Jentek Sensors, Incorporated

Darrell E Schlicker

Neil J Goldfine

Andrew P Washabaugh

David C Grundy

Vladimir A Zilberstein

Ian C Shay

Yanko K Sheiretov

Karen E Walrath

Vladimir B Tsukernik

Robert J Lyons

Mark D Windoloski

Volker Weiss

Markus Zahn

Todd M Dunford

Christopher A Craven

Wayne D Ryan

Scott A Denenberg

Christopher Root

David C Clark

David A Jablonski

J Timothy Lovett

Floyd W Spencer

William M Chepolis

Andrew P Washabaugn

Leandro M Lorilla

James M Fisher

Ian C Shav

Eric L Miller

Vladimir Tsukemik

Eric Hill

Alexander V Mamishev

Methods and apparatus for enhancing performance curve generation, damage monitoring, and improving non-destructive testing performance. Damage standards used for performance curve generation are monitored using a non-destructive testing (NDT) sensor during a damage evolution test performed with the standard. The evolution test may be intermittently paused to permit ground truth data to be collected in addition to the NDT sensor data. A damage evolution model may be used to estimate ground truth data during the intervening periods of the damage evolution test. The NDT sensor data and ground truth data are used to generate performance curves for the NDT system. Multiple sensors may be monitored at multiple locations on the damage standard and multiple damage evolution tests may be performed with multiple damage standards.

Performance curve generation for non-destructive testing sensors

A substantially planar eddy-current sensor having durability enhancing pillars in an active region is provided. The pillars are distributed and sized so as to have limited effect on the sensor's performance. When the sensor is mounted on a component such that the sensor experiences forces on a top and bottom surface, the pillars bear the load reducing the load bore by the active elements (e.g., drive winding, sense elements). A sensor with redundant drive windings and/or redundant sense elements is disclosed. The redundant elements may be connected to separate electronics. Another aspect relates to providing a reference transformer for calibration of a sensor. The secondary windings of the reference transformer are connected in series with the sense elements of the sensor to be calibrated. Transimpedance measurements are made when the drive winding of the reference transformer is excited. The measurements are used to correct transimpedance measurements made when the drive winding of the sensor is excited. A system having an impedance analyzer and a plurality of multiplexing units is disclosed for monitoring a plurality of sensor. Each multiplexing units directs an excitation signal to the drive winding of a respective sensor and returns, serially, the sense element responses back to the impedance analyzer. The system coordinates the excitation of each sensor and return of the sensor response to share a serial network. The multiplexing units may have a reference transformer for calibration of their respective sensors. Optical communication may be used.

Durability enhanced and redundant embedded sensors

A system and method for measuring load and an additional property using a sensor gasket embedded between two components. The sensor gasket may include a sensor layer and a conductive layer. A gap between the sensor layer and conductive layer may be filled with a load sensitive material. The thickness of the load sensitive material varies with the load applied to the two components between which the sensor gasket sits. The sensor operates in a first mode to obtain a sensor measurement that depends on the distance between the sensor layer and conductive layer. The sensor measurement then used to estimate the applied load. The sensor operates in a second mode to estimate a property of one or both of the components. The property of interest may be cracking, material loss due to corrosion, temperature, or another property of the component.

Method and apparatus for load and additional property measurement

An apparatus for the nondestructive measurement of materials that includes at least two layers of electrical conductors. Within each layer, a meandering primary winding is used to create a magnetic field for interrogating a test material while sense elements or conducting loops within each meander provide a directional measurement of the test material condition. In successive layers extended portions of the meanders are rotated so that the sense elements provide material condition in different orientations without requiring movement of the test circuit or apparatus. Multidirectional permeability measurements are used to assess the stress or torque on a component. These measurements are combined in a manner that removes temperature effects and hysteresis on the property measurements. This can be accomplished through a correction factor that accounts for the temperature dependence.

Method for stress assessment that removes temperature effects and hysteresis on the material property measurements

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.

