DE102011109808B4 - Process for producing a component connection by element friction welding - Google Patents

Abstract

Method for producing a component connection, in which at least two components (5, 6) are connected by means of a pin-shaped connecting element (1) which has a shank (3) and an expanded head (4), which is carried out in a joining process (F) under pressure and rotation is driven into the components (5, 6) via a tool (8) and the component connection is produced via friction heating and local deformation of the component materials, with the tool (8) forming the expanded head (4) in the joining process (F) of the connecting element (1) is subjected to a pressing force (FF) and a torque (MF), characterized in that the method for quality testing of the component connection has a test step (P) in which the connecting element (1) is subjected to a test torque (Mp) as axial torque is loaded, and if the test torque (Mp) is reached without damage, the quality test is completed without objection that the test torque (MP) exceeds d he tool (8) used in the joining process (F) is introduced into the connecting element (1), that the test step (P) takes place immediately after the end of the joining process (F), that the tool (8) after the end of the joining process (F ) remains in positive contact with the head (4) of the connecting element (1), so that in test step (P) the test torque (Mp) can be introduced into the head (4) of the connecting element (1) with a contact pressure (FP) such that the size of the test moment (MP) is determined on the basis of a failure moment at which a twisting movement of the connecting element (1) begins after the joining process (F), and that the failure moment is determined empirically on the basis of tests in which the connecting elements of test Component connections are loaded with an increasing torque until the onset of a twisting movement, and that the torque detected at the beginning of the twisting movement corresponds to the failure moment.

Description

The invention relates to a method for producing a component connection according to the preamble of patent claim 1, in which at least two components are connected to one another by friction welding with the aid of a pin-shaped connecting element.

Friction welding processes can be used in large series production in vehicle construction. Typically, a load-bearing component, for example a high-strength sheet steel part, and a component to be fastened to it, for example a soft sheet aluminum part, are connected to one another as the joining partner.

From the WO 2009/003569 A1 a generic component connection is known in which two components are connected to one another by means of a pin-shaped connecting element. The connecting element has an expanded head with an adjoining shank. Above its head, the connecting element is driven into the component assembly under pressure and rotation. The solid connection is created by friction heating and local deformation of the component materials. During this joining process, the still loose component assembly is first positioned. The pin-shaped connecting element is then driven into the component assembly in a so-called setting process with the aid of a drive ram with a specified pressure force and a specified speed. At the end of the setting process, the speed of the drive ram is controlled to zero and the ram is removed from the fastener with a return stroke. After the component connection has cooled down, it is sent for further processing.

In order to ensure process reliability, process monitoring is carried out in such a setting process known from the prior art, in which the process parameters are monitored as part of an online check. However, no direct statement can be made from this about the actual load-bearing behavior of the component connection.

The object of the invention is to provide a method for producing such a component connection in which the connection strength or the load-bearing behavior of the component connection can be checked in a simple manner.

From the U.S. 6,067,839 A a combined rivet-friction welding process is known. From the U.S. 7,346,970 B2 a torsion test of rivets is known. From the GB 2 260 096 A a quality check of a friction-welded joint is known.

The object is solved by the features of claim 1. Preferred developments of the invention are disclosed in the dependent claims. The invention is based on the fact that direct information about the load-bearing behavior of the component connection produced by friction welding is of great importance, particularly in large-scale production in vehicle construction, for reasons of process reliability. Against this background, the method according to the characterizing part of patent claim 1 for quality testing of the component connection has a test step that is not carried out during the setting process, but only after the completion of the component connection. In the test step, the connection element is loaded with a test torque. If the test torque is reached without damage, the test step is completed without any objections. This enables a non-destructive connection test, with which conclusions can be drawn about the load-bearing behavior of the connection. In the event that the connection element loosens when the test torque is applied, the component connection is sent to material waste or marked for post-processing.

The friction welding method according to the invention is therefore divided into a setting process or joining process and a subsequent test step. In the setting process, the still loose component assembly with the two or more joining partners can first be positioned relative to one another. The two parts to be joined can then be pressed together using a hold-down device. The connecting element is then pressed against the composite component under pressure and rotation with the aid of a drive ram and driven in via friction heating and local deformation of the component materials. The joining process ends after the component connection created in this way has cooled down.

