Test device for characterising coatings

Abstract

The invention relates to a test device for characterising coatings, comprising a housing (12); a first and a second contact element (14, 16) each indirectly mounted on the housing (12); a sample holder (20); a first insulating element (28); a second insulating element (30); wherein the first contact element (14) and the second contact element (16) each have electrical connections (36) for connecting electrical power sources and for transmitting electrical energy through the sample body (18), wherein the first contact element (14) is mounted indirectly on the housing (12) and movably relative to the second contact element (16), wherein a pressure force for acting on the test body (18) can be set via the movably mounted first contact element (14), wherein the sample holder (20) can be coupled indirectly or directly to the housing (12), to a first drive means (24) and / or to a second drive means (26) depending on the measurement method to be carried out. A large number of contact-specific properties of coatings can be determined easily, quickly and economically by means of the test device (10).

Description

[0001] Test device for characterizing coatings

[0002] The following statements relate to a test device for characterizing coatings, in particular contact coatings of electrical conductor units, by means of which a simple, fast and cost-effective characterization of a coating can be realized.

[0003] To characterize coatings, especially contact coatings in connectors, five application-specific properties are typically determined using separate testing methods. These properties are electrical sheet resistance, mating cycle count, fretting corrosion resistance, thermal load capacity, and current carrying capacity. Testing these contact-specific properties is relatively complex, requires considerable measuring equipment, and often must be performed in separate locations.

[0004] There is a constant need to simplify the testing of contact-specific properties of coatings while reducing the costs of testing.

[0005] Based on this situation, the present task is to identify measures that enable a cost-effective and easy-to-use test device for the characterization of coatings.

[0006] The present problem is solved by the features of the independent main claim. Advantageous embodiments are specified in the subclaims. To the extent technically feasible, the teachings of the subclaims can be combined arbitrarily with the teachings of the main and subclaims.

[0007] The object is accordingly achieved by a testing device for characterising coatings, in particular contact coatings of electrical conductor units, comprising a housing for accommodating components for carrying out a multiplicity of measuring methods for characterising coatings; a first and second contact element, each mounted indirectly on the housing, for contacting a sample body; a sample holder for receiving and positioning the sample body between the first contact element and the second contact element; a first insulating element for electrically and / or thermally insulating the first contact element; a second insulating element for electrically and / or thermally insulating the second contact element.wherein the first contact element and the second contact element each have electrical connections for connecting electrical power sources and for transmitting electrical energy through the sample body, wherein the first contact element is mounted indirectly and movably relative to the second contact element on the housing, wherein a compressive force for acting on the sample body can be adjusted via the movably mounted first contact element, wherein the sample holder can be coupled indirectly or directly to the housing, a first drive means and / or a second drive means depending on the measuring method to be carried out;

[0008] A variety of components can be arranged inside or outside the housing of the testing device and attached directly or indirectly to the housing. The first and second contact elements serve as clamping devices for the sample body to be tested. The sample body can be arranged between the contact elements and subjected to an adjustable compressive force by the contact elements. By applying pressure to the sample body, a load on the coating in, for example, a plug-in connector can be simulated. To avoid electrical and / or thermal influences, the contact elements are indirectly connected to the housing via insulating elements or are mounted on the housing. The sample body can be exposed to or subjected to an electrical current through the electrical connections.The resistance and heat development measured as a result of the current flow can provide information about the properties of the coating under test. The sample holder is designed in such a way that it can be coupled to the housing, the first drive means, and / or the second drive means. This allows a wide range of tests to be performed on the test device with minimal modification effort. The test device can thus easily, quickly, and cost-effectively determine a wide range of contact-specific properties of coatings.

[0009] Advantageous aspects are explained below, and preferred modified embodiments are described further below. Explanations, particularly regarding advantages and definitions of features, are essentially descriptive and preferred, but not limiting, examples. If an explanation is limiting, this will be expressly stated.

[0010] The sample holder can be made of an electrically and / or thermally non-conductive material. The sample holder can therefore be designed as an electrical and / or thermal insulator. This allows electrical and / or thermal influencing factors that could distort the measurements to be reduced or prevented. The sample holder can be coupled to the housing, the first drive means, and / or the second drive means via a cylinder rod or the like. The sample holder has, in particular, a coupling element for coupling to a piston rod of a first and / or a second drive means (26) acting in the longitudinal direction. This allows the testing device to be quickly and easily converted, and further measuring methods to be carried out with the testing device.

