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Increasing the efficiency of IC engines is a frequently discussed topic and one of the approaches taken is to modify the thermodynamic work cycle of the engine so that it resembles the ideal cycle more closely. This paper attempts to achieve that by altering the kinematics of the piston-crank mechanism by introducing an epicyclic non-circular gear train between the crank and the flywheel. The addition of the non-circular gears alters the work cycle by introducing a state of dwell during key points of the cycle. Possible gear shape solutions were calculated using a known, periodical function to express the gear transmission ratio. The final result was an epicyclic non-circular gear train that has a noticeable effect on the kinematics of the piston-crank mechanism which in turn increases the engine’s efficiency.

Geared reducers are mechanisms designed to reduce the number of revolutions using geared elements and nowadays they present one of the most commonly used types of mechanical transmissions in mechanical engineering. Due to the different shapes of geared elements, there are different types of geared transmissions: helical, bevel, worm, special and combined transmissions. This paper analyses only helical geared transmissions, since there is a great extent of whole this matter. Helical transmissions are analysed only with external helical gearing, since internal geared pairs represent a special and very large group of gears. Within the external helical geared transmissions, only torque transmissions are analysed, while the transmissions of motion are not analysed and they represent another large group of transmissions. Only universal gear reducers with axial, or almost-axial, parallel shafts are considered (two-stage and three-stage transmissions). Although, single-stage gear reducer produced with parallel shafts are not considered by the paper in order to reduce the area of researching. Gear reducers are most commonly delivered to customer with electric motor, known as motor geared reducer, and they are studied here extensively. Gear reducer can be also delivered without motor, only with input shaft. The basic aim of this paper is to present all characteristics and specificities of motor geared reducer in one place.

The deep groove ball bearing is one of the most important components of the rotary motion system and is the research subject in this paper. After factory assembly, new ball bearings need to pass quality control. The conventional approach relies on measuring the vibration amplitudes for each unit and sorting them into classes according to the vibration level. In this paper, based on experimental research, models are created to predict the vibration class and analyze the dynamic behavior of new ball bearings. The models are based on artificial neural networks. A feedforward multilayer perceptron (MLP) was applied, and a backpropagation learning algorithm was used. A specific method of training groups of artificial neural networks was applied, where each network provided an answer to the input within the group, and the final answer was the mean value of the answers of all networks in the group. The models achieved a prediction accuracy of over 90%. The main aim of the research was to construct models that are able to predict the vibration class of a new ball bearing based on the geometric parameters of the bearing rings. The models are also applied to analyze the influence of surface roughness of the raceways and the internal radial clearance on bearing vibrations.

The paper presents the type and dimensional synthesis of intermittent mechanisms for use in a thermoforming machine high-capacity stacking apparatus. The aim of this paper is to realize the intermittent motion of the working part of the stacker – conveyor, with a completely mechanical system that should enable the adjustment of the operating parameters of the stacker at a constant motor speed. Mechanical control ensures high positioning accuracy of the product ejection panel, as well as high repeatability of the motion cycle of the conveyor, which is key. Based on the set requirements, the concept of a planar mechanism of simple structure was chosen, which enables oscillatory movement of the output link for continuous motion of the input link, in combination with a one-way clutch (OWC). Four types of intermittent mechanisms have been proposed. However, multiple configurations of the same mechanism type can achieve the same output link motion interval, which is why 3 configurations for each mechanism type are considered, with a total of 4 output link motion intervals, which is 12 potential solutions for only one mechanism type. Afterwards, dimensional synthesis was performed for each type of mechanism by using the optimization method. Based on the analysis of the results, all of the mechanism types are potentially usable. After additional analyses, the optimal solution was chosen.

The use of 3D models of the human bone system has great utility in the biomechanical study, due to the fact that these structures cannot be analyzed or tested in vivo. Within this paper, taking into consideration its real bone structure, the human femur CAD modelling is established. Firstly, a preliminary anatomical study is done, in order to highlight the fact that the thigh bone is a heterogeneous structure, consisting of several entities with different mechanical characteristics. The modelling starts from a homogenous 3D model of the femur, from which, every single separate entity is designed and finally they are assembled within a single product assembly. Therefore, the final result ensures a complex CAD structure, able to get assigned different material properties, specific for each entity this modelling furtherly allows the characteristic pathological structures studies of the referred entity or to simulate specific surgical interventions.