Magnetic field characterization of stresses and properties in materials

An apparatus for the nondestructive measurement of materials that includes at least two layers of electrical conductors. Within each layer, a meandering primary winding is used to create a magnetic field for interrogating a test material while sense elements or conducting loops within each meander provide a directional measurement of the test material condition in different orientations without requiring movement of the test circuit or apparatus. In a bidirectional implementation the meanders are oriented 90&#xb0; apart while in a quadridirectional implementation the meanders are orientated at &#x2212;45, 0, 45, and 90&#xb0;. Multidirectional permeability measurements are used to assess the stress or torque on a component. These measurements are combined in a manner that removes temperature effects and hysteresis on the property measurements. This can be accomplished through a correction factor that accounts for the temperature dependence. After the correction, the permeability measurement is then used to assess the local stresses and strains in the material of interest.

Test circuit with sense elements having associated and unassociated primary windings

A method is provided for performing inverse interpolation that estimates the values of at least two identified parameters. Initially, a database of sensor responses is generated over a range of values for each of the identified parameters. The sensor responses associated with incremental changes in each parameter value form a grid cell. Each corner of a grid cell is a grid point which represents the sensor response for a specific value of each of the identified parameters. A target point of sensor values is obtained from a sensor. The database is searched to identify the grid cell which contains the target point. Using the grid cell corners as reference values, the final estimate of the parameter values is interpolated. In some cases there are three or more parameters to be estimated. The database may include sensor responses computed at multiple excitation frequencies.

Material property estimation using inverse interpolation

Reference standards or articles having prescribed levels of damage are fabricated by monitoring an electrical property of the article material, mechanically loading the article, and removing the load when a change in electrical properties indicates a prescribed level of damage. The electrical property is measured with an electromagnetic sensor, such as a flexible eddy current sensor, attached to a material surface, which may be between layers of the article material. The damage may be in the form of a fatigue crack or a change in the mechanical stress underneath the sensor. The shape of the article material may be adjusted to concentrate the stress so that the damage initiates under the sensor. Examples adjustments to the article shape include the use of dogbone geometries with thin center sections, reinforcement ribs on the edges of the article, and radius cut-outs in the vicinity of the thin section. A test circuit includes sensing elements between concentric circular segments of the primary winding and located every other half wavelength of the primary winding.

Eddy current sensor with concentric segments

Eddy current sensors and sensor arrays are used for process quality and material condition assessment of conducting materials. In an embodiment, changes in spatially registered high resolution images taken before and after cold work processing reflect the quality of the process, such as intensity and coverage. These images also permit the suppression or removal of local outlier variations. Anisotropy in a material property, such as magnetic permeability or electrical conductivity, can be intentionally introduced and used to assess material condition resulting from an operation, such as a cold work or heat treatment. The anisotropy is determined by sensors that provide directional property measurements. The sensor directionality arises from constructs that use a linear conducting drive segment to impose the magnetic field in a test material. Maintaining the orientation of this drive segment, and associated sense elements, relative to a material edge provides enhanced sensitivity for crack detection at edges.

Material condition assessment with eddy current sensors

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.

Absolute property measurements using electromagnetic sensors

One of the issues with planar eddy-current sensors is the placement of the current return for the primary winding. Often the ends of the primary winding are spatially distant from one another, which creates an extraneous and large inductive loop that can influence the measurements. A sensor geometry featuring a primary winding that reduces the effect of this inductive loop is presented. The primary winding may include a plurality of parallel extended winding segments. The segments further include adjacent individual drive coils. Current flows through individual drive coils in an alternating fashion. Current flows through adjacent drive coil portions in a common direction, thereby imposing a spatially periodic magnetic field with at least two periods.

Surface mounted sensor arrays having segmented primary windings

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.

Quasistatic magnetic and electric field stress/strain gages

Methods are described for the use of conformable eddy-current sensors and sensor arrays for characterizing residual stresses and applied loads in materials. In addition, for magnetizable materials such as steels, these methods can be used to determine carbide content and to inspect for grinding burn damage. The sensor arrays can be mounted inside or scanned across the inner surface of test articles and hollow fasteners to monitor stress distributions. A technique for placing eddy-current coils around magnetizable fasteners for load distribution monitoring is also disclosed.

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Watertown, MA, United States of America

Darrell E Schlicker