An experimental crack detection system is developed based on the natural frequency changes . In the detecting system , we employed a Maharanobis discri 皿 inant analysis , which is a usefU1 way of determining s 血 ilah 耀 of an un 】 mown sample set tO a known one . MonitOring the Mahalanobis distance of unknown specimen and compa 血 g the distance of the 8pecimen with that ef un ・ cra磁 ed specimens , we can detect a crack position and a crack depth simultaneou81y と Usi皿 g both the statis 廿cal

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... 五ca 廿on method and Excel macro program , we have accomphshed the rea 卜t洫 e detect 血 g system . Key Word8 :Crack DetecUon , Mahalanobis Distance , Natural Frequencies, FFT , llinke Element Method