Abstract: Methods and apparatus, including computer program products, are provided for determining rail stress. The method may include generating at least one ultrasonic guided wave to enable the at least one ultrasonic guided wave to propagate through a rail; detecting at least one of a fundamental frequency component of the at least one ultrasonic guided wave, one or more harmonics of the at least one ultrasonic guided wave, and/or a mixing component of the at least one ultrasonic guided wave; and determining a stress of the rail based on at least a nonlinearity parameter determined from the detected at least one of the fundamental frequency component, the one or more harmonics, and the mixing component. Related apparatus, systems, methods, and articles are also described.

Abstract: A method for controlling the combustion in a gas turbine including measuring, with one or more probes situated adjacent to the combustion chamber of the turbine, the amplitude of the pressure oscillations inside the combustion chamber and the persistence time or cycle of the same oscillations, evaluating the behavior under fatigue conditions of the combustion chamber, by constructing the Wohler curve for a certain material which forms the combustion chamber for a predefined combustion frequency and for the amplitude and cycle values of the pressure oscillations measured, measuring the cumulative damage to the combustion chamber during functioning under fatigue conditions of the turbine using the Palmgren-Miner hypothesis and exerting protection actions of the turbine if the cumulative damage value measured is exceeded.

Abstract: Temperature compensation is applied to correct for temperature mismatch between a reference chamber and a disposable chamber in a pneumatic pumping system for dialysis fluid for peritoneal dialysis. The mismatch creates an error in the calculation of pumping volume of dialysate fluid. Applying a correction for the temperature mismatch helps to more precisely control the volume of dialysate that is metered to the patient. Also disclosed are ways to keep temperatures constant and to use temperature sensors to accurately measure the temperatures of the chambers. In other aspects, the temperature of the dialysate fluid itself may be measured and used to apply a correction to the volume of fluid that is pumped to the patient.

Abstract: A sensor-equipped wheel support bearing assembly capable of accurately detecting the load acting on the bearing assembly is provided. The sensor-equipped wheel support bearing assembly includes a sensor unit in an outer member that serves as a stationary member. The sensor unit includes a strain generating member, having two or more contact fixing segments to be fixed to the stationary member, and two or more sensors for detecting strain in the strain generating member. The contact fixing segments are spaced from each other in a direction circumferentially of the stationary member at the same axial positions. An estimating section is provided in the bearing assembly for estimating load thereon based on the difference between respective output signals from the sensors by calculating amplitudes of the output signals or values corresponding to such amplitudes from the difference between the respective output signals.

Abstract: A method, apparatus and computer-readable storage medium are provided for defining a load envelope, such as a three-dimensional load envelope, that envelopes a plurality of load cases. In the context of a system, the system includes a coordinate system redefinition module configured to define three mutually orthogonal axes in a space representative of at least three load components and a surface facet definition module configured to identify load cases on a surface of the load envelope and to define a plurality of surface facets, such as surface triangles, that collectively define the load envelope. Each surface facet includes a plurality of vertices that are formed by load cases identified to be on the surface of the load envelope.

Abstract: A load and stress of a tensioner may be determined from the change in the strain of the tensioner. The strain of the tensioner may be detected by an optical device having a Fiber Bragg Grating (FBG) that is attached to the tensioner. An electrical signal may be generated in response to the detected change in the mechanical strain of the tensioner by processing the light reflected from an optical fiber coupled to the optical device. The electrical signal may be processed to calculate a load on the tensioner. The calculated load may be stored and analyzed, along with previously-stored values for the load, to determine the condition of the tensioner system, and whether the tensioner system requires maintenance.

Abstract: A system and method for monitoring loads applied to aircraft landing gear structure. The method includes the step of interrogating at least one sensor positioned proximate the landing gear structure by way of data acquisition circuitry to yield strain data. The method further includes the step of instructing the data acquisition circuitry with respect to a sampling rate and data resolution for interrogation.

Abstract: A improved method of monitoring a structure by mounting a sensor within a cavity of the structure to measure at least one of strain experienced by the structure and vibration experience by the structure. Mounting a wireless communication unit mounted within the structure and connecting the wireless communication unit to the sensor to receive data from the sensor and transmit the data to a receiver outside the structure. Mounting a power supply within the structure and connecting the power supply to the sensor and the wireless communication unit to supply necessary electrical power to the sensor and the communication unit.