The test step is then carried out, in which the test torque is introduced into the welded connection element. The test torque is preferably introduced directly into the expanded head of the connecting element, which protrudes from the component assembly in the final state. It is particularly preferred in terms of process technology if the drive ram already used in the joining process is also used in the test step. For this purpose, the drive tappet is pressed onto the head of the connecting element in the test step with a specified test torque and a specified pressure force. The pressure force required in the test step is significantly smaller than the pressure force in the joining process. The pressing force in the test step is in particular reduced by at least 50%. For sheet steel parts with Tensile For speeds of less than 800MPa, pressure forces of the order of 0.6kN to 1.6kN can be used. The pressure forces in the test step are designed in such a way that component deformation in the joint area is prevented and falsification of the test result due to increased under-head friction between the head of the fastener and the joint partner connected to it is prevented. However, the pressing force must be sufficiently high to ensure reliable force engagement between the drive plunger (i.e. setting tool) and the head of the connecting element.

In terms of process technology, the test step takes place immediately after the joining process, i.e. immediately after the component connection has cooled down, so that the drive ram (setting tool) remains in contact with the head of the connecting element after the end of the joining process and carries out the test step after the cooling phase can.

The magnitude of the test moment is determined based on a failure moment. The failure moment is determined empirically using tests in which the connecting elements of test component connections are loaded with an increasing torque until the onset of a twisting movement. The torque recorded at the beginning of the torsional movement corresponds to the aforementioned failure torque. For example, the test torque can be between 10% and 20% less than the empirically determined failure torque. The test step carried out after the joining process is free of complaints if the connection element to be tested remains non-rotatable in the component connection despite the application of the test torque, i.e. the application of the test torque does not lead to any twisting of the connection element.

The test device for carrying out the above-mentioned quality test comprises a control module with which the drive ram is subjected to a test torque and a test contact pressure. In addition, the testing device has a sensor with which a destruction of the component connection can be detected when the testing step is carried out. For this purpose, the sensor can preferably detect a rotation angle of the connecting element. If a rotation angle greater than 0 is detected, it is assumed that the component connection has been destroyed. The tested component connection therefore no longer remains in the manufacturing process, but is instead sent to material scrap or post-processing.

After completion of the test step, the drive ram of the setting tool can be removed from the connecting element by one return stroke. The component connection can then be processed further.

In a further refinement, the setting tool for producing the component connection can have a hold-down device which can be placed on the at least one component. The connecting element is arranged inside the hold-down device and can be acted upon by the drive ram in the axial direction and in the direction of rotation. The hold-down device ensures process sequences that can be reliably reproduced and contributes to the fact that the projections and passages that form when the connecting element is driven in are shaped in a targeted manner and unwanted distortions are avoided.

For example, when carrying out the joining process, the contact pressure can be 5kN. The speed of the drive tappet can vary from an initial speed of at least 2000 rpm to a final speed of at least 3500 rpm. Alternatively, the contact pressure in other process variants cannot exceed 2kN.

The advantageous embodiments and/or developments of the invention explained above and/or reproduced in the subclaims can be used individually or in any combination with one another, except, for example, in cases of clear dependencies or incompatible alternatives.

The invention and its advantageous training and developments and their advantages are explained in more detail below with reference to drawings.

• 1 in einem Längsschnitt eine feste Bauteilverbindung zwischen aneinander liegenden Fügeteilen mit Hilfe eines stiftförmigen Verbindungselementes, das über ein Werkzeug selbstbohrend in die Bauteile eingetrieben und in diesen verankert ist;
• 2 in einer Prinzipdarstellung eine Vorrichtung zur Durchführung des erfindungsgemäßen Herstellungsverfahrens; und
• 3 bis 7 unterschiedliche Prinzipdarstellungen zur Veranschaulichung eines Verfahrens zur Herstellung der Bauteilverbindung.

Show it:

• 1 in a longitudinal section, a fixed component connection between adjacent parts to be joined with the aid of a pin-shaped connecting element, which is driven into the components in a self-drilling manner using a tool and is anchored in them;
• 2 in a schematic representation of a device for carrying out the manufacturing method according to the invention; and
• 3 until 7 Different principle representations to illustrate a method for producing the component connection.

