Defect detecting method and apparatus

A detecting apparatus, comprising:

• vibrating means for vibrating an object to be measured for a period time;
• pick up means for picking up the vibration of said object to be measured after vibrating said object for said period of time;
• and
• computation process and determination means for receiving said electric signal from said pick up means, for analyzing the spectrum of the characteristic vibration of said object to be measured, and for determining whether a spectrum due to a defect of said object to be measured is present or absent to detect whether said defect is present or absent;
• and
• wherein said computation process and determination means includes means to determine the width of the resonances of the spectrum.

A defect detecting method for detecting defects in an object, comprising the steps of:

• applying a vibration to said object;
• picking up a vibration waveform from said object;
• recording said vibration waveform from between a first time after a peak value of said vibration waveform and a second time after said first time;
• applying to a recorded vibration waveform, an emphasizing window which emphasizes said recorded vibration waveform, thereby defining an emphasized vibration waveform;
• transforming the emphasized vibration waveform to frequency domain to form a characteristic vibration spectrum, wherein said characteristic vibration spectrum has all peaks corresponding to each vibrational order of said object in a limited frequency range;
• and
• detecting whether or not a peak of said transformed vibration spectrum is separated into two portions, wherein a separation of said peak indicates at least one defect in said object.

A defect detecting apparatus for detecting defects in an object, comprising:

• first applying means for applying a vibration to said object by impacting said object;
• picking up means for picking up a vibration waveform from said object;
• gate means for gating said vibration waveform from between a first time after a peak value of said vibration waveform and a second time after said first time;
• recording means for recording a gated vibration waveform from said gate means;
• second applying means for applying to a recorded vibration waveform, an emphasizing window which emphasizes said record vibration waveform, thereby defining an emphasized vibration waveform;
• transforming means for transforming the emphasized vibration waveform to frequency domain to form a characteristic vibration spectrum, wherein said characteristic vibration spectrum has all peaks corresponding to each vibrational order of said object in a limited frequency range;
• and
• detecting means for detecting whether or not a peak of said transferred vibration spectrum is separated into two portions, wherein a separation of said peak indicates at least one defect in said object.