B. Łazarz

Vibration Processing Techniques for Fault Detection in Gearboxes

Vibration analysis is a very important tool in condition monitoring of operating machines. Many signal processing methods have been developed to extract information about incipient faults from externally measured vibration signals. The article presents the laboratory examinations of some faults in spur and helical gears. In case of spur gears two types of progressing local faults of cracked and chipped gear tooth were simulated and the smoothed pseudo Wigner-Ville distribution was used to demonstrate fault advancement via residual vibration signal analysis. Observing changes in the features of the WV distribution in the contour plots and changes of Kurtosis value monitored the progression of a fault. In case of helical gears some signal changes of transverse vibration velocity of shafts during the process of pitting growth in the tooth working surface have been investigated. Some new indices of pitting wear have been suggested and compared with other non-dimensional discriminants.Copyright

Simulation and Laboratory Studies on the Influence of Selected Engineering and Operational Parameters on Gear Transmission Vibroactivity

The optimization of the construction of gears leading to the minimization of dynamic effects and to meet all basic criteria is in many cases only possible by applying numerical methods. The models allow determining the influence of a range of factors on the dynamic phenomena. Proper experimental tests are often not possible because the number of options of influencing factor sets is very large. Using simulation models allows limiting the volume of experimental studies to the necessary minimum, and hence is beneficial from the economic standpoint. The paper describes numerical and laboratory researches on the influence of selected construction, technological and operational factors on the dynamic effects and vibroactivity in gears. Numerical analyses were performed using a custom-developed dynamic model of a test stand with the gears operating in the circulating power system. The models details were presented at the International Congress on Technical Diagnostics in 2008. The idea behind this article is to present selected results of simulation calculations and laboratory tests to determine the possibility of minimizing the noise and vibration of gears. Selected results of the calculations were also compared with the results of laboratory tests to demonstrate the high compatibility of the two test methods.

Modelling of Power Transmission Systems for Design Optimization and Diagnostics of Gear in Operational Conditions

This article presents the authors dynamic model of power circulating gear test stand. It was assumed, that properly defined and next identified model can be used to analyze dynamic phenomena in meshing and bearings of gears and allows optimizing their construction, especially to minimize their vibroactivity. The article includes description of the construction of a test-stand, as well as short characteristic of the dynamic model. Afterwards it was presented verification, whether the model was correctly fine tuned. For verification purpose, were conducted laboratory measurements of velocity of transversal vibrations at the test-stand using laser vibrometer. Results of laboratory examinations were compared with the results achieved during computer simulation. Developed and presented dynamic model take into account a number of design, technological and operational parameters of gear. It was also presented algorithm of researches aimed at minimizing the vibroactivity of gear.

Coil springs in passenger cars – general theoretical principles and structural requirements

The main role of the coil springs, as any kind of elastic elements is shock absorption caused by the movement of the so called unsprung masses (wheels, brakes, suspension components) on the uneven ground. This is to ensure not only driving comfort, but also protect the car from damage. The article presents the principles of strength calculations for coil springs used in the suspension of contemporary cars. Modern technological and structural solutions in contemporary cars are reflected also in the construction and manufacture of coil springs. A proper construction and the selection of parameters influence the strength properties, the weight, durability and reliability as well as the selection of an appropriate production method. An improper preparation of Finite Element Method calculation models consequently leads to wrong results. It is particularly difficult to interpret the results and to find an error if we do not have a comparative calculation base (such as results of fatigue tests, analytical strength calculations). Coil springs with linear and progressive characteristics were taken into consideration. In article was conducted a comprehensive calculation of these springs (analytically and FEM using) in order to show the differences and problems in the construction process. A proper selection of springs, that is also taking strength parameters into consideration, has a fundamental effect on correct functioning of the suspension of motor vehicles.

Simulation Studies of the Effect of Shaft's Nonlinear Flexural Stiffness Parameters for Critical States of Rotating Power Transmission Systems

The paper presents simulation studies, performed using Simulink, the impact of nonlinear flexural stiffness of shafts for critical speed range and amplitude of vibration. The tests were performed on the selected model of a rotating machine, consisting of a drive, two torsional vibration dampers, shaft with mounted on it two rigid rotors (discs), supported on a three self-aligning roller bearings and mechanical power receiver (brake). The machine startup and braking with crossing the critical states was simulated using specialized Simulink library, which was developed by authors for analysis of transient states in rotating machines and flexural-torsional couplings. In accordance with the concept of modeling adopted by the authors, rotating system is divided into inertial rigid elements (rotors, bearings, clutches, etc..) and compliance elements (parts of the shaft). The main component of the currently developed library is block modeling rigid rotor with 6 degrees of freedom and with the static and dynamic unbalance. By assumption the library is a modular, expandable and allows modeling the systems of any configuration. The goal of the simulation was to verify how nonlinear flexural stiffness of shaft influences the values of critical speeds and the level of flexural and torsional vibrations.