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Simulation of parallel kinematic machine with specific solutions of the passive translatory joint
No full textThe paper discusses ideas for the development of new 3-axis parallel kinematic machines, which have one dominant elongated axis, with the application of specific solutions for a passive translatory joint, which uses mechanisms that generate a straight line, such as the Chebyshev's mechanism.For publisher: PhD Saša Prodanović, associate professor
Editors: PhD Biljana Marković, full professor, PhD Miroslav Milutinović, full professor ,PhD Davor Milić, assitant professo
The ATLAS experiment at the CERN Large Hadron Collider: a description of the detector configuration for Run 3
No full textThe ATLAS detector is installed in its experimental cavern at Point 1 of the CERN Large
Hadron Collider. During Run 2 of the LHC, a luminosity of L = 2 × 1034 cm−2 s−1 was routinely
achieved at the start of fills, twice the design luminosity. For Run 3, accelerator improvements, notably
luminosity levelling, allow sustained running at an instantaneous luminosity of L = 2×1034 cm−2 s−1,
with an average of up to 60 interactions per bunch crossing. The ATLAS detector has been upgraded
to recover Run 1 single-lepton trigger thresholds while operating comfortably under Run 3 sustained
pileup conditions. A fourth pixel layer 3.3 cm from the beam axis was added before Run 2 to improve
vertex reconstruction and �����-tagging performance. New Liquid Argon Calorimeter digital trigger
electronics, with corresponding upgrades to the Trigger and Data Acquisition system, take advantage
of a factor of 10 finer granularity to improve triggering on electrons, photons, taus, and hadronic
signatures through increased pileup rejection. The inner muon endcap wheels were replaced by
New Small Wheels with Micromegas and small-strip Thin Gap Chamber detectors, providing both
precision tracking and Level-1 Muon trigger functionality. Trigger coverage of the inner barrel
muon layer near one endcap region was augmented with modules integrating new thin-gap resistive
plate chambers and smaller-diameter drift-tube chambers. Tile Calorimeter scintillation counters
were added to improve electron energy resolution and background rejection. Upgrades to Minimum
Bias Trigger Scintillators and Forward Detectors improve luminosity monitoring and enable total
proton-proton cross section, diffractive physics, and heavy ion measurements. These upgrades are all
compatible with operation in the much harsher environment anticipated after the High-Luminosity
upgrade of the LHC and are the first steps towards preparing ATLAS for the High-Luminosity
upgrade of the LHC. This paper describes the Run 3 configuration of the ATLAS detector
Structural integrity assessment of the exit convective steam collector superheater
No full textStructural integrity assessment of parts of the boiler pipe system that are exposed to highpressureduring the working life requires primarily determining the nature of the load, with not only the theworkingpressure and temperature, but also all external loads that should be taken into account. Accordingtotheaforementioned facts, the quality of the basic and additional material used for the manufacture of pressurevessel equipment were of great importance as a final confirmation of conducted methodology. Inthespecific case, the integrity assessment of one of the output collectors of the convective steamsuperheater1at Block 1 of the "REK Bitola" thermal power plant, which was the subject of fabrication and replacementdue to increased durability due to operation for over 40 years, is shown. Proof of the structural integrityofthe newly manufactured outlet collector was proven by microstructural material testing, non-destructiveand destructive material testing and hydrotesting. All of the above was used with the aimof provingtheintegrity of the collector that was manufactured, and all with the aim of making the newpressurizedequipment safe for operation
Design of Specialised Unmanned Underwater Vehicle
No full textDepending on the diverse characteristics of the aquatic area, its exploration has always been challenging for people carrying out various missions underwater. For these purposes, unmanned undewater vehicles (UUV) provide a solution to minimise risk for researchers and scientists. Unmanned underwater vehicles can operate independently (autonomous underwater vehicles) or be connected with various cables to a ship and controlled by an operator (remotely operated vehicles). Underwater missions are becoming more successful with the development of technology that provides more sophisticated equipment, such as various sensors, cameras, automatic buoyancy control system, sonars, control systems, etc. This paper explains the development of a simple UUV, relying on the use of additive manufacturing (AM) for the majority of components. AM is used and described as a viable solution for this project, suitable even for harsh environments such as the underwater region. Different chapters of the paper solve various challenges in terms of design, implementation and integration of different innovative solutions for manufacturing a reliable UUV while keeping in mind that it must be within the limits of low-budget production. The prototype is represented in the final chapter as a universal UUV that can be easily modularly prepared for different types of missions. The application of unmanned underwater vehicles is defined by the equipment it carries and varies from ocean floor mapping and exploration, underwater infrastructure maintenance, underwater photography, to disabling underwater mines
Book of Abstracts, Proceedings of the 12th Annual Conference of the Society for Structural Integrity and Life (DIVK12)
No full textRealization of the brachistochronic motion of a rigid body in a vertical plane using real rough centroids
No full textThe rigid-body motion in a minimum time, between two specified
positions in a vertical plane, is considered for the specified value of the
initial mechanical energy. The problem is formulated and solved in a
closed form, which is a contribution of this paper, considering non-linear
differential equations of the two-point boundary value problem of
obtained also represents global minimum time for motion. In the spirit of
the classical brachistochrone problem of the particle the realization of
this motion is also achieved exclusively by ideal mechanical constraints
but without the action of active forces. Parametric equations of a moving
and fixed centroid, as well as the laws of change of the tangential and normal component of the constraint reaction, which occurs in rolling
without slip, are obtained in the analytical form. Based on these laws, the
dependence of the coefficient of sliding friction on time is obtained.
