Felicity ratio

The Kaiser effect (Kaiser 1953) has been applied as to know the initial stress condition of rock materials (Yoshikawa and Mogi 1989). Based on the Kaiser effect, T. Fowler proposed the Felicity ratio (Fowler 1986), which can show the damage quantitatively in tank stractures. The Felicity ratio was established because of the following feet. The Kaiser effect can only hold in the stable condition of the materials (i.e., intact condition). As to progress the internal instability, the Kaiser effect is gradually breaking down. As a result, AE activity starts to be observed even under lower stress than that of the maximum stress experienced. 

Recently, the same idea as the Felicity ratio has been applied for the damage assessment of concrete structures (NDIS2421 2000). In this reference the ratio was referred to as the load ratio (ratio of load at the onset of AE activity to previous load). Fundamentally the load ratio is obtained from Eq. 4.1. Differed from the Felicity ratio, the load ratio is obtained from any kinds of AE parameters at the onset of AE activity Pae-... 

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