Abstract: A load measuring system comprising a collar mounted between the two cables of the bridle on a sucker rod pump and a measuring device to determine the clamping force of the collar. When the cables are clamped together a pre-determined distance at an angle from the vertical, the load on the cables can be determined from the clamping force. The clamping force is measured by a strain gauge or other type of load cell. The load is measured and recorded at frequent intervals during the pump stroke, and by further analysis, critical operational parameters of the pump can be determined, and the information can be used to control the operation of the pump.

Abstract: A distributed optical fiber sensor based on Raman and Brillouin scattering is provided. The distributed optical fiber sensor includes a semiconductor FP cavity pulsed wideband optical fiber laser (11), a semiconductor external-cavity continuous narrowband optical fiber laser (12), a wave separator (13), an electro-optic modulator (14), an isolator (15), an Er-doped optical fiber amplifier (16), a bidirectional coupler (17), an integrated wavelength division multiplexer (19), a first photoelectric receiving and amplifying module (20), a second photoelectric receiving and amplifying module (21), a direct detection system (22), a narrowband optical fiber transmission grating (23), a circulator (24) and a coherence detection module (25). The temperature and the strain can be measured simultaneously, and the signal-to-noise ratio of the system is enhanced.

Abstract: Pedaling torque sensor device for bicycles comprising a crank arm (1) performed in a single-piece element having a cross section closed and symmetrical about a plane of symmetry (10) and also symmetric about the plane which is orthogonal to said plane (10) containing the main longitudinal axis of the crank arm (7). Said crank arm (1) is provided with at least one couple of straight drilled blind holes (5, 6) respectively symmetric about the mentioned plane of symmetry (10), and each one of the mentioned strain gauges (2) are non-detachably fixed on the inside of the crank arm (1) within 10 the straight drilled blind hole (5, 6) walls. It is also object of the invention a power meter apparatus (40) to calculate jointly and separately the instantaneous power delivered for each cyclist's leg, comprising two of the aforementioned pedaling torque sensor devices, means to measure the instantaneous angular velocity of the crankset and a power meter CPU (35) that integrates and processes the signals received.

Abstract: A turbine design method that can easily construct a turbine stage structure in which an unsteady force acting on a rotor blade can be reduced and degradation in performance and increase in rotor shaft length can be prevented is provided. Unsteady forces and exciting forces by the potential field interaction acting on the rotor blade are respectively obtained, exciting forces by the wake interaction acting on the rotor blade are obtained, the exciting forces by the potential field interaction and the wake interaction are mathematically expressed, the unsteady force acting on the rotor blade when the distance between stator and rotor blades is an arbitrary value is calculated, and the distance between stator and rotor blades is determined based on a calculation result.

Abstract: An apparatus for estimating at least one of a dynamic motion of a portion of interest of a drill string and a static parameter associated with the portion of interest, the apparatus having: a plurality of sensors operatively associated with the drill string at at least one location other than the portion of interest; and a processing system coupled to the plurality of sensors, the processing system configured to estimate at least one of the dynamic motion and the static parameter using a measurement from the plurality of sensors as input.

Abstract: The sail force gauge utilizes an electronic system to measure the vectored force of the mainsheet or jib sheet. By gaining the vectored force of the sheet, a relative vectored force upon the sail can be acquired thru simple trigonometric equations. To obtain the vectored force measurement, a multi-axis load cell will measure the force in the lateral and axial directions. These forces can be used to calculate the vectored force of the mainsheet. By knowing the dimensions of the boom length, the sheet block positions, and the vector angle, the resultant angle of the boom can be calculated as well as the perpendicular sail force acting upon the boom. From these calculations, the relative axial force acting upon the boat can be calculated.

Abstract: A method for establishing the deflection and/or the stiffness of a supporting structure which is subjected to a load. The method includes the steps of moving a measurement vehicle along the supporting structure, the vehicle having a loaded axle, a first measuring system being a first versine system and a second measuring system being one of an inertia based system and a second versine system. At a predetermined sampling rate, two sets of levels are measured using the two measuring systems. The two sets of levels are converted or transformed such that they relate to the same reference system and, thereafter, for each pair of sampled levels, the difference between the two levels is calculated such that the contribution to the measurements originating from unloaded irregularities in the supporting structure is eliminated, whereafter the deflection and/or the stiffness of the supporting structure is established from the calculated difference.

