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On-Track Vehicle Dynamics Testing – Obstacle Avoidance and Double Lane Change Test
No full textEvaluating the behavior of vehicles passing through a corner is a very
important task in the testing of passenger vehicles, i.e. in assessing the ability of
vehicles to maintain the specified direction ofmovement. Some of the most important
tests that evaluate these vehicle characteristics are the so-called severe lanechange
maneuver tests: double lane change test or obstacle avoidance test. ISO
3888-1 and ISO 3888-2 standards define the test track dimensions and conditions
under which tests are performed. This paper describes the method of performing
the mentioned tests on the example of theBMW650i 2014 vehicle, the equipment
used for the test, and the comparison of the obtained results for various conditions.
The results of measurements include pitch, roll, yaw rate, and acceleration of the
vehicle body. Lateral acceleration and longitudinal velocity of the vehicle are also
shown for every test
Одређивање броја кашика на основу динамичког одзива горње градње роторног багера
No full textРазвијеним техничким решењем (новом методом) холистички се решава проблем
избора броја кашика на ротору, што представља основну етапу приликом пројектовања или
редизајна подсистема за ископ код роторних багера. Осим код роторних багера, техничко
решење може успешно да се примењује код сродних машина за континуални ископ или
захватање растресеног материјала тла: роторни ровокопачи, роторне претоварне машине
(„риклејмери“) на отвореним складиштима расутог материјала, багери ведричари, као и
претоварне машине–ведричари. Наведене класе машина примењују се, поред осталог, и у
системима допреме угља у термоелектранама. Дакле, применом техничког решења
омогућава се дизајн/редизајн машина за континуални ископ/захватање уз обезбеђивање
повољног динамичког понашања њихових носећих конструкција и смањење негативних
ефеката динамичких напрезања, чиме се продужава век поменутих конструкција
DIFFERENCES BETWEEN BRIDGE AND GANTRY CRANES’ DOWNTIMES
No full textMaintenance is especially crucial when it comes to construction machinery due its capacity to avoid or reduce the
risk of serious accidents by recognizing probable failures and downtimes in a timely manner. To properly implement
maintenance strategy, it is required to identify the existing linkages between downtime and failures that have already
occurred first. This paper aims to analyze and compare data on the length of downtime, as well as the causes of
downtime hazard levels on different bridge and gantry cranes. In order to ascertain whether there is a dependency
between these two types of cranes, a comparison of the failure duration and hazard level between bridge and gantry
cranes is done in this paper. In addition, a comparison of nine different types of bridge and gantry cranes were
compared using the same comparation categories. After performing descriptive statistics and the Kolmogorov-
Smirnov and Shapiro-Wilk normality tests, which revealed that the data did not follow a normal distribution, a
comparison was done using the Mann-Whitney U test and the Kruskal-Wallis tests. All tests revealed no statisticaly
significant differences in failure duration and hazard level within the tested categories, which opens up the possibility
of applying the same risk management strategies and maintenance procedures regarding both examined crane
types
Coefficient of friction of hypereutectic Al-Si alloy: Preliminary investigation
No full textThis study represents a preliminary investigation of the mechanical and friction properties of hypereutectic Al-18Si alloy. Tribological experiments, under the linear reciprocating movement, show a decrease in the coefficient of friction with the increase of normal load. These findings provide valuable insights into the behaviour of the coefficient of friction and represent a starting point for further investigation and application of hypereutectic Al-Si alloys
Exploring role of Eco-friendly elevators in literature
No full textOva studija istražuje ulogu ekološki prihvatljivih liftova u literaturi na osnovu analize 113 radova objavljenih u naučnim časopisima iz baze podataka Scopus. Ovo je prva studija koja je koristila bibliometrijsku analizu za pregled akademske literature u oblasti istraživanja sistema liftova. Analiza je započela postupnim razvrstavanjem sakupljenih radova prema problemu višeciljne optimizacije vertikalnog transporta i analizom citata. Određivanje dominantnih tema i podtema sprovedeno je bibliometrijskom analizom na osnovu zajedničkog pojavljivanja reči u naslovima razmatranih radova unutar dvodimenzionalne matrice. Dobijeni rezultati su istakli istraživački klaster u razvoju (iskorišćenje energije) kao jedan od najvažnijih za budući razvoj sistema liftova. Ovaj klaster se bavi tehnološkim napretkom liftova i predviđa da će se tehnologije eko-liftova široko koristiti u bliskoj budućnosti. Ovo istraživanje bi moglo biti veoma korisno za podsticanje dubljeg znanja o eko-liftovima
POSSIBILITIES OF USING NUMERICAL SIMULATIONS IN DEFINING THE OPTIMAL POSITION OF BURNER HEADS OF THE REGENERATIVE BURNER SYSTEM FOR TUNDISH PREHEATING IN THE STEEL INDUSTRY
No full textThe paper presents the result of numerical simulations performed to optimize the position of burners and offgas exit for a tundish preheating system. The optimization of the position of burner heads and off-gas exit at the tundish top cover has been done by application of StarCD CFD software for numerical simulations. 3D model of a tundish and its top cover consists of 300195 control volumes. Optimization of position for burner heads and off-gas exhaust at the tundish top cover brought a uniform temperature field inside the tundish refractory layer during the transient preheating process with minimal fuel consumption
