LASER ULTROSONIC INSPECTION OF CONCRETE STRUCTURES

AN IMPROVED ULTRASONIC SYSTEM USEFUL FOR THE FIELD INSPECTION OF CONCRETE STRUCTURES IS PROPOSED. IMPROVEMENTSINCLUDE A RELIABLE LASER PULSE METHOD TO GENERATE THE ULTRASONIC SIGNAL AND ANALYSIS OF THE RETURN SIGNAL IN TERMSOF AMPLITUDE, TIME AND FREQUENCY. A NOVEL FLAT FREQUENCY RESPONSE ULTRASONIC TRANSDUCER WILL AID THE FREQUENCY ANALYSIS. THE LOW-POWER LASER INPUT TRANSDUCER IS EXPECTED TO PROVIDE RELATIVELY HIGH IMPULSE AMPLITUDES BECAUSE OF THECHARACTERISTIC ACOUSTIC IMPEDANCE AND THERMAL PROPERTIES OF THE CONCRETE. ONE MAJOR OBJECTIVE OF THE PROGRAM IS THE DETERMINATION OF THE OPTIMUM LASER CONDITIONS IN TERMS OF LASERPOWER, PULSE WIDTH AND SPOT SIZE. SIGNAL DETECTION IN THE PLANNED PULSE-ECHO APPROACH WILL INCLUDE WORK WITH BOTH CONVENTIONAL ULTRASONIC TRANSDUCERS AND A NOVEL FLAT-RESPONSE TRANSDUCER. EACH OF THESE WILL BE INVESTIGATED TO DETERMINE THE SIGNAL ANALYSIS METHOD TO OPTIMIZE INSPECTION INTERPRETATION FOR CONCRETE DEGRADATION AND CRACKING. THE FEASIBILITY STUDY WILL PAVE THE WAY TO DEVELOP A BROADLY USEFUL SYSTEM TO INSPECT CONCRETE. GOOD COMMERCIAL PROSPECTS CLEARLY EXIST FOR AN IMPROVED METHOD TOINSPECT CONCRETE IN THE FIELD.