Today there are no products whose appearance is not important. Of course, the greatest attention is paid to products that are intended for mass consumption and personal use, since the customers want to emphasize their uniqueness. That doesn’t mean the other products are not given any attention but on the contrary. Within this paper, only universal gear reducer with helical gears will be considered. These units are often installed within the other products, so that they are usually invisible to the customers, and this paper will give attention to their design solutions overview. Universal gear reducers are relatively simple products and around the world there is a large number of manufacturers of these gear drives of different concepts and shapes. It is interesting to note that most manufacturers try to adopt the shape of gearbox housing that is significantly different from competing solutions. The reason for that is they want to accentuate their solution in order to and to avoid the possibility of an accusation of copying some other’s solution. Although, there are manufacturers which retain almost identical shape as a competing solution, which is probably a reason of bought licence or a consequence of inexperienced copying.

Increasing the efficiency of IC engines is a frequently discussed topic, and one of the approaches taken is to modify the thermodynamic work cycle of the engine so that it resembles the ideal cycle more closely. This paper attempts to achieve that by altering the kinematics of the piston-crank mechanism by introducing an epicyclic non-circular gear train between the crank and the flywheel. The addition of the non-circular gears alters the work cycle by introducing a state of dwell during key points of the cycle. Possible gear shape solutions were calculated using a known, periodic function to express the gear transmission ratio. The final result was an epicyclic non-circular gear train that has a noticeable effect on the kinematics of the piston-crank mechanism resulting in an increase of the engines work cycle efficiency.

The basic parameters of the universal gear drives, except the axis height, are not defined by the standard, so the manufacturers of universal gear reducers can define them in their way. Most of the manufacturers followed the parameter values of universal gear reducers of leading world producers in order to ensure their interchangeability and the better positioning of their gear units at the market. This paper deals with the analysis of the influence of the gear pair teeth number on the size of the module, as well as on the load carrying capacity of single-stage universal gear units. For defined gear ratio values, different combinations of teeth number of pinion and driven gear were selected. Further, it was made calculation of the basic geometric dimensions of the gear pair, as well as the load capacity.

Universal helical gear motors are among mechanisms that operate with a very high efficiency (about 0.98 per gear pair) [1, 2] and thus their thermal power capacity has not received enough attention, even in the cases when they overheat (usually at higher ambient temperature and high power motors). Therefore, it is necessary to define the thermal capacity in the catalogues of the speed reducer with a solid input shaft, as it is done by worm and helical-worm gear units which operate with much lower efficiency. Some manufacturers [3] pay necessary attention to this factor and thus enable the proper selection of gear reducers; this means they have prepared certain procedures to be undertaken if such occasion occurs, in order to overcome possible problems that may arise due to overheating the gear reducer. With this approach in the universal gear unit selection, some positive benefits can be surely achieved in the market of gear reducers, and that should not be ignored.

This paper presents an analysis of the mechanism found in the clock tower of the Petrovaradin Fortress in Novi Sad. The clock mechanism dates back to the beginning of the XVIII century and thus has great historical value. It consists of three interconnected mechanisms – the timing mechanism that keeps time and powers the clock hands, the quarter striking mechanism that sounds the quarter-hours and the full hour striking mechanism that sounds the full hours.

The paper presents the dynamic analysis and motion simulation of the waist mechanism meant for humanoids. The proposed waist mechanism has a total of 3 DOFs, allowing movements of the robot’s upper trunk around the pitch, roll and yaw axes. Within the dynamic analysis, the decomposition of the waist mechanism is performed and for each link of the mechanism, motion equations are formed. Reactions in the mechanism links are determined by using D’Alembert’s principle and based on those, the equations for calculating of the driving forces are defined. Finally, the dynamic model of the waist mechanism was formed and a motion simulation for several scenarios was performed. Based on the analysis of the results, it was concluded that the waist mechanism requires small driving torques and therefore less and cheaper actuators, which is an important advantage of this solution.

