Research Of Load Spectrum Edition Method Based On The Short-time Fourier Transform To The Durability Tests Of Automotive Components

In order to improve the accuracy and efficiency of the durability test,the aspects including load-time history acquisition method,load spectrum edition method and automotive component bench test are studied in this research.By applying the proposed research method to automotive product development,it can achieve product durability evaluation quickly and accurately.Moreover,it is possible to shorten product development cycle and reduce the research and development costs.The research has important theoretical and engineering application values.The main works in the dissertation are listed as follows:(1)The theory of short-time Fourier transform and window function is discussed,and the window function of intercepting signal in the transform is selected.Taking a typical signal as an example,the signal is subjected to the short-time Fourier transform to obtain accumulative power spectral density of the signal.The accumulative power spectral density is used to identify and extract the damage parts from the signal,which lays the foundation for the subsequent application of the short-time Fourier transform to the load spectrum edition of automotive components.(2)The acquisition process and program for the load signals of automotive components are formulated.The acquisition method of the load-time history for the powertrain rear mount is discussed,and the collected original load-time history has been pre-processed.(3)Based on the theory and method of short-time Fourier transform,a method for editing the load spectrums of automotive components is proposed.The pre-processed load-time history of the powertrain rear mount is edited based on the short-time Fourier transform,and the accumulative power spectral density threshold selection process is optimized by using the genetic algorithm.Moreover,The damage-preservation editing method is also used to edit the load-time history of the powertrain rear mount,and the compression load spectrums under the two editing theories are obtained respectively.(4)The parameters including damage retention,statistical parameters(mean,root mean square,and kurtosis coefficient)and amplitude of the compression load spectrums are compared with the original load-time history.And the compression load spectrums are applied to compare the stiffness changes of the powertrain rear mounts before and after the durability test.The results show that the static stiffness changes of the powertrain rear mounts before and after the test under the two editing methods are basically the same,indicating the compression load spectrum based on the short-time Fourier transform can replace the original load-time history for durability test better and the load spectrum edition method based on the short-time Fourier transform is effective.