Vishu Vardhan Janapati

Bio: Vishu Vardhan Janapati is an academic researcher. The author has contributed to research in topics: Lamb waves & Structural health monitoring. The author has an hindex of 1, co-authored 1 publications receiving 3 citations.

Global material characterization of composite structures using lamb wave stmr array technique

Abstract: Structural health monitoring of plate like structures, using transducer arrays located suitably on the structure, finds applications in monitoring aerospace structures These plates are anisotropic, with wave propagation properties varying with direction Single Transmitter Multiple Receiver (STMR) arrays have been shown before to have the ability to locally characterize the stiffness properties of a composite material with anisotropy The STMR arrays have also been demonstrated for SHM applications using phase reconstruction techniques The guided ultrasonic Lamb waves are used where the central piezoelectric wafer‐active sensor (PWAS) emits the guided waves, and the other PWAS sensors receive the Lamb wave signals In the current work, this technique has been extended to the determination of global elastic moduli using the Lamb wave S0 and A0 mode signals that are reflected from features in the structure such as edge of the plate, bolt holes, etc that are known apriori using STMR array and then reconst

Characterization of the elastic moduli in composite plates via dispersive guided waves data and genetic algorithms

Abstract: In this study, an inverse procedure based on stress guided waves is proposed for the characterization of the elastic moduli of composite plates. The characterization is carried out via genetic algorithms by minimizing the discrepancy between experimental and numerical group delay curves for different directions of propagation along the plate. Experimentally, for a given distance source–receiver, the group delay curves are obtained by processing the guided waves time–transient signals via a time–frequency transform. For the same distance, a fast and reliable semi-analytical finite element formulation is used for the forward computation of the group delay curves. Here, pseudo-experimental data, generated by means of the semi-analytical finite element model for an assumed known set of elastic coefficients, are used to test the reliability of the proposed procedure. The results obtained for three different plates are promising. Since semi-analytical finite element formulations can also handle plates with unif...

Identification of Elastic Properties of Composites by Inversion of Ultrasonic Guided Wave Data

Abstract: Given the inherent manufacturing variabilities and potential for in-service damage of composite parts, the identification of the elastic properties of composites is important to ensuring the safety and the proper performance of the part. The primary objective of this manuscript is to determine, nondestructively, the elastic properties of composite parts, whether as in-situ components that are part of a larger system, or as laboratory coupons. The proposed technique is based on multimode and dispersive ultrasonic guided waves propagating along a single direction, and the inversion of their phase velocity dispersion curves. The inversion procedure utilizes an efficient Semi-Analytical Finite Element method to solve the forward problem, and a Simulated Annealing algorithm as the optimization tool. The method is particularly well-suited for the characterization of composite laminates. In particular, the manuscript presents experimental evidence of the effectiveness of this technique, that was suggested earlier in a solely numerical work previously conducted by the authors. The test results show that reasonable accuracy can be obtained in the identification of four in-plane and three out-of-plane engineering constants of a quasi-isotropic laminate and a highly anisotropic laminate utilizing the single wave propagation direction. Non-obvious sensitivities of certain wave modes to particular constants are explained on the basis of stress coupling phenomena that are revealed by the SAFE wave propagation models. The study gives experimental evidence of the suitability of ultrasonic guided wave inversion schemes to identify the engineering constants of laminated composites, with the potential to properly characterize parts in-situ, because of the insensitivity of guided waves to boundary conditions located outside of the transmitter–receiver path.