Abstract: A structural health monitoring system comprises a first set of sensors operable for coupling to a structure positioned under ground, the first set of sensors further configured to detect an impact upon the structure while the first set of sensors is positioned under the ground; a second set of sensors operable to be positioned on or proximate to a surface of the ground, the second set of sensors further configured to detect an audible event occurring at a distance from the second set of sensors and the structure; and a computer readable memory storing one or more audio signatures that may correspond to the audible event.

Abstract: Methods and apparatuses for monitoring a first structure at least partially according to properties of a second structure. One such method comprises determining a first relationship between a first variable and a second variable, wherein the first variable represents sizes of actual damage to the second structure, and the second variable represents sizes of simulated damage on the second structure; determining a second relationship between a third variable and a fourth variable, wherein the third variable represents sizes of simulated damage on the first structure, and the fourth variable represents values of a damage index determined for the simulated damage on the first structure; and determining an estimate of damage to the first structure according to the first and second relationships.

Abstract: In one embodiment, a sensor network is attached to a structure and employed to detect and analyze load changes such as impacts from projectiles. An analyzer coupled to the sensors can determine where on the structure the projectile impacted. Coupled with information on the origin point of the projectile, i.e. where it was fired from, the analyzer can then estimate the trajectory of the projectile. The analyzer can also determine whether the projectile passed through the structure and, if so, can extrapolate the estimated trajectory to determine an estimation of whether the projectile has also impacted an object behind the structure.

Abstract: A structural health monitoring apparatus is presented. According to an embodiment, the structural health monitoring apparatus comprises: a plurality of transducers configured for coupling to a structure, the structure comprising an outer structure surrounding and coupled to an inner structure, the transducers further configured for coupling to only the outer structure so as to transmit stress waves through the inner structure, and still further configured to receive the transmitted stress waves from the outer structure after they have passed through the inner structure; and an analyzer configured to detect damage within the inner structure according to the received transmitted stress waves from the outer structure.

Abstract: A structural health monitoring system comprises: a flexible substrate configured for attachment to a structure, the flexible substrate having a plurality of sensors affixed thereon. The flexible substrate comprises a first portion configured for attachment to the structure, a second portion extending in continuous manner from the first portion, and a third portion extending in continuous manner from the second portion and being configured for attachment to the structure. The second portion includes a first section extending in continuous manner from the first portion, a second section connected between the first section and the third portion and having an edge extending in a direction different from an edge of the first section.

Abstract: Placement of structural health monitoring sensors within a coupled bearing assembly. An exemplary structural health monitoring system comprises first and second bearings configured for rotatable positioning along a structure, and a spacer positioned between the first and second bearings. The first and second bearings are placed against opposing sides of the spacer, and have a preload force engaging the respective first and second bearings against the opposing sides of the spacer. A plurality of sensors are coupled to the spacer so as to be positioned between the spacer and at least one of the first and second bearings, the sensors further coupled to at least one of the first and second bearings so as to be configured to monitor a structural health of the at least one of the first and second bearings.

Abstract: Placement of structural health monitoring sensors within a coupled bearing assembly. An exemplary structural health monitoring system comprises first and second bearings configured for rotatable positioning along a structure, and a spacer positioned between the first and second bearings. The first and second bearings are placed against opposing sides of the spacer, and have a preload force engaging the respective first and second bearings against the opposing sides of the spacer. A plurality of sensors are coupled to the spacer so as to be positioned between the spacer and at least one of the first and second bearings, the sensors further coupled to at least one of the first and second bearings so as to be configured to monitor a structural health of the at least one of the first and second bearings.

Abstract: A structural health monitoring system capable of maintaining electrical contact with sensors affixed to a rotating structure. One such structural health monitoring system comprises a rotatable structure, a plurality of sensors each affixed to the rotatable structure, and an interface. The interface has an inner housing and an outer housing, and maintains a plurality of individual electrical connections, each of the individual electrical connections being an electrical connection between one of the sensors and an electrical contact maintained on the outer housing, the electrical connections configured to be maintained during rotation of the structure. The inner housing is affixed to the structure and the outer housing is rotationally coupled to the inner housing, so that the inner housing is free to rotate with respect to the outer housing during rotation of the structure and the sensors, while maintaining the electrical connections.

Abstract: A structural health monitoring (SHM) system that protects its active and passive components with filter circuits, instead of switches. The active module of the SHM system utilizes a high pass filter, and the passive module of the SHM system utilizes a low pass filter. The active module transmits its interrogating, or excitation, signals at relatively high frequencies that are filtered out by the low pass filter of the passive module, preventing the passive module from sustaining any damage due to the high voltage excitation signals. Meanwhile, the high frequency interrogating signals are passed to the active module's circuitry by its high pass filter, where they can be analyzed accordingly.

Abstract: A method of performing transducer self-diagnostics and self-healing on an array of sensor transducers bonded to a structure for health monitoring includes measuring impedance to detect whether a transducer is missing, or a connection is damaged. Pitch-catch signals generated between one or more pairs of transducers are analyzed for detecting defects according to selected criteria of defect size and location to determine whether the sensors are damaged or partially/fully disbonded. Based on the resulting map of operational transducers, signal transmission paths are added/extended between additional pairs of transducers to maintain inspection coverage of the structure according to the selected criteria.

