Introduction

In the last lecture, we have shown different types of springs commonly used for isolation. In this lecture, we will consider vibration isolation of a SDOF system using a generalised spring element. Such springs have complex stiffness indicating the capability working both as a spring and a damper. Infact there are two ways in which a spring can also show damping behaviour:

1. if the spring is made of rubbery material then it will have complex elastic modulus and hence will show damping
   
   
2. springs like transversely loaded spring could dissipate energy due to the friction between the spring outer surface and the supporting frame.