Abstract: A system for simultaneously determining strain and temperature characteristics of an object comprising: (i) at least one optical fiber having at least two Brillouin peaks; (ii) at least one connector securing the optical fiber to the object to be monitored; (iii) a laser positioned to provide laser light to said at least one optical fiber; (iv) a device measuring frequencies of said at least two Brillouin peaks, and determining frequency shifts of said at least two Brillouin peaks for said at least one optical fiber along the length of fiber; and (v) a system calculating strain and temperature characteristics along said fiber, based on the coefficients of strain and temperature as well as the measured Brillouin frequency shifts for said optical fiber along the length of said optical fiber.

Abstract: A battery management system for use with a battery under test is disclosed. The system includes a container configured to hold the battery. The system also includes a stress/strain sensor. The container is configured to hold the battery in fixed relationship with respect to the stress/strain sensor. A processor is coupled to the stress/strain sensor, the processor being configured to measure the stress/strain on the battery and determine the state of health (SOH) of the battery based on the measured stress/strain and previously stored SOH relationship data for the battery. The processor may be configured to determine a state of charge (SOC) of the battery based on the measured stress/strain, the SOH of the battery and previously stored SOC relationship data for the battery.

Abstract: A method dynamically reconstructing a stress and strain field of a turbine blade includes providing a set of response measurements from at least one location on a turbine blade, band-pass filtering the set of response measurements based on an upper frequency limit and a lower frequency limit, determining an upper envelope and a lower envelope of the set of response measurements from local minima and local maxima of the set of response measurements, calculating a candidate intrinsic mode function (IMF) from the upper envelope and the lower envelope of the set of response measurements, providing an N×N mode shape matrix for the turbine blade, where N is the number of degrees of freedom of the turbine blade, when the candidate IMF is an actual IMF, and calculating a response for another location on the turbine blade from the actual IMF and mode shapes in the mode shape matrix.

Abstract: A sensor device for measuring the compression travel and/or the compression rate of wheels and/or axles of vehicles, in particular of commercial vehicles, may include at least one sensor measuring in a contactless manner. The sensor device may include a radar and/or high-frequency sensor generating a beam, which is emitted and received after reflection at a reference and reflection surface.

Abstract: This invention is an apparatus and method for measuring or analyzing a golf swing. Measurement or analysis is made relative to energy generation and transfer through a player's body and club. The measurement or analysis data is principally obtained from the player's ground-reaction forces. Processed signals are analyzed with an artificial intelligence system. Ground-reaction forces relate to reaction forces which occur between a standing surface and the player's feet. The apparatus and method measures or analyses a golf swing in an automatic manner or in an automatic and interactive manner.

Abstract: In order to reduce the switching hysteresis in a dynamic positioning system and/or an autopilot system for watercraft, an arrangement is provided for determining a force acting on a rudder for watercraft. This arrangement includes a processing unit, at least one measuring device for determining values of a physical quantity of a rudder, and means for transmitting the determined values of the physical quantity to the processing unit. The processing unit is configured to determine the force acting on the rudder on the basis of the determined values of the physical quantity.

Abstract: A method and test circuit provide measurements to accurately characterize threshold voltage changes due to negative bias temperature instability (NBTI) and positive bias temperature instability (PBTI). Both the bias temperature instability recovery profile and/or the bias temperature shifts due to rapid repetitions of stress application can be studied. In order to provide accurate measurements when stresses are applied at intervals on the order of tens of nanoseconds while avoiding unwanted recovery, and/or to achieve recovery profile sampling resolutions in the nanosecond range, multiple delay or ring oscillator frequency measurements are made using a delay line that is formed from delay elements that have delay variation substantially caused only by NBTI or PBTI effects. Devices in the delay elements are stressed, and then the delay line/ring oscillator is operated to measure a threshold voltage change for one or more measurement periods on the order of nanoseconds.

Abstract: A method is provided for obtaining a quantitative prediction of a magnitude of a maximum horizontal stress (SH/SV) at a point on a horizon within a prospect including the following steps: a) receiving seismic reflection data including a plurality of seismic reflection lines within the prospect; b) interpreting the seismic reflection data to identify at least four horizons produced during a compressional pulse period and at least one anticline and/or syncline; c) mapping in plan the identified anticlines and/or synclines; d) classifying each anticline into one or more predefined stress states based on the length of the anticline and its proximity to adjacent anticlines and/or classifying each syncline into one or more predefined stress states based on the length of the syncline and its proximity to adjacent synclines; wherein each predefined stress state corresponds to a predetermined value for the magnitude of the maximum horizontal stress (SH/SV).