Artificial neural networks are used for diagnosing of ball bearings condition. They are capable to recognize bearing fault from information extracted from signal of vibration. The aim of the work is to investigate the relationship between vibration velocity in the characteristic band frequencies and radial clearance. Changing the radial clearance during operation may indicate changes in the operation of the rotating system. Experimental research is based on deep groove ball bearings and measuring the vibration of the bearings. The vibration velocities for each bearing were measured under laboratory conditions, and the processed signals were used to train the artificial neural network. An artificial neural network trained in this way can predict the size of the radial clearance based on the vibration of the bearing.

By analysing and comparing the existing solutions of universal gear reducers with helical gears of the leading manufacturers, it can be noticed the effort to increase the load capacity of the gear reducer within the same axis height. In this way, the manufacturers can offer smaller (cheaper) gear reducers, as well as to simultaneously increase the values of the largest gear ratios. This concept enables the offer of lower-stage (cheaper) gear reducers with higher gear ratios in certain segments of gear ratios. By these efforts, it is reached the maximum, but the further increase is possible only by changing the current concept of universal gear drives. Within this paper, it is given an overview and analysis of one of the possible new conceptual solutions of modern universal motor gear reducer.

The problem of defining the load (nominal torque on the output shaft - T2N) of universal gear drives depending on the size of the gear ratio is analysed in this paper. It is logical that the load capacity of gear drive depends on the weakest gear component. Since the gears are the most expensive components of gear unit, it tends to maximize their performance. However, for low gear ratio, i.e. for high speeds, the bearings often limit their load capacity since the same bearings are used in all transmission ratios because it is not practiced to oversize the bearings at low speeds. Nowadays, when high values of gear ratio are used, it is interesting to consider the dependence of the nominal torque at the output regarding to gear ratio and operating life of the unit.

The paper presents the kinematic analysis and motion simulation of the waist mechanism for humanoid robots. The waist mechanism with total 3 DOFs is proposed. It consists of two interconnected spatial mechanisms that allow movements around the pitch and roll axes, while the third is planar mechanism for movements around the yaw axis. Due to the structure of links, spatial mechanisms can function independently and/or simultaneously. By kinematic analysis of the waist mechanism, the kinematic parameters are defined and based on that, a kinematic model is formed. Motion simulation of the waist mechanism for initial movements of flexion, extension, lateral flexion and rotation is performed. For the corresponding movement and range of motion, the waist mechanism reaches the kinematic parameters of the human lumbar spine region, which was the basic requirement for realization.

In this paper we present a design method for a modular device used in different types of HIGH TIBIAL OSTEOTOMY surgical procedures. The requirements, necessities and functions of this modular device are presented in the first part of the article. An important aspect is the fact that the device must be designed in a manner which permit to use it for all types of HIGH TIBIAL OSTEOTOMY: opening wedge osteotomies, closing wedge osteotomies, medial osteotomies, lateral osteotomies, uniplanar osteotomies or biplanar osteotomies. This fact is possible using modular elements for the main parts of the devices. The researches could be the starting point for others researches regarding the appropriate materials and the possibility to execution customized several parts of the modular device using Additive Manufacturing facilities.

The purpose of this paper is to determine the effect of the air torque position (ATP) damper hysteresis on the accuracy of air velocity measurements and the adequacy of the ATP damper mathematical model tested in the present study. A total of three dampers with non-cascading blades were examined: a damper with a single flat blade, a damper with two opposed flat blades, and a damper with two flat blades - one of which is a measuring blade and the other is fixed in the horizontal direction. Furthermore, a total of two damper installation locations in a duct system were examined as well: at the duct exit with a straight duct section preceding the damper and within the duct itself with straight duct sections both preceding and following the damper. The ATP damper hysteresis was found to exert a significant effect on the accuracy of air velocity measurements and the adequacy of the ATP damper mathematical model tested if the ATP damper is more open, i.e. with lower blade angles of attack. Moreover, the ATP damper installed at the duct exit was found to be more susceptible to hysteresis effects than the damper located within the duct.