[0011] The first and second contact elements are arranged interchangeably within the test device. The contact elements, in particular, have the same coating as the test specimen and / or are made of the same base material as the test specimen. This common composition allows for improved measurement results and the simulation of the coating's behavior under real-world conditions.

[0012] The compressive force is applied to the test specimen at intervals. The compressive force is in particular in the range from 0.2 N to 4 N. The force applied by means of the compressive force can preferably be increased by 0.2 N per interval. Amount increases of 0.5 N or 1 N or a combination thereof are also conceivable. In a preferred embodiment of the above, in order to characterize the electrical sheet resistance of the coating, the test device has a 4-wire circuit at the electrical connections of the first contact element and the second contact element for measuring the electrical resistance of the test specimen. The electrical resistance can be measured using the 4-wire circuit. Measuring the sheet resistance directly is practically impossible and also not advisable, since the coating cannot be contacted alone.It is more practical to simulate an electrical contact using the test fixture and measure its total resistance. Using the resistance value of a reference sample, a meaningful comparison can then be made.

[0013] The first contact element can be used to simulate the compressive force typically encountered in electrical contacts. This compressive force acts on the specimen clamped between the contact elements, which is connected to two circuits via the contact elements' electrical connections. The constant current source used in the first circuit can provide a current of IF = 10 mA, with a maximum applied voltage of 20 mV (DC). A voltmeter measures the voltage drop U m on the entire simulated contact R xThe test leads used can be attached to the electrical terminals using cable lugs. Furthermore, a measurement recording must be carried out, which records the voltage UM and the test current IF over time and uses this to calculate the resistance R. x In particular, it is provided that the test device has a receiving unit for receiving and reproducing the measured values ​​of the electrical resistance.

[0014] In a preferred embodiment of the above, in order to characterize the number of mating cycles of the coating, the sample holder is mounted displaceably by means of a first drive means, essentially orthogonal to the effective direction of the compressive force of the first contact element. In practice, different contact layers must be able to withstand a certain number of assembly and disassembly processes without being rubbed through. To determine the number of mating cycles, a first drive means can be arranged, in particular, on the housing. The piston rod of the first drive means can be connected to the test specimen via the sample holder. Preferably, the first drive means is designed as a pneumatic actuator, in particular as a short-stroke pneumatic cylinder. The pneumatic actuator can be connected to a compressed air control unit, by means of which a stroke and the retraction and extension times can be adjusted.The stroke can be, for example, 5 mm. The retraction and extension times can be set to a constant 0.5 seconds, with a waiting interval of at least 2 seconds between extension and retraction. Furthermore, a waiting period of at least 3 seconds must be observed after each cycle before a new cycle starts. Furthermore, a suitable pressure force must be used, which can be, in particular, 2 N. The number of cycles completed without any abrasion being detected indicates the number of mating cycles.

[0015] In a preferred embodiment of the above, in order to characterize the resistance of the coatings to fretting corrosion, the sample holder is mounted displaceably by means of a second drive means, essentially orthogonal to the direction of action of the compressive force of the first contact element. To simulate fretting corrosion in the test device, short and rapid movements of the sample body are required. For this reason, it is preferably provided that the second drive means is designed as a piezo actuator, in particular as a piezo stack. It is preferably provided that the second drive means is arranged on the housing.

[0016] The piezo stack is capable of deforming when subjected to voltage excitation. Depending on the stack length, various length changes can occur. Length changes generally range from several micrometers, with a response time in the microsecond range. With suitable control, it is possible to enlarge and shrink the piezo stack over a wide range of frequencies. In particular, the second drive means is provided with a reset mechanism. By combining a piezo stack with a reset mechanism, which is particularly designed as a tension or compression spring, uniaxial vibrations or micro-movements can be performed.

[0017] For example, the control system should be set to ensure a movement frequency ("extension and retraction") of 1 Hz, a friction displacement of 50 pm, and a cycle count of 100,000. A constant compressive force of 2 N should act on the specimen, apart from the frictional stress.

