STRUCTURAL ELASTOGRAPHY METHOD CONSIDERING THE COUPLING EFFECT OF STIFFNESS AND MASS

Elastography is a medical imaging technology that can convert the elastic modulus information of biological tissues into visual images. In order to use elastography for damage identification of mechanical structures and achieve global identification of various damage types such as mechanical structural defects, inclusions, ice, and water accumulation. A structural elastography method considering the coupling effect of both stiffness and mass is proposed. The elastic modulus can only reflect the change in structural stiffness and is not enough to characterize various damage types. It is also necessary to introduce parameters that reflect the change in the mass of the structure. Inspired by the structural topology optimization theory, the proposed method takes the elastic modulus coefficients and material density coefficients of the discrete elements of the structure as the imaging parameters. The imaging parameters are correlated with the elastic modulus and material density to construct a damage characterization considering the coupling effect of structural stiffness and mass. The mapping relationship between damage characterization, mechanical model, and eigenvalue response is constructed based on the finite element model of the undamped free vibration system. The sum of the squares of the eigenvalue response change rates of the digital model and the real structural model is used as the objective function. The finite element equilibrium equation as well as the upper and lower limits of the imaging parameters are used as constraints. Eigenvalue response-based structural elastography model is established based on the objective function and constraints. The derivatives of the elastography objective function with respect to the imaging parameters are derived. The elastography model is solved using a gradient-based optimization algorithm. Numerical examples show that this method can effectively achieve accurate quantification of structural damage location, quantity, and shape without any prior information for damages such as structural defects, inclusions, ice, and water accumulation. The generality of this method is further verified by three-dimensional structural elastography examples.