DE2604651A1 - METHOD AND DEVICE FOR NON-DESTRUCTIVE TESTING OF SHEET METALS AND STRIPS - Google Patents

Description

;,, .Mf-rtsirsäe Π

4V February 1976 MJr / Hk t

11 6o4

i'ianri.? smann Aktiengesellschaft, Mannesmannufer 2, 4000 Düsseldorf

"Method and device for non-destructive testing of sheet metal and strips"

The invention relates to a method for the non-destructive testing of metal sheets and strips, as well as a device to carry out the procedure.

It is known to use various test methods for the non-destructive testing of metal sheets and strips for double-type defects use, e.g. the pulse echo method in single-head operation (one transducer per test head); the pulse echo method in two-head operation (two separate transducers per test head = SE technology) and the intensity method (sound transmission).

These known ancestors can be found in different variants can be used. All of these methods are and can be adequately described in the literature are largely assumed to be known.

As mentioned, the test task is decisive for the selection of one of the above-mentioned test methods, whereby the surface condition and the dimensional range are critical factors. Also the way in which the test is made Product can be important.

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The test systems in use - with the exception of the open water jet systems - are with regard to the mechanical Part of it has mainly been adapted to the test-specific tasks by the users themselves. This includes in particular the Arrangement and number of the probes used, the evaluation and the degree of automation.

When using the pulse echo method in single-head operation with direct coupling, the transmission pulse arises in the Zone of the test object close to the test head is a non-testable area, which is called the "dead zone". This range is depending on the test frequency and transducer material approx. Io mm.

Due to this effect, the possible uses are this Procedure in automatic test systems t, Lark restricted. When coupling by means of a water jet, the dead zone occurs through the reflection on the surface resulting entry echo. This also means that the zone near the surface (approx. 5 mm) is the side facing the probe in the sheet metal not verifiable. If this zone of the device under test has not been tested needs to be, has the pulse echo method in single head operation the advantage that this test can be carried out using the immersion technique, e.g. with a water supply section.

The probe characteristics of standard probes in single-head operation In contrast to that in two-head operation (SE technology), it shows a significantly more uniform test sensitivity over the test Material cross-section, i.e. apart from the dead zone In the area close to the test head, the entire cross-section can be tested with almost the same test sensitivity without any additional equipment being checked.

Because of the influence of the dead zone of the transmission pulse or the entry echo during diving technique testing, this procedure is not applicable for test cross-sections <^ 10 or 5 mm. This lower one For other reasons, the limitation also applies to the impulse

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echo method in two-head operation. H

The disadvantage of the dead zone with the pulse echo method in single-head operation led, among other things, to the development of the SE probes, in particular to be able to detect defects just below the surface in the vicinity of the probe. In the case of probes of this type, the transmitter and receiver are housed separately in a probe housing, with a lead-in section between the transducers and the test item. In addition, the two transducers are mutually shielded by an acoustic separating layer so that the sound cannot reach the receiver directly from the transmitter. These measures partially avoid the disruptive influence of the dead zone of the transmission pulse and the entry echo.

The entry echo (coupling echo) only appears so little that it does not impair the test in the vicinity of the test cap Area is coming.

Because of the very steep drop in sensitivity due to the probe characteristics of the SE probe within the test cross-section - This falls in 1 to 6 mm test depth steel by approx. 2o dB-ist in the case of an automatic check without additional measures, the meaningfulness of the check is very limited here too « As a result of the sharp drop in test sensitivity, depending on the wall thickness, the SE test head becomes tight in the area under the surface facing the test head only the test head characteristics correspondingly larger errors found. For this reason, special device-related measures are required for depth compensation the sensitivity of the SE technology required for the automatic test, if this procedure is used in relation to fault finding Sound transmission method compared as an equivalent test shall be.

Since the maximum test sensitivity of 3E probes is e.g. 5 ° Roof angle is 10 to 15 mm test depth and this depth with the corresponds to the neutral phase of the test object in the case of pipe sheets, are the external and internal in relation to the stresses that occur significantly endangered areas without depth compensation.

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tested significantly less sensitive than with the transmission method.

A major disadvantage of the SE probe is that it is a diving technique test is not possible and therefore the test head by means of special test head brackets over a: very small water gap on the test object must be coupled. As a result, the test head holders are in constant contact with the test object. Due to the associated wear and tear the heads must be replaced at certain time intervals (approx. 4-8 weeks).

One advantage of the SE test head is that, due to the pulse echo method it is possible to determine the position of the fault by measuring the transit time. In addition, statements can be made according to various Making methods about error sizes. This can cause fluctuations in the test sensitivity due to the coupling or weakening in the material can be compensated.