[0018] Subsequently, the contact resistance of the friction partners can be determined using a 4-wire circuit as described above. A second sensor unit can detect a change in the path of the first contact element during the measurement process. This allows conclusions to be drawn about the coating wear. The resistance of the coatings to fretting corrosion can be determined based on the temporal change in contact resistance and layer wear. Advantageously, all measurement procedures can be performed on the test fixture.

[0019] In a preferred embodiment of the above, in order to characterize the thermal resilience and current-carrying capacity of the coating, the testing device has a current source connected to the electrical connections of the first contact element and the second contact element for transmitting an electrical current through the sample body and at least one first sensor unit for measuring the temperature at at least one contact element and / or at the coating of the sample body. In particular, it is provided that the testing device has an evaluation unit for receiving and displaying the measured values ​​of the at least one first sensor unit. It is preferably provided that the at least one first sensor unit is designed as a thermocouple. In particular, it is provided that the at least one first sensor unit can be arranged indirectly on the housing.

[0020] The current-carrying capacity of an electrical contact determines the maximum permissible current that can be conducted through it. This current is limited, among other things, by the thermal load capacity, since real contacts heat up due to the power loss at their contact resistance when current passes through. Since the current-conducting surface in the contact zone of an electrical contact is usually significantly reduced, high temperatures can sometimes result. These influences are also reflected in the behavior of the different coatings.

[0021] To test its thermal resilience and current-carrying capacity, the test specimen can be positioned between the two contact elements and subjected to compressive force. At least one first sensor unit is positioned on the specimen and / or the contact elements for temperature measurement, with the at least one first sensor unit being attached to the housing, in particular by means of a magnetic holder. Furthermore, a current source, in particular a constant current source, and an ammeter are connected to the electrical terminals. By switching on the current source with an initial current of 1 A, the coating of the specimen heats up. The thermal equilibrium of the at least one first sensor unit must then be waited for until a temperature is established and recorded by the evaluation unit. The sequence plan must be repeated with increasing current strengths, with the current being incremented by 1 A after each cycle.The test is completed when the temperature reaches 200 °C.

[0022] In a preferred embodiment of the above, the first insulating element is designed as a cylinder and extends through at least one recess in the housing. Preferably, the compressive force of the first contact element via the first insulating element can be adjusted by means of a screw press or a weight. In particular, the testing device comprises a first spring element mounted on the housing and the first insulating element for generating a first spring force, wherein the first spring force acts on the first insulating element in a direction opposite to the compressive force. Preferably, the first insulating element is made of plastic.

[0023] In a preferred embodiment of the above, the second insulating element is designed as a cylinder with an external thread and extends through a recess with an internal thread on the housing. In particular, the distance between the second contact element and the first contact element and / or the sample body can be adjusted via the thread. Preferably, the second insulating element can be locked by means of a fastening device, in particular a screw nut. In particular, the first insulating element is made of plastic.

[0024] In a preferred embodiment of the above, the first contact element is mounted indirectly on the housing via a lever arrangement, wherein the lever arrangement is rotatably mounted on a joint, in particular a cross-spring joint. Preferably, a spring unit for returning the lever arrangement to an initial position is arranged on a lever arm or in the joint. In particular, the compressive force on the first contact element can be adjusted by the lever arrangement using a screw press or a weight.

[0025] In a preferred embodiment of the above, a force-measuring device, in particular a load cell, for measuring the compressive force is arranged on the second insulating element of the second contact element. Preferably, the force-measuring device is arranged between the housing and the second insulating element. The force-measuring device allows the compressive force introduced via the first contact element to be precisely determined and adjusted. This allows the coating of the sample body to be subjected to a predetermined compressive force in the contact area.

[0026] In a preferred embodiment of the above, it is provided that a second sensor unit for indirectly or directly measuring the movement of the first contact element is arranged on the housing. In particular, it is provided that the second sensor unit is designed as a distance sensor, preferably as an induction sensor. The stroke of the first contact element can be monitored by the second sensor unit. The change in the stroke is a direct indicator of the surface abrasion of the coatings of the sample body as a result of the characterization by the testing device. A preferred technical solution is explained in more detail below with reference to the attached drawings using preferred exemplary embodiments. The wording "figure" is abbreviated to "Fig." in the drawings.

