Methode and device for flaw detection in metalic parts

The invention relates to a method and an apparatus for detecting defects in metallic components.

The non-destructive detection of defects, in particular of overt and covert Cracks in components is becoming increasingly important. This is because Materials and components increasingly adapted to their load limit will. This increases the demands on quality control and on the Error detection capability destructive test.

For non-destructive detection of open and hidden cracks in metallic Materials is well established since more than 40 years, the eddy current testing. in the Unlike thermography examination, the only sensitive to horizontal error (eg Delaminations) reacts, can be personalized with the eddy current testing vertical cracks sensitive evidence.

In the eddy current testing a coil probe is moved over the component. there Point by point measurement signals are recorded. For a comprehensive examination the component must therefore be scanned in each test tracks. For flat or circular components have been developed for this purpose, mechanical scanners. For example, from DE 196 42 981 A1 discloses a method and an apparatus Known for scanning a component surface by means of an eddy current probe.

The US 5,430,376 protects Method and apparatus for a combined Coating thickness measurement and defect testing of surface-coated metal components, such as turbine blades. It is necessary, the component surface with a thermoelectric probe and complete scan with an eddy current probe, ie, scan.

However, the parts and components produced by CAD drawing increasingly by more complex geometries. These often highly curved component surfaces are not or only with reduced sensitivity can be checked with such scanners. at Components of complex geometry is a considerable expense for seamless Verification needed. The test time is long. In addition, part corners and edges This test method is not accessible.

From US 5,562,345 a method for the analysis of cracks in structural components is known, wherein said member is heated by eddy currents and the temperature change as Function of time is measured. By comparison with the data of a proper Component draw conclusions on flaws in the component can be drawn. This Method but can be used successfully only with composite materials in which heat conduction is hindered due to delamination. For complete metallic components, the method is unsuitable.

From WO 99/10731 it is known buried in the ground objects, such as to locate mines or waste, and identify, by directed microwave energy passed into the soil, the heated object in question with it, and a local Temperature difference at the ground surface over the article metrologically is detected, preferably with an infrared camera. This makes use of that Thermal behavior of the object in the microwave field is different than the surrounding soil.

The DE 197 47 784 A1 treated in relatively general and comprehensive way, Object detection using thermal signature analysis. It is energy by means of a electromagnetic alternating field is introduced into the object, by excitation of the converted stotfspezifischen dipole moment in thermal energy and as Thermal signature of the object surface as detected by infrared sensors.

It is an object of the present invention to provide a method and apparatus for indicate presence of flaws in metal parts with a quick, reliable, uninterrupted examination also of components of complex geometry enable.

This object is procedurally by a method for the detection of errors, in particular, dissolved cracks in metal components, in which a component in the high frequency pulsed magnetic field is coupled, and the temperature distribution the induced eddy currents warming immediately to port a magnetic pulse is detected.

In the area to be inspected of the metal component is a pulsed coupled high-frequency magnetic field induced by the eddy currents. By the electric resistance in the component, these currents generate heat. The Temperature of the component increases.

Since the temperature increase due to heat conduction in the initial period after insertion of the eddy currents is negligible, the temperature increase is thus directly proportional to introduced eddy current. be a mistake, especially Located a overt or covert plan, in part, as can be at this point no Eddy currents form. Consequently, there is no direct temperature increase takes place. directly by detecting the temperature of the image of the component following a Magnetic pulse errors can be detected and visualized.

Since the rise in temperature by heat conduction within the first time after Inserting the eddy currents is negligible, has a pulse duration of High frequency magnetic field between 0.1 s and 1 s proven advantageous.

Preferably, the high-frequency magnetic field is generated by a coreless coil, which is connected to a high frequency generator. The area to be tested the component is inserted into the coil. By the high frequency generator is a strong alternating magnetic field is generated which the component to be tested surface penetrates and induced in the component eddy currents.

Favorable test parameters have frequencies of the high frequency generator of 50 to 200 kHz, in particular 100 kHz, proved. To a significant heating of the to reach to the component under test, is a power of the high-frequency generator from 0.5 to 2 kW, in particular 1 kW, advantageously.

Preferably, for detecting the heating of a component to be checked Thermographic camera used.

Further, the object of the invention is a device by device standpoint for the detection of faults, especially cracks, in metallic components dissolved, the generating of a pulsed high-frequency magnetic assembly and means for detecting the temperature distribution of the to be tested Component is.

Preferably the assembly is for generating a magnetic Alternating field from a high frequency generator and a coreless coil. The to checked area of ​​the component can then by the novel Procedures are introduced in the coreless coil. By the high-frequency generator a strong alternating magnetic field is generated inside the coil, which in turn induces eddy currents within the component.

As means for detecting the temperature distribution of the component is in the A device according to the invention preferably uses a thermal imaging camera.

The inventive method and the inventive device have the special advantage that the entire area of ​​the component to be tested in can be a single operation checked. The component does not have step by step be scanned. Thus, short component testing times arise. Moreover, even the component edges and corners, which with the known in the prior art method can not be verified, accessible.

An embodiment of the invention is illustrated by the accompanying Figure explained: <dl tsize="8" compact="compact"><dt><b>Fig. 1</b></dt><dd>schematically shows a test apparatus according to the invention, in which a to Inspection item is.</dd></dl>

In <b>Fig. 1</b> schematically shows a turbine blade <b>1</b> illustrated whose curved Blade tip <b>6</b> cracks <b>7</b> is to be checked. For this purpose, the Verify Area <b>6</b> in the interior of a coreless coil <b>3</b> introduced with a High-frequency generator <b>4</b> connected is. The high-frequency generator<b>4</b> will with an output of 1 kW and a frequency of 100 kHz is operated pulsed. The optimum pulse duration depends on the starting component to be tested, and is typically between 0.1 and 1 s or slightly above.

The high-frequency generator <b>4</b> generated within the coreless coil <b>3</b> a strong alternating magnetic field, the surface of the blade tip <b>6</b> of the turbine blade <b>1</b> penetrates and is schematically indicated eddy currents<b>2</b> induced.

By eddy currents <b>2</b> there is a heating of the blade tip <b>6</b>, Within the pulse duration of the high-frequency generator <b>4</b> the heat conduction effects yet negligible. The temperature increase is determined functionally with the introduced Eddy current strength together. In the case of a crack<b>7</b> in part, arise at this Place no eddy currents <b>2</b> and therefore no increase in temperature.

A temperature image of the component to be tested is of the thermographic camera <b>5</b>recorded. It provides the thermographic camera<b>5</b> a unique Snapshot of the temperature distribution at a predetermined time after Pulse start of the high-frequency generator <b>4</b>, Usually directly in to port a magnetic pulse.

Based on the temperature of the image can also vertical cracks <b>7</b> sensitive in the component be detected. The examination of the entire component<b>1</b> or test of region <b>6</b> the component can be done in one operation. laborious Scanning the component is no longer necessary. Also corners and edges of a geometrically complex shaped component are testing accessible.