KLASSON JAN (SE)
| SU815610A1 | 1981-03-23 | |||
| US4906927A | 1990-03-06 |
PATENT ABSTRACTS OF JAPAN, Vol. 8, No. 79, (P-267); & JP,A,58 223 058 (FLAW DETECTOR EMPLOYING MAGNETIC POWDER) 24 December 1983.
| 1. | A method of using a separate non magnetic, electric conductive object (3) for generating signals on electric conductive test object (1) in Non Destructive Testing, method ET, Electromagnetic Testing (2) characterised by that the electric conductive object as a reference (3) to a reference (5) has a known reproducible signal generating relationship (6) with traceability to international standardised reference objects (4), as the electric conductive object (3) can be applied to the test object (1) on events of free choice, whereupon will be obtained, against referred test standard, a complete calibration without stopping or disturbing the process of production. |
| 2. | A method as claimed in claim 1, characterised by that the signal generating object (3) is passive as the electromagnetic properties of the object is a load to the applied electromagnetic field. |
| 3. | A method as claimed in claim (1), characterised by that the signal generating object (3) is active as the object (3) by external fed power is generating an electromagnetic wave movement apart from that by the applied electromagnetic field decided. |
HELD OF INVENTION This invention refers to the use of the method due to the introduction of patent claim No 1.
DESCRIPTION Measuring systems for Non Destructive Testing (NDT) are generally working with some electromagnetic or mechanical waves interfering to test objects and their discontinuities for examination. The degree of influence from the object under test and present discontinuities are there upon base for judgement of condition and status for the object. If for example an injury on a surface will be detected by aid of light, the behaviour to light of the injury and the normal optical properties of the object, will contribute to a common influence to the measuring results, and the so received measuring value will be base for determine the type of injury, size etc. As NDT methods generally are working indirectly, it is described in standards so as a reference object with the same properties, form etc. will be furnished with in standards described notches, holes or other machined arrangements with the intention to receive a known reference to those discontinuities of interest for validation. SS 114305 is an example of such a national standard.
Those reference discontinuities, daily called reference defects, described in named standards are since past based on the idea that the reference defect will be suggestive to the defect searched for in the product. The notch is then supposed to look like a crack and a drilled hole consequently refers to a natural hole in the product (SS, SEP, ASTM, API etc.).
However the purpose with the reference is to secure a known and reproducible influence to the actual wave motion so the system as a whole, including lest objectX measuring system etc. will show a recognised measurement test result. I NDT this is known as calibrating or checking the settings of the system. Methods of checking the electronics of the installation working by means of a defined electric signal fed trough the instrumentation are well known to the market.
This method however is nor including the test object or its dynamic or static behaviour in the control set up and is therefore not suitable to calibrate the complete measuring system. In most cases is not even the sensor involved in those so named electronic calibration methods.
In the case of a continuously manufactured product, the problem to bring in a reference object, similar to the test object, appears as particular complicated. By continuously manufacturing of products like strip-tube-or wire material it is necessary to brake the process, bring a reference object to the space of the test object, so the reference object will have the same position an dynamic behaviour as the test object and then calibrate the test set up. By some standards this operation has to be repeated in intervals like every 4". hour. Very strong production losses will be the result. Furthermore, a process in balance should not be disturbed.
The reference object will also be very fast destroyed as every run will wear. The cost of production for a reference object is normally very high.
The purpose of the invention is to perform a calibration of the complete measuring case without interrupting neither the measuring process nor the continuously ongoing production so as all demands of standards and prescriptions will be contained.
The invention represents a solution of related problem. The characteristic part of the patent claim 1. is describing the solution.
A search for reports of available 6000 data bases is performed, where no references has been found indicating the invention.
The invention is working as follows. On the actual product, the test object, being measured by the NDT method, on all events for calibration or checking the settings, a signal generating element will be adapted to the test object. The signal source can be a passive article, a piece of metallic sheet or similar or an active article like a semi conductor or similar. The signal generating article having a well defined measurement relationship to the standards reference object, with reference discontinuities, has equal defined measurement relationship to the test object. The reference discontinuity of the standard and the signal generating article are by comparably measurements giving a traceable and reproducible signal relationship, and if the signal source is attached to the test object, a signal will be received with traceable and reproducible relationship to the standard. The signal source is a reference to a reference as gauge blocks works as traceable references to the defined length unit by calibration of such as micrometer gauges.
The procedure is mainly applicable in Electromagnetic Testing (ET) of electric conductive material. The signal source may consist of an article which to design and electromagnetic properties is carefully defined and as when passing an electromagnetic coil will generate a defined signal as a result of all involved properties.
The so from the signal source arised signal will therefore be a complex result of common electromagnetic influences from the test object and the signal source as well from other electromagnetic influences such as the speed of the test object, the relative position to the probe etc.