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1
Content available Design of Dry Friction Damper to Reduce Vibration Impacts to Circuit Cards at Critical Frequencies
Kovtun Igor, Goroshko Andrii, Petrashchuk Svitlana
Advances in Science and Technology. Research Journal
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2024
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Vol. 18, no 2
78--87
EN
The paper is focused on providing strength and stiffness for circuit cards exposed to vibration at critical frequencies. Since the dry friction damping is more effective than viscous damping and in case when application of viscous dampers is restricted by electronic package design the dry friction damper is proposed to be embedded to design of enclosure case in order to reduce oscillation amplitudes of circuit cards at critical frequencies. Dry friction damper produces dissipative forces – non-elastic resistance forces due to friction in kinematic pairs undergoing oscillations. The mathematical model has been developed for estimation of maximal dynamic stress and deflection in critical cross-section of circuit card with embedded dry friction damper at critical frequencies. Developed mathematical model specifies minimal limit value for stiffness of dry friction damper, which is used in engineering calculations to determine its geometric parameters. Design of dry friction damper is introduced by semi-elliptical beam with rectangular profile. The effectiveness of dry friction damper to reduce dynamic stress and deflection in circuit cards has been analytically proved and experimentally testified.
2
Content available Mathematical Modeling of Stress in Circuit Cards Represented by Mechanical Oscillatory Systems
Kovtun Igor, Goroshko Andrii, Petrashchuk Svitlana
Advances in Science and Technology. Research Journal
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2022
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Vol. 16, no 1
303--315
EN
The represented paper is aimed at stress calculation in circuit cards with their representation as a type of mechanical oscillatory systems in purpose of their strength assessment especially in resonance conditions. Three types of oscillatory systems are researched: single-mass; multiple mass and oscillatory system with uniformly distributed mass. In all types the cylindrical bending of circuit cards is considered to be a set of beam-strips with rectangular cross-sections so their stress calculation is performed by conventional methods applied in strength of materials and civil engineering. Mathematical model has been developed for maximal dynamic stress and deflection estimation in circuit card assemblies represented by unique oscillatory system as prismatic beam set on two oscillating supports under inertial resonance excitation generated by constant dynamic force. Comparative analysis of mathematical modeling, MatLab simulation and experimental determination of maximal dynamic stress and deflection accomplished for three types of oscillatory systems verified proximity of obtained results. Single-mass oscillatory system is proposed as equivalent to multiple mass or uniformly distributed oscillatory systems on condition of their equal mass, geometric, elastic and dissipation characteristics in resonance frequency correspondent to the main mode of oscillation, so mathematical model designed for single-mass oscillatory system is recommended for strength and stiffness assessment in engineering calculations where possible difference in determination of stress in equivalent systems can used as safety factor.
3
Content available Design Principles of Horizontal Drum Machines with Low Vibration
Drach Ilona, Goroshko Andrii, Dwornicka Renata
Advances in Science and Technology. Research Journal
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2021
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Vol. 15, no 2
258--268
EN
Using the example of washing machines using the linear theory of vibrations, the dynamics of horizontal rotary drum machines is investigated and the basic requirements for their layout are formulated to reduce vibration activity. The mathematical equations of vibrations of the multiply connected system tub-drum on elastic suspensions are compiled for main types of washing machines and centrifuges with horizontal axis of rotation. The problem is solved in a linear setting based on the Lagrange equation of the second kind. The accuracy and adequacy of the mathematical model was tested directly on a full-scale object by measuring noise, vibrations, support forces and stress distribution in individual elements and units of the washing machine in the entire range of drum rotation frequencies. Investigations of the nature of system vibrations depending on changes in the position and attachment points of elastic and damping elements were carried out using simulation in the Simulink environment. As a result of the research, the basic requirements for the layout of horizontal rotary drum machines were experimentally confirmed. Experimental verification was carried out to confirm the results obtained. It has been experimentally proven that the improvement of the experimental setup to reduce its vibration activity increases the efficiency of using direct-acting liquid autobalancers.
4
Content available The smoothed bootstrap fine-tuning
Dwornicka Renata, Goroshko Andrii, Pietraszek Jacek
System Safety : Human - Technical Facility - Environment
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2019
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Vol. 1, nr 1
716--723
EN
The bootstrap method is a well-known method to gather a full probability distribution from the dataset of a small sample. The simple bootstrap i.e. resampling from the raw dataset often leads to a significant irregularities in a shape of resulting empirical distribution due to the discontinuity of a support. The remedy for these irregularities is the smoothed bootstrap: a small random shift of source points before each resampling. This shift is controlled by specifically selected distributions. The key issue is such parameter settings of these distributions to achieve the desired characteristics of the empirical distribution. This paper describes an example of this procedure.
5
Content available Surface quality of the materials used for lighting columns
Dudek Agata, Goroshko Andrii
Quality Production Improvement - QPI
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2019
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Vol. 1, Iss. 1
417--424
EN
Quality of the lighting columns plays a major role in the comfort and safety of life of road users. The surface quality of the materials used in the columns is especially critical during extreme weather conditions. Road infrastructure, including street lighting, uses modern lightweight materials from the group of non-ferrous materials or composites. The materials used in the manufacturing process ensure important advantages, such as durability, electrical safety, aesthetic qualities, low maintenance costs, light weight, and easy transport and assemble. This paper presents an analysis of the quality of coatings used for street lighting columns.
6
Content available Reliability of variability source detection in Shainin's component search procedure
Pietraszek Jacek, Dwornicka Renata, Goroshko Andrii
Quality Production Improvement - QPI
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2019
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Vol. 1, Iss. 1
358--362
EN
Shainin's component search procedure uses variability source detection based on specific median test. This approach has only two triple subsets and the certainty of inference can be weak for this reason. This paper checks this approach by series of numerical simulations.
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