WO2003060487A1

WO2003060487A1 - Tribometer

Info

Publication number: WO2003060487A1
Application number: PCT/EP2003/000500
Authority: WO
Inventors: Dirk Spaltmann; Helmut Börner; Falko Frindt; Olaf Mollenhauer
Original assignee: Bundesanstalt für Materialforschung und -Prüfung (BAM)
Priority date: 2002-01-18
Filing date: 2003-01-20
Publication date: 2003-07-24
Also published as: DE10390125D2; DE10203070A1; DE10390125B4

Abstract

The invention relates to a tribometer for determining the material properties of at least one of two counter-displaced samples (470). The above are fixed on mountings in a tightly sealed vessel which may be evacuated to give a ultra-high vacuum, the one on a table (90) and the other on a load arm (370). A manipulator (510) is provided in the vessel for releasing and removing the samples from the mounting thereof and for introduction of the samples into the corresponding mounting. The vessel is preferably sealed with a sealing flange (10), through which connector elements pass with a tight seal, each running between an external drive on one side and the table, load arm or manipulator on the other side.

Description

tribometers

The invention relates to a tribometer according to the preamble of claim 1.

Devices for the friction and wear test, so-called tribometers, are known in various shapes and sizes. In most cases, a rod or pin is pressed against a rotating ^■ disc and sizes such as normal force and friction force are measured and a wear quantity is registered. Some special tribometers such as the high-temperature tribo eter by Woydt and Gienau et al. (Proc. 3 ^rd European Workshop on Thermal Protection Systems, ESA publications division, WPP-141, pages 457-467) can also be heated up to temperatures of 1600 ° C. There are also tribometers in climatic chambers in which the air humidity can be adjusted. In these cases, the tribometers are not capable of ultra-high vacuum. Furthermore, they are based on a limited load range.

US Pat. No. 6,094,967 describes a tribometer which has a device for generating sliding friction between two samples and at the same time gives the possibility of carrying out examinations during the rubbing process using a light microscope. However, only one of the two samples is designed to be heatable. Cooling is not provided. This known tribometer is also not intended for use in the ultra-high vacuum range.

In Wear, 6 (1963), 353-365 a tribometer is disclosed, which has a glass recipient and is capable of an ultra high vacuum (UHV) of 7 ^~ ^■ 10 to produce ^u mbar. This tribometer is permanently melted into the glass recipient and cannot be replaced. Additional examination methods cannot be carried out. The recipient must be aerated to change the samples.

Another UHV tribometer is shown in Proceedings Eurotrib'93. Here the tribometer sits in a steel UHV apparatus and the samples can be examined by further experimental methods. However, it is not evident that the samples can be changed without opening the apparatus. The tribometer is also divided into different flanges.

In Rev. Sei. Instrum. 58 (4), April 1987, 593-597, a tribometer is described for which a vacuum of less than 1.5 x 10 ^"8 Torr can be established. A mounting flange closes an airtight container that holds the tribometer. A pen and , a disk-shaped sample is located inside the barrel and are movably supported. A drive device arranged outside the vessel and a connecting element guided through the flange bring about a mutual displacement of the pin and the disk in three mutually perpendicular directions.

Proceeding from this known tribometer, it is the object of the present invention to provide a tribometer for determining the material properties of at least one of two specimens that can be moved against one another, in a tightly closable container that can be evacuated to an ultra-high vacuum, on the one hand on a table and on the other hand on a load arm in holders are releasably attached to create a sample exchange without breaking a vacuum created in the vessel.

This object is achieved by a tribometer with the features of claim 1. Advantageous further developments of the tribometer according to the invention result from the subclaims.

To determine the friction and wear behavior, it should be possible to rub samples in the form of balls and planes against each other. This sample configuration has several advantages due to the initially well-defined contact conditions. However, the samples are not necessarily bound to this form. The friction of the samples against one another should take place in the context of a reversing sliding movement with a frequency of approximately one Hertz. The amplitude of this sliding movement should be up to 5 mm. It should also be possible to provide different speed profiles (eg constant speed, sinusoidal speed profiles, sawtooth profiles, etc.). There should be several rub marks at a distance of about 0.2 mm can be set, so that there is a frictional area of about 5 mm x 5 mm. The surface created in this way can then be examined for chemical changes using surface examination methods such as Auger electron spectroscopy (AES). The samples should also be able to be heated and cooled separately in order to be able to study the influence of temperature on their own or in combination with other environmental influences.

