Damage Inversion And Transient Wave Propagation In Damaged Concrete Media

According to wave propagation theories, the transient wave propagation in the inhomogeneous damaged media is researched. The inverse theories and calculated methods of the material constant (damage degree) of damaged concrete media are studied using both of incident impulse signal and received impulse response.Firstly, theories of wave propagation in inhomogeneous damaged solid media which are needed as the basic knowledge for inverse problems are briefly recounted. Secondly, the concise concepts of direct problem and inverse problem are also introduced in this section. Some essential problems about inverse problem are in retrospect. The disposal for ill-pose in inversion is emphasized. Furthermore, damage degree is quoted to describe the damage mechanics model of single parameter.Material's modulus of elasticity is often weakened and inhomogeneous due to damage. The continuously inhomogeneous concrete media is approximately treated as stratiform homogeneous during process of calculation. By means of this way, using spectra transfer-matrix, impulse responses of several typical damaged models are numerically simulated.In the process of opposite test simulation, aiming at the ample spectrum information, the PST (pulse-spectrum technique) method whose hypostasis is Newton iteration is adopted to inverse damage degree of the concrete media. The problem is transformed to linearity in frequency-domain. The way dealing with ill-pose here is TSVD method which bases on Tikhonov regularization. Some typical damaged models including catastrophe, linearity, quadric are inversed. In addition, if the priori information that the damage degree can not be negative were considered, the inversed result would be improved distinctly.Method of damage inversion in segments for concrete long beam is discussed. The same side non-destructive test in transient wave field for concrete structure is simulated. The damage degree described by elastic module is considered as the parameter for inversion. The norm of difference between receiving signals' amplitudes and amplitudes stimulated by inversion at receiving end is regarded as target function. Based on the conjugate gradient of optimization which is known as one of non-linear inversion methods, inverse results which considerably accord with true value are obtained. It is found that the inverse method is convergent as long as receiving end...