<div class="section abstract"><div class="htmlview paragraph">The vehicle industry being in the middle of transformation, the development of electric drives has come into engineers’ focus. The parameter evaluation of dynamic systems can be cumbersome when having nonlinearity in the structure, for example nonlinear stiffness characteristics. In such case, the standard linear approach, including EMA (Experimental Modal Analysis), modal superposition, FRF measurement (Frequency Response Function) and modal synthesis can not be applied. However, one of the main challenges in addressing nonlinearities is the lack of general tools to approach them. In this paper, a general framework to study nonlinearities in a structural dynamic context is presented. The method relies on standard random and sine sweep testing approaches to detect and localize nonlinearities, and on dedicated processing techniques to analyze the data and extract information on the nature of the analyzed nonlinearity. This approach is then used to study the behavior of an assembly of a lamella package of PMSM (Permanent Magnetic Synchronous Machines), where permanent magnets are embedded in the laminations. The magnets are surrounded by resin that holds them in place in their grooves. Characterizing the dynamic properties of such a structure is a relevant task in engineering development, for verifying numerical predictions. In this case, the relative motion of lamellas as well as the heavy influence of the polymer resin’s properties may result in nonlinear behavior.</div></div>
Frequency resolution is an essential parameter in acoustical testing, even if we are using numerical or experimental method, for example when determining frequency response function (FRF) of a dynamic mechanical system, or executing modal analysis based on the FRFs. Finer resolution leads to more accurate results, at the expense of longer calculation/measurement process and larger data size. This parameter is generally set based on rules of thumb, prior practice or with big margin for safety. This results in waste time and data storage if the required frequency resolution is overestimated, or even significant errors in the results, if it is underestimated. Present paper offers a direct, method for the conscious determination of optimal frequency resolution. It is based fully on theoretical considerations, and investigates amplitude and phase distortion at resonances as target parameters. Beside defining the steps of the process, it is tested on a real structure, and the results are presented as well, proving the applicability and the appropriateness of the method. With this method, development engineers get a practical tool for adjusting the parameters of dynamic measurements and simulations.
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