Additive manufacturing (AM) technology refers to the process of producing 3D objects by adding material in successive layers. Fused deposition modeling (FDM) is one of the AM technologies where objects are built by adding layers of melted thermoplastic filament onto the printing surface. Mechanical properties of FDM printed part depend on many influencing factors such as material composition, extruding temperature, printing parameters and environment temperature. The aim of this study was to investigate consistency of mechanical properties of elements produced by FDM additive manufacturing technology. To do so, mechanical tensile and compression tests were conducted on ten samples using polylactic acid (PLA) and ten samples using acrylonitrile butadiene styrene (ABS) thermoplastic material. Tensile tests were conducted using Shimadzu Compact Tabletop Testing Machine EZ-LX and the compression tests were done using VEB ZDM 5/91 testing machine. The ultimate tensile strength, strain, Young modulus and compression yield strength values were analyzed. The ABS thermoplastic material showed greater consistency in mechanical properties during tensile tests. Tensile strength values for PLA material varied between samples thus showing greater inconsistency in repeatability of mechanical properties. Compression tests, on the other hand, showed that PLA samples had greater consistency in mechanical properties compared to ABS samples. Keywords: additive manufacturing, FDM, mechanical properties.

The paper presents the structural design and motion simulation of the robotic eyes with the characteristics of the female eye. The eyeballs/eyelids drive system with total 7 DOFs is proposed. The eyeballs drive system has 3 DOFs and enables the rotation of both eyeballs together around the pitch axis and their independent rotation around the yaw axis. The proposed solution enables the installation of cameras directly into the eyeballs. Also, it is possible to independently rotate the upper/lower eyelids of each eye, where the eyelids, in relation to the eyeballs, are rotated in two planes. Motion simulation of eyeball and upper/lower eyelids is performed. For the range of the motion that corresponds to the human eye, the angular velocities of the eyeball and upper/lower eyelids reach and exceed the kinematic parameters of the human eye.

Having in mind that humans use non-verbal communication extensively is very important to enable social robots with this capacity. There are two basic ways how it can be expressed. First one is by facial expressions by appropriate moving face parts, like eyebrows, eyeballs, eyelids, lips, either as manufactured real parts or by presenting them on screen—combining them is also possible. The second way of non-verbal communication is by gestures. This paper presents the kinematic-dynamic analysis of shrug mechanism for humanoid robots. Based on the set requirements, the cam-worm mechanism that has 1 DOF and enables the simultaneous shrug of both shoulders is proposed. It consists of a worm which is meshed with two worm gears whose directions of rotation are opposite and the two cam mechanisms whose input links—cams, are rigidly attached to the worm gears. Within the kinematic-dynamic analysis, the cam profile and the worm parameters are defined and the torque on the cam/worm gear and the driving torque of the complete cam-worm mechanism are determined. The cam mechanism has a high efficiency in all positions because the values of the pressure angle are within the prescribed ones during the entire movement. Worm mechanism enables a significant reduction of the driving torque and has acceptable efficiency. The rotation range of worm gear/cam is small and the movement of mechanism is very fast wherefore the shrug speed is large, which was one of the main requirement for realization.

Significant aspect of the socially interactive robots are eyes which present the most expressive part of the face, especially when it is rigid as is the case with majority of the robots. For this reason to the design and realization of the eyes a particular attention should be dedicated. This paper presents the drive system of the robot eyeballs and eyelids with 8 DOFs. Eyeballs drive system has 4 DOFs and consists of two symmetrical planar mechanisms that enable independent motion of the eyeballs about the yaw axis—abduction/adduction movements and two identical spatial mechanisms that enable independent motion of the eyeballs about the pitch axis—elevation/depression movements. Eyelids drive system has 4 DOFs and consists of four structurally equal spatial mechanisms that enable independent motion of each eyelid—mechanisms for driving the upper and lower eyelids, respectively, are symmetrical. Based on the kinematic analysis, motion simulation of eyeball and upper/lower eyelid is performed. Velocities of the eyeball/eyelids movements are within the parameters of the human eye. The structure of the eyeballs drive system is such that enables inserting the camera directly into the eyeballs. In this way it is possible to achieve some of the functions of robots artificial vision such as recognizing objects, distance estimation etc.

