Abstract: Systems and methods for analyzing structural test data are disclosed. In one embodiment, a method includes applying a sequence of loads to a test article, receiving raw test data indicative of the applied loads from at least one sensor operatively associated with the test article, receiving predicted test data indicative of the predicted loads on the test article, filtering out invalid test data, cycle counting to pair loads in the test data, performing a first fatigue damage computation based on the raw test data, performing a second fatigue damage computation based on the predicted test data, and comparing the first and second fatigue damage computations. The filtering, cycle counting, and performing of the first and second fatigue damage computations, and the comparison of the first and second fatigue damage computations, may be performed simultaneously using a spreadsheet program.

Abstract: A method comprises storing data relating to the wear of a component of at least one turbine system in a database of a system for processing wear related information, generating a displayable menu containing a plurality of user-selectable links respectively associated with software modules of the system, and receiving an on-line selection of one of the user-selectable links to enable the associated software module of the system to generate displayable content including information relating to the wear of the component of the turbine system. The selected module may enable a quantitative amount of the wear of the component or qualitative wear range characterizing the amount of the wear of the component to be input and received on-line. Alternatively, the selected module may enable a component type to be input and received on-line and display a component fleet leader.

Abstract: The present invention provides systems and methods to used a measured driving-point response of a nonlinear material to determined one or more elastic properties of the material. The present invention takes advantage of the full information represented by the transient component, the steady-state component, the anharmonic components, and the nonlinear response components of a measured driving-point response of a real nonlinear material, without limitation in the use of large-amplitude forces. The elastic properties are determined by forming and solving a time-domain system of linear equations representing a differential equation model of the driving-point motions of the material. Based on a single, short duration, large-amplitude driving point measurement, both linear and nonlinear properties can be determined; both large-amplitude and near-zero amplitude properties can be determined; and elastic-wave speed and elastic moduli and their variation with depth can be determined.

Abstract: A system for identifying a signal source in a predetermined space, the system including multiple sensing units arranged at different locations to detect signals in the predetermined space. The system also includes one or more recording units arranged to separately and simultaneously record a detected signal at each of the sensing units that detects the signal. The system further includes a processing unit including a first storage area configured to store a set of identified signatures corresponding to multiple signal sources in the predetermined space, and a second storage area configured to store parameters related to the conditions under which the recordings of the signal are made. The processing unit also includes an identifying unit that is programmed to identify a signal source by comparing a determined signal spectrum with some or all of the signatures included in the set of identified signatures.

Abstract: In a method of identifying a source of a signal, the signal is recorded and then analyzed in order to determine its spectrum. The method includes the following steps: in parallel with recording the signal, storing parameters significant of the conditions under which the recording is made; after analyzing the signal and determining its spectrum, detecting lines emerging from the background noise of the signal, using a predetermined emergence threshold; comparing each line detected with some or all of a set of signatures of sources identified and inventoried in a database established prior to the recording; and for each line, and where applicable, selecting signatures that may correspond to the line and, as a function of the resulting signature/line pairs, consolidating, resolving ambiguity of, or quantifying the source corresponding to said line.

Abstract: A method for identifying a signal source in a predetermined space, the method including inventorying a set of identified signatures corresponding to a plurality of signal sources and recording a signal simultaneously at different locations of the predetermined space. Parameters related to the conditions under which the recordings are made are then stored, and a spectrum of the signal is determined. The method also includes detecting a line emerging from background noise of the spectrum by using a predetermined emergence threshold. The line is then compared with some or all of the signatures included in the set of identified signatures, and at least one signature corresponding to the line is selected to create at least one signature/line pair. Finally, a source of the signal is identified based on the selecting step.

Abstract: A fatigue test device for thin plates can reliably perform tests. The fatigue test device has a rod having ends in a longitudinal direction thereof; a vibration source for excitating a longitudinal end of the rod in the longitudinal direction thereof so as to form a standing wave having node portions and antinode portions formed therebetween and a mounting means for mounting a test piece having a longitudinal direction at one of the antinode portions, the test piece being positioned such that the longitudinal direction thereof is perpendicular to the longitudinal direction of the rod.