It should also be possible to carry out friction tests in an ultra-high vacuum. This is intended to exclude the influence of oxide and water layers and to enable investigations on pure materials. By defined insertion of e.g. Oxygen can then be used to investigate the influence on the friction behavior of the corresponding materials.

To generate an ultra-high vacuum with pressures less than 10 ^{~ 9} mbar, preferably less than 2-10 ^" ¹⁰ mbar, the entire system has to be heated at temperatures of around 200 ° C. So that the tribometer can be used on various UHV systems depending on the requirements of the experiments to be carried out. Vessels can be attached, it is advantageously to be attached to a flange, including the sample transfer mechanism, signal lines, supply lines for heating and cooling, and the corresponding rubbing movement together with the associated bushings in the UHV.

The force measuring devices for normal and frictional forces are to be designed in such a way that the force measuring range can be set. The forces should be measured by direct conversion, for example via piezo elements or, as in the embodiment described below, via the deflections of Deformation bodies. By changing these deformation bodies, it should be possible to adapt the force measuring range to the respective requirements of the experiment and / or the samples. The deformation bodies should preferably be able to be changed in the UHV.

Should be able to be carried out with the tribometer adhesion measurements also by changing the deformation body and / or ^'suitable by the use of sample carriers.

Only stainless steel or comparable materials are permitted for the execution of the UHV tribometer, which enable heating at approx. 200 ° C. Enclosed volumes must be avoided by taking appropriate measures (e.g. ventilation holes).

The UHV tribometer consists of four main components. The first is the flange (so-called base flange) on which the entire tribometer is built. The second main component is the drive mechanism for the reversing movement, and the third component consists of the sample holders. The sensor or load arm is the last main component. It transfers the load applied in the form of a static weight or by means of an electromagnetic device to the sample. At the same time, it returns the signals for normal and frictional force optically.

The invention is explained in more detail below on the basis of exemplary embodiments illustrated in the figures. Show it:

1 is a UHV tribometer in perspective view looks without sample assembly, load arm and manipulator according to a first embodiment of the invention,

2 is a drive device for the table in the tribometer of FIG. 1,

3 shows the device for mounting the load arm in the tribometer according to FIG. 1,

Fig. 4 is a perspective view and a

Sectional view of the load arm in the tribometer of FIG. 1,

5a, the sample holder on the table and at the end of the load arm in the tribometer of FIG. 1,

5b the sample carrier at the end of the load arm in the tribometer of FIG. 1,

6 the UHV tribometer according to FIG. 1 with sample assembly, load arm and manipulator viewed from two opposite directions,

Fig. 7 shows another embodiment of the end of the

Load arm and the associated sample carrier,

8 is yet another embodiment of the end of the load arm and the two sample carriers,

9 shows a further embodiment of the load arm end and the sample carrier, which is designed for an adhesion measurement,

Fig. 10 and 11 each show yet another embodiment of a sample carrier for the adhesion measurement in a perspective view and in a side view, and

Fig. 12 is a UHV tribometer in perspective view according to a second embodiment of the invention.

For reasons of clarity, the UHV tribometer is shown in FIG. 1 without sample construction, load arm and manipulator. It is built on a modified NW150CF base flange 10. The flange l schließt hermetically closes an opening in a vessel, not shown, which encloses a sample table 90. The flange 10 has a directly applied CF38 feed-through flange 20 for the manipulator for the sample change. At least one further, in the embodiment according to FIG. 1, two further CF-38 bushing flanges 30 and 40 attached to pipes are provided with bushings for, for example, signal lines, heating lines and thermocouple lines or with a viewing window. To cool the samples, the UHV tribometer has a reservoir (not shown) for liquid nitrogen inside the vessel. It is detachably suspended from the inflow and / or the outflow by means of suitable connecting elements. These leads sitting on two CF19- ^• Durchführungsflanschen 50 and 60. Instead of liquid nitrogen may also be provided liquid helium for cooling. The connection between the samples and the reservoir can be made via a copper wire, which can be brought into contact with the samples by means of the manipulator.

In the embodiment according to FIG. 1, three further CF19 Feed-through flanges 70 applied directly to the flange 10. The uppermost of these feedthrough flanges 70 serves to feed through the load arm, which is not shown in FIG. 1. The two lower feedthrough flanges 70 are covered by the feedthrough flange 30 and other structures of the tribometer. These flanges are used to pass one table arm 80 to the sample table 90.

