Subhendu K. Datta

Bio: Subhendu K. Datta is an academic researcher from University of Colorado Boulder. The author has contributed to research in topics: Scattering & Wave propagation. The author has an hindex of 25, co-authored 101 publications receiving 1484 citations. Previous affiliations of Subhendu K. Datta include Cooperative Institute for Research in Environmental Sciences.

Acoustic-phonon dispersion in nanowires

Abstract: We study phonon dispersion in layered prismatic nanowires that can have an arbitrary cross-sectional geometry. We calculate phonon dispersion using a hybrid analytical/numerical approach that models propagation along the wire analytically, but deformation in the plane of the cross section using the finite element method. In our results we consider only two layers, but the calculational approach is applicable to multiple layers.

Transient Ultrasonic Guided Waves in Bi‐Layered Anisotropic Plates with Rectangular Cross Section

Abstract: Transient ultrasonic guided waves in anisotropic bi‐layered plates with finite‐width are investigated in this paper Composite bi‐layered plates consisting of GaAs substrate coated with Nb sheath is considered as an example because of its application to electronics and calorimetry The purpose is to investigate the acoustic mode coupling (“pinching”) phenomena for phonon transport A semi‐analytical finite element (SAFE) method is adopted to study the guided wave dispersion behavior in finite‐width elastic plates Nine‐noded quadrilateral elements are used to model the cross section of the finite‐width plate Propagation in the axial direction is modeled by analytical wave functions Elastodynamic Green’s functions are derived using modal summation in the frequency‐wavenumber and time‐space domains Results for dispersion and transient analysis of guided waves in finite‐width plates are presented and compared for different aspect ratios Group velocities are calculated and wave arrival times are computed for different plate cross sections as well as different excitation frequency Numerical results show significant influence of the plate aspect ratio on the dispersion and transient wave response Complex nature of quasi‐mode dispersion and propagation due to pinching phenomena in anisotropic plates require such quantitative analysis to afford easy interpretation These results would be important for nondestructive material evaluation and for characterization of phonon transport in anisotropic bi‐layered plates

Transient Response of a Composite Plate With Delamination

Abstract: Transient response of a composite plate with a near-surface delamination has been studied in this paper A new technique developed by the authors to evaluate the Cauchy Principal Value integrals and the weakly singular integrals involved in the boundary integral equations has been employed and modifided to treat the corner points on the boundary The time harmonic Green's functions appearing in the bound-ary integral equation are evaluated by combining a stiffness method and the modal summation technique To circumvent the difficulties associated with the evaluation of hypersingular integrals for cracks, the multidomain technique is employed, The accuracy and efficiency of the method are checked by comparing the displacements in a uniaxial graphite-epoxy plate containing a delamination with results obtained by a hybrid method It is shown that the presence of the delamination significantly alters the surface response spectra of the plate, Results are presented in both time and frequency domains The results show that the technique would be useful for ultrasonic nondestructive evaluation of defects in composite and anisotropic plates, and for studying dynamic response of such plates to impact

Variational and Related Methods for the Overall Properties of Composites

Abstract: Publisher Summary This chapter focuses on variational and related methods for the overall properties of composites. A wide range of phenomena that are observable macroscopically are governed by partial differential equations that are linear and self-adjoint. This chapter is concerned with such phenomena for materials, such as fiber-reinforced composites or polycrystals, whose properties vary in a complicated fashion from point to point over a small, “microscopic” length scale, while they appear “on average” (that is, relative to the larger, macroscopic scale) to be uniform. This chapter treats the elastic behavior of composites, and emphasizes that a number of other properties (conductivity, viscosity of a suspension, etc.) are described by the same equations. Extensions to viscoelastic and thermoelastic behavior are presented, for both of which the variational characterization given is believed to be new. Problems, such as the resistance to flow of viscous fluid through a fixed bed of particles are mentioned, and a model problem that involves diffusion is presented in some detail. This displays the same difficulty in relation to divergence of an integral and is one problem of this type that has so far been approached variationally. Methods related to the Hashin–Shtrikman variational principle are also described in the chapter.

Ultrasonic Guided Waves in Solid Media

Abstract: Preface Acknowledgments 1. Introduction 2. Dispersion principles 3. Unbounded isotropic and anisotropic media 4. Reflection and refraction 5. Oblique incidence 6. Waves in plates 7. Surface and subsurface waves 8. Finite element method for guided wave mechanics 9. The semi-analytical finite element method (SAFE) 10. Guided waves in hollow cylinders 11. Circumferential guided waves 12. Guided waves in layered structures 13. Source influence on guided wave excitation 14. Horizontal shear 15. Guided waves in anisotropic media 16. Guided wave phased arrays in piping 17. Guided waves in viscoelastic media 18. Ultrasonic vibrations 19. Guided wave array transducers 20. Introduction to guided wave nonlinear methods 21. Guided wave imaging methods Appendix A: ultrasonic nondestructive testing principles, analysis and display technology Appendix B: basic formulas and concepts in the theory of elasticity Appendix C: physically based signal processing concepts for guided waves Appendix D: guided wave mode and frequency selection tips.

Guided wave based structural health monitoring: A review

Abstract: The paper provides a state of the art review of guided wave based structural health monitoring (SHM). First, the fundamental concepts of guided wave propagation and its implementation for SHM is explained. Following sections present the different modeling schemes adopted, developments in the area of transducers for generation, and sensing of wave, signal processing and imaging technique, statistical and machine learning schemes for feature extraction. Next, a section is presented on the recent advancements in nonlinear guided wave for SHM. This is followed by section on Rayleigh and SH waves. Next is a section on real-life implementation of guided wave for industrial problems. The paper, though briefly talks about the early development for completeness,. is primarily focussed on the recent progress made in the last decade. The paper ends by discussing and highlighting the future directions and open areas of research in guided wave based SHM.

A Baseline and Vision of Ultrasonic Guided Wave Inspection Potential

Abstract: Ultrasonic guided wave inspection is expanding rapidly to many different areas of manufacturing and in-service inspection. The purpose of this paper is to provide a vision of ultrasonic guided wave inspection potential aswe move forward into the new millennium. An increased understanding of the basic physics and wave mechanics associated with guided wave inspection has led to an increase in practical nondestructive evaluation and inspection problems. Some fundamental concepts and a number of different applications that are currently being considered will be presented in the paper along with a brief description of the sensor and software technology that will make ultrasonic guided wave inspection commonplace in the next century.