In practice, the so-called Open water jet systems enforced. With this procedure you can Because of the uniform test sensitivity over the entire test cross-section, all defects of the same size also in those near the surface Find areas. The ability to detect errors (approx. Io mm substitute error size) is overall smaller than with the pulse echo method (approx. 5 mm substitute error size). The advantage, however, is that the specified Substitute defect size that can still be found applies to the entire test area. With the SE process, however, the ^ can only be achieved with considerable technical equipment Effort can be achieved.

A decisive advantage of the sound transmission method lies in the coupling, which can be carried out using the lighting technology. This enables optimal operating conditions to be established. Although with the through-transmission method, the test heads are arranged below and above the test object and thus twice the number of test heads is required, the transmission / experience is a more user-friendly method with regard to malfunctions and maintenance, with which in practice run times of 98 f can be achieved.

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There is also a putting on or taking off at the beginning or end of the test item is not necessary, the risk of damage to the system is almost completely eliminated and the otherwise necessary is not necessary complicated system control. Even sheets with scales do not lead to probe wear. As a disadvantage of the transmission method results from the process-related fact that it is a matter of intensity measurement and for the estimation There is no reference point such as the back wall echo for the size of the defect. Every slightest influence on the sound beam, e.g. by the Surface properties, temperature, sound attenuation etc. are included in the intensity measurement and can be adjusted depending on the sensitivity setting Cause interference.

A relative measurement between the error display and the back wall echo display is not possible due to the lack of a reference point. This also essentially determines the limits of the fault detectability and this also results in the need for a safety margin between the theoretically possible test sensitivity and that of the Ad registration threshold in operation.

The transmission method has no lower cross-sectional limitation of the test objects and can also be used for test cross-sections <"5 mm.

It is the object of the invention. a method for the non-destructive testing of sheet metal and strips for double-type defects create, with the use of ultrasonic testing methods known per se, an improvement of the test results with regard to the evaluation; an increase in the test sensitivity of the transmission method and an optimization of the test areas is achieved, as well as a device for carrying out the method.

In order to achieve this object, the invention provides a method for the non-destructive testing of metal sheets and strips for double-type Suggested error, which is characterized by the fact that the pulse-echo is known per se in clock mode Combined transmission method for the decision comes the test takes place here from both sides of the test object, whereby the

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operational runtime factor of the scanning method is fully transferred to the pulse-echo method. Depending on the test task According to the invention, the processes can be used individually or in combination. For example, the test cycles run one after the other in such a way that in the first cycle in the pulse echo mode from above, in the second cycle in the sound transmission mode from above, in the third bar in impulse clioboard operation from below and in the fourth Clock is worked in sound transmission from below.

The device for carrying out the method according to the invention is characterized by the arrangement on both sides with one each Single-transducer probe head in known transmission systems; each test head is connected to a SE device (transmitter-receiver device); also a main amplifier for both SE devices (transmitter-receiver device) and an evaluation device coupled to the main amplifier.

By combining the pulse echo with the transmission method The non-destructive testing of sheets and strips is optimally solved in a testing system. The Advantages of both methods are used and the disadvantages are essentially eliminated. While with the pulse echo method both in the single head and Even in two-head operation, the testability begins at approx. Io or 5 mm wall thickness and upwards, can be done with the sound transmission method also check thin sheets. The upper limit is generally around 100 mm for the TmpuNacho method in two-head operation and with the transmission ujs method at about 40 mm. The above as a disadvantage described problem of the "dead 7one" in the area close to the probe with the normal test copper in single head operation can with the invention Procedures are neglected because the test heads are arranged on both sides of the test object. Another advantage of the invention The method lies in the fact that for the error assessment only the zones remote from the probe are used for testing near the surface Area can be used. By this measure, the test sensitivity is over the entire test cross-section due to the test

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_g 260A651

Kopfcharak'Tisitk much more constant than with the SE method of onei ^ oite, if no considerably complex measures (depth compensation) be seized.

The advantages of the pulse echo method, especially with regard to the size of the defect still to be found, are achieved when the probe is arranged on both sides fully used. The most important advantage in contrast to probes in two-head operation (SE technology) results from the Possibility of diving technique test. The test objects can be tested right up to their edges, regardless of whether, for example, a Sheet metal is present as a rolled plate or in the trimmed state. The complicated control measures for raising and lowering are no longer necessary of the probes. The inventive method can be used in existing open water jet systems are used.

