Methods for testing welded or adhesive joints

Abstract

Method for testing welded or adhesive joints (13), comprising the following steps: Providing an arrangement (10) to be tested, consisting of at least two sheet metal components (11, 12) connected by at least one welded or adhesive joint (13), Excitation of Lamb waves (16) in the provided arrangement (10) to be tested with laser impulses (15) from a laser source (14), Detection of leaky waves (17) in an air layer adjacent to the provided arrangement to be tested (10) using a diaphragmless optical microphone (18), wherein the laser source (14) and the membraneless optical microphone (18) are both arranged on the same side of the arrangement (10) to be tested, consisting of at least two sheet metal components (11, 12), and are moved together linearly or translationally along the arrangement (10) to be tested, Evaluating the leaky waves (17) detected using the diaphragmless optical microphone (18) by determining a sound pressure profile (19) of the leaky waves (17), wherein the sound pressure profile (19) recorded during the linear or translational movement of laser source (14) and diaphragmless optical microphone (18) is evaluated using the half-value method in such a way that a distance between such points of the sound pressure profile (19) in which the sound pressure corresponds to half of a maximum sound pressure is determined, Testing the respective welded or adhesive joint (13) on the basis of the determined sound pressure profile (19) by determining at least one geometric dimension of the respective joint (13), wherein the distance between such points of the sound pressure curve (19), in which the sound pressure corresponds to half of the maximum sound pressure, is determined as the dimension of the respective joining connection (13) in the direction of movement.

Description

[0001] The invention relates to a method for testing welded or adhesive joints.

[0002] DE 10 2004 030 154 A1 discloses a method for testing the quality of a mechanical joint. A sample of joining partners joined by a welding process is exposed to a laser beam, and a laser vibrometer detects the resulting wave for quality testing of the mechanical joint.

[0003] Membraneless optical microphones are known in practice as innovative devices for sound measurement. Membraneless optical microphones of this type are marketed by Xarion Laser Acoustics GmbH. Membraneless optical microphones of this type do not use any mechanically moving parts.

[0004] EP 3 173 781 A1 discloses a test system that uses a membrane-less optical microphone.

[0005] From ROHRINGER, Wolfgang [et al]; Optical microphone as laser-ultrasound detector. In: Conference proceedings - DAGA 2018 : 44th German Annual Conference for Acoustics : March 19-22, 2018, Munich. Berlin: German Acoustic Society eV / DEGA), 2018. ISBN 9783939296133 a method for testing welded or adhesively bonded joints is known, comprising the following steps: Providing an arrangement to be tested consisting of at least two sheet metal components connected by a welded joint. Exciting Lamb waves in the provided arrangement to be tested with laser pulses from a laser source. Detecting leaky waves in an air layer adjacent to the arrangement to be tested using a membrane-free optical microphone. Evaluating the leaky waves detected using the membrane-free optical microphone. Testing the respective welded joint and determining a geometric dimension of the joint.

[0006] The object of the invention is to create a novel method for testing welded or adhesive joints.

[0007] This object is achieved by a method for testing welded or adhesive joints according to patent claim 1.

[0008] The method according to the invention comprises at least the following steps: Provision of an arrangement to be tested consisting of at least two sheet metal components connected by at least one welded or adhesive joint.

[0009] Excitation of Lamb waves in the provided arrangement to be tested with laser pulses from a laser source.

[0010] Detection of leaky waves in an air layer adjacent to the provided arrangement to be tested using a membrane-less optical microphone.

[0011] The laser source and the membrane-less optical microphone are both arranged on the same side of the assembly to be tested consisting of at least two sheet metal components and are moved together linearly or translationally along the assembly to be tested.

[0012] Evaluation of the leaky waves recorded with the aid of the membrane-less optical microphone by determining a sound pressure curve of the leaky waves, whereby the sound pressure curve recorded during linear or translational movement of the laser source and the membrane-less optical microphone is evaluated using the half-value method in such a way that a distance between those points of the sound pressure curve at which the sound pressure corresponds to half of a maximum sound pressure is determined.

[0013] Testing the respective welded or adhesive joint on the basis of the determined sound pressure curve by determining at least one geometric dimension of the respective joint, whereby the distance between those points of the sound pressure curve at which the sound pressure corresponds to half of the maximum sound pressure is determined as the dimension of the respective joint in the direction of movement.