Abstract: Methods and systems are described for the identification and determination of loads by inverse analysis. A new combination of instrumentation and measurements is provided which allows accurate identification/measurement of static and/or dynamic forces, or loads, working on arbitrary test-objects or systems (i.e. test objects), through measurements of the results of the loads on the test object, signals like pressures, electrical potential, magnet flux displacement, strain, etc. This procedure allows the measurement/identification of arbitrary single or multiple loads, in arbitrary combinations, and multiple directions. The procedure also allows the measurement/identification of loads with arbitrary evolution in time, including static and dynamic loads.

Abstract: A hardness test method includes a measurement step of forming an indent by indenting a surface of a sample with an indenter loaded with a predetermined load and detecting a displacement quantity of the indenter and a test force loaded on the indenter at a time of forming the indent to measure an indentation curve, a work load calculation step of calculating a work load by plastic deformation (Wp) from an area of an indentation curve obtained by the measurement step, and an estimation calculation step of calculating an estimation (HVe) of Vickers hardness by using the work load (Wp), calculated at the work load calculation step, and a previously determined coefficient K in conformity with HVe=(K/Wp)2.

Abstract: A method of predicting distortion in a workpiece may include measuring residual stress induced in a coupon surface of a plate coupon by a selected manufacturing operation. The induced residual stress measurements may be fitted to a curve shape function. A moment coefficient may be calculated based upon the fitted induced residual stress measurements. The moment coefficient may be used to calibrate a stress function and corresponding stress magnitude. The calibrated stress function may be applied to a model of the workpiece such that the distortion of the workpiece may be predicted.

Abstract: A system comprises a sensing node that includes a sensor, a processor, an energy harvesting circuit, a time keeper, a first energy storage device, and a second energy storage device. The energy harvesting circuit is connected for recharging the first energy storage device. The processor is connected for receiving all its power derived from the energy harvesting circuit. The second energy storage device is connected for powering the time keeper.

Abstract: A system includes a first sensor, a second sensor and a processing portion. The first sensor can wirelessly transmit a first detected signal based on a detected parameter of a structure. The second sensor can wirelessly transmit a second detected signal based on the detected parameter of a second portion of the structure. The processing portion can wirelessly transfer energy to the first sensor and the second sensor. The processing portion is operable to wirelessly transfer electromagnetic energy to enable the first and the second sensors.

Abstract: A method of optimizing machine performance in a plurality of load cases may involve the steps of: Determining a maximum load case for the machine, the maximum load case involving the application of a maximum force to at least one member of the machine; determining, for each of a plurality of member joints of the machine, a maximum member joint load for the maximum load case for the machine; and operating the machine by applying a force to the at least one member of the machine in each of the plurality of load cases so as not to exceed the maximum member joint load, the applied force exceeding the maximum force during at least one of the plurality of load cases.

Abstract: A method for press forming analysis includes (1) performing a coordinate transformation to calculate a distribution of stress (a) before a release from the press die in a local coordinate system; (2) performing a springback analysis which includes (i) calculating a distribution of residual stress after the release and performing the coordinate transformation to calculate a distribution of residual stress (b) in the local coordinate system, and (ii) calculating shape data (d) after the release; (3) calculating a difference (a-b) as SB effective stress, performing a coordinate transformation to calculate a distribution of SB effective stress in a global coordinate system, changing or removing the SB effective stress in an analysis target region and performing the springback analysis to calculate a shape data (c) after the release; and (4) calculating a difference (c-d) to determine a degree of influence of the analysis target region.

Abstract: A fracture determination method for determining a fracture of a metal structure includes, when a fracture determination target portion has returned from a plastic state to an elastic state, given that a stress when the portion returned to the elastic state is (x, y)=(?2, ?1) (maximum principal stress: ?1, minimum principal stress: ?2) on a (x, y) coordinate plane, performing fracture determination of the fracture determination target portion using a re-yield stress R determined by the intersection between a straight line satisfying a relation y=(?1/?2)x and an yield curve obtained from the plastic state of the fracture determination target portion. Fracture determination can be performed with high accuracy even when the fracture determination target portion has returned from a plastic state to an elastic state.