A plate 110 lying in the plane of the flange 10 is welded directly to it. It is used to fasten a base plate 120 and guide shafts 180 of a drive mechanism. This drive mechanism has two functions. It first ensures a relative movement of a sample stored on the sample table 90 with respect to a sample stored on the load arm. This movement takes place in the longitudinal direction of the load arm and can be reversing or take any shape controlled by a computer program. The second function of the drive mechanism is the height adjustment of the moving sample. For this purpose, the sample table 90 is connected to a table guide device via the table arms 80. This consists of a dovetail guide 130 and an assembly rider 140. The dovetail guide 130 allows the height of the sample table 90 to be adjusted and has adjustment options to minimize play. The possibility of providing further dovetail guides perpendicular to the height adjustment is not shown. Flanges 150 welded to the table arms 80 provide a UHV-tight seal against the flange 10 by means of two membrane bellows 160. The membrane bellows 160 are dimensioned such that they allow a height adjustment of +3 mm with a simultaneous linear displacement of ± 30 mm. The assembly rider 140 with screwed-on dovetail guide 130 sits on two guide tubes 170. In each of these guide tubes 170 there are two guide bushings one behind the other. This arrangement was chosen to intercept the moment exerted on the ball guides by the sample table 90 via the table arms 80. A total of four ball cages run on the guide shafts 180. The dimensions of the ball cages are chosen so that all balls remain in engagement. Furthermore, each ball of the ball cage runs on its own track. These measures ensure a smooth and smooth run. The guide shafts 180 are fixed on the one hand in the plate 110 and on the other hand in a guide shaft block 190 screwed onto the base plate 120. The assembly rider 140, including the parts fastened to it, can thus move freely along the guide shafts 180.

The drive unit for the assembly rider 140 can be seen in FIG. 2. The heart of this drive unit is a direct current geared motor 200 with an incremental position sensor. The geared motor 200 is connected on the transmission side to a motor shield 210, which can be made from plain bearing polymer materials such as PTFE to reduce noise. The motor 200 and the motor shield 210 are attached to a motor carriage 220, which enables the starting point of the movement to be adjusted in the direction of the guide shafts 180. An eccentric 230 sits on the shaft of the geared motor 200 and is connected to the assembly rider 140 by means of a sliding block 240 and a drive shaft block 250. The rotation of the motor shaft is thus converted into a reversing linear movement of the assembly tab 140 and thus of the sample table 90. The length of the linear displacement can be set depending on the eccentricity. The tension Supply to the geared motor 200 can be programmed via electronics by a computer in such a way that any movement sequences (for example constant speed, uniformly accelerated speed, etc.) of the sample table 90 are made possible. Depending on the area of application, the drive unit can also be arranged in a suitable manner on the UHV side. Linear motors and / or piezoelectric drives can also be used.

In Fig. 3, the flange 10 and the components for the storage of the load arm and the application of the load (frictional force) are shown. For the sake of clarity, the components producing the linear movement have been omitted. A diaphragm bellows is mounted on the NW19CF bushing flange 70. The load arm is guided through this and closes the diaphragm bellows with its welded NW19CF flange UHV-tight. Both the diaphragm bellows and the NW19CF flange of the load arm are located within the cylindrical receptacle of the load arm bearing 260 and are firmly screwed to it. Two shafts are welded to the cylindrical receptacle of the load arm bearing 260 and are mounted in ball bearings 270 and 280. The lower ball bearing 270 is located in the base plate 120 and the upper ball bearing 280 is accommodated in an axle holder 290. A support fork 300 ensures a defined distance between the two ball bearings. These can be braced against one another by a suitable mechanism in order to remove any play from the structure. 1, the outer ring of the lower ball bearing 270 is fixed in the base plate 120 by means of a ring 310 with an external thread. By turning a clamping piece 320 with thread, the load arm bearing 260 can be Tension circlip 330 for ball-bearing ball bearing 280.

This type of mounting of the load arm enables it to be rotated by about 10 ° about a vertical transverse axis in the manner indicated by the arrow in FIG. 3. A sample change can be made in the deflected position. The bearing of the load arm is dimensioned such that when the load arm is not deflected, the sample carried by the sample table 90 and the sample carried by the load arm just touch. In this position, the load in the form of a static weight 360 is applied via a load lever 340 and a deflection roller 350. Instead of a static weight, an electromagnetic device can be used to generate the load.

