Internal material condition monitoring for control

Abstract

The condition of internal or hidden material layers or interfaces is monitored and used for control of a process that changes a condition of a material system. The material system has multiple component materials, such as layers or embedded constituents, or can be represented with multiple layers to model spatial distributions in the material properties. The material condition changes as a result of a process performed on the material, such as by cold working, or from functional operation. Sensors placed proximate to the test material surface or embedded between material layers are used to monitor a material property using magnetic, electric, or thermal interrogation fields. The sensor responses are converted into states of the material condition, such as temperature or residual stress, typically with a precomputed database of sensor responses. The sensor responses can also be used to determine properties of the test material, such as electrical conductivity or magnetic permeability, prior to conversion to the material state. The states are used to support control decisions that control the process or operation causing the material condition to change.

What is claimed is: 
     
         1 . A method to measure a usage state at a hidden material interface comprising:
 placing a sensor near a surface interface of a test material, the test material also containing a hidden interface;   projecting an interrogating field and receiving a signal with the sensor to measure an absolute property of the material proximate to the hidden interface; and   relating the absolute property to a usage state of the hidden interface.   
     
     
         2 . The method as claimed in  claim 1  wherein the usage state is temperature. 
     
     
         3 . The method as claimed in  claim 1  wherein the usage state is stress. 
     
     
         4 . The method as claimed in  claim 1  wherein the usage state is cure state. 
     
     
         5 . The method as claimed in  claim 1  wherein the sensor uses a magnetic field. 
     
     
         6 . The method as claimed in  claim 1  wherein the sensor uses an electric field. 
     
     
         7 . The method as claimed in  claim 1  wherein the sensor uses a thermal field. 
     
     
         8 . The method as claimed in  claim 1  further comprising using a model to create a layered material representation of a nominally uniform material, with the thickness of each layered assumed and an absolute property of each material layer measured. 
     
     
         9 . The method as claimed in  claim 8  further comprising using the model to create a database of precomputed databases for obtaining an absolute property. 
     
     
         10 . A method for controlling a process, the method comprising:
 providing a sensor proximate to a material, the material having a first component and a second component, the first component having a state different than that of the second component;   measuring the sensor's response, the response comprising a plurality of measurements;   providing the plurality of measurements as inputs to a precomputed database, the precomputed database relating a plurality of inputs to the state of the first component, wherein the relationship between the plurality of inputs and the state of the first component is precomputed using at least a model of the sensor and the material;   processing the plurality of measurements with the precomputed database to provide one estimate of the state of the first component of the material; and   controlling the process in real-time based on the estimated state of the first component of the material.   
     
     
         11 . The method of  claim 10 , wherein the process is a manufacturing process. 
     
     
         12 . The method of  claim 10 , wherein two of the plurality of measurements comprise an impedance measurement. 
     
     
         13 . The method of  claim 10 , wherein the state of the first component is a temperature of the first component. 
     
     
         14 . A method for temperature control of a multiple material system comprising:
 placing a sensor proximate to a material system, the material system containing first and second distinct materials with different thermal behaviors;   using a model based method to generate a precomputed database to relate sensor response to temperatures in the material system, the precomputed database including a first absolute property that is related to a first temperature of the first distinct material and a second absolute property that is related to a second temperature of the second distinct material;   performing a process that changes at least one of the first temperature and the second temperature of the material system;   monitoring the sensor response; and   using the sensor response to determine a control action used to control at least one of the first and second temperatures.   
     
     
         15 . The method as claimed in  claim 14  wherein the multiple material system is an operating device. 
     
     
         16 . The method as claimed in  claim 14  wherein the material system has multiple material layers. 
     
     
         17 . The method as claimed in  claim 14  wherein the material system has a first material embedded in a matrix of a second material. 
     
     
         18 . The method as claimed in  claim 14  wherein the absolute property is an electrical conductivity.