Resonant frequency method for bearing ball inspection

A method for inspecting a test object for defects, comprising the steps of:

• focusing expansion inducing energy at a first limited area on said test object, thereby inducing expansion of said test object at said first location;
• allowing said first location to contract from said expansion, such that wave action is excited within and on the surface of the test object, thereby creating waves;
• determining displacement data by detecting, at a second location on the test object, displacement of said waves caused by said defects, said displacement data comprising amplitude and phase of said waves;
• determining resonant frequencies of said test object from said detected displacement data;
• calculating quality factors of said resonant frequencies;
• comparing said quality factors to predetermined defect data;
• and
• indicating whether the test object contains defects according to said comparing step.

A photoacoustic test object inspection system for detecting defects in a test object, comprising:

• generating means for pulse generating expansion inducing energy, such causing expansion of said test object;
• directing means for directing said energy on to the surface of the test object at a first location wherein wave action may be excited within and on the surface of the test object, thereby creating acoustic waves;
• detecting means at a second location for detecting the amplitude and phase of normal displacement of said acoustic waves;
• determining resonant frequencies of said test object from said amplitude and said phase of said acoustic waves;
• calculation means for calculating quality factors of said resonant frequencies;
• correlation means for correlating said quality factors to predetermined defect data;
• and
• indication means for indicating the correlation between said quality factor and said predetermined defect data.