The load arm is shown in Fig. 4. It essentially consists of a support tube 370, an NW19CF end flange 380 and a deformation body to which a sample holder is attached. A glass fiber rod 390 is guided centrally through the support tube 370. This fiber optic rod 390 can be a single fiber, a bundle of fibers, or a plurality of fiber bundles. The glass fiber rod 390 ends flush with the enveloping support tube 370 at both ends. The end faces of the glass fiber rod 390 are polished. At its ends, the glass fiber rod 390 is UHV-compatible via a casting compound 400 with the support tube 370. It is expedient that the entire space 410 between the glass fiber rod 390 and the support tube 370 is filled with potting compound. The end flange 380 is welded on in a UHV-tight manner on one side of the support tube 370. This part of the load arm will passed through the membrane bellows located on the feed-through flange 70 and closes this UHV-tight. This part of the load arm is located within the load arm bearing 260.

The deformation body, which essentially consists of leaf springs 420, a clamping body 430 and a spring holder 440, is fastened to the UHV-side end of the support tube 370. The spring holder 440 is connected to the clamping body 430 via two leaf springs 420 arranged in parallel. The clamping body 430 contains a cylindrical bore so that it can be pushed over the end of the support tube 370. Two clamping screws 450 press the support tube 370 against the opposite side of the clamping body 430, into which two longitudinally extending edges 460 are milled. The support tube 370 thus rests on the two edges 460 and is held by the opposing clamping screws 450. This results in a practically rigid but detachable three-point bearing. This arrangement also allows the sample 470 to be aligned in the axial direction (z direction) and by the angle of rotation φ.

The two parallel leaf springs 420 enable the spring holder 440 to be displaced with respect to the clamping body 430 in the y direction. The normal force (F _N ) with which the sample 470 is pressed against the other sample can thus be determined. For this purpose, the deflection must be measured with a known spring constant of the leaf springs 420. This can be done optically in a known manner. For this purpose, the light of a light-emitting diode (not shown) is passed onto a normal force reflector 480 by means of the glass fiber rod 390. Depending on the deflection of the leaf springs 420, the normal force reflector 480 is opposite more or less shifted the light spot of the LED at the end of the glass rod 390 and accordingly more or less light is returned to a light detector. By means of a suitable calibration, the intensity of the detected light is a direct and sensitive measure of the bending of the leaf springs 420 and, if the spring constant is known, of the normal force (F _N ).

A spiral leaf spring 490 is located at the front and at the rear end of the spring holder 400. These are connected to one another via a stabilizing sleeve 500. This arrangement thus only allows a shift in the longitudinal direction (z direction). The entire sample holder is attached to the stabilizing sleeve 500 in a suitable manner. If the sample stored on the sample table 90 (not shown in FIG. 4) is displaced with respect to the sample 470 attached to the load arm upon pressure contact, this leads to a deflection of the spiral leaf springs 490. If the spring constant is known, the frictional force F _R can be measured , The deflection of the spiral leaf springs 490 is measured optically analogously to that of the leaf springs 420. For this purpose, the light of another LED is directed through the glass fiber rod 390 onto a friction force reflector 520. This is attached to the stabilization sleeve 500. The further the spiral leaf springs 490 are deflected, the further the friction force reflector 520 is removed from the end of the glass fiber rod 390 with the diverging light emitted by the second LED, and the less light is reflected. With a suitable calibration, the intensity of the reflected light from the second LED is thus a direct and sensitive measure of the frictional force. Outside the ultra-high vacuum, this calibration can be done, for example, by applying weights respectively. The measuring ranges of the normal and frictional forces depend on the spring constants of the leaf springs 420 and the spiral leaf springs 490. To change the force measuring ranges, the corresponding springs must therefore be replaced. This change can also be made in an ultra-high vacuum with the aid of the manipulator. Instead of an optical force measurement, the forces can also be measured at the location of the sample via pressure-sensitive layers. Such layers change their physical properties (eg their electrical resistance) under the influence of an external force.

