Method and apparatus for visualization of internal stresses in solid non-transparent materials by ultrasonic techniques and ultrasonic computer tomography of stress

An apparatus for visualization of internal stresses in solid materials by scanning acoustic imaging comprising:

• means for supporting a sample to be examined;
• ultrasonic transmitter means supported in spaced relationship to said sample support means for producing and directing transmitted ultrasonic waves toward said sample to produce acoustic waves reflected by said sample;
• ultrasonic receiver means for receiving said acoustic waves produced by said transmitted ultrasonic waves and reflected from said sample, said ultrasonic receiver means emitting signals representing said acoustic waves received by said receiving means;
• motor drive means operatively connected to said ultrasonic transmitter means and said ultrasonic receiver means for moving said ultrasonic transmitter and receiver means with respect to said sample for scanning said sample;
• imaging means operatively connected to said ultrasonic transmitter means, said ultrasonic receiver means and said motor drive means for operating said motor drive means, for exciting said ultrasonic transmitter means to produce said transmitted ultrasonic waves, and for receiving said signals from said ultrasonic receiver means produced by said reflected acoustic waves so that said imaging means detects differences in intensity of said reflected acoustic waves as an indication of internal stress in said sample, said imaging means emitting signals indicating said differences in intensity;
• and
• computer means operatively connected to said imaging means for controlling said imaging means and receiving said signals therefrom indicating said differences in intensity of said signals transmitted by said ultrasonic receiver means and for visually displaying said signals from said imaging means to show said differences in intensity.

A process for visualization of internal stresses in solid materials by scanning acoustic imaging for ultrasonic computer tomography of stress comprising:

• providing an ultrasonic means comprising an ultrasonic transmitter and an ultrasonic receiver;
• supporting a sample comprising a body of solid material to be examined;
• supporting said ultrasonic means in spaced relationship to said sample;
• exciting said ultrasonic transmitter to produce transmitted ultrasonic waves;
• directing said transmitted ultrasonic waves toward said body to produce a surface polarized mode, a shear polarized mode and quasi-longitudinal polarized modes in said body;
• scanning said sample by moving said ultrasonic means relatively to said sample for receiving with said ultrasonic receiver means polarized acoustic waves reflected from said sample and produced by said transmitted ultrasonic waves;
• producing acoustic images using said polarized modes;
• measuring the amplitude of said received acoustic waves to analyze distribution of internal stress in said sample;
• calculating an initial estimate of stress distribution values of said images;
• determining a stress-depth profile from said shear polarized mode images;
• determining a stress-depth profile from said surface polarized mode images;
• determining a stress-depth profile from said quasi-longitudinal polarized mode images;
• and
• determining when said profiles are equal to said calculated stress distribution values as a function of depth.