[0027] In the drawings

[0028] Fig. 1 is a perspective view of a first embodiment of a testing device,

[0029] Fig. 2 is a schematic side view of a second embodiment of a testing device,

[0030] Fig. 3 is a schematic front view of the test device according to Fig. 2, Fig. 4 is an electrical circuit diagram of a 4-wire circuit.

[0031] The described embodiment is merely an example which can be modified and / or supplemented in many ways within the scope of the claims.

[0032] Fig. 1 shows a perspective view of a first embodiment of a testing device 10 for characterizing coatings, comprising a housing 12 for accommodating components for carrying out a plurality of measuring methods, a first contact element 14 mounted indirectly on the housing and a second contact element 16 for contacting a sample body 18, wherein the sample body 18 can be positioned between the first contact element 14 and the second contact element 16 by means of a sample holder 20. The sample holder 20 is displaceably mounted on the housing 12 via a piston rod 22 of a drive means 24, 26. The drive means 24, 26 can in particular be designed as a first drive means 24 or a second drive means 26. To avoid electrical and / or thermal influences, the contact elements 14, 16 are indirectly connected to the housing 12 via insulating elements 28, 30 or are mounted on the housing 12.The first contact element 14 is mounted displaceably in the axial direction via the cylindrical first insulating element 28 and can be subjected to a compressive force FD in the direction of the second contact element 16. The testing device 10 further comprises a first spring element 32 mounted on the housing 12 and the first insulating element 28 for generating a first spring force, wherein the first spring force acts on the first insulating element 28 in a direction opposite to the compressive force FD into an initial position of the first insulating element 28. The second insulating element 30 is designed as a cylinder with an external thread and extends through a recess with an internal thread on the housing 12. As a result, the distance of the second contact element 16 from the first contact element 14 and / or from the test body 18 can be adjusted via the thread, wherein the second insulating element 30 can be locked by means of a fastening device 34, in particular a screw nut.The contact elements 14, 16 have electrical connections 36 for connecting electrical power sources and for transmitting electrical energy through the sample body 18. A second sensor unit 38 is arranged on the first insulating element for directly or indirectly measuring the movement of the first contact element 14 on the housing 12. The second sensor unit 38 can monitor the stroke of the first contact element 14.

[0033] Fig. 2 and Fig. 3 show schematic side views of a second embodiment of the testing device 10. This embodiment differs from the embodiment of Fig. 1 in that the first contact element 14 is movable by a lever arrangement 40, can be pivoted about the joint 42, is mounted, and can be subjected to the compressive force FD. In addition, the testing device 10 has a force measuring device 44, which is arranged between the housing 12 and the second contact element 16 for measuring the compressive force FD. The first drive means 24 and the second drive means 26 are arranged on two opposite housing walls on the housing 12. As a result, the sample holder 20 can be coupled to the first drive means 24 or the second drive means 26 without much retooling.

[0034] Fig. 4 shows an electrical circuit diagram of a 4-wire circuit connected to the electrical terminals 36 of the contact elements 14, 16 and designed to determine the electrical resistance of the sample body 18. List of reference symbols

[0035] 10 Test device

[0036] 12 housings

[0037] 14 first contact element

[0038] 16 second contact element

[0039] 18 Sample body 0 Sample holder 2 Piston rod 4 First drive means 6 Second drive means 8 First insulating element

