Mechanical vibrations have attracted the attention of engineers and researches long time ago. Vibration problems require a deep understanding of mathematical modelling and signal analysis, but they also require practical experience. Even though there is abundant literature about the subject, there are still many unknown answers from modelling through measurement interpretation. The scope of it is the identification of discontinuities in the stiffness properties of mechanical systems, and how these discontinuities affect its behaviour. The authors seek to find, with a practical perspective, those parameters that cause non-linearities, or modify the stiffness properties.