The paper analyses the way to increase the resistance of HCR external involute gearing from a scuffing point of view. The scuffing is the most important damage of teeth flanks of HCR involute gears. In the case of warm scuffing; it is the combined action of high pressure between surfaces, high sliding speeds, and excessive contact temperature, resulting from pressure and sliding speed values, which cause oil film rupture between the teeth flanks. Adopting suitable geometry of the tooth curve profile, it will be defined certain values addendum heights for meshing wheel according to criteria of specific slips and corrected head shape of the teeth of both wheels. The paper deals with assessment and theoretical analysis of the impact of the HCR tooth profile resistance to scuffing on the basis of integral temperature criterion according to Winter-Michaelis criterion, researching especially two factors: factor of load distribution (Xe) and factor of gear geometry (XG).

The paper deals with an issue of increasing the resistance of HCR external involute gearing from a scuffing point of view. It reports on a difference between involute gears with low contact ratio (LCR) and those with high contact ratio (HCR). The paper describes scuffing as the most significant damage done to the teeth flanks of HCR involute gears. In the case of warm scuffing, it is the combined action of high pressure between surfaces, high sliding speeds, and excessive contact temperature, resulting from pressure and sliding speed values, which consequently cause oil film rupture between the teeth flanks. Adopting a suitable geometry of the tooth curve profile, certain values of addendum heights for the meshing wheel will be defined according to the criteria of specific slips and corrected head shapes of the teeth of both wheels. The paper deals with the assessment and theoretical analysis of the impact of the HCR tooth profile resistance to scuffing on the basis of integral temperature criterion according to the Winter-Michaelis criterion. The basic relations for assessing the scuffing properties of an HCR involute gearing profile are derived, as well as the optimization of geometrical parameters of HCR gearing based on theoretical considerations on the properties of HCR gearing in terms of its resistance to warm scuffing combined with geometrical constraints against interferences. Finally, the results of the obtained optimization are compared with experimental results provided in previous research. A significant benefit in a theoretical area is the generalization of the integral temperature criterion for involute HCR gearing. By optimizing the criterion for the integral temperature of involute HCR gearing, the minimal flash temperature is obtained and the condition for the occurrence of scuffing is minimized.

Today, for almost all products, the appearance is very important. Thus, for example, the appearance of universal gear reducers was not given so much attention, but today there are many very interesting solutions of shape, colour and graphic design. It should have in mind that universal gear reducers have much complex construction comparing them with special gear reducers. In the same time, they have to provide different positions and way of mounting and different speeds with different powers (torques) at the output shaft. Particularly, it should be noticed, that within all universal gear reducers single-stage gear units are nowadays increasingly used because their gear ratio values are increased (values of gear ratio can go up to 15) so that these reducers largely cover most of the two-stage gear reducers with their gear ratio values, so thereby their exploitation is significantly increased. Single-stage gear reducers are very simple products, and today there is a large number of manufacturers of such product. However, their mounting dimensions and way of mounting are not defined by a standard, so there is a variety of units with different dimensions and way of mounting. Although, most manufacturers look up to dimensions of leading manufacturers (usually SEW) in order to ensure greater exchangeability of their gear units. It is interesting to note, that most manufacturers tend to adopt the design of housing that will be substantially different from competing solutions. The reason is probably to avoid the possibility of being accused of copying someone else’s solution. However, there are manufacturers that retain almost identical housing design as a competing solution (probably they bought the licence or the solution is copied without permission). This paper considers only the design solutions of single-stage gear reducer in order to indicate the expected directions of their further development.

The issue of design and dimensioning of HCR gearing, particularly of the gearings with an internal engagement, it nowadays, especially in the design of hybrid cars drives, highly topical. This kind of gearing has many advantages in operation, but at the same time it is more complicated in stage of its design and load capacity calculation. Authors in this contribution present some results of temperature scuffing research of internal and external HCR gearing. There are given the equations for calculation of warm scuffing resistance of both external and internal HCR gearing derived according to the integral temperature criterion.

