DE102020107151A1 - Test tool, arrangement and method for testing the frictional behavior of test specimens - Google Patents

Abstract

The invention relates to a test tool (1) for testing the friction behavior of specimens (2a, 2b), comprising two clamping plates (3), a tensile body (4) which is arranged between the clamping plates (3), and a clamping device (5), which is set up to brace the two clamping plates (3) against one another with a prestressing force (F), with a pair of recesses (6) for receiving a pair of specimens (2 ) is formed, and wherein each of the tensioning plates (3) and the tension body (4) has a connecting device (7) for connection to a tension device (11) to the tension body (4) perpendicular to the pretensioning force (F) relative to the two tensioning plates (3) to move.

Description

The invention relates to a test tool, an arrangement and a method for testing the frictional behavior of test specimens.

Test devices for determining the friction behavior of test specimens are known from the prior art. For example shows DE 10 2018 125 141 B3 such a testing device. Such test devices are usually very complex and expensive. In addition, changing the specimen to be checked is often time-consuming.

It is therefore an object of the present invention to provide an arrangement for testing the frictional behavior of specimens, which has a simple and inexpensive construction and allows specimens to be changed quickly and easily. Furthermore, it is an object of the present invention to provide a method for testing the friction behavior of test specimens which can be carried out easily and quickly and which can produce reliable results.

This problem is solved by the features of the independent claims. The dependent claims relate to advantageous embodiments of the invention.

The object is thus achieved by a test tool for testing the frictional behavior of specimens, comprising two clamping plates and a tensile body which is arranged between the two clamping plates. Furthermore, the test tool comprises a clamping device which is set up to clamp the two clamping plates against one another with a prestressing force. The prestressing force is in particular perpendicular to flat surfaces of the clamping plates. The clamping device is preferably set up to apply different pretensioning forces to the clamping plates in order to be able to examine the frictional behavior of specimens in a wide variety of states.

A pair of recesses is formed between each of the two clamping plates and the tension body. That is, the two pairs of recesses are formed on both sides of the traction body. Each pair of recesses is designed to receive a pair of specimens. Each pair of recesses has two recesses. Each recess is designed, in particular, to accommodate precisely one specimen of the pair of specimens.

Each of the two clamping plates and the tension body have a connecting device. Each of the connecting devices can be connected to a pulling device in order to be able to move the pulling body perpendicular to the prestressing force relative to the two clamping plates. The tensile body can thus preferably be pulled out of the clamping plates by means of the connecting devices.

The test tool thus has a particularly simple design with a few components that can be manufactured at low cost. Due to the design with two clamping plates and two pairs of recesses on both sides of the tensile body, the test tool preferably has a symmetrical construction. In particular, a uniform pretensioning force can thereby be applied in a particularly simple manner. Tilting or tilting, and thus falsification of the measurement results, can thus be avoided. In addition, the test tool is versatile and suitable for flexible use in a wide variety of pulling devices. For example, the test tool can be used as a pulling device in a tensile testing machine. In this way, tests to test the frictional behavior of specimens can be carried out with simple and inexpensive means.

The two recesses of the recess pairs are preferably designed as pockets in the tension body and in the clamping plates. A first recess is in the tension body and a second recess is formed in the clamping plate. The pockets are preferably arranged in such a way that the specimens can be pushed laterally into the test tool along an insertion direction. In particular, the insertion direction for this purpose is arranged perpendicular to the pulling direction and perpendicular to the direction of the pretensioning force. This results in particularly simple handling of the test tool during a test process. In particular, the recesses are thus easily accessible, so that the pairs of specimens can simply be inserted into the test tool or removed from it.

Particularly preferably, an area ratio of mutually facing end faces of the recesses of each recess pair is at least 2, preferably at least 5, in particular a maximum of 10. The end faces of the first recesses of the tension body are preferably smaller than the end faces of the second recesses of the clamping plates. Alternatively, the end faces of the recesses in the clamping plates are smaller than the end faces of the recesses in the traction body. In particular, a symmetrical geometry of the test tool is provided here. Due to the front surfaces of the cutouts of different sizes, it is easily possible to rub specimens of different sizes against one another. It can thereby be made possible that during a test process over a certain test path which the test specimens are moved against each other, there is always a constant contact surface of the test specimens rubbing against one another.

