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 MART 2024.

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Ukoliko želite da učestvujete u radu seminara ili da postavite pitanja na kraju predavanja, a još niste registrovani na miteam platformi Matematičkog instituta, možete se registrovati popunjavanjem forme:
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Arhiva snimljenih predavanja se nalazi na stranici:
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Utorak, 05.03.2024. u 17:00, sala 301f, Kneza Mihaila 36 i Live stream
Marina Škondrić, Faculty of Civil Engineering, University of Belgrade, Serbia
INFRARED THERMOGRAPHY IN MONITORING OF THE EARLY-AGE CEMENT PASTE TEMPERATURE
Infrared thermography is an advanced technique of obtaining the intensity of heat radiation invisible to the human eye. In civil engineering, it is usually applied for the assessment of thermal losses through different elements of the building envelope or as a method for the detection of damage (cracks) in reinforced concrete structures, such as bridges. The use of this method for the investigation of temperature development during early cement hydration is still an evolving area of research. The hydration of cement, which enables the hardening of cement composites, is an exothermal process. Heat develops rapidly during setting and initial hardening and gradually declines and finally stabilizes as hydration slows. Hence, 50% of the heat is generated in the first 3 days. The temperature rise during this process that occurs within the concrete element can lead to cracks and damage development in the concrete micro-structure, especially in the case of massive concrete structures. Temperature is, when necessary, monitored by thermo-sensors embedded in the concrete elements. Although the method is very precise, it gives temperature values only in the close surrounding of the sensor. Also, in most cases sensors stay embedded in the concrete element, and cannot be reused. This lecture will introduce the basic concepts of the infrared thermal camera use in civil engineering, with the special focus on the possibilities of temperature monitoring of the early age cement-based composites.

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Utorak, 19.03.2024. u 17:00, sala 301f, Kneza Mihaila 36 i Live stream
Ivana Atanasovska, Mathematical Institute SANU, Belgrade
Dejan Momčilović, The Innovation Center of the Faculty of Mechanical Engineering in Belgrade
THEORY OF CRITICAL DISTANCES (TCD) AND APPLICATIONS. II – THIN COMPOSITE PLATES WITH STRESS CONCENTRATORS ANALYZED BY THE THEORY OF CRITICAL DISTANCES
The potential of the Theory of Critical Distances to be used for analysis and prediction of crack initiation in composite elements with stress concentrators will be discussed. The composite thin plates with stress concentrators in the form of a few different hole shapes were investigated, and the influence of different lay-ups was also analyzed. A modified Theory of Critical Distances will be proposed for analyzing the composite structures with stress concentrators. The obtained results will be discussed to assess the specific potential and efficiency of the presented approach, as well as to define the directions for further research in this field.

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Četvrtak, 28.03.2024. u 13:00, Pariske Komune bb, Niš i Live stream
Marija Stamenković Atanasov, Faculty of Mechanical Engineering, University of Niš, Serbia
FORCED VIBRATION ANALYSIS OF THE COUPLED NANO-STRUCTURES
This lecture studies the oscillatory behavior of different types of elastically coupled nano-structures comprising two carbon nano-tubes modeled as two nano-beams, two graphene nano-sheets modeled as two nano-plates and a combination of nano-plates and double-curved shallow nano-shells. For the mentioned nano-systems, by applying Eringen's non-local stress theory, Euler-Bernoulli's beam theory, Kirchhoff-Love's plate theory, and Novozhilov's linear theory of shallow shells, differential equations are given to describe the vibrations (small transverse displacements) of elastically coupled nano-structures. Analytical and numerical methods are applied to solve the presented differential equations of motion. Forced vibrations (damped and undamped) of elastically coupled nano-structures are studied in detail. The paper also provides a detailed determination of analytical solutions of eigenfrequencies, transverse displacements due to the action of different types of external loads. Analytical solutions and numerical analysis of forced vibrations are presented for the following load types: uniformly distributed continuous harmonic load, concentrated harmonic force, and moving constant and harmonic force. Various parameters that influence the dynamic responses of the upper and lower elements of the presented elastically coupled nano-structures are analyzed in detail. These are: non-local parameter, magnetic field, radius of curvature of a doubly curved shallow nano-shell, damping proportionality coefficients and different values of external loads. The objective of the study of these nano-systems is to show that such systems have a damping effect on the amplitudes of vibrations of the nano-system transverse displacements for all observed external loads, due to the increase in the intensity of the magnetic field and the increase in the non-local parameter. The influence of the radius of curvature of the nano-shell, which stems from the nano-plate and nano-shell with an elastically coupled system composed from the two nano-plates, is of great importance. During this analysis of elastically coupled nano-structures, it is proved that the excited upper element of the nano-system (in this case the nano-plate) has a smaller amplitude of the transverse response vibrations only if the lower element is curved (in this case the nano-shell). In addition to being affected by the decrease in the value of the radius of curvature of the nano-shell and the increase in the value of the non-local parameter, the dynamic absorption or the decrease in the amplitude of the excited upper nano-plate of the presented nano-system is also influenced by the increase in the value of the damping proportionality coefficient and the decrease in the value of the external excitation. The simulation of molecular dynamics for some of the aforementioned elastically coupled nano-structures will be used as a confirmation of the obtained analytical results.
Zajedničko predavanje sa seminarom Odlučivanje - teorija, tehnologija, praksa

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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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