This paper reports a fundamental study of the coupling between highly nonlinear waves, generated in a one
dimensional granular chain of particles, with linear elastic media, for the development of a new Non Destructive
Evaluation and Structural Health Monitoring (NDE/SHM) paradigm. We design and use novel acoustic actuators
to excite compact highly nonlinear solitary waves in a one-dimensional linear elastic rod and investigate the pulse
propagation across the interface. To model the actuator and rod system we use Finite Element Analysis (Abaqus)
and obtain excellent agreement between the experimental observations and the numerical results. We also study
the response of the system to the presence of defects (cracks) in the steel rod, by comparing the wave propagation
properties in pristine and cracked test objects. The obtained results encourage the use of highly nonlinear waves
as an effective tool for developing a new, viable NDE/SHM method.
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.
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