The clamping device preferably comprises at least one screw for clamping the two clamping plates against one another. The pretensioning force can be adjusted particularly easily via a torque by means of which the screw is tightened. Particularly preferably, each of the two clamping plates has a through opening through which the screw extends. For example, the clamping device can additionally have a nut which can be screwed onto the screw extending through the clamping plate. The test tool particularly preferably comprises a plurality of screws, in particular two or four screws, in order to enable the plates to be pretensioned against one another in a particularly uniform manner. More preferably, the screws can have strain gauges in order to simplify uniform tightening of the screws in order to avoid tilting of the clamping plates.

Furthermore, the invention leads to an arrangement comprising the test tool described above and a pulling device. The pulling device is connected to each of the connecting devices of the test tool. The pulling device is set up in particular to move the pulling body and the two clamping plates relative to one another in a pulling direction which is perpendicular to the prestressing force. The pulling device can be, for example, a tensile testing machine. The pulling device preferably has a stationary machine table to which the connecting devices of the two clamping plates are connected. The pulling device preferably also has a traverse which is movable relative to the machine table and which is connected to the connecting device of the pulling body. The arrangement thus offers a particularly simple and inexpensive structure, by means of which friction tests can be carried out to test the friction behavior of specimens.

The arrangement preferably further comprises a detection device which is set up to detect a tensile force and / or a friction path when the tensile body is moved.

The arrangement preferably further comprises a force measuring device which is set up to detect the pretensioning force. For example, at least one of the clamping plates can be designed in two parts for this purpose, the force measuring device being arranged between the two parts of this two-part clamping plate. In this case, the pre-tensioning force can be recorded in a simple manner as a compressive force, in particular which the two parts of the tensioning plate exert on the force measuring device.

1. (i) Einlegen von zwei Probenkörper-Paaren zwischen einen Zugkörper und zwei Spannplatten, wobei der Zugkörper zwischen den Spannplatten angeordnet ist, wobei zwischen jeder der beiden Spannplatten und dem Zugkörper ein Aussparungs-Paar zur Aufnahme eines Probenkörper-Paares ausgebildet ist, und wobei jedes Probenkörper-Paar in eines der beiden Aussparungs-Paare eingelegt wird,
2. (ii) Aufbringen einer Vorspannkraft auf die Probenkörper durch gegeneinander Verspannen der Spannplatten, und
3. (iii) Relativbewegen von Zugkörper und Spannplatten senkrecht zur Vorspannkraft.

The invention also relates to a method for testing the friction behavior of specimens. The procedure consists of the following steps:

1. (i) Insertion of two pairs of specimens between a tensile body and two clamping plates, the tensile body being arranged between the clamping plates, a pair of recesses for receiving a pair of specimens being formed between each of the two clamping plates and the tensile body, and each The pair of specimens is inserted into one of the two pairs of recesses,
2. (ii) applying a pretensioning force to the specimen by bracing the clamping plates against each other, and
3. (iii) Relative movement of the tensile body and the clamping plates perpendicular to the prestressing force.

The method enables the friction behavior of the specimen to be tested in a particularly simple and inexpensive manner. By moving the tensile body and the clamping plates relative to each other, the two specimens of each pair of specimens are pulled apart tangentially. With such a tangential pulling apart, the adhesive force can periodically exceed and fall below the adhesive force through jerky sliding of the two test specimens pressed against one another, which is also known as the stick-slip effect. The method thus enables in particular the investigation of the stick-slip behavior of the test specimens.

The method preferably further comprises the step of: detecting a tensile force and / or a friction path when the tensile body and clamping plates move relative to each other. The tensile force is considered to be that force which the tensile device exerts on the tensile body and which is, in particular, parallel to the contact surfaces of the adjoining sample bodies of the sample body pairs. The tensile force is thus oriented tangentially to the friction surfaces of the specimen.