In the 1 a component connection is shown in which a connecting element 1 firmly connects two components 5, 6 lying flat against one another. The pin-shaped, rotationally symmet Technical connecting element 1 can be made of steel, for example, and is composed essentially of a shank tip 2, a shank 3 and a head 4 with a larger diameter. The connecting element 1 is according to 1 driven into the components 5, 6, annular passages 5a, 6a being formed downwards and annular projections 5b, 6b upwards due to the material displacement next to the corresponding bore reveals. Correspondingly, the passages 5a, 6a extend in the joining direction of the connecting element 1, while the projections 5b, 6b extend upwards counter to the joining direction. That in the 1 The lower, load-bearing component 5 shown can, for example, be a high-strength sheet steel part. The component 6 fastened to it on top, on the other hand, can be a soft aluminum sheet metal part. The tip 2 of the connecting element 1 is in accordance with 1 embodied by several sections (no reference numbers) with an initially larger and then decreasing cone angle in such a way that they can expand the flat components 5, 6 during the joining process essentially without destroying them. The shank tip 2 can be hardened or provided with a hard metal cap.

How from the 1 further shows that the tip 2 merges into the larger-diameter shank 3, which is designed cylindrical or slightly conical towards the head 4 with an increasing diameter. In the area of the lower component 5, the shank 3 has a corrugation with several elevations and depressions (identified uniformly with 3a). With the help of this, only in the 1 The elevations/depressions 3a shown can be used to create a form fit between the connecting element 1 and the components 5, 6, which increases the strength of the connection. The elevations/depressions 3a are shown as corrugations only by way of example. Alternatively, the elevations/depressions 3a can have any desired surface structure.

In the 2 a machining tool 8 for driving the connecting element 1 into the components 5, 6 to be connected is shown in a roughly schematic manner. The machining tool 8 has, among other things, a hold-down device 9 that can be lowered, in which, in order to carry out a joining process F ( 3 until 5 ) a connecting element 1 is inserted. A drive ram 10 is also guided in the hold-down device 9 in a rotatable and axially displaceable manner. The end face of the drive plunger 10 has a form-fitting contour with a web 11 which is in form-fitting engagement with a groove on the head 4 of the connecting element 1 . In addition, both the hold-down device 9 and the drive ram 10 can be controlled via a control device 14 . To carry out the joining process F ( 3 until 5 ) the drive ram 10 can be driven hydraulically, pneumatically or by an electric motor. Below the two components 5, 6, a counter-holding matrix (not shown here) can optionally be provided.

In the 3 until 5 the joining process F for producing the component connection is shown roughly schematically. First, the components 5, 6 lying loosely on top of one another must be adjusted. Subsequently, the processing tool 8 guided, for example, on a robot arm is applied to the components 5, 6 and the hold-down device 9 is moved against the components 5, 6 with a predetermined hold-down device force F _N ( 3 ). The drive ram 10 is then also moved against the components 5, 6 with a contact pressure force F _F , specifically while rotating at an initial speed of approximately 2000 rpm, as a result of which the connecting element 1 first heats the upper component 6 . A brief, massive increase in the contact pressure F _F in the millisecond range then controls a driving impulse that initiates the penetration of the tip 2 of the connecting element 1 into the upper component 6 . Such a pulsed application of force represents an extension that can optionally be accepted to the standard joining process.

By increasing the speed n of the connecting element 1 with simultaneous axial feed, the driving-in and the process temperature that occurs are controlled in such a way that the desired process parameters and connection properties are generated by more or less strong frictional loads. The final speed of the connecting element is preferably approx. 3500 rpm.

Immediately following the joining process F is according to 6 a test step P is carried out, in which a quality check of the component connection takes place. The test step P is carried out by means of a test device 13, which is in the 2 only indicated roughly as a block diagram. The test device 13 has a test unit integrated in the control device 14, which is not shown in detail and with which the drive ram 10 is subjected to a predetermined test force F _P and a predetermined test torque M _P when the hold-down device 9 is lowered. In addition, the checking device 13 has a rotation angle sensor 15, with which a twisting movement of the drive plunger 10, which is in a positive connection with the head 4 of the connecting element 1, is detected. The angle of rotation sensor 15 is signal-connected to a comparison unit 17, in which the signal detected by the angle of rotation sensor 15 is evaluated and a test result is determined. With the detection of the angle of rotation, an angle of rotation α covered by the connecting element 1 is to be detected. It is therefore self-evident for the person skilled in the art that a rotational angle component which changes due to the torsion is to be subtracted from the detected rotational angle α of the drive plunger 10 or due to bearing play.