[0014] The present invention proposes, for the first time, the use of a membrane-free optical microphone for testing welded or adhesive joints. Laser pulses from a laser source are applied to a provided assembly to be tested, consisting of at least two sheet metal components connected by at least one welded or adhesive joint, in order to excite Lamb waves within the assembly to be tested, namely at least one sheet metal component of the assembly to be tested.

[0015] The excited Lamb waves propagate within the respective sheet metal component, with antisymmetric Lamb waves causing leaky waves in adjacent air layers due to out-of-plane movement on the sheet metal surface. These leaky waves are recorded using a membraneless optical microphone and evaluated by determining a sound pressure profile of the leaky waves. The respective welded or adhesive joint is tested based on the thus determined sound pressure profile of the leaky waves in order to determine at least one geometric dimension of the respective joint.

[0016] This provides a completely new, non-contact and non-destructive method for testing welded or adhesive joints.

[0017] The laser source and the membrane-free optical microphone are both arranged on the same side of the assembly to be tested, consisting of at least two sheet metal components, and are moved together along the assembly to be tested. The excitation of Lamb waves via the laser source and the detection of leaky waves via the membrane-free optical microphone preferably begins in a section outside the respective joint and is carried out as the laser source and membrane-free optical microphone move together across the respective joint into a further section outside the respective joint, with the sound pressure profile of the leaky waves being determined along this movement. This is particularly advantageous for testing welded or adhesive joints.The laser source and the membrane-free optical microphone are both arranged on the same side of the assembly to be tested, consisting of at least two sheet metal components. The laser source and membrane-free optical microphone are moved together along the assembly to be tested. Based on the sound pressure profile recorded along this movement, a geometric dimension of the respective joint can be determined particularly advantageously in the direction of this movement.

[0018] Preferably, an assembly to be tested consists of at least two sheet metal components connected by at least one spot-shaped or circular welded joint or of at least two sheet metal components connected by a bead-shaped adhesive joint. These sheet metal components are preferably sheet metal components made of steel or aluminum of a motor vehicle body. The invention is used in particular for sheet metal components made of steel or aluminum of a motor vehicle body to test welded joints or adhesive joints.

[0019] Preferred developments of the invention will become apparent from the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail, without being limited thereto, with reference to the drawings. Herein: Fig. 1 a highly schematic test arrangement to illustrate the method according to the invention; Fig. 2 shows an exemplary damage pressure curve determined when carrying out the method according to the invention.

[0020] The invention relates to a method for testing welded joints or adhesive joints of sheet metal components. The invention is described below using the example of testing welded joints on sheet metal components. However, the invention can also be used for sheet metal components joined by adhesive joints.

[0021] Fig. Figure 1 shows an assembly 10 to be tested, consisting of two sheet metal components 11 and 12, which are connected to each other via a welded joint 13. This welded joint 13 is a point-shaped or circular welded joint 13, formed, for example, by stud welding or resistance spot welding. The welded joint 13 should have a defined target dimension. It must be checked whether the actual dimension corresponds to the target dimension.

[0022] Such an assembly 10 to be tested, consisting of sheet metal components 11, 12 joined together by a welded joint 13, is subjected to laser pulses via a laser source 14 in order to excite Lamb waves 16 in the assembly 10, here in sheet metal component 11 of the assembly 10. Laser pulses are also referred to as laser pulses.

[0023] Such Lamb waves 16 have an antisymmetric mode and a symmetric mode, with the antisymmetric mode having a dominant out-of-plane motion and the symmetric mode having a dominant in-plane motion.

[0024] The antisymmetric mode and thus the out-of-plane movement of the Lamb waves 16 causes leaky waves 17 in an air layer adjacent to the arrangement 10 to be tested. The leaky waves 17 are recorded using a membrane-less optical microphone 18.

[0025] The leaky waves 17 detected by the membrane-less optical microphone 18 are evaluated by determining a sound pressure curve of the leaky waves 17.

[0026] To test the respective welded joint 13, at least one geometric dimension of the respective welded joint 13 is determined based on the sound pressure profile, specifically, in the case of a point-shaped or circular welded joint 13, its diameter. The respective determined geometric dimension of the respective welded joint 13 corresponds to the respective actual dimension of the respective welded joint 13.

[0027] If the respective actual dimension of the respective welded joint 13 deviates from the respective target dimension of the respective welded joint 13 by more than a limit value, the welded joint 13 is defective. Otherwise, the welded joint 13 is correct.