The method preferably further comprises the step of: detecting the pretensioning force. The pretensioning force and the tensile force are particularly preferably detected simultaneously, a coefficient of friction being determined in particular from the pretensioning force and the tensile force. In addition, the friction path is preferably recorded and, in particular, set in relation to the coefficient of friction in order to be able to obtain clear information about the friction behavior of the test specimens, for example using a coefficient of friction / friction path diagram.

Preferably, the size ratio of mutually facing, in particular touching, friction surfaces of the two specimens of each specimen pair is at least 2, preferably at least 5, particularly preferably a maximum of 10. The specimens arranged on the tensile element are preferably smaller than the opposing ones arranged on the clamping plates Specimens of each pair of specimens. Alternatively, the sample bodies arranged on the clamping plates can also be smaller than the sample bodies arranged on the tensile body. In particular, the arrangement with inserted pairs of specimens has a symmetrical geometry. Different sized recesses make it easy to rub specimens of different sizes against one another. The different friction surfaces of the specimens of each pair of specimens can ensure that there is always a constant contact surface between the specimens rubbing against each other during the testing process over a certain test path, which the specimens are moved against each other.

Particularly preferably, the method further comprises the step: removing the test specimens from a component. The two specimens of a pair of specimens can preferably be removed from the same component. Alternatively, these can be taken from different components. In the case of specimens made of different components, it is particularly preferable for the two pairs of specimens to be arranged symmetrically with respect to the test tool. This means that the same or comparable friction pairings are provided on both sides of the traction body.

The sample bodies are preferably removed by means of wire eroding, as a result of which sample bodies with a particularly precise geometry can be produced. This makes it possible to prevent the arrangement from tilting, for example due to geometric deviations in the pairs of specimens, which are to be arranged in particular symmetrically in the test tool.

The component, in particular from which at least one of the test specimens is taken, is also preferably a wheel and / or a wheel bearing flange and / or a brake disc of a vehicle. Preferably, each of the two specimens of a pair of specimens is taken from a different component. Particularly preferably, a first sample body can be removed from the wheel and a second sample body can be removed from the wheel bearing flange. As a result, the method can be used, for example, to carry out tests to better understand the stick-slip behavior of these components, in particular with regard to the acoustic effects of the stick-slip effect, such as, for example, a noise that can occur when the vehicle is in operation . Components with different degrees of wear are preferably compared by means of several test tests, for example new or already used components. In addition, for example, components that generate noise during operation can be examined in a targeted manner in order to be able to uncover possible causes or countermeasures.

• 1 eine schematische Ansicht einer erfindungsgemäßen Anordnung mit einem erfindungsgemäßen Prüfwerkzeug gemäß einem ersten Ausführungsbeispiel der Erfindung,
• 2 eine Detail-Ansicht des Prüfwerkzeugs der 1, und
• 3 eine perspektivische Ansicht eines Prüfwerkzeugs gemäß einem zweiten Ausführungsbeispiel der Erfindung.

Further details, features and advantages of the invention emerge from the following description and the figures. In the figures, functionally identical components are always identified with the same reference symbols. Show it:

• 1 a schematic view of an arrangement according to the invention with a test tool according to the invention according to a first embodiment of the invention,
• 2 a detailed view of the test tool of 1 , and
• 3 a perspective view of a test tool according to a second embodiment of the invention.

the 1 shows a schematic view of an arrangement according to the invention 10 for testing the friction behavior of test specimens 2a , 2 B . The order 10 includes a pulling device 11 and a test tool according to the invention 1 . In the 1 is a state of the arrangement 10 shown before the test is carried out.

The draw gear 11 is a tensile testing machine and includes a crossbeam 14th which relative to a, in particular stationary, machine table 15th is movable.

The test tool 1 includes two clamping plates 3 and a tensile body 4th . The tensile body 4th is between the two clamping plates 3 arranged. By means of a clamping device 5 which total of four screws 50 has, are the clamping plates 3 in a direction perpendicular to the direction of pull 100 with a preload force F. braced against each other. Via a tightening torque of the screws 50 is the preload force F. adjustable. Any screws 50 can through a screw hole 51 through clamping plates 3 and tensile body 4th be passed through.

