| 0. Complete issue |
- 1. Strength-Wear-Thermal Based Multi-Objective Geometric Design Optimization of Cylindrical Roller Bearings using Genetic Algorithms
- Pages: 113-130
- Raghavendra Rohit DABBARA, Rajiv TIWARI
- Abstract | Download | View
Abstract
For satisfactory performance of cylindrical roller bearings (CRB), they need to have long life which depends
on a variety of factors such as dynamic load capacity, wear and heat generation and distribution in bearings. Also,
little research has been found which takes thermal effects into consideration in multi-objective optimization even though
it plays an important role in bearing design. Hence, the motivation came from the enthusiasm to find the effect of
thermal interactions on bearing performance and on its design. In view of these, a design optimization process is put
forward for optimizing the dynamic load carrying capacity (CD), elasto-hydrodynamic film thickness (hmin) and
maximum temperature developed (Tmax) inside the bearing. The design variables chosen for optimization of CRBs
include the bearing inner dimensions (pitch diameter, diameter of roller, roller effective length and number of rollers),
five design constraint factors along with 19 constraint equations. These non-linear constraint optimization problem is
tackled by using a genetic algorithm called the Elitist Non-dominating Sorting Genetic Algorithm (NSGA-II). NSGA-II
algorithm is implemented for a set of standard catalogue CRBs, first taking one objective function at a time (single
objective optimization) and taking objective functions simultaneously (the double and triple objective optimizations),
respectively. While performing optimization on multiple objectives simultaneously, Pareto fronts are drawn and knee
point solution is chosen as the optimum solution. Comparison of results obtained with those of commercially available
bearings showed that lives of bearings with optimized dimensions have improved than the former. Sensitivity analysis
has also been done to see assess sensitivity of objective functions to variation in design variables. Finally, for
visualization, radial dimensions of one of the optimized bearings have been shown.
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- 2. Analysis Static Behaviour of Ball Bearing with Two and Four Contact Points
- Pages: 131-134
- Aleksandar ZIVKOVIC, Milos KNEZEV, Milan ZELJKOVIC, Mirjana BOJANIC SEJAT, Milovoje MIJUSKOVIC, Slobodan NAVALUSIC
- Abstract | Download | View
Abstract
Today, more than ever, design engineers are challenged to simplify designs in order to reduce cost and
weight. In many applications, a four point contact ball bearing saves space, because it can be seen as the combination
of two single row angular contact ball bearings into one. Ball bearings with two contact point are suitable for high and
very high speeds under radial and axial loads in both directions. Other hand, a four point contact ball bearing can
stand under combination of moment loads, axial loads in both directions, in combination with radial loads up to a
certain level, and provides a very tight axial shaft position tolerance. This paper presents compared analysis of ball
bearings with two and four contact points from the standpoint of static behavior and their life, as well as load capacity.
The modelling of static behavior of ball bearing consists of finite element (FE) model to describe the deformation and
stress of the rings and balls. The loads used in this analysis are chosen in order that the maximum contact stress at the
raceway remains 4200 MP according to EN ISO 76:2006. The maximum load capacity of the ball bearing has obtained
when the most loaded ball reaches this stress value. The results show that the four points contact ball bearing have
higher load capacity and less stress on the raceways.
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- 3. The Use of Matlab Software for the Design of Hydrodynamic Bearings
- Pages: 135-138
- Julio Cézar de ALMEIDA, Lucas dos Santos COELHO
- Abstract | Download | View
Abstract
Hydrodynamic bearings are supporting elements aimed at reducing the movement friction improving
equipment life. Despite the wide range applications, its dimensioning is limited due to the phenomenon of present
lubrication. Because it is a complex phenomenon, there are no exat solutions for the calculation of parameters and
related properties. The data for these variables are obtained by measurements on graphs created from computational
iterations as a function of the Sommerfeld number. The purpose of the work is to eliminate the use of graphics by
creating a routine in the software MABLAB to minimizing measurement inaccuracy and error issues. The
computational routine first determines the Sommerfeld number and, from developed subroutines, the necessary
adjustments are made in order to calculate all hydrodinamic bearings parameters.