Abstract: The apparatus and method for moving a sensor over a workpiece includes a sensor, and an actuating member. The sensor, such as a non-destructive test sensor, is carried by the actuating member, and the actuating member is at least partially disposed within a housing. The actuating member is adapted for automated movement in one direction, and the housing may be configured to be grasped by an operator and manually moved in another direction. As such, the sensor may automatically move in one direction with respect to the workpiece without manual intervention, and manually move in another direction, such that the sensor is moved by the combination of automated and manual movement. In addition, the actuating member may have at least two substantially parallel arms extending from near the sensor, which permits the sensor to slide along the workpiece while maintaining a substantially normal relationship to a surface of the workpiece.

Abstract: A method, system and computer program product are provided for automated fatigue and structural analysis of a structural element. The method, system and computer program product consolidate and manage the fatigue and structural analysis tools and are responsive to user requests for fatigue and structural analysis of elements based upon user-provided information regarding the element. As such, the appropriate fatigue and structural analysis tools are automatically selected and run, and the output of the tools is automatically evaluated to provide immediately useful fatigue and structural analysis results to the user without requiring further manual input. Thus, people without specialized training can quickly obtain fatigue and structural analysis results for an element. In addition, because the fatigue and structural analysis tools are integrated, the tools may be accessed from remote locations via a computer network.

Abstract: In a method of detecting damage in materials or objects (4) the material or object is physically influenced to produce a physical change of the material or object inducing transient slow dynamics in case of damages in the material or object. Slow dynamics induced material elastic modulus changes are detected as indication of damages of the material or object. In a device for non-destructive detection of damage in materials or objects (4), an impact source (16) is provided to impact the material or object to physically influence the material or object to produce a physical change of the material or object inducing transient slow dynamics in case of damages in the material or object. A detector (2,8,10,12,14,6) is provided to detect by said slow dynamics induced material elastic modulus changes as indications of damages of the material or object.

Abstract: Disclosed are a device and a corresponding method to test the fretting of a ball bearing under precisely controlled conditions. The device employs a first piezoelectric actuator to deliver a pre-determined force to the surface of a ball bearing or other object to be tested. The force is applied in a first axis of motion. A second piezoelectric actuator, coupled to a flexure hinge platform, translates the workpiece in a second axis of motion that is different (and preferably substantially orthogonal) to the first axis. The combination of the relative motion between the workpiece and the force exerted upon it produces predetermined dynamic patterns of the stress and strain on the surfaces of the workpiece being tested. Closed-loop control architecture, piezoelectric actuators, and force/displacement sensors included in the device provide highly accurate and rapid tests.

Abstract: A method for determining the sensitivity of the fatigue life of a structural component with respect to specific design parameters includes obtaining the stress profile for a structural component under random process establishing a relationship between the stress profile and the fatigue life of the structural component, developing the sensitivity of the fatigue life with respect to design parameters, optimizing the design of the structural component based upon the design parameters to which the fatigue life is most sensitive.

Abstract: A method and system for nondestructively detecting and characterizing defects in articles, including assemblies that may include components formed of composite materials. The method entails vibrating an entire article/assembly to induce an oscillating strain in the article/assembly so that any flaws in the article/assembly are heated by localized friction, as would occur between opposing surface portions of a defect or an interface between components of the assembly. The article/assembly is then infrared imaged to detect any localized temperature rises associated with the localized friction at the defect or interface.

Abstract: A fatigue test device for thin plates can reliably perform tests. The fatigue test device has a rod having ends in a longitudinal direction thereof; a vibration source for excitating a longitudinal end of the rod in the longitudinal direction thereof so as to form a standing wave having node portions and antinode portions formed therebetween and a mounting means for mounting a test piece having a longitudinal direction at one of the antinode portions, the test piece being positioned such that the longitudinal direction thereof is perpendicular to the longitudinal direction of the rod.

Abstract: An apparatus and method for screening combinatorial libraries of materials by measuring the response of individual library members to mechanical perturbations is described. The apparatus generally includes a sample holder for containing the library members, an array of probes for mechanically perturbing individual library members, and an array of sensors for measuring the response of each of the library members to the mechanical perturbations. Library members undergoing screening make up a sample array, and individual library members constitute elements of the sample array that are confined to specific locations on the sample holder. During screening, the apparatus mechanically perturbs individual library members by displacing the sample array (sample holder) and the array of probes. Typically, all of the elements of the sample array are perturbed simultaneously, but the apparatus also can also perturb individual or groups of sample array elements sequentially.

