Method for Non-Destructively Determining Material Properties
1. A method for non-destructive determining of material properties of electrically conductive components, comprising the act of:
- moving an electromagnetic eddy current testing sensor at least one of on and near a surface of at least one sample cast component in a manner producing a varying magnetic field in the sample cast component;
sensing with the sensor eddy currents in the at least one sample cast component; and
displaying in human-readable form a measurement signal indicative of the eddy currents resulting in the at least one sample cast component from the varying magnetic field,wherein the electromagnetic eddy current testing sensor in a high-resolution eddy current sensor adapted to a conductivity of the at least one sample cast component.
An approach to determining the crash dynamic behavior of structural castings made of a AlSi10MnMg alloy in a simple and cost-effective manner is provided. In this approach eddy current testing is carried out using a high-resolution measuring coil which is adjusted to the cast-specific conductivity.
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Patent #US 20090288740A1
Current AssigneeBDW TECHNOLOGIES GMBH A COMPANY OF GERMANY
Sponsoring EntityBDW TECHNOLOGIES GMBH A COMPANY OF GERMANY
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Patent #US 20040000447A1
Current AssigneeA Wen Yu
Sponsoring EntityA Wen Yu
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Patent #US 6,087,830 A
Current AssigneePICA PIPELINE INSPECTION AND CONDITION ANALYSIS CORPORATION
Sponsoring EntityHYDROSCOPE INC.
- 1. A method for non-destructive determining of material properties of electrically conductive components, comprising the act of:
moving an electromagnetic eddy current testing sensor at least one of on and near a surface of at least one sample cast component in a manner producing a varying magnetic field in the sample cast component; sensing with the sensor eddy currents in the at least one sample cast component; and displaying in human-readable form a measurement signal indicative of the eddy currents resulting in the at least one sample cast component from the varying magnetic field, wherein the electromagnetic eddy current testing sensor in a high-resolution eddy current sensor adapted to a conductivity of the at least one sample cast component.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
This application is a continuation of PCT International Application No. PCT/EP2015/077357, filed Nov. 23, 2015, which claims priority under 35 U.S.C. §119 from German Patent Application No. 10 2014 226 389.1, filed Dec. 18, 2014, the entire disclosures of which are herein expressly incorporated by reference.
The invention relates to a method for non-destructive determining of material properties of electrically conductive components using electromagnetic eddy current testing.
Light metals are increasingly used in vehicle construction in order to save weight. The structural components used in this context are frequently made as cast aluminum parts. It is desirable to be able to assess these simply and quickly with regard to their ductility/deformation properties. Hitherto, this involved the use of crash tests, bend angle tests, ductility testing by means of punch rivet tests and drop tower tests for test samples. All of these test methods have substantial drawbacks. For example, the crash test is a destructive, extremely cost-intensive and time-intensive testing method, often with difficult evidence and conclusions. Bending angle measurement is also destructive and permits no real testing of the material properties.
Eddy current testing is known as a non-destructive testing method for determining mechanical material properties of electrically conductive materials. It uses the effect that most impurities and defects in an electrically conductive material also have an electrical conductivity or a permeability that is different to that of the actual material.
Thus, the eddy current principle in the context of non-destructive determining of mechanical material properties is described for example on pages 19-21 of Mock'"'"'s dissertation “Qualitätsbewertung und -regelung für die Fertigung von Karosserieteilen in Presswerken auf Basis neuronaler Netze [Quality evaluation and control for the production of bodywork parts in pressing plants on the basis of neural networks]” dated 05.30.2011 and published by Herbert Utz Verlag of Munich in Forschungsberichte IWB [IWB Research Papers], Band [Volume] 251. These properties include tensile strength, yield strength, extension and others. Electrically conductive materials can be measured contactlessly and in a very short time by applying a temporally changing magnetic field. Both mechanical and electrical properties depend on the material state and therefore on the structure, the alloying constituents, the grain size, the dislocation density, the anisotropy and so forth. There is therefore a relationship of correlation between electromagnetic and mechanical properties of a material. This dissertation describes the eddy current testing method for determining mechanical, that is to say static, material properties, in the pressing plant during production of bodywork parts, in order to identify production errors in a timely fashion and as fully automatically as possible.
The present invention has the object of replacing the known destructive testing methods in the context of cast structural components.
It has surprisingly been found that eddy current testing can safely and reliably identify, in addition to the known static material properties, also the impact-dynamic deformation behavior of cast samples, in particular their behavior in the event of a crash, if use is made of a high-resolution eddy current sensor that is adapted to the cast-specific conductivity. Thus, a cost-effective, rapid and reproducible measurement method with objective crash evaluation criteria for cast parts is available. The term sample in the context of this invention is to be understood not only to mean cast samples but also finished cast components, in particular structural components for vehicle construction.
In order to quickly obtain, objective and reliable conclusions regarding the crash behavior of the samples, the performance of the samples may be compared to a reference sample.
The comparability of the measurement results may be enhanced by measuring the samples at the same testing temperature.
Particularly advantageously, the method according to the invention can be used in the context of structural components such as longerons in motor vehicles, which are made of an AlSiMg alloy.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.
This cast sample undergoes eddy current testing in a manner known per se, the measurement sensor used being a high-resolution measurement coil that matches the cast-specific conductivity.
This measurement coil is moved over the cast sample at a variable distance, tilting back and forth, so as to produce a changing magnetic field. The measurement values produced in this manner are mutually aligned dot clusters which, as shown in
The gain of the measurement values of the reference line 1 is set such that the measurement line runs through the center 2 of the crosshairs of the display in
Then, a new cast sample with unknown crash behavior undergoes eddy current testing, the gain of the measurement values which was used during the reference measurement being retained.
This again produces dot clusters which form a measurement line 3 and 4 in
Choosing an elevated testing temperature results in the measurement line 4. This could suggest that the ductility in the event of a crash will be worse than that of the sample producing the measurement line 3, but in fact this is solely due to the different testing temperatures of identical cast samples.
An elevated testing temperature corresponding to measurement line 6 again changes the measurement result, not due to the material but purely due to the temperature, toward a worse crash behavior.
Regarding the cast samples, it is immaterial whether these are samples from the melt or already finished cast components.
Conventional tensile testing of the same cast samples shows no different results, regardless of how high or low the testing temperature was. Therefore, this allows no conclusions to be drawn regarding crash-dynamic behavior, or the wrong conclusions would be drawn from such results.
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.