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- 4. Computer-Aided Design of 30 kW Horizontal Axis Wind Turbine Blades
- Pages: 139-144
- Davor JOVANOVIC, Vanja SUSTERSIC
- Abstract | Download | View
Abstract
Blade geometry optimization for 30 kW wind turbine with 6.5 tip speed ratio is applied via Betz and Schmitz
formulas, using “QBlade” software. These formulas were applied to modify chord distribution and twist angle of airfoil
SD7062. Using the same software, 3D model of blades and rotors for both cases are generated. Afterwards, BEM
simulation is conducted in the “QBlade” for both cases and values of power coefficient depending on tip speed ratio, as
well as power output depending on wind speed for both optimised wind turbines is obtained. These values for both
cases are used to determine annual energy production, while using Weibull distribution to determine probability for
certain wind speeds to occur. Shape (k) and scale (c) parameters were identical in both simulations. After conducted
simulations, it is noted that Betz optimised rotor has higher peek for power production, compared to the Schmitz
optimised rotor. Also, both rotors have slightly different power coefficients depending on tip speed ratio. Using Weibull
equations, it is estimated that Betz optimised rotor has 2.79% higher annual energy production, compared to the
Schmitz optimised rotor.
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- 5. Determination of the Parasitic Forces that Occur as a Consequence of the Movement of the Roller Over the Miniature Profiled Guide
- Pages: 145-148
- Vladimir KOČOVIĆ, Sonja KOSTIĆ, Saša VASILJEVIĆ, Željko SANTOŠI, Aleksandar KOŠARAC
- Abstract | Download | View
Abstract
In order to achieve a greater efficiency degree of electrical, mechanical or other assemblies that work by
consuming any form of energy, the frictional force that occurs between all moving elements of the system should be
minimized. Nowadays, a lot of standard sliding and rolling pairs have been developed, which provide linear movement.
Since manufacturers of these elements do not prescribe coefficient of friction when moving movable rollers on a fixed
rail, it is often necessary to know the resistance to motion of these elements due to the correct selection of the drive
system, and therefore it is necessary to determine them. In this paper, the resistance to motion of roller through the
miniature profile guide 15 mm in width and 10 mm in height was tested.
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- 6. Anchorage Type and Tension Rope Force Impact on Zipline’s Kinematic Characteristics
- Pages: 149-154
- Tanasije JOJIĆ, Jovan VLADIĆ, Radomir ĐOKIĆ
- Abstract | Download | View
Abstract
This paper provides an analysis of the influencing parameters, relevant model forming, and the procedure for
determining kinematic quantities of a person traveling along a tightened rope, so-called zipline. The theoretical
background consists of two parts, i.e. the first one, which includes static analysis based on catenary theory, and the
second, which takes into account inertial forces, movement resistance, air resistance, wind effect, the position of a
person during lowering, etc, on the basis of which it is possible to determine all necessary kinematic quantities which
are essential for defining the so-called “driving characteristic” of zipline. The analyses are made by computer
simulations for concrete conditions of a zipline which was planned to be installed on Fruška Gora, Serbia. In the
simulations, the size of significant parameters such as a person’s weight, rolling resistance, air resistance, wind, rope
tension, lowering position, etc. were varied. Analysis results are given through diagrams that show a person’s velocity
characteristics in relation to time or a traveled distance.
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- 7. Tightens as Required and Responsible Elements of Equipment
- Pages: 155-160
- Dusan JESIC, Pavel KOVAC, Nenad KULUNDŽIĆ, Dražen SARJANOVIC
- Abstract | Download | View
Abstract
The tiles represent the mechanical element, which is widely used in mechanical engineering, and orders its
wide application in shipbuilding. These elements are standardized where they are specially standardized, dimensions
and loads, as well as the technical conditions for design, delivery and marking. The work will show sections of the tent,
as well as an example of labeling.
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