The paper analyses the problems of the influence of direction of helical teeth in the universal helical gear reducer on service life of the bearings that support the reducer shaft, i.e. on the overall load carrying capacity of universal gear reducer. Directions of helical teeth for all gear units is adopted in that way that the overall axial force at the reducer shaft is lowest as possible, i.e. axial forces of a shaft are in counterbalance. It is a practice the same output gear pair is used within a helical gear reducer made in universal casing for two- and three-stage gear reducer. However, these gears are produced with different directions of helical teeth in order to obtain the lowest axial force on the fifth geared shaft. However, some gear reducer manufacturers, trying to simplify the production and reduce the number of manufactured components, produce the gears with the same helical teeth direction for both two- and three-stage gear reducers. In that way, they do not reduce the value of axial force on the fifth geared shaft in three-stage gear unit, but they make addition of axial forces that certainly affects the service life of the bearings and thus the overall load carrying capacity of the gearbox. Analysing the concrete case, this paper researches the justification of implementation this procedure.

Considering that the most important use of thermoforming is in the production of plastic packaging for the food and pharmaceutical industry, it is essential that formed products remain sterile through the entire thermoforming process. Most machines used for thermoforming have a tool holder with one degree of freedom—DOF, which allows only vertical motion of the tool. After the thermoforming process, the formed products are ejected from the tool with compressed air, which may cause contamination and/or deformation of the products. We propose a working mechanism for driving the tool, which, compared to conventional machines, guarantees both a shorter working cycle and sterility of the formed products during the entire process. Products are punched out after forming and accepted and transported with an adequate mechanism to the manipulation module, where they are sorted and packed. This paper presents a dynamic optimization of the thermoforming machine working mechanism with 2 DOFs which consists of two cam-lever mechanisms that enable translation, rotation and complex motion of the tool. Based on the set of technical requirements, kinematic synthesis of the cam-lever mechanism is performed. SVAJ diagrams for the cams and the dimensions of the lever mechanism links are defined. Based on the kinetostatic analysis, a dynamic model of the cam-lever mechanism is formed and the driving torque for both lifting and rotation of the tool is determined. The optimization problem is formed and the objective function is defined as the minimization of the required driving torque. Based on the set constrains, a dynamic optimization is performed using the method of genetic algorithm. By comparing the results before and after optimization, it is concluded that the driving torque is lower by 50.3%.

In the area of universal gear reducers, standard does not prescribe relations between load capacity, gear ratios and axis heights. Therefore, larger load capacity of some gear reducers manufacturers has advantage for lower gear ratio and, vice versa, smaller load capacity of the gearbox achieves higher values of gear ratio. However, there are some manufacturers who produce gear reducers with smaller or larger load capacity for higher or lower gear ratio, within the same axis height. This paper deals with analysis of justification of applying two gear sets, especially in the case when so-called intermediate sizes of gear reducer are not used.

The article deals with possibility of increasing the resistance of HCR spur gearing from a scuffing point of view. Scuffing is the process that occurs when the surfaces of two contacting bodies are joined by localized welding and then pulled apart. A material transfer occurs between the two contacting surfaces due to high metal-to-metal contact and hence produces a weld. Since there are great pressures between teeth flanks and the load is higher, the scuffing is the most important damage of teeth flanks of HCR involute gears. The scuffing traces appear in the form of streaks or scratches with rough bottoms and sides, often appearing as bands of variable depth width oriented in the direction of the height of the tooth, and affect isolated zones or their whole width. In the case of warm scuffing; the combination of high pressure exists between teeth surfaces, high sliding speeds, and excessive contact temperature, resulting from pressure and sliding speed values, which cause oil film rupture between the teeth flanks. HCR profiles are more complicated than standard involute profiles, they have greater predisposition for occurring interference, pointed tip thickness, but also undercut of teeth during the production (primary production interference). Due to increased addendum height, there is larger possibility of occurring some interference or pointed tooth tip. Therefore it should prevent these errors and check if all equation and constraints are satisfied. This paper describes finding optimal solutions for geometry of the tooth curve profile. It will be defined certain values addendum heights for meshing wheel according to criteria of specific slips and corrected head shape of the teeth of both wheels. In the same time, this optimization is joined with assessment and theoretical analysis of the impact of the HCR tooth profile resistance to scuffing on the basis of integral temperature criterion according to Winter-Michaelis criterion. A significant benefit in a theoretical area is generalization of the integral temperature criterion for involute HCR gearing.