Maximum value of this coefficient must be smaller than the Coulomb
coefficient of friction for the case of real rough surface. If this is not
satisfied, an appropriate optimal control problem is formulated, whose
solution yields constant value of the friction coefficient equal to the
Coulomb coefficient, over some of the time intervals of motion
Numerical and metallographic analysis of a welded joint with microcrack in the root
No full textThe goal of this research was to determine the behaviour of a welded joint with an incomplete root
penetration defect, which was subjected to tensile loads. After the actual experiments, small cracks were observed in near the fusion line, on the root side of the weld, with lengths of 0.2 and 0.3 mm, depending on the test specimen. Following the previous experience with welded joints that have multiple defects, it was concluded that further analysis is required, and for this reason, numerical models based on finite element method, which would simulate the tensile behaviour of real specimens with previously identified cracks were developed. In addition, there was the question of microstructure in this critical area of the welded joint. Metallographic tests were performed in order to determine if there was anything out of the ordinary in terms of microstructures and their distribution in the heat affected zone and the fusion line. This was decided based on previous experiments, wherein failure of tensile test specimens made of this material (which was low-alloyed low-carbon steel with commercial designation S275J2) would more often than not occur in the fusion line. Microstructural investigation, along with the numerical simulations, did not reveal anything unusual, both due to the nature of the material used and the fact that the observed cracks were too short to have a significant effect on the integrity of the welded joint. This approach, however, could prove quite valuable for materials which are more demanding in terms of welding and heat treatment
RESPONSE SPECTRA OF RECORDING OF VRANCEA EARTHQUAKES OF 1977 AND 1986
No full textResponse spectra are used in the design of seismically resistant structures, and evaluation of (ground motion records) accelerograms. The spectrum represents the set of maximum responses of a series of systems with one degree of freedom (SDOF) using the method of linear dynamic analysis. The aim is to use the spectrum to cover as much of the frequency range of the respective location as possible. The paper discusses the response spectra of the Vrancea earthquake records in 1977 and 1986 and one spectrum of the Imperial Valley. These diagrams-spectra indicate the possibility of significant amplifications of structures and the occurrence of resonance effects if the natural period of the structure coincides with the maximum values of the spectrum. The positions of the Vrancea 86 measuring stations are in different locations and soil-structure conditions, but they are arranged on the semicircle of the Carpathians. The theoretical foundations of response spectra including the Fourier transform (FT) and inverse transform (IFT) as well as fast FT (FFT and IFFT) are briefly commented.9th International Conference
Contemporary Achievements in Civil Engineering, Subotica, SERBIA
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Fractional order time delayed acceleration feedback control of inverted pendulum system
No full textThe issue of human balancing in the sagittal plane using fractional order time delayed acceleration feedback is studied in this contribution. The problem of asymptotic stability of closed-loop fractional order neutral time delay system is solved by applying the D-decomposition approach. Stability regions in the control parameters space are determined using this method. Special attention was focused on the consideration of the influence of the time delay on the asymptotic stability of the system. Finally, simulation results are presented to illustrate the superiority and effectiveness of the proposed method