Abstract: A plurality of wires (33, 34; 35, 36) are disposed near the bottom (23-25) of blade root sockets (16-18) of a rotating disk 39 of a gas turbine engine by vapor deposition and etching, the wires including connections to excitation nodes (40, 42) and detection nodes (41, 43). A nearby stationary member of the engine mounts an oscillator amplifier (55) which drives a coil (57) that excites the circuitry, and a coil (62) drives an amplifier (65) and a processor (67) which provides an indication of whether or not one or more of the wires are broken by a crack.

Abstract: A method and device for visually detecting crack length of a temperature sensitive paint coated test structure during excitation of the test structure. The method and device of the invention capitalizes on surface temperature changes of the test structure as structural fatigue increases. Test structure surface temperature changes are realized in corresponding fluorescence intensity changes in the temperature sensitive paint and recorded with a CCD camera. Improvements over conventional structural fatigue systems include the ability to detect fatigue during flight testing, to record fatigue without stopping the electrodynamic excitation and the ability to detect crack onset and crack length resulting in more accurate cycles-to-fatigue analysis.

Abstract: A method and apparatus for low-power sensing and processing are provided. A method preferably includes collecting a plurality of sensor signals. The plurality of sensors include sensed data representative of at least shock and vibration. The method also includes converting the plurality of sensor signals into digital data, processing the digital data, generating a data communications protocol for communicating the digital data, and simultaneously and remotely detecting the generated communications protocol having the processed data to determined the occurrence of at least one predetermined condition. An apparatus preferably includes a low-power, data acquisition processing circuit responsive to a plurality of sensor signals representative of at least shock and vibration for acquiring and processing the sensed data.

Abstract: A system and method for identifying characteristics of a physical system applies substantially identical drive ensembles to the physical system and obtains corresponding responses from the physical system. A repeatable bandwidth of the physical system is estimated as a function of the applied drive ensembles and the corresponding obtained responses. Instructions can be provided on a computer readable medium to perform the method.

Abstract: An acoustic non-linearity parameter (&bgr;) measurement method and system for Non-Destructive Evaluation (NDE) of materials and structural members obviates the need for electronic calibration of the measuring equipment. Unlike known substitutional measuring techniques requiring elaborate calibration procedures, the electrical outputs of the capacitive detector of a sample with known &bgr; and the test sample of unknown &bgr; are compared to determine the unknown &bgr;. In order to provide the necessary stability of the present-inventive reference-based approach, the bandpass filters of the measurement system are maintained in a temperature-controlled environment, and the line voltage supplied to said amplifiers is well-regulated.

Abstract: Devices and methods for producing mechanical vibration for the purpose of evaluating the durability or vibration response of a test article. More particularly, the devices and methods produce mechanical vibration of a test fixture without mechanical contact, thereby enabling the evaluation of the durability and vibration response of a test article connected to the test fixture. The device and method are particularly suitable for testing disk drives for portable computers and similar articles.

Abstract: A hardened steel ball presses against a vibrating sample to be subject to fretting. The amplitude and frequency of vibration can be precisely controlled by a stack of piezoelectric transducers. The biasing force of the steel ball against the sample can also be precisely controlled by a pulley supported weight that pulls against a movable mass coupled to the steel ball. The movable mass has sufficient inertial mass to eliminate the movement of the ball which might otherwise be produced in reaction to the vibration of the sample, which need not be absolutely flat.

Abstract: For automatically predicting machine failure a transducer sensor, such as piezoelectric crystal, is applied to a machine for sensing machine motion and structure-borne sound, including vibration friction, and shock waves. The structure-borne sound and motion sensed is converted to electrical signals which are filtered to leave only the friction and shock waves, which waves are processed, as by detecting the envelope and integrating beneath the envelope, resulting in a measure of friction and shock wave energy, i.e., stress wave energy. This measure is computed and processed for producing fault progression displays for periodic and aperiodic damage. This is accomplished in a personal computer, menu-driven environment.

Abstract: A system and method of the present invention measures the relative stress in the cladding of a nuclear fuel rod caused by the internal gas pressure of the rod. This is done by determining the attenuation ratio of two specific frequencies from a broadband low frequency acoustic energy spectrum. Relative pressure differentials are measurable and therefore any loss of fuel rod gas pressure is a direct indication of fuel rod cladding failure.