By combining the two test methods, the The test system can be operated according to the most optimal Vex drive, depending on the test task

a) the transmission method,

b) the pulse echo method in single-head operation,

c) the combined pulse echo transmission method in cyclic operation.

This combination possibility creates further variants with regard to the fault assessment. For example, it is possible to use the Dux h sound test sensitivity based on reference values (Surface echo and back wall echo) of the pulse echo method to change cyclically and to adapt to the test object.

If the US displays of both methods are evaluated, it is possible to detect errors that are recognized with both methods, double confirm. This could also significantly increase the confirmation rate of US advertisements in the automatic check.

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Another possible variation would be for the test to be carried out using the combined pulse echo transmission method in cyclic operation is carried out, whereby the transmission method should take precedence with regard to the assessment. In this case it serves the simultaneous test according to the pulse echo method as a confirmation test.

It has already been stated above that in the case of the transmission method Ripples, impurities, etc. lead to fault displays if the safety margin between theoretical and operational notification threshold is selected too low. In order to keep these false displays within acceptable limits, the test threshold (Operating threshold) can be set so that the intensity fluctuations are not caused by the external test conditions either lead to unnecessary US fault reports.

When combining both methods as described above the transmission method can also be improved at the same time and, in particular, the test sensitivity can be increased. The test threshold can then be moved to the sensitive side in such a way that even the slightest loss of intensity occurs US ads lead. This means that considerably smaller errors from the test item are displayed. This also increases the number of occurrences US fault indications caused by external test conditions can be eliminated in the combined test will.

The pulse echo procedure, because it is more sensitive, is used as a confirmation test applied. By linking the measured test data from both methods, only such US displays are then displayed counted as error indications that were displayed simultaneously in both procedures.

In the accompanying drawings, a possible arrangement of a device according to the invention is shown schematically.

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It show: * ®

Figure 1 shows the arrangement of a test head pair

a conventional transmission system,

Figure 2 shows the block diagram of the new test method,

Figures 3 and 4 show the screens of the new process.

In Figure 1, above and below the test piece 1 are two water chambers 2 and 3 arranged. The probes 4 and 5 are located in the water chambers. The coupling to the test object is via the water jets 6 and 7. The coupling medium is fed to the water chambers 2 and 3 through the openings 8 and 9.

Existing transmission systems can be used for the system according to the invention to be used.

Here, however, the test heads and the entire test electronics be replaced.

From FIG. 2 it can be seen that the test heads 2 and 3 are arranged on both sides of the test piece 1. Hs are probes for single-head operation. By means of a clock control known per se, the probes are clocked in such a way that the pulse echo of the transmission and the combination of both methods are used virtually simultaneously, i.e. in the first cycle pulse echo operation from above, in the second cycle transmission operation from above, in the third cycle pulse echo from below and in the fourth bar sound transmission from below. ^The cycle sequence can also be carried out in a different order.

Serve to generate or receive signals in the individual cycles the transmitters 9, Io and the receivers 7 and 8. The recorded US signals are amplified in the main amplifier Π. The capture and the signals are evaluated in the evaluation unit 12.

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The evaluation and evaluation of the received signals is carried out according to specifications, with origin, quality and the production route of the test item must be taken into account.

In Figure 3 is a screen image when using the pulse echo method, namely the bars I and III from FIG. 2 are shown.

FIG. 4 shows the image when the sound transmission method is used, and two bars II and IV from FIG. 2.

In Figures 3 and 4:

Ε _ς = echo of the transmission pulse E ^ ₁ = 1st surface echo Ε _Λη = 2nd surface echo

^E R1 " 1. Back wall echo E _R2 = 2. Back wall echo E ₀ = Transmission echo tw = Water supply line AEB = Ad expectation area

- patent claims -

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Claims (4)

Patent claims: 1. Procedure for the non-destructive ultrasonic testing of Sheets and strips for duplicate-like defects, characterized in that the known per se in cyclic operation Impulse echo combined with the transmission method is applied and the test from both sides of the Test item takes place. 2. The method according to claim 1, characterized in that the operational runtime factor of the transmission method is fully transferred to the pulse echo method. 3. The method according to claims 1 and 2, characterized in that that the methods are used individually or in combination. 4. Device for performing the method according to the invention, characterized by the double-sided arrangement per se known transmission systems, consisting of the water tanks (2 and 3) each with a single transducer probe (4 and 5); each probe is equipped with an SE device (7, Io or 8,9) connected, also a main amplifier (11) for both SE facilities (3, 9 and 7, lo) and an evaluation device (12) coupled to the main amplifier (11). • üjpi.-i i. , j-. '■■' -.- T) Z INSPECTED 70984 3/0016