Method, system, device and medium for online monitoring of plane stress field without baseline data based on piezoelectric transducer array

A system for online monitoring of a plane stress field without baseline data, based on a piezoelectric transducer array, comprising:

• a dispersion curve establishing module, wherein by using the dispersion curve establishing module, according to geometric dimensions and material parameters of a measured object, a dispersion curve of Lamb waves is established, a cut-off frequency of a first-order Lamb wave mode is determined, then a suitable frequency is selected within the cut-off frequency to excite piezoelectric wafers, and pure S0-mode Lamb waves are generated by means of symmetrical excitation;
• a stress field characterization module, wherein by using the stress field characterization module, according to the invariant property of acoustoelastic coefficients of isotropic materials in different coordinate systems, acoustoelastic equations in different propagation directions are obtained, then a difference is calculated to obtain a linear relationship between a difference of velocity changes in different directions and stress, and at the same time, according to a linear superposition relationship between stresses in different directions, a magnitude of a plane stress field of the measured object is calculated through a difference of three groups of velocity changes in different directions, thereby finally realizing characterization of the plane stress field by means of measurement results of the piezoelectric transducer array in different directions;
• and
• a stress field solving module, wherein by using the stress field solving module, Lamb wave signals are excited and received inside the measured object, Hilbert transform is performed on the received signals, signal envelopes are extracted, then acoustic time differences in different propagation directions are calculated through a cross-correlation algorithm, according to a linear relationship between acoustic time differences and velocity differences, it is determined that there is still a linear relationship between stresses and acoustic time differences in different propagation directions, and then, three groups of acoustic time differences in different directions are substituted into pre-calibrated acoustoelastic equations to solve the plane stress field of the measured object.