The friction samples to be examined are fetched from their ready positions with the aid of the manipulator in the form of a so-called wobble stick 510 and placed in their friction positions. The receptacles for the samples must have a sufficiently large clearance, since after heating in the ultra-high vacuum, tilting of the samples in their receptacles can easily lead to jamming. In most cases, this can only be remedied by opening the vessel. From a tribological point of view, however, a minimal or if possible no play of the samples in their holders is desirable. Under tribological stress, the samples should move against each other and not their holders. The arrangement shown in FIGS. 5a and 5b is used to meet both the vacuum-technical requirement for a game and the tribological requirement for freedom from play. The front sample in FIG. 5 a is rigidly connected to the sample table 90. It is set in reversing linear motion by the drive unit shown in FIG. 2. The same sample holder is attached to the load arm. Both brackets are designed so that they are each equipped with a heater and a temperature sensor and can be connected to a cold reservoir. Depending on the design of the triboter and the type and shape of the sample, resistance heaters, direct heaters or electron pulse heaters should be considered.

5b shows a sample carrier 530 in the clamped state. At least one lever 540 of the clamping device is designed V-shaped on one side of the sample holder 530. A frame 550 and the sample carrier 530 are located between the legs of the V-shaped arrangement. Due to the inclined position of the legs of the lever 540, the sample carrier 530 and the frame 550 are pressed together, the force required for this is applied by a suitable spring 560. At least one of the two levers 540 is provided with an extension 570 which can be actuated by the manipulator, so that the associated spring 560 is relaxed and the sample carrier 530 is released. This can then be removed from its holder by the manipulator.

6 shows the tribometer with the sample table 90 equipped with samples, the load arm equipped with a sample and with the manipulator in the form of a wobble stick 510 viewed from two opposite directions. The sample table 90 carries one sample arrangement in the rubbing position and several sample arrangements in the ready position. The sample arrangements on the load arm and on the sample table in the rubbing position can be exchanged for the sample arrangements 100 arranged in the ready position with the aid of the wobble stick 510. 6 also shows a displacement sensor 580 for determining the travel path between the two samples 470 located in the friction position. The friction force and the normal force (and thus the friction coefficient) can thus be specified as a function of the sample location. The displacement sensor 580 works according to the same principle of optical distance measurement as was described in connection with the force sensors. All path measurements can also be measured capacitively and / or inductively. With the smallest path changes, their measurement can also be carried out with the aid of the piezoelectric effect. In the embodiment according to FIG. 6, the displacement sensor is located outside the vessel on the atmosphere side. However, it is also possible to mount the displacement sensor in the UHV directly at the location of the samples.

At least one further displacement sensor 770 registers a wear quantity. If wear occurs between the sample on the load arm and the sample on the sample table 90, the distance between these samples changes. This change in distance is transferred to the load arm and thus to the load lever 340 via the load arm bearing 260. The displacement sensor 770 attached there registers the movement of the load arm lever and thus the amount of wear. This displacement sensor can also be provided directly at the location of the samples. The signals from both the force sensors and the displacement sensors are processed for digital further processing by a computer via appropriate electronic electronics.

Fig. 7 shows another embodiment of the load arm end. Here too, the clamping body 430 is fastened to the support tube 370 with the aid of the clamping screws 450. A pair of parallel leaf springs 420 will deformed under the influence of the normal force acting in the y direction. This deformation is measured optically. However, the spring holder 440 is designed here in such a way that the second pair of leaf springs 490 are not designed as spiral springs, but are also leaf springs. This pair of leaf springs 490 is deformed in the z direction by the action of the frictional force. This deformation is also measured optically using the method described above. The receptacle for the sample carrier 530 with the samples 470 fastened thereon is placed between the leaf springs 490. The sample carriers 530 are locked by levers 540 and springs 560. Several of these levers 540 can be arranged one behind the other. A heating element in the form of a sample holder can then be placed directly behind the sample 470 to be heated. The heating elements are replaced in the same way as that of the sample holder. Furthermore, a cooling element in the form of a sample carrier, which is connected, for example, via a copper braid to a reservoir containing a refrigerant, can be arranged behind a sample 470 to be cooled. When a heating and a cooling element are used at the same time, the sample temperature can be continuously adjusted between the temperature of the cooling reservoir and the maximum temperature of the heating element by means of a suitable control unit.