[0040] 30 second insulating element

[0041] 32 first spring element

[0042] 34 Fastening device

[0043] 36 electrical connections

[0044] 38 second sensor unit

[0045] 40 Lever arrangement

[0046] 42 joint

[0047] 44 Force measuring device

[0048] FD compressive force

Claims

Claims 1. A test device for characterizing coatings, in particular contact coatings of electrical conductor units, comprising a housing (12) for accommodating components for carrying out a plurality of measuring methods for characterizing coatings; a first and second contact element (14, 16), each mounted indirectly on the housing (12), for contacting a sample body (18); a sample holder (20) for receiving and positioning the sample body (18) between the first contact element (14) and the second contact element (16); a first insulating element (28) for electrically and / or thermally insulating the first contact element (14); a second insulating element (30) for electrically and / or thermally insulating the second contact element (16);wherein the first contact element (14) and the second contact element (16) each have electrical connections (36) for connecting electrical power sources and for transmitting electrical energy through the sample body (18), wherein the first contact element (14) is mounted indirectly on the housing (12) so as to be movable relative to the second contact element (16), wherein a compressive force for acting on the sample body (18) can be adjusted via the movably mounted first contact element (14), wherein the sample holder (20) can be coupled directly or indirectly to the housing (12), a first drive means (24) and / or a second drive means (26) depending on the measuring method to be carried out; 2. Testing device according to claim 1, wherein for characterizing the electrical layer resistance of the coating, the testing device (10) has a 4-wire circuit for measuring the electrical resistance of the sample body (18) at the electrical connections (36) of the first contact element (14) and the second contact element (16), wherein in particular the testing device (10) has a receiving unit for receiving and reproducing the measured values ​​of the electrical resistance.

3. Testing device according to claim 1 or 2, wherein for characterizing the number of mating cycles of the coating, the sample holder (20) is mounted displaceably substantially orthogonally to the effective direction of the pressure force of the first contact element (14) by means of a first drive means (24), wherein in particular the first drive means (24) is designed as a short-stroke pneumatic cylinder, wherein in particular the first drive means (24) is arranged on the housing (12).

4. Testing device according to one of the preceding claims, wherein, in order to characterise the resistance of the coatings to fretting corrosion, the sample holder (20) is mounted displaceably substantially orthogonally to the direction of action of the compressive force of the first contact element (14) by means of a second drive means (26), wherein in particular the second drive means (26) is designed as a piezo actuator, in particular as a piezo stack, wherein in particular the second drive means (26) has a return mechanism, wherein in particular the second drive means (26) is arranged on the housing (12).

5. Testing device according to one of the preceding claims, wherein, for characterizing the thermal load capacity and the current-carrying capacity of the coating, the testing device (10) has a current source connected to the electrical connections (36) of the first contact element (14) and the second contact element (16) for transmitting an electrical current through the sample body (18) and at least one first sensor unit for measuring the temperature at at least one contact element (14, 16) and / or at the coating of the sample body (18), wherein in particular the testing device (10) has an evaluation unit for receiving and reproducing the measured values ​​of the at least one first sensor unit, wherein in particular the at least one first sensor unit is designed as a thermocouple, wherein in particular the at least one first sensor unit can be arranged indirectly on the housing (12).

6. Testing device according to one of the preceding claims, wherein the first insulating element (28) is designed as a cylinder and extends through at least one recess in the housing (12), wherein in particular the compressive force of the first contact element (14) via the first insulating element (28) can be adjusted by means of a screw press or a weight, wherein in particular the testing device (10) has a first spring element (32) mounted on the housing (12) and the first insulating element (28) for generating a first spring force, wherein the first spring force acts on the first insulating element (28) in a direction opposite to the compressive force, wherein in particular the first insulating element (28) is made of plastic.

7. Test device according to one of the preceding claims, wherein the second insulating element (30) is designed as a cylinder with an external thread and extends through a recess with an internal thread on the housing (12), wherein in particular the distance of the second contact element (16) to the first contact element (14) and / or to the sample body (18) can be adjusted via the thread, wherein in particular the second insulating element (30) can be locked by means of a fastening device (34), in particular a screw nut, wherein in particular the first insulating element (28) is designed from plastic.

8. Testing device according to one of claims 1 to 5, wherein the first contact element (14) is mounted indirectly on the housing (12) via a lever arrangement (40), wherein the lever arrangement (40) is rotatably arranged on a joint (42), in particular a cross spring joint, wherein in particular a spring unit for returning the lever arrangement (40) to an initial position is arranged on a lever arm or in the joint (42), wherein in particular the pressure force on the first contact element (14) can be adjusted by the lever arrangement (40) by means of a screw press or a weight.

9. Test device according to one of the preceding claims, wherein a force measuring device (44), in particular a load cell, for measuring the compressive force is arranged on the second insulating element (30) of the second contact element (16), wherein in particular the force measuring device (44) is arranged between the housing (12) and the second insulating element (30).

10. Testing device according to one of the preceding claims, wherein a second sensor unit (38) for indirectly or directly measuring the movement of the first contact element (14) is arranged on the housing (12), wherein in particular the second sensor unit (38) is designed as a distance sensor, preferably as an induction sensor.

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