Abstract: The fatigue integrity of metallic materials may be determined by either one of two methods. In a first method, an impulse of energy is introduced into the material, such as by striking the material (20), and the induced vibration is sensed and analyzed in order to compute the damping factor thereof, the damping factor being directly related to the fatigue thereof. With this method, a transducer (28) is coupled to the material and its output is amplified by an amplifier (30) before input to a computer (32) which determines the damping factor. In a second method, a continuous energy input is provided to the material, such as by utilizing a frequency generator coupled to a power amplifier whose output drives a transducer such as a speaker or the like for inducing a continuous vibration in the metallic material. This continuous vibration is measured with a transducer, an amplifier, and a damping factor calculated with a computer as in the first method.

Abstract: A device and method are provided which non-destructively detect crack length and crack geometry in thin metallic plates. A non-contacting vibration apparatus produces resonant vibrations without introducing extraneous noise. Resulting resonant vibration shifts in cracked plates are correlated to known crack length in plates with similar resonant vibration shifts. In addition, acoustic emissions of cracks at resonance frequencies are correlated to acoustic emissions from known crack geometries.

Abstract: The magnetoelectric coefficient in iron-based alloys has a stress value of about 0.6 of that of the elastic limit. A reversal in sign is caused by structural phase slip which is the basis for the onset of metal fatigue. Based on this phenomenon, a method is provided for determining the onset of metal fatigue. The method includes applying a periodic mechanical stimulus at a given frequency to a test structure, and using a magnetometer, sensing the magnetic field of said structural element during the application of stimulus, and then determining whether or not there is a 180 degree difference between the phase of the stimulus and that of the magnetic response for various regions of the test structure.

Abstract: A method and apparatus is provided for testing dissipative mechanical phenomena, including fretting wear. An actuator (54) effects frictional oscillatory slip motion between a stylus (32) and a workpiece (30) in contact. A displacement transducer (62) detects the amplitude of the slip motion, and a control loop (60) responds to the displacement transducer controls the actuator to provide constant amplitude slip motion under changing frictional fretting wear conditions of the workpiece as the workpiece wears during the oscillatory slip motion. The oscillator is driven at its resonant frequency, and the power required to maintain constant amplitude slip motion at resonant frequency is monitored (64).

Abstract: Reflection wave forms obtained from aged and unaged material samples can be compared in order to indicate trends toward age-related flaws. Statistical comparison of a large number of data points from such wave forms can indicate changes in the microstructure of the material due to aging. The process is useful for predicting when flaws may occur in structural elements of high risk structures such as nuclear power plants, airplanes, and bridges.

Abstract: A method for detecting damage in the structure includes a plurality of steps. These steps include determining first data indicative of pre-damage modal parameters of the structure, determining second data indicative of post-damage modal parameters of the structure, and identifying at least one location of the damage based upon first and second data applied to an indicator function. The damage detection method is capable of localizing damage in the structure, and subsequently estimating the magnitude of such damage, using limited modal information.

Abstract: A system for locating a fatigue point on a structure (10) employing a smart sensor patch (12) having three triangularly adjacent acoustic sensors (40 a,b,c). The smart sensor patch (12) has a local processor (34) associated therewith, which triangulates the location of the fatigue point.

Abstract: A system for determining the magnitude of loads on rotating helicopter components from sensor signals remotely measured on the helicopter fuselage is characterized by a controller which samples the sensor signals according to phase. These measured signals are presented to a coefficient programming module where they are combined with correlation signals to correlate the measured signal components with the desired parameter, such as flatwise bending moments of a helicopter blade. The correlation signals are established in a calibration process that determines the independent values of the measured signals using a Jones orthoganization process. The signals output from the module are recombined to provide a time dependent signal corresponding to the desired parameter. The present system avoids decomposition and recomposition of the measured signals and therefor operates in real time.

Abstract: The weight fractions of the phases of a composite material working specimen are determined nondestructively by first performing a sufficient number of nondestructive and destructive calibration measurements on the properties of calibration specimens. The information learned from the calibration specimens is used in combination with nondestructive measurements of the working specimen to determine the fractions of the phases therein, without damaging the working specimen. In one version of this approach, ultrasonic measurements are used to determine fractions of the fiber and matrix in a nonmetallic composite material.