FIG. 8 shows a further embodiment of the load arm end and of the sample assembly on the sample table 90. The load arm has a clamping body 430 similar to that shown in FIG. 4. However, the deformation body here consists of a solid block 780, which contains an H-shaped milling 790. In the end areas of their two parallel This causes a strong reduction in the wall thickness in the end areas of its two parallel grooves. When a normal force (F _N ) is exerted, this leads to a deformation at these points, which can be registered using strain gauges (DMS) 590 attached there. Another deformation element in the form of a block 800 is connected directly to the sample table 90. The counter sample is attached to this block by means of an appropriate holder. The Block-800 is aligned so that the friction force (F _R ) can be measured with the help of strain gauges attached to it. However, this deformation body could also be arranged in the load arm instead of on the sample table 90.

The glass fiber rod can be extended to transfer the image of the friction point to the sample. For this purpose, a curved glass fiber rod or light guide 610 is provided via a clamping piece 600, which leads the light directly to the back of a transparent hemisphere sample 620. This means that a great deal of information can be obtained directly from the frictional contact, while simultaneously recording the location as well as the frictional and normal force. If, for example, a CCD camera is held directly at the end of the glass fiber rod outside the UHV tube, information about the change in the sample surface during the rubbing process can be obtained. If the CCD camera is replaced by a spectrometer with a multi-channel analyzer, for example, the tribologically induced heat radiation and thus the temperature or the photoluminescence / triboluminescence can be examined directly at the point of friction. In principle, when laser light is injected into the glass fiber rod via a beam splitter, lattice vibrations can be excited (Raman scattering). give logically induced chemical reactions on the surface of the friction samples. To do this, the signal must be routed via the beam splitter into a corresponding spectrometer with a suitable analyzer. All of these examination methods can be carried out before, after and even during the rubbing process.

The arrangement of load arm end and sample table 90 shown in FIG. 9 enables the measurement of the adhesion. For this purpose, the load arm is rotated with a stop 630 against a lock 640 and clamped in this. The clamping is carried out analogously to the clamping of the sample carrier 530 according to FIG. 5. By folding the extension 570 of the lever using the wobble stick 510, the end of the load arm can be fixed. The sample arranged on the sample table 90 is mounted on an adjustment mechanism, which consists of a rough positioning 650 and a fine positioning 660. With this, the sample can be moved in the direction of the sample attached to the end of the load arm. The possibility of providing adjustment mechanisms in all three spatial directions is not shown.

For the adhesion measurement, one of the samples is attached to a modified sample carrier 530 according to FIG. 10 or 11. A spring element 680 is interchangeably attached to this modified sample carrier 530 via spacers 670, which can be made of insulating or non-insulating material depending on the intended use. The sample 470 is fixed in the middle of the spring element 680. If this sample 470 is approximated to the opposite sample on the locked load arm via the sample holder 530 by means of the coarse and fine positioning 650, 660, depending on the distance between the samples, an attractive interaction can result in deflection of the spring element 680. If the distance between the two samples is reduced, the attractive interaction can cause the samples to come into contact with one another. If the samples are then brought apart again, the adhesive force initially ensures that the samples stick to one another and the spring element 680 bends. 10, the attractive interaction and the adhesive force are measured by optically determining the distance between the rear side of the spring element 680, which is provided with a magnetic medium 690, and a permanent magnet 700 (analogously to the normal / friction force measurement) , If the spring constant of the spring element 670 is known, then the adhesive force can be determined from this. In order to be able to determine the attraction potential, the spring constant should be small at a great distance from the sample and large at a small distance. In order that the spring constant can be influenced, the permanent magnet 700 is arranged on a piezoelectric actuator 710. In order to increase the spring constant of the spring element 680, the distance between the magnetic medium 690 and the permanent magnet 700 is reduced. This is done by control electronics that apply the corresponding voltage to the piezoelectric actuator 710 and keep it constant.

In the arrangement according to FIG. 11, the deflection of the spring element 690 can also be measured optically. In a further development, there is the possibility that the distance measurement and the regulation of the spring constants of the spring element 680 are combined. Another possibility for determining the deflection of the spring element 680 is the measurement of the capacitance of a plate capacitor, which is formed from the spring element 680 itself and a capacitor plate 730 mounted behind it on insulators 720. If the spring element 680 is deflected, the capacitance of the capacitor changes, which is a measure of the deflection and, for a known spring constant of the spring element, of the adhesive force. If the deflection of the spring element 680 is measured optically, its spring constant can be influenced in a targeted manner by applying a voltage to the capacitor formed by the spring element 680 and the capacitor plate 730 via control electronics.

