13th International Conference on Fracture June 16–21, 2013, Beijing, China -3- initial crack length, C and m are empirical constants of Paris law and f(α) is the shape factor of the stress intensity factor. Indexes 1 and 2 represent smart patch 1 and 2, respectively. By substituting the normalized crack lengths α1 and α2 detected from two smart patches into Eqs. (1) and (2), the cyclic number and the stress amplitude can be estimated as shown in Figure 2. Furthermore, fatigue life will be assessed by substituting the estimated cyclic number and stress amplitude into Miner’s rule.[8] Figure 2. Principle of estimation of cyclic number from crack lengths in two smart patches.[6] 2.2. Estimation of corrosivity in atmospheric environment by ACM Sensor An ACM (Atmospheric Corrosion Monitor) type corrosion sensor, consisting of a Fe-Ag galvanic couple was developed and applied for the evaluation of corrosivity of atmospheric environments. The sensor was designed considering mass-production and good reproducibility of results, making it convenient for long-term corrosion data acquisition. Besides the sensor output, I, temperature, relative humidity (RH) were also recorded by a microcomputer. By analyzing the magnitude and time variation of I, the occurrence and duration of rain, dew and dry periods, Train, Tdew and Tdry, could be distinguished and determined, respectively. And by referencing to the empirical I-RH calibrating curve, the amount of deposited sea salt, Ws, could also be estimated. It was also found that the corrosion loss could be estimated in both indoor and outdoor sites by analyzing sensor output. Corrosivities of some kinds of exposure sites, not only outdoor environments but also indoor environments, were evaluated by using the ACM sensor. Figure 3. Schematic representation of the sensor.[7]
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