A special kind of the basic involute profile of non-standard gearing is called high contact ratio (HCR) gearing, where the contact ratio is higher, there are always at least two pairs of teeth in contact and the unit addendum height is not equal to one like for standard gearing. Thus, the tooth height is increased. When HCR gearing is used, it is not necessary to achieve a greater gear load capacity, but nevertheless there is a greater risk of interference due to the greater tooth height. The advantages of HCR gearing is higher resistance (load is distributed on more pairs of teeth at the same time) and a lower relative noise level of gearing, which can be significantly reduced by using an integer HCR factor. HCR profiles are more complicated than standard involute profiles, they have a greater predisposition for interference, pointed tip thickness and undercut of teeth during production (primary production interference). Due to increased addendum height, there is a larger possibility of some interference or pointed tooth tip occurring. Therefore, these issues need to be prevented in the design phase, and ensured that all relevant equations and constraints are satisfied. The described method of finding optimal gear parameter values uses a Generalized Particle Swarm (GPS) optimization algorithm and MATLAB. The GPS optimization is shown to be a very fast and reliable method.

A considerable slide exists between the flanks of worm and gear during the work, which results in flank wear and considerable loss of energy. The energy is, thereby, converted into heat, which leads to the warming-up of gear drive, compromising its correct operation, and to scuffing in critical cases. Oil temperature has an important role in thermal stability. Viscosity depends on temperature. Viscosity significantly affects the processes in the contact zone, i.e. the energy losses, and hence the temperature. Optimal lubrication can be provided only in the relevant field of temperatures. The paper presents experimental and theoretical research on the effect of temperatures and thermal stability of a worm and gear set with a gear made of sintered steel Fe1.5Cr0.2Mo on their ability and appearance of boundary conditions.

The temperature of rubber or rubber-metal springs increases under cyclic loading, due to hysteresis losses and low rubber thermal conductivity. Hysteresis losses correspond to energy dissipation from the rubber, which is primarily converted into heat. This well-known phenomenon, called heat build-up, is the primary reason for rubber aging. Increase in temperature within the rubber compound leads to degradation of its physical and chemical properties, increase in stiffness and loss of damping capability. This paper presents a novel procedure of heat generation prediction in rubber or rubber-metal springs. The procedure encompasses the prediction of hysteresis loss, i. e. dissipated energy within the rubber, by finite element analysis and application of a modern visco-plastic rubber constitutive model. The obtained dissipated energy was used as an input for transient thermal analysis. Verification of the proposed procedure was performed by comparison of simulation results with experimentally obtained data during the dynamic loading of the rubber specimen. The proposed procedure is highly computationally efficient and it enables time integration, which can be problematic in coupled mechanical thermal analysis. [Projekat Ministarstva nauke Republike Srbije, br. TR35005: Research and Development of New Generation of Wind Turbines of High Energy Efficiency]

Possible concept solutions of chain drives are analysed in this paper in order to point out the benefits of chain drive application and, in particular, the possibility of application of multi-level chain drive. The paper also analyses the possibility of replacing the gear drives with chain drives, which, in the case of short-term drive and using the same direction of rotation, enables a slightly simpler drive solution. The paper doesn’t consider difference between the roller and gear chains application because these two types of chains can be used very successfully. Also, the possibility of using timing belt drive is not considered, but it can be also used very successfully in this type of drive, but only as a transmission of motion.

The operating principle of rolling bearings generates vibrations that come from the periodic change in the stiffness of the bearing. The vibration level of the bearing depends on a large number of factors such as waviness, surface roughness of the raceways, deviation of the raceway radius, exploitation conditions, amount of lubrication in the bearing and other. This paper presents the influence of the roughness of the raceways and the amount of lubrication on the level of vibrations of the ball bearing, designation 6006. The determination of the influence of these parameters was done experimentally. The experiment was performed according conditions prescribed by ISO 15242-2, and the analysis of the measured signals was performed according to the guidelines given by the standard ISO 15242-1.

