Highly nonlinear waves' sensor technology for highway infrastructures

Abstract

This paper describes preliminary results towards the development of an innovative NDE/SHM scheme for material characterization and defect detection based on the generation of highly nonlinear solitary waves (HNSWs). HNSWs are stress waves that can form and travel in highly nonlinear systems (i.e. granular, layered, fibrous or porous materials) with a finite spatial dimension independent on the wave amplitude. Compared to conventional linear waves, the generation of HNSWs does not rely on the use of electronic equipment (such as an arbitrary function generator) and on the response of piezoelectric crystals or other transduction mechanism. HNSWs possess unique tunable properties that provide a complete control over tailoring: 1) the choice of the wave's width (spatial size) for defects investigation, 2) the composition of the excited train of waves (i.e. number and separation of the waves used for testing), and 3) their amplitude and velocity. HNSWs are excited onto concrete samples and steel rebar. The first pilot study of this ongoing effort between Caltech and the University of Pittsburgh is presented.

Coupling of highly nonlinear waves with linear elastic media

“…chains of spherical particles) 9, 10 and have, since then, gained increasing attention in the scientific community. 7,[11][12][13][14][15][16][17] Highly nonlinear media support acoustic pulses that have intrinsically different properties than those found in conventional linear acoustic signals, allowing for a stronger degree of tunability.…”

“…We propose the use of a granular system to generate highly nonlinear solitary waves which will be used to interrogate structures, as an alternative approach to the classical instrumented hammers. 7,8 In this paper we study experimentally and numerically the formation and propagation of highly nonlinear solitary waves in a granular chain and their interactions with a linear elastic rod (Fig 1). We study the impulse's behavior at and across the interface between the nonlinear and the linear system.…”

Dark breathers in granular crystals

“…On one hand, the relevant mathematical model is difficult to be analyzed due to, among other things, the lack of smoothness of the corresponding potential function, calling for new ideas to study this nonlinear lattice problem [1,2]. On the other hand, the ability to conduct experiments for a wide range of setups, including chains consisting of beads of various geometries and masses, nonlinearity strength, and even dimension [3][4][5][6], make the subject of granular crystals exciting for its potential relevance in applications including shock and energy absorbing layers [7][8][9][10], actuating devices [11], acoustic lenses [12], acoustic diodes [13,14], and sound scramblers [15,16], to name a few.…”

Introduction

“…The excitation of the solitary waves in the homogeneous chains, their interactions with the boundaries [151,152] and the characteristics of the reflected pulses are taken into account in the practical applications. The granular materials have found use in the non-destructive evaluation -NDE [153], in the orthopedics [154], in the composite delamination [155], in the monitoring of hydration of cement [156], in the NDE of the adhesive joints [157] and in highway infrastructure [158]. In all these applications, a strongly nonlinear solitary wave is created in the granular medium and is directed towards the intended test object.…”