Time-frequency analysis (TFA) for mechanical vibrations in non-stationary operations is the main subject of this article, concisely written to be an introducing tutorial comparing different time-frequency techniques for non-stationary signals. The theory was carefully exposed and complemented with sample applications on mechanical vibrations and nonlinear dynamics. A particular phenomenon that is also observed in non-stationary systems is the Sommerfeld effect, which occurs due to the interaction between a non-ideal energy source and a mechanical system. An application through TFA for the characterization of the Sommerfeld effect is presented. The techniques presented in this article are applied in synthetic and experimental signals of mechanical systems, but the techniques presented can also be used in the most diverse applications and also in the numerical solution of differential equations.

非平稳操作中的机械振动的时频分析（TFA）是本文的主要主题，简明扼要地是作为比较非平稳信号的不同时频技术的入门教程。该理论经过仔细地揭示，并辅以机械振动和非线性动力学方面的示例应用程序。在非平稳系统中也观察到的一种特殊现象是Sommerfeld效应，它是由于非理想能源与机械系统之间的相互作用而发生的。提出了通过TFA表征Sommerfeld效应的应用。本文介绍的技术适用于机械系统的合成和实验信号，