Abstract: A method for predicting and controlling the strength development of concrete includes placing test concrete having the same composition as the subject concrete in a vessel which may be temperature regulated. The temperature inside the vessel is measured and recorded in a data memory and a data processor. The data is transmitted either in real time or from the data memory and data processor by way of a data transmission line to a temperature regulator for regulating the temperature inside the vessel. The temperature history of the test concrete can then simulate the temperature history of the reference concrete. The strength of the test concrete is measured at different times and the strength data of the test concrete is collected, processed and interpreted. A vessel for receiving the test concrete, a temperature regulator, a temperature controlling unit, a data recorder, a data transmitter and a computer are included.

Abstract: An apparatus for processing acoustic emissions or stress waves in order to recognize features indicative of variations in the process producing the acoustic emissions. The apparatus comprises a transducer acoustically coupled to a machine or industrial process and arranged to detect the acoustic emissions and produce an electrical signal. The electrical signal is amplified by an amplifier and the mean level of the electrical signal is measured by a mean level detector and the minimum level of the electrical signal is measured by a minimum level detector. A ratio measurer measures the ratio of the mean level of the electrical signal to the minimum level of the electrical signal. This method is self compensating for variations in the operating conditions of the machine or industrial process, is not significantly affected by electromagnetic switching transients, and can cope with very high numbers of transient excursions.

Abstract: An on-line vibratory fatigue monitor measures displacement of an object such as the blade of a turbine rotor to generate a displacement signal and calculates accumulated fatigue in the object in dependence upon the displacement signal. The displacement of the object may be detected by passive proximity probes which generate signals indicative of changes in magnetic flux or capacitance between the sensor and the turbine blade. An analog/digital converter converts the signals from the probes to digital signals indicating displacement of the turbine blades. The digital signals are processed, preferably by taking a Hilbert transform, to detect the amplitude envelope and instantaneous frequency of the displacement. The amplitude and frequency are combined with steady state stress on the object to determine fatigue usage which is accumulated by constantly monitoring vibratory displacement and changes in the steady state stress.

Abstract: The weight fractions of the phases of a composite material working specimen are determined nondestructively by first performing a sufficient number of nondestructive and destructive calibration measurements on the properties of calibration specimens. The information learned from the calibration specimens is used in combination with nondestructive measurements of the working specimen to determine the fractions of the phases therein, without damaging the working specimen. In one version of this approach, ultrasonic measurements are used to determine fractions of the fiber and matrix in a nonmetallic composite material.

Abstract: A novel system for determining the magnitudes of loads on rotating helicopter components from signals remotely measured on the helicopter fuselage is characterized by a processor which decomposes the measured signals into corresponding Fourier components and extracts selected components therefrom. A programming module performs a multiplication on the respective Fourier components to correlate the measured components with corresponding determinative parameter values. The parameter values are established in a calibration process which is characterized by determination of the independent values of a measured signal set using a Jones orthogonalization process. The signals output from the coefficient programming module are provided to a multiplying resolver which receives synthesized reference sinusoids from a digital processor and generates time dependent signal components therefrom. These signals are ultimately summed in an analog summer circuit whose output signal corresponds to the desired parameter signal.

Abstract: The weight fractions of the phases of a composite material working specimen are determined nondestructively by first performing a sufficient number of nondestructive and destructive calibration measurements on the properties of calibration specimens. The information learned from the calibration specimens is used in combination with nondestructive measurements of the working specimen to determine the fractions of the phases therein, without damaging the working specimen. In one version of this approach, ultrasonic measurements are used to determine fractions of the fiber and matrix in a nonmetallic composite material.

Abstract: The device concerns a method for detecting the position of at least one point of the crack front within a part (4) subjected to fatique stresses or to a ductile rupture. An ultrasonic beam is used focused in the plane P of the crack growth; the axis of this beam forms an angle comprised between 50.degree. and 80.degree. with P. The beam is displaced until the echo passes through a maximum, in which case the focusing is situated at the tip of the crack in the plane of displacement. The invention also concerns a device for the implementation of the method.

Abstract: Axial cracks in the rotor assembly of a variety of rotating machinery are detected while the rotor is being rotated, by sensing mechanical vibrations of the rotor at a location along the length thereof to produce a corresponding rotor vibration signal. A background vibration signal representing the vibration response at an earlier time is provided, as well as a monitor vibration signal representing the vibration response of the rotor at the time the monitor signal is obtained. A speed-dependent first harmonic difference signal is found by vectorially subtracting the first harmonic of the background vibration signal from the first harmonic of the monitor vibration signal.