The pressure force F _P of the drive ram 10 generated during the testing process P is around 0.6 kN to 1.6 kN for steel sheets with tensile strengths of less than 800 MPa, which prevents component deformation in the joint area and falsification of the test result due to increased underhead friction between the connecting element 1 and the upper member 5 is prevented. With tensile strengths of up to 800MPa, the test force should be between 0.3kN and 1kN. The test force should be selected so that it prevents the drive from lifting off the element head 4 and does not damage the connection or the joint itself.

In the test step P, the connecting element 1 is therefore loaded with the test torque M _P and the contact pressure F _P . If the test torque M _P is reached without damage, the quality test is completed without any objections. In contrast, when a rotation angle α greater than 0 is detected in the comparison unit 17, it is assumed that the component connection will be destroyed. Accordingly, the tested component connection is decoupled from the manufacturing process after the end of the test step P and sent to the material scrap or marked for post-processing.

After completion of the test step P, a return stroke R ( 7 ), in which both the hold-down device 9 and the drive ram 10 are raised. The processing tool is then removed from the component connection and - if the test is free of objections - sent for further processing.

Reference List

1

fastener

2

Top

3

shaft

3a

corrugation

4

head

5

component

5a

Draft

5b

cantilever

6

component

6a

Draft

6b

cantilever

8th

editing tool

9

hold-down

10

drive tappet

11

web

13

testing facility

14

control device

15

angle of rotation sensor

17

comparison unit

f

joining process

P

testing process

a

angle of rotation

MP, MF

torques

FP, FF

pressure forces

Claims (4)

Method for producing a component connection, in which at least two components (5, 6) are connected by means of a pin-shaped connecting element (1) which has a shank (3) and an expanded head (4), which is carried out in a joining process (F) under pressure and rotation is driven into the components (5, 6) via a tool (8) and the component connection is produced via friction heating and local deformation of the component materials, with the tool (8) forming the expanded head (4) in the joining process (F) of the connecting element (1) is subjected to a pressing force (F _F ) and a torque (M _F ), characterized in that the method for quality testing of the component connection has a test step (P) in which the connecting element (1) is subjected to a test torque (M _p ) is loaded as an axial torque, and if the test torque (M _p ) is reached without causing any damage, the quality test is completed without objection, that the test torque (M _P ) is introduced into the connecting element (1) via the tool (8) used in the joining process (F), that the test step (P) takes place immediately after the end of the joining process (F), that the tool (8) after the end of the Joining process (F) remains in positive contact with the head (4) of the connecting element (1), so that in the test step (P) the test torque (M _p ) with a pressing force (F _P ) is applied to the head (4) of the connecting element (1 ) can be initiated that the size of the test moment (M _P ) is determined on the basis of a failure moment at which a twisting movement of the connecting element (1) begins after the joining process (F), and that the failure moment is determined empirically on the basis of tests which the connecting elements of test component connections are loaded with an increasing torque until the onset of a torsional movement, and that the torque detected at the beginning of the torsional movement corresponds to the failure torque. procedure after claim 1 , characterized in that in a test step (P) without any complaints, the connecting element (1) remains non-rotatably in the component connection when the test torque (M _P ) is applied, i.e. the application of the test torque (M _P ) does not result in any twisting of the connecting element (1 ) and/or that, in the case of a component connection that is the subject of a complaint, this is sent for reworking or material scrap. Procedure according to one of Claims 1 or 2 , characterized in that the contact pressure (F _P ) of the tool (8) in the test step (P) is at least 50% smaller than the maximum contact pressure (F _F ) in the joining process. Method according to one of the preceding claims, characterized in that in the test step (P) a rotation angle is detected, in which a rotation angle (a) covered by the connecting element (1) is detected and/or after the test step (P) has taken place, a return stroke (R) of the tool is initiated.

Images