In both sample carriers 530 according to FIGS. 10 and 11, the electrical contacting takes place automatically when they are inserted into the corresponding holders at the end of the load arm and on the sample table 90 by means of suitable contact springs or sliding contacts.

Fig. 12 shows a second embodiment of the UHV tribometer, which is inserted vertically into the UHV vessel. For reasons of clarity, the NW19CF bushing flanges 50 and 60 for cooling with liquid or gaseous nitrogen or helium have been omitted. The sample table 90 is connected to the flange 10 by four flexible table arms 80. The flexible table arms 80 allow the sample table 90 to be reversed in the X direction. This movement is generated by a DC geared motor 200 with an incremental encoder, which is connected in a suitable manner to a rotating union 740. A shaft 750 of the rotary union 740 protruding into the UHV vessel is set in rotation by the geared motor 200. At the end of shaft 750 there is an eccentric 230 The sliding block 240 and a drive shaft block 250 connected to the sample table 90 convert the rotation of the eccentric 230 into a linear movement of the sample table and thus the sample 470 fastened thereon in the x direction. The counter test is located at the end of the load arm, which can be recognized by the support tube 370 and the end flange 380, which is placed on the feedthrough flange 30. A membrane bellows concealed by the flange 10 within the UHV area and storage by means of solid-state joints (under the cover 760) enable the load arm to move in the y direction. In this way, on the one hand the force of a weight acting on the loading lever 340 can be transmitted to the sample and on the other hand this enables the insertion and removal of the samples in their or from their holders. To generate a plurality of rubbing tracks one above the other, at least one of the samples 470 can be moved in the z direction by means of rough and fine positioning 650, 660. If necessary, rough and fine positioning can be provided in each of the three spatial directions. This is preferably UHV-compatible piezoelectric drives.

For loading with the samples 470, the frame 550 is moved roughly in the y direction by the positioning 650, 660. The load can be applied by first bringing the samples 470 into mutual contact through the rough positioning 650. The fine positioning 660 then leads to an exact setting of the normal force acting in the y direction. This normal force is measured by means of a suitable layer system which is integrated in the sample carrier 530 and whose electrical resistance is proportional to the applied standard. Painting power changes. The force signal can be dissipated for digital further processing by contacts integrated in the sample carrier 530 and in the frame 550. A conductive connection between the contacts in the sample carriers 530 and in the frame 550 is created directly when the sample carrier 530 is inserted into the frame 550 and / or by turning the lever 540. The determination of the frictional force can be achieved by deforming spring elements and measuring this deformation in the already described way. If rough and fine positioning 650, 660 is additionally provided in the x direction, the sliding movement can be generated by the expansion and contraction of a piezoelectric drive. In this case, the geared motor 200 and the rotating union 740 can be omitted and the table arms 80 can be made rigid. If a sample carrier according to FIG. 10 or 11 is used, the adhesion between two samples 470 can be determined in the manner described above by moving a sample 470 using the coarse and fine positioning 650, 660.

Claims

claims

Tribometer for determining the material properties of at least one of two mutually movable samples (470), which are detachably fastened in holders in a tightly closable vessel that can be evacuated to an ultra-high vacuum, characterized in that a manipulator (510) for a Detachment and removal of the samples (470) from their respective holders and for feeding the samples (470) to their respective holders and fastening them is provided.

Tribometer according to claim 1, characterized in that the vessel is closed with a sealing flange (10), through the sealing elements, sealing elements between an external drive on the one hand and a table (90) carrying the sample (470) and the other Sample (480) carrying load arm and the manipulator (510) on the other hand.

Tribometer according to claim 2, characterized in that the flange (10) has its own passage for each connecting element.

Tribometer according to one of claims 2 or 3, characterized in that the manipulator (510) between the holders on the table (90) and on the load arm and holders for receiving alternating or exchanged samples (160) can be moved within the vessel.

5. Tribometer according to one of claims 1 to 4, characterized in that the manipulator is a wobble stick (510).

6. Tribometer according to one of claims 2 to 5, characterized in that the flange (10) has a sealed feedthrough for lines for.fluid media and / or electrical or optical signals.

7. Tribometer according to one of claims 2 to 5, characterized in that each bushing has its own bushing flange (20-70) placed on the flange (10).

8. Tribometer according to one of claims 1 to 1, characterized in that a reservoir for receiving a refrigerant for cooling at least one sample (470) is provided.

9. Tribometer according to claim 8, characterized in that the sample (470) attached to the table (90) and the sample attached to the load arm

(470) can be cooled separately.