Abstract: Apparatus for determining the life usage of components subject to variable operating conditions particularly helicopter gears subject to variable torque. A monitor 10 provides an analogue signal of the level of operating parameter which is passed through conditioning means 26 including pre-amplifier 29, filter stage 31, multiplexer 38 and analogue to digital converter 40. A memory 42 stores life usage data for the component and a microprocessor 43 repeatedly samples the monitored level of the parameter and determines the life usage in successive time intervals. Electromechanical counter 53 provides a cumulative output of the life usage of the components. The microprocessor 43 also analyses the parameter levels into ranges or bands and the total time each component is operating in each range is stored and printed out.

Abstract: First and second devices (8,9) measure the speed of rotation at two widely separated points H and J along a line of shafts, e.g. through a turboalternator unit. Parameters representative of the opposing torque are determined by a third device which is responsive to signals derived from said measured speeds and to a signal representative of the travel of a controlling servomotor (7). Apparatus are provided that determine the torsion damage suffered, if any, on the basis of the signals provided by said first, second and third devices. The system avoids the prior art need to use expensive, high-current transformers, and can also provide more accurate measurement of damage suffered.

Abstract: Provided is apparatus suitable for continuous long-term monitoring of acoustic emissions, particularly from large structures such as pipelines. The apparatus comprises a plurality of detector-analyzer units coupled to a central control unit via a communications link. Each detector-analyzer unit comprises an acoustic detector, signal processing means, and a microprocessor. Preferably, the signal processing means comprises at least one signal conditioner, and at least one measuring circuit which provides digital output signals representing a set of emission parameters. The microprocessor preferably periodically receives and compares the digital output signal representing each of the emission parameters with the base values thereof, and provides a warning signal if a problem situation is perceived as a result of such comparison.

Abstract: The present invention utilizes a wire wool slug packed inside a helical coil of an aircraft engine sensor in order to reduce vibration damage to the coil.

Abstract: The invention is a method of determining whether an adhesively bonded joint between two structural elements meets established strength requirements. The method comprises the following steps: (1) Determining by test the levels of acoustic energy to be directed and/or focused by a transducer 12 on a minute area of the adhesively bonded joint 14 and further the application times thereof.

Abstract: Ampules may be cleaned and quality controlled by submerging frangible, sealed, partly filled, floatable ampules in a container in an ultrasonic cleaning tank bath in such manner as to not only clean all the ampules but also break a large portion of any flawed ampules, thereafter separating the intact ampules from the shattered ampules, collecting, washing, drying and packaging the former.

Abstract: Traversing energy flux transmitted into a fiber/matrix composite structure is propagated through the structure in directions which vary depending upon the elastic stiffness condition of the composite. Degradation in elastic stiffness of the composite, from any cause, will result in variations in the direction of travel of the flux through the composite. By determining the direction of flux propagation in the composite, or the portion of the composite structure from which the flux is detected as it exits the structure, the condition of the composite structure, independent of the source of degradation, can be determined.

Abstract: A method is disclosed for detecting incipient cracks in the rotor of a turbine-generator while the turbine-generator is on-line operating under normal conditions. Vibration signature analysis is performed on a set of difference signals produced by superposing and subtracting corresponding enhanced background and foreground vibration signals. Each enhanced vibration signal is created by superposing and summing an integral number of vibration signal segments, each segment corresponding to one revolution of the rotor. An incipient crack is manifested principally by the appearance and increase in relative amplitude of signal harmonics at twice the rotational speed of the rotor. The method of the invention is sufficiently sensitive to detect cracks having a depth on the order of less than one-percent the diameter of the rotor.

Abstract: A data acquisition system utilizing a microcomputer and incorporating a plurality of monitors each adapted to produce an electrical signal indicative of a physical condition of apparatus to be monitored. The electrical signals are fed via multiplexing equipment and analog-to-digital converters into the microcomputer which is equipped with print-out means. The system is such that the level of any one or all of the signals from the respective monitors can be printed out as well as a change in the condition of any signal. Means are incorporated into the computer for calculating and printing the trend (i.e., the slope of a plot of signal amplitude versus time) of a succession of stored signals from any monitor which would indicate a probable malfunction of a device being monitored and the probable time to failure. In the case where the signals from the monitors comprise, vibration signals, the system performs an automatic frequency spectrum analysis whenever a probable or actual malfunction is detected.