Energetic materials or explosives are a class of granular composite materials consisting of explosive grains dispersed in a polymer matrix. An accidental low velocity impact during transportation may cause damage in the material, which may lead to weakening and possibly ignition of the material. Traditional SHM methods such external sensors or imaging techniques may not reveal changes in the internal microstructure of the material. It is proposed that dispersing carbon nanotubes in the polymer phase of the explosive material will introduce piezoresistivity by which the health of the material can be monitored in real time. In this work, a coupled electromechanical computational framework is developed to investigate nanocomposites and applied to model deformation and damage sensing in nanocomposite bonded explosive materials.

Oil and gas infrastructures may be exposed to landslides, earthquakes, corrosion and fatigue, and to damage from thefts or vandalism, leading to leakage and failure with serious economic and ecologic consequences. For this reason, an increasing interest in applied research on monitoring and protecting pipelines (for fuel, oil and natural gas transportation) arises. Aimed at the mitigation of catastrophic effects of human and natural damage, the present paper proposes a smart real-time Structural Health Monitoring (SHM) system capable to control structural integrity continuously, focusing on the issue of spillage for thefts of fuels which are not detectable, in real-time, by the existing monitoring systems. The system consists of a smart-pipeline containing a health monitoring integrated measurement chain, i.e. an enhanced Fiber Bragg Gratings-based fiber optics neural network on the pipes, for displacement and acceleration monitoring (gathering many other different measurements such as: ground motion, permanent ground displacement, pipeline temperature, pipeline deformation, leakage, etc.). Specifically, the ability to measure these characteristics at hundreds of points along a single fiber and the great accuracy of each point of measure, are particularly interesting for the monitoring of structures such as pipelines in order to detect hazardous and unauthorized intrusion and damage.

A new class of self-powered acceleration event detection sensors are presented that are powered by electrical energy harvested during munitions launch by integrated piezoelectric elements. The sensors are provided with a novel safety electronic and logic circuitry that is used to differentiate the firing event from all accidental events such as accidental drops, transportation vibration, and the like. When the launch conditions are detected from the magnitude of the experienced acceleration as well as its duration, the remaining electronics and logics circuitry of the device is enabled. The developed self-powered sensors may also be used in place of G-switches in munitions and other industrial and commercial devices with the advantage of activating not only from the magnitude of the experienced acceleration but also from its duration. The latter capability is essential in many munitions and commercial applications to avoid false switching event. For example in some cases dropping of around over a hard surface may impart higher peak acceleration than actual firing. And in many industrial and commercial devices and equipment, high-G and very short duration shock loadings do not cause damage and G-switches used to deactivate the device may not be desired to trip. Prototypes of the developed piezoelectric-based self-powered event detection sensors as standalone sensors and as switches for detecting and opening or closing circuitry upon detection of shock or vibration loading with prescribed magnitude and duration thresholds with integrated electronics and logics circuitry have been designed, fabricated and successfully tested for a number of munitions and industrial applications. In this paper the design and operation of such devices and their testing are described.

Alfenol (Fe x Al 100−x ) is an alloy similar to Galfenol (Fe-Ga alloys) in crystal lattice structure and magnetostriction trend (peaking at ∼20% composition). Although single-crystal Fe 80 Al 20 exhibits lower magnetostriction (∼184 ppm, about half of Fe 80 Ga 20 ), its magneto-elastic coupling coefficient is on par with that of Fe-Ga. In addition, characteristics such as machinability and rollability are superior to that of Galfenol, making it possible to achieve textured sheets (thickness∼200 μm) which, while having a high elastic modulus, are very flexible. Furthermore, Aluminum is non toxic, cheap (∼1% the cost of Ga) and is available in abundance. These attributes make Alfenol an ideal candidate for a bio-inspired whisker-like tactile sensor (mimicking mystacial vibrissae of cats, sea lions, etc.). This work deals with the design and development of an accurate, cost efficient, real-time, and non-invasive sensor prototype that tracks displacements, vibrations and scour on bridge piers with minimal signal conditioning. Making such a sensor is possible thanks to Alfenol’s linear response to strain in the presence of appropriate bias magnets. The change in its magnetic state due to inverse magnetostriction from applied bending stresses will be observed using Hall Effect sensors to derive deflection information. A protocol to manufacture rolled and textured Alfenol whisker samples will be presented in this research. The effect of bias conditions on sensor performance will be studied empirically and by using multi-physics simulations. Optimization of the sensor by varying the dimensions of the whisker, and its correlation to flux leakage will also be examined followed by an effort to understand the micro-magnetic response of Alfenol to mechanical stimulation. Finally, results from using this biomimetic sensor to measure displacements and vibrations, and its viability to be used as a flow sensor will be discussed. The robustness of this sensor has been exploited to develop a novel real-life application to provide an early warning system for bridge pier scour due to soil transportation during a weather event. The effectiveness of these sensors for scour detection in riverbeds will subsequently be simulated in a water flume and analyzed.