10. Tribometer according to claim 8 or 9, characterized in that a cold connection from the reservoir to the respective sample (470) can be produced and released by the manipulator (510).

11. Tribometer according to one of claims 1 to 10, characterized in that a heating device for at least one sample (470) is provided.

12. Tribometer according to claim 11, characterized in that the heating device is movable by the manipulator (510).

13. Tribometer according to claim 11 or 12, characterized in that each sample (470) has its own heating device.

14. Tribometer according to one of claims 1 to 13, characterized in that at least one device for measuring the temperature of a sample (470) is provided.

15. Tribometer according to one of claims 11 to 14, characterized in that at least one sample (470) can be heated and cooled at the same time in order to set a desired temperature.

16. Tribometer according to one of claims 1 to 15, characterized in that further holders for optical lenses to be replaced or exchanged and / or deformation bodies are provided in the vessel and are located in the range of motion of the manipulator (510).

17. Tribometer according to one of claims 2 to 16, characterized in that the table (90) and / or the load arm is provided with a drive (200 - 250), through which the sample (470) held by this in at least one spatial direction is defined displaceable.

18. Tribometer according to claim 17, characterized in that at least one drive has an electric geared motor (200) with an incremental encoder or a linear motor.

19. Tribometer according to one of claims 2 to 18, characterized in that at least one of the connecting elements is supported by ball guides.

20. Tribometer according to one of claims 2 to 19, characterized in that at least one of the connecting elements is mounted in a dovetail guide (130).

21. Tribometer according to one of claims 2 to 20, characterized in that at least one of the drives a path profile can be programmed.

22. Tribometer according to one of claims 2 to 21, characterized in that at least one of the connecting elements is pivotable about a transverse axis.

23. Tribometer according to claim 17, characterized in that at least one drive is a piezoelectric actuator arranged in the vessel.

24. Tribometer according to one of claims 2 to 23, characterized in that at least one of the drives (200 - 250) is provided for generating frictional forces between the two samples (470).

25. Tribometer according to one of claims 1 to 24, characterized in that a mechanism

(340-360) for generating normal forces ^* to the contacting surfaces of the two samples (470) is provided.

26. Tribometer according to one of claims 1 to 25, characterized in that at least one e- Mechanism for measuring friction and / or normal forces is provided.

27. Tribometer according to claim 26, characterized in that deflectable spring elements (420, 490, 680) are provided in at least one connection between a drive and a sample holder for measuring the forces.

28. Tribometer according to claim 27, characterized in that an optical distance measuring device is provided for measuring the deflection of the spring elements (420, 490, 680).

29. Tribometer according to claim 27 or 28, characterized in that the spring constants of the spring elements (420, 490, 680) can be changed in a defined manner.

30. Tribometer according to claim 29, characterized in that the spring constants of the spring elements (680) can be changed in a defined manner by means of a displaceable permanent magnet (700) or a plate capacitor arrangement (730).

31. Tribometer according to one of claims 27 to 30, characterized in that the spring elements (420, 490, 680) can be replaced by the manipulator (510).

32. Tribometer according to one of claims 26 to 31, characterized in that a strain gauge arrangement (590) is provided for measuring the forces.

33. Tribometer according to claim 26, characterized in that a piezoelectric device is provided for measuring the forces.

34. Tribometer according to claim 26, characterized in that thin layers (590) with changing physical properties under mechanical load are provided for measuring the forces.

35. Tribometer according to one of claims 17 to 34, characterized in that at least one device (580) for measuring the displacement path of a sample (470) is provided.

36. Tribometer according to one of claims 1 to 35, characterized in that at least one device for measuring the abrasion of a sample (470) is provided.

37. Tribometer according to claim 36, characterized in that an optical device for measuring the distance between the sample holders is provided for measuring the abrasion.

38. Tribometer according to one of claims 1 to 37, characterized in that at least one light guide (390, 610) is provided for transmitting the electromagnetic radiation emitted by a friction point between two samples (470).

39. Tribometer according to one of claims 1 to 38, characterized in that at least one light guide (390, 610) is provided for coupling electromagnetic radiation to the friction point between two samples.

40. Tribometer according to one of claims 1 to 39, characterized in that at least one clamping mechanism (540 - 570) which can be actuated by the manipulator (510) for fastening and releasing there would be a (470) sample in its holder.