The vibration testing of components in the automotive industry requires long testing times and the use of expensive facilities. To shorten these testing times an accelerated vibration-testing approach is usually applied. This research tries to shorten these testing times by considering the parameters that define vibration-testing techniques. With special attention to the excitation types sweep-sine and random, a damage-based approach is applied. The phenomenon of fatigue damage is closely observed from the frequency-domain point of view but also by considering the relationship between the time and the frequency domains. The Palmgren-Miner cumulative rule is applied to calculate the fatigue life. Two case studies of measured responses are used to compare the times to failure. The results show that proposed predictions can be used to compare different testing techniques, but they are not so accurate when predicting the actual times to failure.
COBISS.SI-ID: 14012955
In the design process of every modern car, the appropriate acoustic behaviour of each integral part is of great importance. This is particularly so for gearboxes. The stiffness of a rolling-element bearing is one of the main contributors to the transmission of vibrations from the interior of the gearbox to the housing. Many methods have been proposed to determine the bearing stiffness; this stiffness is related to the load in a nonlinear way. In this article, a new method for defining the proper bearing stiffness of statically overdetermined gearboxes is proposed. To achieve this an iterative process is conducted, with an initial guess for the loads on the bearings, which provides the initial values for their stiffnesses. The calculated stiffnesses are then inserted into a finite element method (FEM) model of a gearbox, where the new load vectors on the bearings are calculated. The described process runs until the convergence of the loads on the bearings is reached. Afterwards, the frequency-response functions (FRFs) are numerically calculated. As a reference point for our calculations, the measured FRFs are obtained. The measurements were performed on a simple, but statically overdetermined, gearbox with the option for moment adjustments between the two shafts. The calculated results in the form of FRFs are compared with the measurements.
COBISS.SI-ID: 14009883