Abstarct: Structural health monitoring is an area that has been widely considered by many aerospace, civil and mechanical engineers due to its importance and significant impact on increasing life safety and economic benefits. Among the various methods proposed in the field of structural health, the method baxsed on electromechanical impedance, while being simple in the implementation stage, has provided acceptable results in identifying structural damage. This method makes it possible to detect structural damage by examining the frequency response using piezoelectric transducers installed on the structure. In which the transducer acts simultaneously as an actuator and sensor, and by reducing the electrical wiring and the number of transducers, facilitates damage detection with ease of execution. Despite the promising benefits, there are significant limitations in identifying small defects in the structure because the methods proposed so far were linear methods that could only detect large defects in the structure. To address the limitations, this dissertation has presented a new method in which the use of structural health monitoring baxsed on nonlinear electromechanical method has reliably identified small damages caused in the structure. This is achieved by installing a piezoelectric converter on aluminum foil. And loosening the screw is considered damage. In order to detect the screw loosening damage, a voltage of 10 to 120 V at high frequencies up to about 32 kHz is applied to the structure and the piezoelectric frequency response is analyzed by two methods of frequency change and harmonic formation around the resonant frequency. In order to detect screw looseness, the piezoelectric frequency response in the healthy and damaged state is compared. To do this, voltages of 10, 40, 80 and 120 volts with high frequencies in different ranges from about 8.5 to 32 kHz are applied to the structure. Comparing the obtained results, it is observed that in the linear method and voltage of 10 volts, there is no change in the frequency response of the healthy and damaged state, but by increasing the voltage and applying the nonlinear method, a significant change in the frequency response of the healthy state and damage occurs. These changes indicate damage to the structure. And the higher the applied voltage, the easier it is to detect damage.