK BEHAVIOUR APPROACHING AN INTERFACE BASED ON THE ENERGY RELEASE RATE CRITERION
A problem of a dynamically growing crack, which is approaching an interface between the two elastic isotropic materials at an arbitrary angle, is considered. That crack could behave in three ways: (i) it can disappear (i.e., it can arrest in contact with the interface), (ii) it can deflect into the interface and continue to propagate along it or (iii) the crack can penetrate the interface and continue to propagate in the material across it. The competition between the two cases can be estimated by considering the ratio of the energy release rates necessary for the crack penetrating the interface and for the crack deflecting into the interface. A concept that the criterion for the dynamic crack growth in homogeneous solids could be based on the static stress field, with addition of the stress intensity factor dependent on time, is used to explain the behaviour of the crack attacking the interface in dynamic loading conditions. Obtained results provide the possibility for comparison of the dynamic fracture toughnesses of the interface and of the material without the interface, in order to determine whether the incoming crack would deflect into or would penetrate the interface. If the ratio between the dynamic fracture toughness of the interface and the dynamic fracture toughness of the material into which the crack continues to propagate, were less than the ratio of the dynamic release rates for the deflecting and penetrating crack, the incoming crack would deflect into the interface. If the case were reversed, the crack would cross the interface and continue to propagate in the material across it. Comparison of results for the load phase angle dependence on the crack tip propagation speed and on the approaching angle, obtained by this criterion and results obtained by the maximum stress direction criterion proves the validity of the energy release rate concept adopted in this analysis.

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UTORAK, 26.02.2019. u 17:00, Sala 301f, MI SANU, Kneza Mihaila 36
Slobodanka Boljanović, Mathematical Institute of SASA, Belgrade, Serbia
FAILURE ANALYSIS OF STRUCTURAL COMPONENTS UNDER CYCLIC LOADING
Fatigue is perhaps the most common cause of crack initiation and growth which ultimately results in the fracture of a structure or components. For prevention of such failures, it is very important to establish efficient methods that enable determination of fatigue strength. In view of complexity of fatigue as process, the strength analysis has to be considered through the following phases: crack initiation, crack propagation and failure. This presentation examines the fatigue performance of damaged structural components through fracture mechanics based computational models. Potential sources of crack-like damages are geometric discontinuities. Such stress concentrators represent positions where an extremely high magnitude of stresses could appear. Thus, the nonlinear behaviour of cracks is analyzed employing analytical models which are linked with relevant fracture mechanics concepts. Also, numerical approaches based on the finite element method are used to evaluate stress state field under cyclic loading. In the residual strength evaluations the stress-ratio dependence failure models are implemented.
The computational models proposed are verified by employing available experimental data and comparisons between different crack growth results show a good correlation. Additionally, for safety-critical component such as pin-lug connection the effects of width, diameter of hole and thickness are discussed.

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Seminar Mehanika mašina i mehanizama - modeli i matematičke metode započeo je sa radom u junu 2018.god. Seminar se održava do dva puta mesečno, utorkom u periodu od 17.00 - 19.00 u Matematičkom institutu SANU.

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