Each of the two clamping plates 3 as well as the tensile body 4th has a connecting device 7th for connection to the draw gear 11 on. The connecting device 7th can for example comprise a pull rod which is inserted into a connecting bore 71 (see. 2 using the example of the traction body 4th ) can be screwed in. Alternatively, the connecting devices 7th also other means encompass to or the tensile body 4th or the clamping plates 3 in another way with the target facility 11 connect to. To move the clamping plates 3 in the direction of the preload force F. to allow can the clamping plates 3 movable on the machine table 15th be arranged.

The tensile body 4th is with the traverse 14th connected and each of the two clamping plates 3 is with the machine table 15th tied together. This allows the tensile body 4th by means of the traverse 14th along a pulling direction 100 and perpendicular to the preload force F. relative to the clamping plates 3 be moved.

Between each clamping plate 3 and the tensile body 4th is a pair of recesses 6th arranged. Each pair of recesses 6th can be a pair of specimens 2 to record. In detail is on the two opposite sides of the traction body 4th a first recess each 6a for receiving a first specimen 2a educated. To the tensile body 4th facing sides of the clamping plates 3 is a second recess 6b for receiving a second specimen 2 B educated.

The recesses 6a , 6b each pair of recesses 6th have different sized end faces, so that these test specimens of different sizes 2a , 2 B be able to record. Here are the first cutouts 6a smaller than the second recesses 6b . Thus, the first sample body accordingly has 2a a first friction surface 20a which is smaller than a second friction surface 20b of the second specimen 2 B is. A size ratio of the first friction surface 20a to the second friction surface 20b is thereby 2 .

The recesses 6a , 6b are as pockets in the train body 4th or in the clamping plates 3 formed, as for example on the tensile body 4th in the 2 shown. The pockets extend perpendicular to the direction of pull 100 and perpendicular to a direction of the biasing force F. . Thus the specimens are 2a , 2 B laterally in one direction of insertion 101 can be inserted or removed in the opposite direction.

Each of the specimens 2a , 2 B has a thickness which is greater than a depth of each recess 6a , 6b is so that each of the specimens 2a , 2 B on the mutually facing sides of the tensile body 4th and clamping plates 3 survives. Like in the 1 to recognize, thus touching tensile bodies 4th and clamping plates 3 not, but only both specimens 2a , 2 B a pair of specimens 2 when this is in the test tool 1 are inserted. When moving the traction body 4th along the direction of pull 100 , so when performing the tensile test, the specimens slide 2a , 2 B at their contact surface on each other.

In the in the 1 The state shown before the test was carried out are recesses 6a , 6b each pair of recesses 6th arranged offset to one another, so that each of the first specimens 2a on a lower side of the corresponding second specimen 2 B is arranged. When performing the test, i.e. when moving the tensile body 4th along the direction of pull 100 thus slide the first specimens 2a over as large a part of the second friction surface as possible 20b the second specimen 2 B so that the contact area between the two specimens 2a , 2 B by shifting the two specimens as far as possible 2a , 2 B has a constant surface area against each other.

Each of the two clamping plates 3 is designed in two parts. Any clamping plate 3 thus comprises a first plate part 3a and a second plate part 3b . Between the two plate parts 3a , 3b the left clamping plate 3 of the test tool 1 is a force measuring device 13th arranged. By means of the force measuring device 13th can be the preload F. are recorded.

The arrangement also includes 10 a detection device 12th , which is set up, a tensile force which is applied to the tensile body 4th is applied, and a friction path around which the tensile body 4th relative to the clamping plates 3 is moved to capture.

A coefficient of friction of the test specimens rubbing against one another can thus be determined on the basis of the tensile force and pretensioning force 2a , 2 B be determined. Using the coefficient of friction and the friction path, particularly detailed information can be obtained about the friction behavior of the specimens 2a , 2 B can be obtained.