Influence of Ultrasonic and Chemical Pretreatments on Quality Attributes of Dried Pepper (Capsicum annuum)
Get PDFThis study investigates the effects of ultrasound, in combination with chemical pretreatments, on the quality attributes (total phenolic and carotenoid content, antioxidant activity
(2,2-Diphenyl-1-picrylhydrazyl assay (DPPH)), ferric-reducing ability (FRAP), CIE L* a* b* color,
non-enzymatic browning, rehydration ratio, textural and morphological properties) of red pepper
subjected to drying (hot air drying or freeze drying). The fractional factorial design was used to
assess the impact of factors. The global Derringer desirability function was used to determine the
optimal conditions for the best quality attributes of dried pepper. The drying method influenced total
phenolic content, a* (redness), and initial rehydration ratio; pretreatment time significantly affected
FRAP antiradical activity, a*, chroma and non-browning index, while pH-value had a significant
effect on the texture of dried pepper. Non-enzymatic browning was reduced to 72.6%, while the
DPPH antioxidant capacity of freeze-dried peppers was enhanced from 4.2% to 71.9%. Ultrasonic
pretreatment led to changes in the pepper morphology, while potassium metabisulfite (KMS) was a
more effective additive than citric acid
Thermal Spraying of Ti2AlC coatings
No full textCompound Ti2AlC is a MAX phase discovered in the early 1960s. It is well known that Ti2AlC has excellent physical and mechanical properties and chemical stability [1]. On the surface of Ti2AlC, at high temperatures, a stable, protective oxide layer, Al2O3, is usually formed [2], whose coefficient of thermal expansion is approximately equal to the coefficient of thermal expansion of Ti2AlC [3]. If this Al2O3 layer is compact, it stops further oxygen penetration and protects Ti2AlC from further oxidation. Due to its excellent oxidation resistance, MAX phase Ti2AlC has great potential in producing protective coatings for components in the industry that are exposed to high temperatures [4,5]. Coating Ti2AlC can be applied to the substrate by different thermal spraying processes. Cold spraying (CS), high velocity air fuel (HVAF), and high velocity oxygen fuel (HVOF) processes can be singled out as particularly interesting due to the possibility of applying thicker coatings to the substrate [6].
This paper describes the technology of applying the Ti2AlC phase on heat-resistant steel using the HVOF system of the third generation, which uses a mixture of oxygen and kerosene as fuel. Also, the filler material, which was in the form of powder, and the microstructure of the obtained coating were characterized by scanning electron microscopy (SEM). The Ti2AlC coating was successfully applied and a relatively good mechanical bond was achieved with the substrate. The goal of surfacing the Ti2AlC coating was a potential application for protecting steel from oxidation at elevated temperatures.
[1] F. Zhang et al., Surf.Coat. Tech., 441(2022) 128584.
[2] X.H. Wang, Y.C. Zhou, Oxid. Met., 59(2003) 303.
[3] W.H. Gitzen (Ed.), Westerville, Ohio, (1970) ISBN 0-916094-46-4.
[4]Q.M. Wanget et al, Surf.Coat.Tech., 204(2010) 2343.
[5] X.H. Wang and Y.C. Zhou, J. Mater. Sci. Technol., 26(2010) 385.
[6] N. Markocsan et al., Сверхтвердые материалы, 5(2017) 73
EXPERIMENTAL INVESTIGATION AND MATHEMATICAL MODELLING OF VORTEX STRUCTURES FOUND AT IMPINGING TURBULENT AXISYMETRIC AIR JET MODIFIED BY LOW-AMPLITUDE SOUND MODULATION
No full textThe controlled modulation of the nozzle exit velocity acts as a disturbance source, superimposing the natural disturbances in axisymmetric turbulent air jets. The modulation controls the vortex roll-up, and thus the overall vortex structure in the jet. The vortex structures have a significant influence on the heat transfer properties of the jet configurations. The jet can be modulated by an external source of low amplitude oscillations or by self-sustaining oscillations generated by the operation of the specially designed whistler nozzles. The aim of the experimental investigations, mathematical modelling and numerical simulations was to investigate the properties and vortex structures of acoustically modified and non-modified jets and to find an efficient way to control them.
This study can serve as a basis for further development and optimisation of technological processes related to air nozzles. The paper presents the results of experimental research and mathematical modelling and numerical simulation of free and impinging turbulent axisymmetric modified and not modified air jets
Comparison of signal features from time and frequency domain for chatter detection
Get PDFThis paper presents the results of the research into the applicability of the features derived by statistical analysis of signals from the machining process in the recognition of occurrence and evolving of chatter vibration. Selected set of statistical features were discussed, 3 of them in the time domain, an one in the frequency domain. Effects of these signal features were discussed through analysis of the results of two experiments with machining. It was shown that standard deviation and the skewness of the force or acceleration signal have some desirable properties in recognition of the moment when chatter vibrations occur