Airflow over/under/around a vehicle can affect many important aspects of vehicle performance including vehicle drag (and through this vehicle fuel economy), vehicle lift and downforce, and cooling/heat exchange for the vehicle powertrain and A/C systems. While active devices are present on all aircraft, the majority of known airflow control devices in current use in ground transportation are of fixed geometry, location, orientation, and stiffness. The project, conducted during the 2004–2006 timeframe, whose performance requirements, design, and bench-top prototype build phases, are described in this paper was successful in developing an SMA actuator based approach for opening and closing a vertically-oriented-blade louver system to be used for on-demand control of the airflow into the engine compartment, i.e. for on-demand control of both cooling airflow as well as aerodynamic drag. Beyond feasibility, the initial full scale bench top working models demonstrated an active materials based approach which would have decreased weight and a smaller packaging envelop than a comparable motor driven unit. This demonstration showed that actuation speed, force, and cyclic stability all could meet the application requirements. The specific design that was selected, a set of parallel vertically oriented blades each linked through a gear to a common rack that is translated by a linear SMA actuator, uses straight linear actuation to produce a reversible synchronous 90 degree rotation of the blades, i.e. a full opening and closing capability for the louver system. Key technical issues that remained to be demonstrated and resolved through design modifications if necessary in Part 2 — on-vehicle performance testing — of this study were related in most part to robustness in the harsh vehicle front-end environment, a prime example being mechanism stalling due to ice or mud buildup.

The University of California at San Diego (UCSD), under a Federal Railroad Administration (FRA) Office of Research and Development (R&D) grant, is conducting research to develop a system for in-situ measurement of the rail Neutral Temperature in Continuous-Welded Rail (CWR). It is known that CWR can break in cold weather and can buckle in hot weather. Currently, there is a need for the railroads to know the current state of thermal stress in the rail, or the rail Neutral Temperature (rail temperature with zero thermal stress), to properly schedule slow-order mandates and prevent derailments. UCSD has developed a prototype for wayside rail Neutral Temperature measurement that is based on non-linear ultrasonic guided waves. Numerical models were first developed to identify proper guided wave modes and frequencies for maximum sensitivity to the thermal stresses in the rail web, with little influence of the rail head and rail foot. Experiments conducted at the Large-scale Rail NT Test-bed indicated a rail Neutral Temperature measurement accuracy of a few degrees. Field tests are planned at the Transportation Technology Center (TTC) in Pueblo, CO in June 2012 in collaboration with the Burlington Northern Santa Fe (BNSF) Railway.

Optical membranes are being pursued for their ability to replace the conventional mirrors that are used to correct wave front aberration and space based telescopes. Among some of the many benefits of using optical membranes, is their ability to considerably reduce the weight of the structure. As a secondary effect, the cost of transportation, which is of great interest in space applications, is reduced as well. Another interesting advantage is the ability to have a continuous surface for the attenuation of wave front aberrations, instead of a discrete grid of rigid mirrors that have to be individually controlled. The effects of adding a pressurized cavity behind an optical membrane are examined in this paper by coupling an acoustic cylindrical cavity to a cylindrical membrane at the top boundary. This paper also looks at using a positive position feedback controller for vibration suppression of the membrane. This is done by using a centralized acoustic source in the cavity as the method of actuation. The acoustic actuation is of great interest since it does not mass load the membrane in the conventional way, as most methods of actuation would.