A methodology for analyzing radial ball bearing vibrations

This paper presents the development of a methodology for calculating radial ball bearing vibrations. First, analytical and numerical models were developed and then, the obtained results were experimentally verified. In the experiment, a test rig for a dynamic testing of bearings subjected to an external load was used. Special attention was paid to the analysis of the total bearing deformations and stiffness, being the main parameters that define the dynamic behaviour of a bearing. In order to determine total deformations of a ball bearing as an assembly, a finite element model of the bearing was developed. The results obtained from the new methodology for a particular ball bearing type have been verified by experimental results. The obtained correlations of the experimental and the numerical results are about 2.5%. Based on the calculations and the experimental testing of the chosen ball bearing type, under conditions of a variable radial load, the analysis of the influence of the radial load on the dynamic behaviour of a ball bearing was performed. The analysis of the obtained results showed that the vibration amplitude increases with a similar multiple factor as loads increase

Effects of operation temperature on thermal expansion and main parameters of radial ball bearings

The research of influence of operation temperature on the thermal expansion and main parameters of radial ball bearings is presented in this paper. The main bearing parameters are identified in accordance with the increasing requests concerning stability and load capacity. A series of finite element analyses is performed for quasi-static analysis of all identified bearing parameters during contact period in referent temperature. Then, the dependence of bearing material characteristics on the operation temperature is discussed. Few series of finite element analyses are performed for a particular radial ball bearing type, with characteristics in accordance with manufacturer specifications, for several operation temperatures. These two problems analyses include consideration of relation between the initial radial clearance, thermal expansion strains, and contact deformations of the parts of the bearing assembly. The results for radial ball bearing parameters are monitored during a ball contact period for different temperatures and the appropriate discussion and conclusions are given. The conclusions about the contribution of developed procedure in defining the optimum operation temperature range are shown

Effects of operation temperature on thermal expansion and main parameters of radial ball bearings

The research of influence of operation temperature on the thermal expansion and main parameters of radial ball bearings is presented in this paper. The main bearing parameters are identified in accordance with the increasing requests concerning stability and load capacity. A series of finite element analyses is performed for quasi-static analysis of all identified bearing parameters during contact period in referent temperature. Then, the dependence of bearing material characteristics on the operation temperature is discussed. Few series of finite element analyses are performed for a particular radial ball bearing type, with characteristics in accordance with manufacturer specifications, for several operation temperatures. These two problems analyses include consideration of relation between the initial radial clearance, thermal expansion strains, and contact deformations of the parts of the bearing assembly. The results for radial ball bearing parameters are monitored during a ball contact period for different temperatures and the appropriate discussion and conclusions are given. The conclusions about the contribution of developed procedure in defining the optimum operation temperature range are shown

The analysis of impact of intensity of contact load and angular shaft speed on the heat generation within radial ball bearing

This paper considers the factors that influence the heat generation within ball bearing. Various lubrication regimes are taken into consideration and a mathematical model for determination of the coefficient of heat generation is set up. Due to the complexity of mathematical tools, and in order to perform better and easier analysis of the considered phenomenon, the application that integrates the mathematical models of load distribution and heat generation was developed. The impact of the contact load and angular shaft speed on the level of heat generated in radial ball bearing was analyzed

A New Collision Model for Analysing the Vibro-Impact of Spur Gears

A model of a central centric collision of two fictive rolling disks, with radii equal to the radii of pitch diameters of coupled gears, is used to describe the vibro-impact dynamics of spur gears. Total deformations vary during the operation of spur gears with involute profile, particularly as a result of variable number of pairs of teeth in contact. These variations, as well as tooth profile misalignments or damages, lead to the backlash, the appearance of internal dynamic forces, and impact. Particular values of tooth profile parameters and transmission ratio create the conditions for a vibro-impact vibration regime. The vibro-impact gear dynamics is characterized by vibro-impact vibrations in the contact between the pinion tooth and the wheel tooth during a short period of time after the collision. New formulas for the calculation of the time periods between two tooth collisions, as well as between two successive tooth collision impacts, are devised. Also, a set of equations for the calculation of the disturbance angular velocity of the pinion called the transmission error is developed; the transmission error has a role of an excitation for vibro-impact vibrations in the gear tooth contact