3 Figure 10 shows a perspective view of a test tool 1 according to a second embodiment of the invention. The second exemplary embodiment corresponds essentially to the first exemplary embodiment from FIG 1 and 2 with the difference of an alternative clamping device 5 and alternative clamping plates 3 ', 3 ". In the second embodiment, the clamping device comprises 5 just a single screw 50 in order to offer a particularly simple construction and to enable simple pretensioning. For this purpose, the left clamping plate 3 ″ comprises an additional third plate part 3c , which is stationary on the machine table 15th is attached. The screw 50 is through the third plate part 3c screwed through and presses centrally against the second plate part 3b ″ of the left clamping plate 3 . The second plate part 3b 'of the right clamping plate 3 is stationary, i.e. immovable, on the machine table 15th attached. Thus, in the second exemplary embodiment, the preload can be carried out in a particularly simple manner by tightening the single screw 50 take place.

List of reference symbols

1

Test tool

2

Specimen pair

2a, 2b

Specimen

3rd

Clamping plates

3a

first plate part

3b

second plate part

3c

third plate part

4th

Tensile body

5

Jig

6th

Recess pair

6a, 6b

Recess

7th

Connecting device

10

arrangement

11

Drawbar

12th

Detection device

13th

Force measuring device

14th

traverse

15th

Machine table

20a, 20b

Friction surface

50

screw

51

Screw hole

71

Connecting hole

100

Direction of pull

101

Direction of insertion

F.

Preload

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102018125141 B3 [0002]

Claims (14)

Test tool for testing the friction behavior of specimens (2a, 2b), comprising: - two clamping plates (3), - A tension body (4) which is arranged between the clamping plates (3), and - a clamping device (5) which is set up to clamp the two clamping plates (3) against one another with a prestressing force (F), - wherein a pair of recesses (6) for receiving a pair of specimens (2) is formed between each of the two clamping plates (3) and the tensile body (4), and - Each of the tensioning plates (3) and the tension body (4) having a connecting device (7) for connection to a tensioning device (11) to the tension body (4) perpendicular to the pretensioning force (F) relative to the two tensioning plates (3) move. Test tool according to Claim 1 Each pair of recesses (6) has two recesses (6a, 6b) designed as pockets, and a first recess (6a) is formed in the tension body (4) and a second recess (6b) is formed in the clamping plate (3). Test tool according to one of the preceding claims, wherein an area ratio of mutually facing end faces of the recesses (6a, 6b) of each recess pair (6) is at least 2, preferably at least 5, particularly preferably a maximum of 10. Test tool according to one of the preceding claims, wherein the clamping device (5) comprises at least one screw (50) for clamping the two clamping plates (3). Arrangement comprising: - A test tool (1) according to one of the preceding claims, and - A pulling device (11) which is connected to each of the connecting devices (7). Arrangement according to Claim 5 , further comprising a detection device (12) which is set up to detect a tensile force and / or a friction path during the relative movement of the tensile body (4) and the clamping plates (3). Arrangement according to one of the Claims 5 or 6th , further comprising a force measuring device (13) which is set up to detect the pretensioning force (F). A method for testing the friction behavior of specimens (2a, 2b), comprising the steps: - Insertion of two pairs of specimen bodies (2) between a tensile body (4) and two clamping plates (3), the tensile body (4) being arranged between the clamping plates (3), between each of the two clamping plates (3) and the tensile body (4) a pair of recesses (6) is designed to receive a pair of specimens (2), and each pair of specimens (2) is inserted into one of the two pairs of recesses (6), - Applying a pretensioning force (F) to the specimens (2a, 2b) by bracing the clamping plates (3) against each other, and - Relative movement of the tension body (4) and clamping plates (3) perpendicular to the pre-tensioning force (F). Procedure according to Claim 8 , further comprising the step of: detecting a tensile force and / or a friction path during the relative movement of the tensile body (4) and the clamping plates (3). Method according to one of the Claims 8 or 9 , further comprising the step of: detecting the pretensioning force (F). Method according to one of the Claims 8 until 10 , the size ratio of mutually facing friction surfaces (20a, 20b) of the two specimens (2a, 2b) of each specimen pair (2) being at least 2, preferably at least 5, particularly preferably at most 10. Method according to one of the Claims 8 until 11 , further comprising the step: removing the sample bodies (2a, 2b) from a component. Procedure according to Claim 12 , the sample bodies (2a, 2b) being removed by means of wire EDM. Method according to one of the Claims 12 or 13th , wherein the component is a wheel and / or a wheel bearing flange and / or a brake disc of a vehicle.

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