Safe life and damage tolerance aspects of railway axles – A review

Modeling and analysis of a spur gear pair considering multi-state mesh with time-varying parameters and backlash

Calculation of the boundary values of rolling bearing deflection in relation to the number of active rolling elements

Tooth profile shift will change the thickness of gear teeth and a part of geometrical parameters of a gear pair, thus influencing its mesh stiffness and consequently the dynamic performances. In this paper, an analytical mesh stiffness calculation model for an internal gear pair in mesh considering the tooth profile shift is developed based on the potential energy principle. Geometrical representations of the tooth profile shift are firstly derived, and then fitted into the analytical tooth stiffness model of gears. This model could supply a convenient way for mesh stiffness calculation of profile shifted spur gears. Then, simulation studies are conducted based on the developed model to demonstrate the effects of tooth profile shift coefficient on the tooth compliances and the mesh stiffness of the internal spur gear pair. The results show that tooth profile shift has an obvious influence on the mean value, amplitude variation and phase of the mesh stiffness, from which it can be predicted that the dynamic response of an internal gear transmission system will be affected by the tooth profile shift.

Mesh stiffness evaluation of an internal spur gear pair with tooth profile shift

Catcher bearings (CB) are an essential component for rotating machine with active magnetic bearings (AMBs) suspensions. The CB’s role is to protect the magnetic bearing and other close clearance component in the event of an AMB failure. The contact load, the Hertzian stress, and the sub/surface shear stress between rotor, races, and balls are calculated, using a nonlinear ball bearing model with thermal growth, during the rotor drop event. Fatigue life of the CB in terms of the number of drop events prior to failure is calculated by applying the Rainflow Counting Algorithm to the sub/surface shear stress-time history. The numerical simulations show that CB life is dramatically reduced when high-speed backward whirl occurs. The life of the CB is seen to be extended by reducing the CB clearances, and by applying static sideloads to the rotor.Copyright © 2011 by ASME

Catcher Bearing Life Prediction Using a Rainflow Counting Approach

Studying the load carrying capacity of spur gear tooth flanks

The load distribution in machine elements is the first step in the analysis of their operating condition. Because of influence of many various factors, constructional and technological, it is very difficult to determine precisely a real condition – real load distribution without the approximations – hypotheses. The load distribution is basic input in mechanical and mathematical modelling with the purpose of the analysis of machine parts operating conditions from different relevant aspects: durability, stiffness, reliability and stability. Because of that, the modelling of load distribution is a very responsible and difficult task. The existing models of load distribution in rolling bearings [1], gear transmissions, chain transmissions etc. contain many approximations and empirical coefficients, which have no the appropriate physical basis. Load distribution in rolling bearings, which operate in condition of the time limited endurance, has a dominant influence on bearing durability. The small vibrations, noise and friction losses are required from the rolling bearings. The large operational safety, load carrying capacity, durability, and accuracy of rotation are required, as well. Hence, developed mathematical models of rolling bearings, their technology of manufacturing and assembly, as well as design optimization were improved. The special place at designing and optimization of rolling bearings has load distribution between rolling elements. The mathematical model developed in this paper establishes correlation between elastic deformations of the bearing parts in contact, internal radial clearance and external radial load distribution between rolling elements of the ball bearing. Developed mathematical model can be used for more exact analysis of load distribution between rolling elements, and for more reliable determination of the bearing carrying capacity, durability and power losses.

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Mathematical model of load distribution in rolling bearing

Research of rail traction shafts and axles fractures towards impact of service conditions and fatigue damage accumulation

Investigation of causes of fan shaft failure

Tramway transit has an important place within the public transportation system of Belgrade. However, due to the very unfavorable age structure, the bad condition of tramway tracks and infrastructure, as well as the maintenance system that require significant advancement, Belgrade tramways are in very bad repair, so the transport requirements are not properly met. The principal task of the analysis presented in this paper is to recognize and estimate the justifiability of investment into various solutions for revitalization of Belgrade tramway rolling stock. We have chosen a somewhat different from usual approach to decision making, that is, applied a combination of cost-benefit, life-cycle cost and multi-criteria analysis.

Tatjana Lazović

Papers

Studying the load carrying capacity of spur gear tooth flanks

Mathematical model of load distribution in rolling bearing

Research of rail traction shafts and axles fractures towards impact of service conditions and fatigue damage accumulation

Investigation of causes of fan shaft failure

Application of new decision making model based on modified cost-benefit analysis — a case study: belgrade tramway transit