Structural damage detection system, device and method

A structural damage detection device, comprising:

• a tapper being configured to tapping on a surface of the structure under detection with, a tapping force at a predetermined frequency band;
• a sensor being configured to measure tapping response signals transmitted from the surface of the structure under detection to the tapper, wherein the tapping response signals measured by the sensor comprises at least one of displacement, velocity and acceleration;
• wherein the tapper and the sensor are integrated together, so that the sensor measures the tapping response signals transmitted from the surface of the structure under detection to the tapper while the tapper is tapping on the surface of the structure under detection;
• a signal processor being configured, to process the signals measured by the sensor in the structural damage detection device so as to determine a position of damage in the structure under detection, the signal processor being configured to execute programs comprising instructions to perform the following:
• transform the signals measured by the sensor so as to acquire the signal spectrum at positions of the structure surface;
• intercept from the signal spectrum a spectrum envelope corresponding to the predetermined frequency band of the tapping force;
• calculate a damage indicated value at each of the positions of the surface of the structure, the damage indicated value reflecting a degree of similarity between the spectrum envelope at one position and the spectrum envelope at other positions;
• and
• determine a position of damage in the structure based on the damage indicator at each of the positions of the surface of the structure;
• wherein the signal processor generates a spectrum vector corresponding to the spectrum envelope at a corresponding position, wherein each component of the spectrum vector comprises the spectrum value corresponding to a certain frequency in the spectrum envelope;
• wherein the signal processor calculates the damage indicated value to reflect the degree of similarity between the spectrum vector at the current position and the spectrum vector at other positions;
• and
• wherein the signal processor calculates the damage indicated value as:
• (
• ∑
• j
• =
• 1
• ⁢
• …
• ⁢
• ⁢
• n
• ⁢
• Y
• i
• ·
• Y
• j
• 
• Y
• i
• 
• ×
• 
• Y
• j
• 
• )
• ⁢
• /
• ⁢
• n
• where Yi and Yj are the spectrum vectors at one position, represented by i, and at other positions, represented by j, in the structure respectively, a calculator • is an inner product calculation of the
• spectrum vector, |Yi| and |Yj| are lengths of the vectors Yi and Yj, and n is the number of the measured positions in the structure.

A structural damage detection method for detecting damage of a structure, comprising:

• scanning along a structure surface with a tapper, wherein the tapper taps with a tapping force at a predetermined frequency band while scanning;
• measuring tapping response signals transmitted from the structure surface to the tapper at positions of the structure surface by a sensor, wherein the tapping response signals measured by the sensor comprises at least one of displacement, velocity, and acceleration;
• transforming the tapping response signals measured by the sensor to acquire a signal spectrum at the position of the structure surface;
• intercepting from the signal spectrum a spectrum envelope corresponding to the predetermined frequency band of the tapping force;
• calculating a damage indicated value at each of the positions of the structure surface which reflecting a degree of similarity between the spectrum envelope at each of the positions and the spectrum envelope at other positions;
• and
• determining a position where the damage indicated value changes abruptly as a position of structural damage;
• wherein calculating the damage indicated value at each of the positions of the structure surface comprises:
• generating a spectrum vector corresponding to the spectrum envelope at each of the positions, wherein each component of the spectrum vector is the spectrum value corresponding to a certain frequency in the spectrum envelope;
• calculating the damage indicated value to reflect the degree of similarity between the spectrum vector at one position and the spectrum vector at other positions by calculating a MAC coefficient matrix as:
• MAC
• ⁡
• (
• i
• ,
• j
• )
• =
• Y
• i
• ·
• Y
• j
• 
• Y
• i
• 
• ×
• 
• Y
• j
• 
• where Yi and Yj are the spectrum vectors of the ith position and the jth position in the structure respectively, a calculator • is an inner product calculation of the spectrum vector, |Yi| and |Yj| are lengths of the vectors Yi and Yj;
• and determining the damage indicated value at the ith or jth position based on the relative magnitude of the element in a line or a column of the MAC coefficient matrix corresponding to the ith or ith position.