Abstract: A system for monitoring and documenting the installation of at least one rock reinforcement bolt in a tunnel or a mine, wherein bolt installation related information is stored and related to the identity of the bolt is distinguished by means (S1, S2, S3, 4) for registering of at least one bolt installation related parameter and means for storing the corresponding installation parameter data in a related memory (M), and means (S4, 4) for registering the installation position and means for storing the corresponding installation position data in a related memory (M). The invention also concerns a method.

Abstract: The present invention provides a system and a method monitoring the health of structural joints by monitoring the strain developed near the joint due to perturbation applied away from that joint and comparing the monitored ratio between near field and far field strain to strain ratio which develops in a healthy joint due to comparable perturbation. The system for monitoring joints comprises: at least one near field strain measuring device installed near a monitored joint for monitoring the induced strain; at least one far field strain measuring device installed away from monitored joint indicating, measuring or producing the perturbation; and a data processor connected to said near field strain measuring device and to said near field strain measuring device for analyzing the response of the structure to the perturbation and determining the integrity of said joint.

Abstract: A method of analyzing a cause of springback of the invention includes: performing a forming analysis to calculate forming data of a formed product; decomposing a component into an in-plane stress component and a bending moment component; generating a before-calculation individual decomposition forming data; performing a calculation to generate an after-calculation individual decomposition forming data; analyzing a first springback configuration and a second springback configuration; obtaining a degree of influence of a stress in each of the areas with respect to springback deformation; and displaying the degree of influence with respect to the springback deformation.

Abstract: When discretizing an analysis target part into plural elements and performing analysis, sheet thickness reduction rate or maximum principal strain at an equivalent position including a same element is compared by either a manner of combining two adjacent elements after the analysis or a manner of changing an element discretization size with two types and performing the analysis, and the element where the difference is large is extracted as a fracture risk portion. With this structure, a fracture risk portion can be extracted reliably when a fracture is predicted by a finite element method.

Abstract: A strain measurement device to assess the integrity of a structural repair to a surface comprises a detector, a processor, and a memory module coupled to the processor. The memory module comprises logic instructions stored in a computer readable medium which, when executed by the processor, configure the processor to use the detector to obtain a first strain measurement from an external strain indicator, use the detector to obtain a second strain measurement from the measurement sensor after at least one stress test is applied to the structural repair, and generate a signal when a difference between the first strain measurement and the second strain measurement exceeds a threshold.

Abstract: A method of determining face paper properties of all types of wallboard including providing a core strength value of the wallboard, determining a required nail pull value based the wallboard specifications and calculating a face paper stiffness value based on the provided core strength value and the determined nail pull value. The method includes displaying the calculated face paper stiffness value on a display device.

Abstract: A system for measuring forces from a rotating object is presented. In one aspect, the measurement system has a plurality of strain sensors that are configured to attach to the sidewall of a tire of a vehicle and measure the strain on the sidewall. The system can also have a data processor to relate the strain on the sidewall to the normal force exerted on the driving surface from the tire.

Abstract: Virtual sensors can be used to monitor the loads on the system in determining damage accumulation, remaining useful life or retirement time of the components. A virtual sensor is a mathematical construct to infer a desired system measurement (e.g. a structural load) from readily available system state parameters (e.g. speed, weight, load factors, control settings, etc.). The accuracy of the virtual sensor depends upon the mapping between the desired measurement and the state parameters. A hybrid load monitoring system and method includes one or more direct or physical sensor measurements in addition to the plurality of virtual sensors. Signals from the physical sensors are included as an input (as opposed to an output) to the mapping between system state parameters and the various target sensor feature amplitudes.

Abstract: A pressure sensitive device interface including a display screen, a framing structure that receives a force applied to the portable electronic device and exhibits strain within the framing structure, a strain gauge that identifies the strain within the framing structure, and a processor coupled to the display screen and the strain gauge and configured to measure the strain identified by the strain gauge and control the user interface according to the measurement of the strain. Among aspects, the framing structure may include a first pair of parallel elements that form opposing elongated outer edges of the portable electronic device, and a second pair of parallel elements that extend perpendicularly between the first pair of parallel elements. Among additional aspects, the processor may be further configured to identify a plurality of gestures with reference to strain metrics.

