Mannesmann Aktiengesellschaft

Mannesmannröhren

Friedhelm Schlawne

Alfred Graff

Heinz Schneider

Wolfgang Bottger

Michael Wachter

Willi Weingarten

Wolfgang Boettger

In a method of detecting discontinuities on elongated workpieces, in particular tubes and bars, using ultrasonic testing system, a test object is positioned in relationship to a test head of the testing system, with the test object and the test head being moveable to one another. Signals from the test head are transmitted to an evaluation unit, where they are digitized and evaluated. The digitized signals of a test shot of a length position X are compared with digitized signals of a test shot of a length position X+&#x394;X, wherein &#x394;X is a multiple of a shot distance, and the difference is evaluated.

Method of detecting discontinuities on elongated workpieces

A process for detecting flaws on stretched workpieces, especially tubes and bars, in which the test specimen is passed in the axial direction and without rotation by fixed electrodynamic transducers arranged separately in the peripheral direction. Wave pulses travelling in both peripheral directions are generated in the test specimen at different locations in alternating fashion in the test cycle, and the location of reception for the reflection signals is different from that for the transmission signals. The wave pulses travelling in both directions are generated at at least four locations separated symmetrically from one another in the peripheral direction in alternating fashion in the test cycle. Each particular sequence of reception signals is evaluated separately, and for each cycle the reception signal and a burst signal are fed to a peak detector and the output signal of the peak detector is transmitted in digital form to a computer. The device for carrying out the process includes electrodynamic transducers, which have separate transmitting and receiving coils, and lie on a peripheral plane, and are staggered around the perimeter of the test specimens. The transducers are arranged in a fixed manner, and are connected to an analysis unit. The device calls for 2.multidot.n transducers, where n&gt;2, arranged symmetrically around the perimeter, whereby every two transducers are placed together on one transducer carrier and the spacing of the transducer carriers is 360.degree./n. Furthermore, each transducer has its own local electronics system and its own analysis channel.

Process and device for detecting flaws on stretched workpieces,

The invention furnishes an electrodynamic transducer head for a non-destructive testing of workpieces with electrically conductive surfaces by way of ultrasound. A magnet system is employed for generating of a static or a low-frequency magnet field, and at least one transducer coil is disposed at the front face of the magnet system disposed toward the workpiece. The transducer coil is furnished on the side toward the workpiece with a wear-resistant layer, and the transducer coil exhibits between itself and this front face of the magnet system an intermediate part with an insulating layer, which is solidly connected with the front face and with the coil adjoining at the insulating layer. The invention discloses production of a transducer coil, in a way which is simple and economical and results in a transducer head which can be universally employed, and where the eddy current formations, resulting in interfering signals, and the mechanical vibrations, both in the transducer coil as well as in the magnet system, are substantially suppressed or, respectively, damped. The intermediate part (10) comprises at least two layers (11, 12), where one of the layers (12) is electrically conductive and which layer ( 12) is made of a material thickness which is larger than the skin depth for a given high-frequency field.

Electrodynamic transducer head

Defects are detected in cylindrical rods, tubes or the like by a stationary transmission and receiving device arranged along the path which the test object passes axially by providing per test cycle a particular pulse being split for propagating bidirectionally azimuthally in the test object; both pulses are received repeatedly, once per circulation, so that a plurality of pulses appear with gradually declining amplitude; a sequence of burst signals, each of limited duration, is provided for purposes of timing and gating the burst being repeated per circulation on the basis of the expected and known propagation time between transmission and receiving portions; peaks of the received signal are detected once or twice per circulation and in synchronism with the timing and gating signal; the respective detected peak signals are digitized, summed in groups and the quotient of the sums is formed as quality indicator.

Defect detection in cylindrical objects

An electrodynamic transducing device includes two staggerdly coils with a distance of staggering equal to a quarter of a wavelength of ultrasonic waves; unidirectional transmission characteristics of the transducer is obtained by feeding the two coils separately with HF current at a time difference of feeding of the respective two signals to be equal to a quarter of the wavelength such that a reinforcing ultrasonic signal is produced in the direction of the coil receiving said signal earlier in time and complete cancelation of acoustic waves obtains in the opposite direction, whereby in case of equal pitch of said coils the HF signals are of equal contour but of opposite polarity while in case of opposite winding pitch the signals not only have equal signal contour but also the same polarity.

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Duisburg, Germany

Friedhelm Schlawne