DETERMINATION OF CRITICAL SIZE OF CORROSION PIT ON MECHANICAL ELEMENTS IN HYDRO POWER PLANTS

Researchers in the field of fracture mechanics, predominantly developing appropriate solution algorithms for problems of solid bodies with cracks. Problems in mechanics generally, related with fracture and fatigue for solid bodies with various geometries of sharp notches, are studied to a much lesser extent. This situation can be explained by analytical difficulties arising in solving problems of elasticity theory for bodies with rounded notches. To solve problems of such class, starting from data on stress concentration in the rounded notch tip with a significant radius of curvature, simplified solutions with are therefore of great importance. Recent years, due to constant rise of computing power and development of numerical methods, re-evaluation of stress concentration factors from a viewpoint of theory of elasticity is present. This is mainly as a feedback from industry, which have requirements toward mega and nanostructures. Corrosion represents an important limitation to the safe and reliable use of many alloys in various industries. Pitting corrosion is a form of serious damage on metals surface such as high-strength aluminum alloys and stainless steel, which are susceptible to pitting when exposed to a corrosive attack in aggressive environments. This is particularly valid for dynamic loaded structures. The basic idea behind this paper is finding links between different scientific and engineering disciplines, which will enable useful level of applicability of existing knowledge. The subject of this paper is application of new method of determine length scale parameter for estimating the mechanistic aspect of corrosion pit under uniaxial/multiaxial high-cycle fatigue loadin

New trends in machine design within industry 4.0 framework

The basic framework of the Industry 4.0 as an approach and philosophy implies the introduction of new procedures and principles, as well as the development and improvement of machine systems towards the introduction of a high level of manufacturing digitalization. In order to meet the achievements of Industry 4.0, very significant changes are also required in the design, monitoring and maintenance phases of machinery. Therefore, all the research and advancements in the field of calculation and design of machine elements and assemblies have to be observed within the paradigm of Industry 4.0. This paper outlines the main research tasks and aims within the determination of basic principles and methods for suiting and improving machine elements and systems in the context of the requirements of the Industry 4.0. Also, the part of the paper gives the description of the new improved methodology and systems for monitoring the parameters of rolling bearings during their operation, which would significantly contribute to the prediction of the possible failure of the rolling bearings and lead to important savings. The developed methodology is a sample for new trends in the context of the vision of Industry 4.0 machinery and respects the requirements for safety, energy efficiency and reliability

Numerical study of the effect of dental implant inclination

© 2017, Journal of the Serbian Society for Computational Mechanics. This paper contains the results of a research focused on the determination of the influence of an implant inclination on the strain state throughout the acrylic block with implant. The aim of the presented research is to qualitatively determine the regions with the greatest strain fields on the models. The finite element models of implant and acrylic block are developed for predefined implant inclinations in order to analyze the influence of implant inclination on deformations on the outer surface of acrylic block. The comparative contour plots of stress and strain state of analyzed models, as well as the comparative diagrams with obtained results, are presented. The conclusions about the inclination angle which leads to the higher strains in the block-implant are explained. Obtained results could be applied for the planning of future experimental studies which could utilize this and similar models to determine their load transfer characteristics, and could be included in the planning of dental implant position, and prediction of successful dental therapy

Effects of operation temperature on thermal expansion and main parameters of radial ball bearings

The research of influence of operation temperature on the thermal expansion and main parameters of radial ball bearings is presented in this paper. The main bearing parameters are identified in accordance with the increasing requests concerning stability and load capacity. A series of Finite Element Analyses is performed for quasi-static analysis of all identified bearing parameters during contact period in referent temperature. Then, the dependence of bearing material characteristics on the operation temperature is discussed. Few series of Finite Element Analyses are performed for a particular radial ball bearing type, with characteristics in accordance with manufacturer specifications, for several operation temperatures. These two problems analyses include consideration of relation between the initial radial clearance, thermal expansion strains and contact deformations of the parts of the bearing assembly. The results for radial ball bearing parameters are monitored during a ball contact period for different temperatures and the appropriate discussion and conclusions are given. The conclusions about the contribution of developed procedure in defining the optimum operation temperature range are shown. [Projekat Ministarstva nauke Republike Srbije, br. TR 35029 i br. OI 174001

Nonlinear Dynamics as a Tool in Selection of Working Conditions for Radial Ball Bearing

This paper contains elements of a comprehensive research devoted to the dynamic behavior of radial ball bearings in real working conditions. The general motivation for this topic comes from the requirements for high performance operation of bearings within complex mechanical systems, defined in many industrial branches during the last decades. The discussion of the fundamental postulates of the approach used for analyzing the vibration response of rolling ball bearings in order to select the optimal working conditions is given. The certain simplifications and reductions used for analyzing the radial ball bearings are explained. The developed procedure can be used for research of influence of different damages and variable operation conditions on the rolling bearings dynamics. The detail analyses of the dynamic behavior of rolling bearings are performed for particular types of radial ball bearings in two case studies: For the damaged outer raceway surface in accordance with real fatigue damage shapes and dimensions and, for variable working temperature. Obtained results are shown by comparative diagrams of vibration and phase plane portraits. Presented results could be a base for more widely research of nonlinear dynamics of radial ball bearings with different damages and for the application of phase plane analysis in order to choose the optimal operation conditions