Abstract: A method for simulating the behavior of a tire mounted on a vehicle in running conditions on the ground, wherein a mechanical model is provided for essentially computing the longitudinal (Fx) and transverse (Fy) stresses transmitted by the tire between the ground and the vehicle in accordance with dynamic parameters related to the physical conditions of the tire running and use and in accordance with physical tire-specific parameters. The mechanical model is set and solved in an iterative manner, under the assumption that the tire in contact with the surface of the ground has an adherence contact area and a sliding contact area and under the assumption that there is a unique x-coordinate point b that is indicative of the transition between the two contact areas.

Abstract: A simplified tool is provided for simultaneous prediction of dent resistance and snap-through buckling resistance of roof panels including the effect of roof bow placement, curvatures of the roof panel, thickness of the roof, and steel grade. In one embodiment, a method of predicting snap-through buckling resistance of a sheet metal panel to an applied load under localized loading conditions is provided, wherein the sheet panel has certain defined geometries. The method includes the steps of: identifying first and second principal radii of curvature of the panel; identifying a thickness of the panel; identifying the distance of a portion of the panel between structural supports; creating a mathematical function to determine load deflection behavior for snap-through buckling; and determining the likelihood of the panel to display snap-through buckling characteristics under various localized applied loads by inputting the parameters.

Abstract: In one aspect, embodiments of a method of using one or more stress factors to determine whether or when to perform a maintenance activity are described. One embodiment of the method comprises identifying one or more maintenance activities for a system; associating one or more stress factors to each of the identified one or more maintenance activities for the system; determining a value for each of the one or more associated one or more stress factors; and determining, using a computing device, whether to schedule one of the one or more maintenance activities for the system based on the determined value of each of the one or more stress factors associated with the one of the one or more maintenance activities.

Abstract: A method to estimate the fatigue life of a component operable under cyclic stress is provided. A system including testing device for performing a strain controlled test of a component or a representative specimen of the component, to obtain therefrom a first set of data samples including measured stress amplitude values for varying applied strain levels, and a second set of data samples including measured number of cycles to crack initiation for varying applied strain levels is also provided. The system further includes a modeling device for fitting a first low cycle fatigue material curve on the first set of data samples and a second low cycle fatigue material curve on the second set of data samples.

Abstract: A system (20) for monitoring deformation of a substantially cylindrical casing (14). The system (20) includes at least two strings (22) of interconnected sensors (24) that are wrapped around the casing (14) so as not to intersect one another. At least one of the strings (22) includes a series of at least two segments (S). The series of segments (S) includes a segment (S) arranged at one wrap angle (?) and another segment (S) arranged at a different wrap angle (?).

Abstract: A mechanical seal monitoring system and method that measure the wear of seal faces of a mechanical seal where the mechanical seal seals a rotating machine portion from another portion of the machine. The system preferably uses a wear probe movable relative to a rotating seal component so that the wear probe can contact the rotating component. The wear of the seal is preferably determined by the relative movement that is required for the wear probe to contact the rotating component. Preferably, stress waves induced by the rubbing between the probe and the rotating component are detected by a stress-wave sensor, processed by a signal processor, and either displayed to the user numerically or reported to a monitoring computer. A signal intensity comparison method is preferably used to make the detection process insensitive to background noise generated by sources other than the contact of the wear probe and the rotating component.

Abstract: Information provided with a direct deposit, a deposited check, or other negotiable instrument may be used to determine state, city, county, and/or other local income tax liability. Based on information associated with the deposit, the financial institution may determine where a user performed the work that triggered the income payment, where the income payment took place, what type of work is associated with the income payment, etc. This information may be used by the financial institution to provide income itemization and income tax liability information to the user via a user computing device.

Abstract: A computer implemented method is provided for analyzing the health of a structure by measuring the value of preload on each of a plurality of fasteners installed on the structure and correlating the measured values of preload with a set of specifications. A report is generated for each of the fasteners representing the results of the correlations. Groups of the fastener reports are used to infer the health of the structure.

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: Methods and apparatus are described to use real-time measurement systems to detect the onset of compression induced microfracturing of fiber-reinforced composite materials. Measurements are described to detect the onset of compression induced microfracturing of fiber-reinforced composite materials to prevent catastrophic failures of aircraft components containing such materials. Methods and apparatus are described to prevent fluids and gases from invading any compression induced microfractures by coating surfaces of fiber-reinforced materials to reduce the probability of failure of such fiber-reinforced materials.