Application Cases

Experiment Name: Research on Damage Identification of Wood Connections Based on Piezoelectric Sensing Technology

Research Direction: Nondestructive testing, damage localization

Experiment Objective: To conduct experimental research on damage identification at mortise-tenon joints in wooden structures based on the piezoelectric active sensing method, and to explore the feasibility of using this method to detect damage at such joints.

Testing Equipment: ATG-2021B power signal source, laptop computer, test specimen

Experimental Procedure:
PZT1, acting as the actuator, generates stress waves that propagate through the structure and are received by PZT2, acting as the sensor. When damage occurs in the structure, the energy of the propagating stress wave decreases. The stress wave signal received by PZT2 weakens compared to that in the healthy state. An increase in damage severity correspondingly leads to a further reduction in the received stress wave energy, thereby enabling the identification of structural damage.

Figure 1: Sensor-based active monitoring method

The experimental setup consists of a piezoelectric signal monitoring and analysis system, a laptop computer, and a test specimen. The piezoelectric patches are circular discs with a diameter of 15 mm and a thickness of 0.3 mm. They are encapsulated in a stainless steel shell for protection, allowing the patches to be reused. The sampling frequency of the data acquisition system is 1 MHz. A sinusoidal sweep signal with an amplitude of 10 V and a frequency range of 100 kHz–300 kHz is input to the piezoelectric ceramic actuator. The actuator generates stress waves that propagate through the mortise-tenon joint wooden specimen. When the stress waves reach the other end of the mortise-tenon joint, they are sensed by the piezoelectric sensor at the receiving end. Based on the direct piezoelectric effect, the collected stress wave signals are converted into voltage signals. By comparing the differences in the voltage signals from the receiving sensor before and after damage, information about the damage at the mortise-tenon joint connection can be obtained.

Figure 2: Damage condition setup

Experimental Results:

Figure 3: Signal diagram for Condition A

Figure 4: Signal diagram for Condition B

Figure 5: Signal diagram for Condition C

For Conditions A, B, and C, the stress wave signals collected by the receiving piezoelectric sensor are shown in Figures 3, 4, and 5, respectively. Due to differences in the connection methods and the types of damage introduced, the signals vary among the three conditions. Even for the same type of damage, the signals exhibit unique characteristics because of significant changes in the connection interface. In Conditions A, B, and C, the signal intensity shows a decreasing trend as the damage severity increases. Among the three damage conditions, the signal intensity decrease is most pronounced in Condition B. The signal diagrams qualitatively reflect the gradual increase in damage severity.

Figure: Specifications of the ATG-2000 Series Power Signal Source