Damping factor as an indicator of crack severity

When a material is subjected to an alternating stress field there are tempe rature fluctuations throughout its volume due to thermoelastic effect. The resulting irreversible heat conduction leads to entropy production, which i n turn is the cause for thermodynamic damping. An analytical investigation of the entropy produced during a vibration cycle due to the reciprocity of temperature rise and strain yielded the change of the material damping fact or as a function of shape and magnitude of existing crack in the structure. A homogeneous, isotropic, elastic bar of orthogonal shape is considered wi th a single-edge crack under alternating uniform axial stress. The analytic al determination of the dynamic characteristics of the cracked structure yi elded the damping factor of the bar, the material damping factor and a good correlation of depth of crack with the damping factor. Experimental result s on cracked bars are in good correlation with the analysis. (C) 2001 Acade mic Press.