Structured materials with atomic-lattice mimicking features at the microscale, e.g., microlattices, have demonstrated extreme mechanical properties. Elastoacoustic hybridization of water-saturated microlattices can be exploited to achieve a gradient of refractive index for underwater wave focusing. We characterize the acoustic properties of fluid-saturated elastic lattices and construct an ultrasonic wave focusing device with a modified Luneburg lens index profile. Our approach showcases a computationally efficient homogenization design approach that enables accelerated design of acoustic wave manipulation devices. By matching the acoustic impedance with surrounding fluid, microlattices with extraordinary stiffness-to-density ratio and enhanced transmission will prove useful for biomedical applications.
We present investigations into the collision of co-travelling solitary waves in a granular chain. Impulses are injected into
the system by means of a piezo stack and the results are compared to a numerical model of discrete masses connected by
non-linear springs. Similar to other solitary wave-carrying systems, a phase shift in both interacting solitary waves is
observed due to their collision. Additionally, the formation of small secondary waves is observed in both numerical and
experimental results. Insight into solitary wave interactions will be important for high-frequency excitation of a granular
crystal, which may allow for improved Non-Destructive Evaluation (NDE) and Structural Health Monitoring (SHM)
methods.
This paper describes the application of a novel actuator/sensor technology for the generation and detection of stress
waves in structural materials like concrete. The technology is aimed at developing an innovative NDE scheme 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. The results of using these new actuator/sensors to test concrete slabs are presented and
discussed.
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.
Conference Committee Involvement (3)
Smart Sensor Phenomena, Technology, Networks, and Systems Integration VIII
9 March 2015 | San Diego, California, United States
Smart Sensor Phenomena, Technology, Networks, and Systems Integration VII
10 March 2014 | San Diego, California, United States
Smart Sensor Phenomena, Technology, Networks, and Systems Integration VI
10 March 2013 | San Diego, California, United States
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