Applied Numerical Analysis. By C.F. Gerald. Pp. xii, 340. £3·60. 1970. (Addison-Wesley.)

Acoustic source localization.

Acoustic source localization in anisotropic plates.

The growing use of composite structures in aerospace structures has attracted much interest in structural health monitoring (SHM) for the localization of impact positions due to their poor impact resistance properties. The propagation mechanism and the frequency dispersion features of signals on complex composite structures are more complicated than those on simple composite plates. In this paper, a time reversal focusing based impact imaging method for impact localization of complex composite structures is proposed. A complex Shannon wavelet transform is adopted to extract frequency narrow-band signals of impact response signals of a PZT sensors array at a special time–frequency scale and to measure the phase velocity of the signals. The frequency narrow-band signals are synthesized using software, depending on the time reversal focusing principle, to generate an impact image to estimate the impact position. A demonstration system is built on a composite panel with many bolt holes and stiffeners on an aircraft wing box to validate this method. The validating results show that the method can estimate the position of impact efficiently.

https://iopscience.iop.org/article/10.1088/0964-1726/20/10/105014/pdf

A time reversal focusing based impact imaging method and its evaluation on complex composite structures

Laminated composites are susceptible to delamination due to their weak transverse tensile and interlaminar shear strengths as compared to their in-plane properties. Delamination damage can occur in...

Delamination detection and quantification on laminated composite structures with Lamb waves and wavenumber analysis

Locating point of impact in anisotropic fiber reinforced composite plates

Structural health monitoring (SHM) technologies, which use integrated sensing for damage detection, are expected to
improve system reliability, availability, and operational cost. Guided waves can propagate great distances while
experiencing low attenuation. They have been successfully used for damage detection in structures of relatively low
geometric complexity such as plates and cylindrical pipes. The use of guided waves for this purpose becomes
increasingly difficult as the geometric complexity of the structure increases. Aerospace structural components such as
fuel tanks, wings, etc. often are comprised of substructures that consist of plates with integral stiffeners. This work
reports on finite element simulations of guided waves in integrally stiffened plate structures. In these studies, the guided
waves are generated by PZT wafer-type transducers mounted on the structure. Transient dynamic finite element
simulations using PZFlex, in 2D and in 3D, were used to model both the structure and transducers. The interaction of the
guided waves with cracks, simulated by notches of varying dimensions, is also modeled. This allows appraisal of the
sensitivity of various modes for crack detection by providing insight into mode conversion and scattering resulting from
the guided wave and crack interaction.

FEM modeling of guided wave behavior in integrally stiffened plate structures

: This paper will address analytical research work performed on impact location in an anisotropic multilayered thermal protection structure. The propagation of elastodynamic waves through the multilayer structure and the possibility that the layers are transversely isotropic are two complications that are addressed. The method used is an extension of classical triangulation based on the use of the fixed geometry of the multilayer plate structure, quasi-longitudinal modes, and the generalized Snell's law for transversely isotropic materials. The impact localization problem is recast as a minimization problem whose objective function is the sum of the distances between all combination pairs of constant time difference curves for the sensor pairs. An initial estimate is made for the parameter values for the collection of constant time difference curves. The Newton-Kantorovich algorithm is then used to generate a sequence of iterations which converge to the minimum of the objective function. This generates a point on each of the collection of curves. The centroid of this point set is calculated and used for the approximation for the impact point.

Impact Location for a Multilayer Transversely Isotropic Plate

ABSTRACT Previous research outlined the genesis of a new body of surf tourism research based on a wide array of gray and published literature (Martin, S. A., & Assenov, I. (2012). The genesis of a new body of sport tourism literature: A systematic review of surf tourism research (1997–2011). Journal of Sport and Tourism, 17(4), 257–287). The aim of this paper is to further investigate the development of the field through an evidence-based informetric analysis of international journal articles listed in Web of Science or Scopus databases. Employing a systematic review of journal papers published from 2011 to 2020, the study addresses the previous gray literature problem of accessibility and eligibility criteria for citation. Findings are drawn from explicit and tangential studies which capture an up-to-date overview of the evolution of surf tourism research. The study identifies active journals, authors, field locations, and leading areas of research, suggesting that the field has entered a period of ‘academic professionalization’. A bibliography of 96 journal articles presents academics and readers with a corpus of accessible research.

Steven A. Martin

Papers

Locating point of impact in anisotropic fiber reinforced composite plates

FEM modeling of guided wave behavior in integrally stiffened plate structures

Impact Location for a Multilayer Transversely Isotropic Plate

From shades of grey to Web of Science: a systematic review of surf tourism research in international journals (2011–2020)