[0028] When depicting the Fig. Figure 1 is a highly schematic representation of a test setup. The laser source 14 and the membraneless optical microphone 18 are both arranged on the same side of the assembly 10 to be tested, which consists of at least two sheet metal components 11, 12.

[0029] When carrying out the test method according to the invention, the laser source 14 and the membrane-less optical microphone 18, which are preferably combined to form a structural unit, are moved together along the arrangement 10 to be tested on the same side of the arrangement 10 to be tested.

[0030] Here, the excitation of Lamb waves 16 via the laser source 14 and the detection of the leaky waves 17 triggered thereby by the membrane-free optical microphone 18 begins in a section outside the respective joint 13. The laser source 14 and the membrane-free optical microphone 18 are both arranged on the same side of the assembly 10 to be tested on a first side of the respective joint 13, viewed in the direction of movement thereof, at the beginning of the movement and measurement.

[0031] The laser source 14 and the membrane-free optical microphone 18 are moved together along the assembly 10 to be tested, across the respective joint 13, into a further area outside the respective weld joint 13. During this movement, the laser source 14 continuously applies laser pulses 15 to the assembly 10 under test, and the membrane-free optical microphone 18 continuously detects the resulting leaky waves 17. A sound pressure profile of the leaky waves 17 is determined along this movement.

[0032] If, at the beginning of the movement and measurement, the laser source 14 and the membrane-free optical microphone 18 are both arranged on the first side of the respective joint 13, as seen in the direction of movement thereof, this changes when the laser source 14 and the membrane-free optical microphone 18 move together. At the end of the movement and measurement of the laser source 14 and the membrane-free optical microphone 18, the laser source 14 and the membrane-free optical microphone 18 are both arranged on a second side of the respective joint 13 opposite the first side, as seen in the direction of movement thereof, and are again moved on the same side of the arrangement 10 to be tested.

[0033] During the movement of the laser source 14 and the membrane-less optical microphone 18, they always remain on the same side of the assembly 10 to be tested.

[0034] Fig. Figure 2 schematically shows a sound pressure curve 19 recorded during a movement of the laser source 14 and the membrane-free optical microphone 18, depending on the path s of the joint movement of the laser source 14 and the membrane-free optical microphone 18.

[0035] In the Fig. The sound pressure curve 19 shown in Figure 2 is a standardized sound pressure curve. The maximum sound pressure of such a standardized sound pressure curve is 1.

[0036] The sound pressure curve 19 is evaluated using a half-value method such that a distance between those positions s1 and s2 along the path of movement of the laser source 14 and the membrane-free optical microphone 18, in which the sound pressure corresponds to half the maximum sound pressure, is determined as the actual dimension x of the respective welded joint 13 in the direction of movement of the laser source 14 and the membrane-free optical microphone 18, i.e. here as the diameter of the punctiform or circular welded joint 13 between the sheet metal components 11, 12. Half of the maximum sound pressure curve corresponds to a value of 0.5 for a standardized sound pressure curve.

[0037] The movement of the laser source 14 and the membrane-free optical microphone 18 along the assembly 10 of the sheet metal components 11, 12 is a linear or translational movement. The length or magnitude of the joint linear or translational movement of the laser source 14 and the membrane-free optical microphone 18 corresponds to at least twice, preferably at least three times, the nominal dimension of the respective joint 13 in the direction of movement of the laser source 14 and the membrane-free optical microphone 18.

[0038] If the nominal dimension of the respective joint connection 13 is 5 mm, the length or the amount of the joint, linear or translational movement of the laser source 14 and the membrane-less optical microphone 18 along the arrangement 10 to be tested is at least 10 mm, preferably at least 15 mm.

[0039] The length or amount of the joint, linear or translational movement of the laser source 14 and the membrane-less optical microphone 18 along the arrangement 10 to be tested is between twice and five times the nominal dimension of the respective joint connection 13 in the direction of the joint movement of the laser source 14 and the membrane-less optical microphone 18.

[0040] The sheet metal components 11, 12 of the assembly 10 are, in particular, sheet metal components of a vehicle body made of steel or aluminum. As already explained, the welded joint is preferably a stud weld or resistance spot weld.

