摘要:
Magnetic or electric field sensors are mounted against a material surface and used for stress, strain, and load monitoring of rotating components such as vehicle drive trains. The stationary sensors are mounted at multiple locations around the component and used assess the stress on the component at multiple rotational positions. The sensor response is typically converted into a material property, such as magnetic permeability or electrical conductivity, which accounts for any coating thickness that may be present between the sensor and mounting surface. The sensors are not in direct contact with the rotating component and are typically mounted on an annular material or ring that encircles the rotating component. Measurements of the annular material properties, such as the stress, are related to the stress on the rotating component and discrete features on the component. As a particular example, the rotating component is a planetary gear system, with sensors mounted on the ring gear and the discrete features are carrier plate posts. The sensors are preferably mounted at equal distances around the circumference of the component. The sensors and instrumentation may be removable and reusable for monitoring of additional components.
摘要:
Observability of damage precursor, damage and usage states, or event occurrence may be enhanced by modifying component materials to include self-monitoring materials or by processing test material to alter the surface properties. The properties of the self monitoring materials, such as magnetic permeability or electrical conductivity, are monitored with electromagnetic sensors and provide greater property variations with component condition than the original component material. Processing includes shot peening or laser welding.
摘要:
Methods are described for assessing material condition. These methods include the use of multiple source fields for interrogating and loading of a multicomponent test material. Source fields include electric, magnetic, thermal, and acoustic fields. The loading field preferentially changes the material properties of a component of the test material, which allows the properties of the component materials to be separated. Methods are also described for monitoring changes in material state using separate drive and sense electrodes with some of the electrodes positioned on a hidden or even embedded material surface. Statistical characterization of the material condition is performed with sensor arrays that provide multiple responses for the material condition during loading. The responses can be combined into a statistical population that permits tracking with respect to loading history. Methods are also described for measuring the stress in the material by independently estimating effective electrical properties, such as magnetic permeability or electrical conductivity, using layered models or predetermined spatial distributions with depth that are then correlated with the stress.
摘要:
Observability of damage precursor, damage and usage states, or event occurrence may be enhanced by modifying component materials to include self-monitoring materials or by processing test material to alter the surface properties. The properties of the self monitoring materials, such as magnetic permeability or electrical conductivity, are monitored with electromagnetic sensors and provide greater property variations with component condition than the original component material. Processing includes shot peening or laser welding.
摘要:
Combined wound and micro-fabricated winding constructs are described for the inspection of materials and the detection and characterization of hidden features or flaws. These constructs can be configured as sensors or sensor arrays that are surface mounted or scanned over conducting and/or magnetizable test materials. The well-defined geometry obtained micro-fabricated windings and from carefully wound coils with known winding positions permits the use of model based inversions of sensed responses into material properties. In a preferred embodiment, the primary winding is a wound coil and the sense elements are etched or printed. The drive or sense windings can also be mounted under fasteners to improve sensitivity to hidden flaws. Ferrites and other means may be used to guide the magnetic flux and enhance the magnetic field in the test material.
摘要:
Inductive sensors measure the near surface properties of conducting and magnetic material. A sensor may have primary windings with parallel extended winding segments to impose a spatially periodic magnetic field in a test material. Those extended portions may be formed by adjacent portions of individual drive coils. Sensing elements provided every other half wavelength may be connected together in series while the sensing elements in adjacent half wavelengths are spatially offset. Certain sensors include circular segments which create a circularly symmetric magnetic field that is periodic in the radial direction. Such sensors are particularly adapted to surround fasteners to detect cracks and can be mounted beneath a fastener head. In another sensor, sensing windings are offset along the length of parallel winding segments to provide material measurements over different locations when the circuit is scanned over the test material. The distance from the sensing elements to the ends of the primary winding may be kept constant as the offset space in between sensing elements is varied. An image of the material properties can be provided as the sensor is scanned across the material.
摘要:
Described are methods for monitoring of stresses and other material properties. These methods use measurements of effective electrical properties, such as magnetic permeability and electrical conductivity, to infer the state of the test material, such as the stress, temperature, or overload condition. The sensors, which can be single element sensors or sensor arrays, can be used to periodically inspect selected locations, mounted to the test material, or scanned over the test material to generate two-dimensional images of the material properties. Magnetic field or eddy current based inductive and giant magnetoresistive sensors may be used on magnetizable and/or conducting materials, while capacitive sensors can be used for dielectric materials. Methods are also described for the use of state-sensitive layers to determine the state of materials of interest. These methods allow the weight of articles, such as aircraft, to be determined.
摘要:
The condition of insulating and semiconducting dielectric materials is assessed by a sensor array that uses electric fields to interrogate the test material. The sensor has a linear array of parallel drive conductors interconnected to form a single drive electrode and sense conductors placed on each side of and parallel to a drive conductor. Subsets of the sense conductors are interconnected to form at least two sense elements sensitive to different material regions. The sense conductors may be at different distances to the drive conductors, enabling measurement sensitivity to different depths into the test material. The material condition is assessed directly from the sense element responses or after conversion to an effective material property, such as an electrical conductivity or dielectric permittivity.
摘要:
Methods and apparatus are described for absolute electrical property measurement of materials. This is accomplished with magnetic and electric field based sensors and sensor array geometries that can be modeled accurately and with impedance instrumentation that permits accurate measurements of the in-phase and quadrature phase signal components. A dithering calibration method is also described which allows the measurement to account for background material noise variations. Methods are also described for accounting for noise factors in sensor design and selection of the optimal operating conditions which can minimize the error bounds for material property estimates. Example application of these methods to automated engine disk slot inspection and assessment of the mechanical condition of dielectric materials are presented.
摘要:
Quasistatic sensor responses may be converted into multiple model parameters to characterize hidden properties of a material. Methods of conversion use databases of responses and, in some cases, databases that include derivatives of the responses, to estimate at least three unknown model parameters, such as the electrical conductivity, magnetic permeability, dielectric permittivity, thermal conductivity, and/or layer thickness. These parameter responses are then used to obtain a quantitative estimate of a property of a hidden feature, such as corrosion loss layer thicknesses, inclusion size and depth, or stress variation. The sensors can be single element sensors or sensor arrays and impose an interrogation electric, magnetic, or thermal field.