Abstract: Methods and apparatuses for monitoring a first structure at least partially according to properties of a second structure. One such method comprises determining a first relationship between a first variable and a second variable, wherein the first variable represents sizes of actual damage to the second structure, and the second variable represents sizes of simulated damage on the second structure; determining a second relationship between a third variable and a fourth variable, wherein the third variable represents sizes of simulated damage on the first structure, and the fourth variable represents values of a damage index determined for the simulated damage on the first structure; and determining an estimate of damage to the first structure according to the first and second relationships.

Abstract: Placement of structural health monitoring sensors within a coupled bearing assembly. An exemplary structural health monitoring system comprises first and second bearings configured for rotatable positioning along a structure, and a spacer positioned between the first and second bearings. The first and second bearings are placed against opposing sides of the spacer, and have a preload force engaging the respective first and second bearings against the opposing sides of the spacer. A plurality of sensors are coupled to the spacer so as to be positioned between the spacer and at least one of the first and second bearings, the sensors further coupled to at least one of the first and second bearings so as to be configured to monitor a structural health of the at least one of the first and second bearings.

Abstract: A structural health monitoring system capable of maintaining electrical contact with sensors affixed to a rotating structure. One such structural health monitoring system comprises a rotatable structure, a plurality of sensors each affixed to the rotatable structure, and an interface. The interface has an inner housing and an outer housing, and maintains a plurality of individual electrical connections, each of the individual electrical connections being an electrical connection between one of the sensors and an electrical contact maintained on the outer housing, the electrical connections configured to be maintained during rotation of the structure. The inner housing is affixed to the structure and the outer housing is rotationally coupled to the inner housing, so that the inner housing is free to rotate with respect to the outer housing during rotation of the structure and the sensors, while maintaining the electrical connections.

Abstract: A self-sufficient structural health monitoring system that can monitor a structure without need for external power input. Embodiments of the invention provide a structural health monitoring system with a power supply integrated within, so that the system relies on itself for operational power. Systems with such an on-board electrical power source, independent of an external power source (and in particular, independent of the power system(s) of the structure being monitored), are much more self-contained and self-sufficient.

Abstract: Detecting damage in a structure without comparing sensor signals to a baseline signal. Once a structure is interrogated, a process based on a Gaussian Mixture Model is applied to the resulting data set, resulting in quantities for which Mahalanobis distances and Euclidian distances can be determined. A damage index is then determined based on the calculated Euclidian distance. A high value of this damage index coupled with an abrupt change in Mahalanobis distance has been found to be a reliable indicator of damage. Other embodiments may employ a baseline, but determine damage according to ratios of energy values between current and baseline signals.

Abstract: A trigger circuit for use with a structural health monitoring system. To save power, a structural health monitoring system is programmed with a sleep mode and a wake, or operational, mode. In its operational mode, the structural health monitoring system can perform its usual tasks, e.g. monitoring a structure and determining its structural health. In sleep mode, many functions are suspended, so that the system requires less power. The trigger circuit wakes the system when the sensors of the structural health monitoring system emit a sufficiently large signal, i.e. when an event occurs. That is, when not in use, the system enters sleep mode, and when some event occurs (e.g., impact, or some other stresses that are of concern), the trigger circuit alerts the system, prompting it to shift from sleep mode to operational mode and to begin taking/analyzing data.

Abstract: A structural health monitoring system using ASICs for signal transmission, reception, and analysis. Incorporating structural health monitoring functionality into one or more ASICs provides a durable yet small, lightweight, low cost, and portable system that can be deployed and operated in field conditions. Such systems provide significant advantages, especially in applications such as armor structures.

Abstract: Sensors affixed to various such structures, where the sensors can withstand, remain affixed, and operate while undergoing both cryogenic temperatures and high vibrations. In particular, piezoelectric single crystal transducers are utilized, and these sensors are coupled to the structure via a low temperature, heat cured epoxy. This allows the transducers to monitor the structure while the engine is operating, even despite the harsh operating conditions. Aspects of the invention thus allow for real time monitoring and analysis of structures that operate in conditions that previously did not permit such analysis. A further aspect of the invention relates to use of piezoelectric single crystal transducers. In particular, use of such transducers allows the same elements to be used as both sensors and actuators.

Abstract: Predicting the probability of detection of major and minor defects in a structure includes simulating a plurality of N defects at random locations in a region specified by an array of transducers. Defect size is incremented until it intersects one path between two transducers. The defect size is again incremented until it intersects two or more adjacent paths between pairs of transducers. The number of major defects up to a selected size is determined by the total number of single path intersections by defects up to the selected size. The number of minor defects up to a selected size is determined on the basis of the total number of defects intersecting two or more paths up to the selected size. The probability of detection up to a selected size is the cumulative number of major or minor defects up to the selected size normalizing by N.

Abstract: A method for determining optimal locations of a plurality of sensors for damage detection in a structural health monitoring system includes providing a one or more signal performance characteristics, spatial parameters describing a layout of a structure, and generating a layout for the plurality of sensors according to the signal performance characteristics and the spatial parameters. An estimated largest critical damage size that may not be detected by sensors arranged according to the first layout is determined. The layout is edited so as to reduce the estimated largest critical damage size to be less than or equal to a selected maximum size requirement.