[0041] When the invention is used in an assembly to be tested whose sheet metal components are connected via an adhesive joint, the adhesive joint is preferably provided via a bead-shaped adhesive joint, which is therefore not point-shaped or circular, but rather bead-like and thus elongated. Using the method according to the invention, the dimensions of such an adhesive joint can be measured in the longitudinal direction as well as transversely to the longitudinal direction.

[0042] The invention proposes a completely novel method for the non-destructive, non-contact testing of welded joints or adhesive joints 13 on sheet metal components 11, 12 connected to one another via the respective joint 13.

[0043] The laser source 14 excites Lamb waves 16 in a sheet metal component of an assembly 10 under test, with the Lamb waves 16 triggering leaky waves 17 that are detected by the membraneless optical microphone 18. The laser source 14 and the optical microphone 18 are arranged in a pitch-catch arrangement on the same side of the assembly 10 under test, which consists of the interconnected sheet metal components 11, 12. The pitch-catch arrangement comprising laser source 14 and membrane-less optical microphone 18 is moved along the joint 13 to be tested, starting from an area outside the respective joint 13 across the respective joint 13 into an opposite area outside the joint 13. The recorded, movement-path-dependent sound pressure curve 19 of the leaky waves 17 is evaluated in order to determine the respective geometric dimension of the respective joint 13, using a half-value method.

[0044] For point-shaped or circular joints 13, measurement and evaluation in a single direction of movement of the laser source 14 and the membraneless optical microphone 18 is sufficient. For non-point-shaped joints 13, corresponding actual dimensions can be recorded in several intersecting directions of movement of the laser source 14 and the membraneless optical microphone 18.

[0045] A determined sound pressure curve 19 can be displayed and output as a color-coded image, particularly as a so-called C-scan. C-scans are commonly used in ultrasonic testing.

Claims

[1] Method for testing welded or adhesive joints (13), comprising the following steps: Providing an arrangement (10) to be tested comprising at least two sheet metal components (11, 12) connected by at least one welded or adhesive joint (13), Excitation of Lamb waves (16) in the provided arrangement to be tested (10) with laser pulses (15) of a laser source (14), detecting leaky waves (17) in an air layer adjacent to the provided arrangement to be tested (10) by means of a membrane-free optical microphone (18), wherein the laser source (14) and the membrane-free optical microphone (18) are both arranged on the same side of the assembly (10) to be tested, comprising the at least two sheet metal components (11, 12), and are moved together linearly or translationally along the assembly (10) to be tested, Evaluating the leaky waves (17) recorded by the membrane-less optical microphone (18) by determining a sound pressure curve (19) of the leaky waves (17), wherein the sound pressure curve (19) detected during the linear or translational movement of the laser source (14) and the membrane-less optical microphone (18) is evaluated using the half-value method in such a way that a distance between those points of the sound pressure curve (19) at which the sound pressure corresponds to half of a maximum sound pressure is determined, Testing the respective welded or adhesive joint (13) on the basis of the determined sound pressure curve (19) by determining at least one geometric dimension of the respective joint (13), wherein the distance between those points of the sound pressure curve (19) at which the sound pressure corresponds to half of the maximum sound pressure is determined as the dimension of the respective joint connection (13) in the direction of movement. [2] Method according to claim 1, characterized by that an arrangement (10) to be tested is provided comprising at least two sheet metal components (11, 12) connected by at least one point-shaped or circular welded joint (13). [3] Method according to claim 1, characterized by that an arrangement (10) to be tested is provided comprising at least two sheet metal components (11, 12) connected by at least one bead-shaped adhesive joint (13). [4] Method according to one of claims 1 to 3, characterized bythat an arrangement (10) to be tested is provided comprising at least two sheet metal body components (11, 12) of a motor vehicle body connected by at least one welded or adhesive joint (13). [5] Method according to one of claims 1 to 4, characterized by that the excitation of Lamb waves (16) via the laser source (14) and the detection of the leaky waves (17) via the membrane-free optical microphone (18) begins in a section outside the respective joint connection (13), and is carried out during the joint movement of the laser source (14) and the membrane-free optical microphone (18) over the respective joint connection (13) into a further section outside the respective joint connection (13), wherein the sound pressure curve (19) of the leaky waves (17) is determined along this movement. [6] Method according to one of claims 1 to 5, characterized bythat the length of the joint, linear or translational movement of the laser source (14) and the membrane-less optical microphone (18) corresponds to at least twice, preferably at least three times, a desired dimension of the respective joining connection (13) in the direction of movement.

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