A real time algorithm for monitoring the gearbox reliability test Niola V., Quaremba G., Avagliano V. Department of Mechanical Engineering for Energetics University of Naples “Federico II” Via Claudio 21, 80125, Napoli, ITALY vincenzo.niola@unina.it http://niola.dime.unina.it/ Abstract – The aim of this paper is to illustrate a new method for monitoring a gearbox during the reliability test (or duration test). In particular it is illustrated the tune-up of an algorithm for monitoring this test in order to stop it if an unexpected event occurs. In the first part it is explained the reliability test, why and how it is performed on a gearbox. In the second part it is showed the selection of the best points for the measurement and the equipment used for the assessment. In the third part it is presented the algorithm for improving the reliability test. We have settled the algorithm in order to stop the test if the gearbox will be damaged for any reason. By using this algorithm, we can early detect a gear crack, having so the advantage both of providing the integrity of the gearbox and the possibility of inspecting it. Key-Words: - Gearbox, Fourier Analysis, Pitting, Side Bands. 1 Introduction Measurement and analysis of vibration, in order to monitor the working condition of industrial equipments during their life, had a great development during the last 30 years. The vibration analysis is now employed in many fields: from steel factories to petrochemical ones, from mechanical industries to the aviation and aerospace applications. The measurement of vibrations performed on a generic equipment during its working process contains many information on the working condition. Generally, the set-up development or inner mechanical adjustment show a characteristic vibrational pattern; a significative changing of this pattern should reveal the presence of some anomalies in the dynamical system [1,2]. The theoretical basis of the algorithm, subject of this paper, is based on the knowledge that the vibrational signal obtained by the accelerometer processed by means of the spectral analysis is the most efficient technique for monitoring car gearbox; in fact, by monitoring the spectrum signal, we analyze the time evolution of characteristic frequencies of the gearbox components. With such as technique it is possible to detect the anomalies. In fact, every gearbox has a characteristic frequency spectrum but the presence of defects may change this inner spectrum in several ones depending on the type of defect itself [3,4]. It is well known that before the production and commercialization of a new designed gearbox it is necessary to assess many reliability tests. One of these concerns the gearbox with the duration test. 2 Duration test assessment The duration test is performed after the gearbox passes the check on the lubrication test. Therefore, a running-in for all the gears is planned. During this one, the gear transmission works at low rotation velocity (2000 – 2500 rpm) with low value of torque (roughly the 10% of the maximum torque). When this phase is termed, and after the substitution of the lubricate, the reliability test (duration test) can start. This test consists of a gearbox running for a huge number of kilometres for all the gears, both in condition of maximum torque and in condition of maximum rotation velocity. The maximum torque and power, and the relative rotation velocity, are set on the basis of the features of engine and gear ones. Because the test is the same for all the gears, this paper shows the test for one gear only. For that the first gear was chosen. The rotation velocities are: • 2500 rpm, condition of maximum torque • 4000 rpm, condition of maximum power. The total distance that the gear transmission must realize in first gear is named 1 D . The 1 D distance is not realize in one step, but in N steps of equal length 1 1 d D N = . The value chosen for N is 100, so if a gear transmission doesn’t show any damage after 100 steps, it means that the 100% of the test is achieved. As said before, each single step includes two others: the first, in which the gearbox is in the condition of maximum torque, the second one when it is in the condition of maximum power. WSEAS TRANSACTIONS on SYSTEMS V. Niola, G. Quaremba, V. Avagliano ISSN: 1109-2777 866 Issue 7, Volume 8, July 2009