Universal gear reducers are quite simple products, so today there are many manufacturers around the world that produce this kind of reducers. Their connecting dimensions and shape are not defined by the standard, so there is a large number of solutions. The most of manufacturers produce gear reducers with connecting dimensions and axis height, usually the same like the biggest manufacturers do (mainly company SEW), because they want to provide interchangeability of their gear reducers. It is interesting to note that most manufacturers are trying to adopt such a form of reducer that will be different from competing solutions in order to avoid an accusation of coping with someone else's solution, although manufacturers have almost identical shape and competing (copied) solutions. The paper presents, due to the volume of matter, only the analisys of forms of the housing of modern single-stage universal gear reducers in order to point out the expected directions of their further development.

The paper deals with problematic of gear units and machine foundating and consequences that occur by foundation screws releasing. Namely, reliable operating of gear units, as well as other stationary machines, requires properly foundating. However, after certain period of time, relaxation of screw material, self-untightening of nuts and looseness of foundation screws influence on reducing the force of preload screw tightening and unequal load distribution. This unequal load distribution causes unequal deformations, which generate occuring vibrations. In extreme cases, breakages of screws and heavier accidents of systems driven by that gear units or machines can happen. With this paper authors want to indicate influence of deterioration degree on its load capacity.

Multivariate research is important in areas of cast?iron brake shoes manufacturing, because many variables interact with each other simultaneously. This article focuses on expressing the multiple linear regression model related to the hardness assurance by the chemical composition of the phosphorous cast irons destined to the brake shoes, having in view that the regression coefficients will illustrate the unrelated contributions of each independent variable towards predicting the dependent variable. In order to settle the multiple correlations between the hardness of the cast?iron brake shoes, and their chemical compositions several regression equations has been proposed. Is searched a mathematical solution which can determine the optimum chemical composition for the hardness desirable values. Starting from the above?mentioned affirmations two new statistical experiments are effectuated related to the values of Phosphorus [P], Manganese [Mn] and Silicon [Si]. Therefore, the regression equations, which describe the mathematical dependency between the above?mentioned elements and the hardness, are determined. As result, several correlation charts will be revealed.

The cast hipereutectoid steel (usually named Adamite) is a roll manufacturing destined material, having mechanical, chemical properties and Carbon [C] content of which stands between steelandiron, along–withitsalloyelements such as Nickel [Ni], Chrome [Cr], Molybdenum [Mo] and/or other alloy elements. Adamite Rolls are basically alloy steel rolls (a kind of high carbon steel) having hardness ranging from 40 to 55 degrees Shore C, with Carbon [C] percentage ranging from 1.35% until to 2% (usually between 1.2˜2.3%), the extra Carbon [C] and the special alloying element giving an extra wear resistance and strength. First of all the Adamite roll's prominent feature is the small variation in hardness of the working surface, and has a good abrasion resistance and bite performance. This paper reviews key aspects of roll material properties and presents an analysis of the influences of chemical composition upon the mechanical properties (hardness) of the cast hipereutectoid steel rolls (Adamite). Using the multiple regression analysis (the double and triple regression equations), some mathematical correlations between the cast hipereutectoid steel rolls' chemical composition and the obtained hardness are presented. In this work several results and evidence obtained by actual experiments are presented. Thus, several variation boundaries for the chemical composition of cast hipereutectoid steel rolls, in view the obtaining the proper values of the hardness, are revealed. For the multiple regression equations, correlation coefficients and graphical representations the software Matlab was used.

Pitting and temperature scuffing evidenced by damage to teeth flanks of gears are the most important problems needing to be solved in the process of gearing design and calculation. According to current valid standards, such calculations can be resolved with a high level of reliability for all the usual gearing types. However, suitable calculations for High Contact Ratio (HCR) gears have not been adequately researched to date. It has been identified that in HCR gears some different process of scuffing and pitting formation occurs during the gear’s operation. Therefore it is actual to deal with optimization of HCR gearing just from these kinds of teeth flanks damages. In article, the authors describe a new method for finding optimal solutions for geometrical parameters \( h_{a1}^{*} ,h_{a2}^{*} \) and x1, using a Generalized Particle Swarm Optimization Algorithm for both above mentioned optimization tasks.