System and method for measuring damage length

1. A damage length measurement system for measuring a length of damage that occurred in an object being measured, the system comprising:

an oscillator that applies an ultrasonic vibration to the object;

a plurality of vibration detection sensors at mutually different positions that detect a vibration wave that propagates through the object from the oscillator; and

a measurement apparatus that controls the vibration of the oscillator, and analyzes the vibration wave that was detected by the vibration detection sensors by means of processing detected signals from the vibration detection sensors,

wherein the measurement apparatus is constructed such that it:

(1) executes a process of calculating arrival times of maximum peaks of the vibration wave detected by at least two vibration detection sensors that are selected from the plurality of vibration detection sensors, and calculating a difference between the arrival times;

(2) executes a process, following process (1), of determining whether or not the difference between the selected sensors is within a set reference range considering a vibration propagation time between the at least two vibration sensors;

(3) executes a process, when it is determined in process (2) that the difference is within the reference range, of calculating the damage length based on a delay time with respect to a calibration value of the arrival times of the maximum peaks;

(4) executes a process, when it is determined in process (2) that the difference is not within the reference range, of detecting a peak that arrived before the maximum peak and has a specified vibration amplitude or greater for at least one of the at least two vibration detection sensors related to the difference; and

(5) executes a process, when the peak having the specified vibration amplitude or greater is detected in process (4), of replacing the arrival time of the maximum peak with the arrival time of that peak and calculating the difference in the process (1), and then executing processes (2) and (3).

2. The damage length measurement system according to claim 1 , wherein

the system has three or more vibration detection sensors, and

the measurement apparatus is constructed such that:

in process (1) it calculates the difference between the maximum peak of the vibration wave detected by a specified vibration sensor and the maximum peak of the vibration wave detected by each of the other vibrations sensors

in process (2) it determines whether or not each difference is within the reference range; and

in process (4), when none of the differences is within the reference range, for the specified vibration detection sensor, it detects a peak that arrived before the maximum peak and that has the specified vibration amplitude or greater.

3. A damage length measurement method for measuring a length of damage that occurred in an object being measured, the method comprising the steps of:

applying an ultrasonic vibration to the object by an oscillator;

detecting at mutually different positions a vibration wave that propagates through the object from the oscillator by a plurality of vibration detection sensors; and

executing a measurement process of controlling the vibration of the oscillator, and analyzing the vibration wave that was detected by the vibration detection sensors by means of processing detected signals from the vibration detections sensors,

wherein the measurement process:

(1) executes a process of calculating arrival times of maximum peaks of the vibration wave detected by at least two vibration detection sensors that are selected from the plurality of vibration detection sensors, and calculating a difference between the arrival times;

(2) executes a process, following process (1), of determining whether or not the difference between the selected sensors is within a set reference range considering a vibration propagation time between the at least two vibration sensors;

(3) executes a process, when it is determined in process (2) that the difference is within the reference range, of calculating the damage length based on a delay time with respect to a calibration value of the arrival times of the maximum peaks;

(4) executes a process, when it is determined in process (2) that the difference is not within the reference range, of detecting a peak arrived before the maximum peak and that has a specified vibration amplitude or greater for at least one of the at least two vibration detection sensor related to the difference; and

(5) executes a process, when the peak having the specified vibration amplitude or greater is detected in process (4), of replacing the arrival time of the maximum peak with the arrival time of that peak and calculating the difference in the process (1), and then executing processes (2) and (3).

4. The damage measurement method according to claim 3 , wherein

the method uses three or more vibration detection sensors, and

the measurement process:

in process (1) calculates the difference between the maximum peak of the vibration wave detected by a specified vibration sensor and the maximum peak of the vibration wave detected by each of the other vibrations sensors

in process (2) determines whether or not each difference is within the reference range; and

in process (4), when none of the differences is within the reference range, for the specified vibration detection sensor, detects a peak that arrived before the maximum peak and that has the specified vibration amplitude or greater.