Four-Parameter Model

Figure 13.2: Four parameter model

Figure 13.2 shows a four parameter model. In the frequency domain, the equivalent model could be shown as

Figure 13.3: Equivalent 4 parameter model

The stress-strain relationship may be expressed as

or

After inverse Laplace transformation one may write it as:

Considering the characteristic length of the system to be ‘l' and cross sectional area A, we can represent the above relationship in terms of stress and strain

as

After inverse laplace transformation, the governing equation in time domain may be expressed as

Hence, the system parameters are