WO2012143528A1

WO2012143528A1 - High-speed compression test device for carrying out compression tests

Info

Publication number: WO2012143528A1
Application number: PCT/EP2012/057311
Authority: WO
Inventors: Andreas HAMANN; Peter LÖWE
Original assignee: Bam Bundesanstalt Für Materialforschung Und -Prfüfung
Priority date: 2011-04-21
Filing date: 2012-04-20
Publication date: 2012-10-26
Also published as: DE102011002242A1; DE102011002242B4

Abstract

The invention relates to a test device for a high-speed traction-compression test device for carrying out compression tests, comprising a first compression die (1) and a second compression die (3) which act upon a compression sample (6). According to the invention, the second compression die (3) comprises a cutting die (7) which is supported on a shearing plate (11). The shearing plate is designed in such a manner that it is cut abruptly by the cutting die (7) when a predefined force is exceeded during the compression test. After shearing the shearing plate, the cutting die can move further and freely in guiding means (12, 16) so that no further compression forces can be exerted upon the compression sample and the test device, which would go beyond the force defined by the type and embodiment of the shearing plate. By limiting the forces exerted upon the test device and the compression sample, which can be individually adjusted as a function of the respective shearing plate, an overload of the test device is prevented.

Description

High-speed pressure test device for performing compression tests

description

The invention relates to a high-speed pressure testing device for a high-speed testing machine for performing upsetting tests for material testing with two compression punches acting on a compression sample according to the preamble of claim 1 and a method for performing compression tests. In order to carry out high-speed compression tests, it is known to use special high-speed tensile pressure testing machines which are suitable for compression tests and are therefore expensive. In particular, high-speed compression tests serve the purpose of investigating the behavior of a material at high deformation rates, which occur, for example, in vehicle crashes, in impact processes or in high-speed forming processes.

Apart from the fact that many of the known high-speed train-pressure testing machines are not suitable for high-speed compression tests, high compression speeds can result in erroneous force measurement as a result of high inertia forces and the commonly used force sensors. In the case of high-speed testing machines, moreover, in the case of very high degrees of deformation - that is, when the test apparatus "drives to block" (the sample is crushed) - there is conventionally no control technology for limiting the compression force in order to purposefully end the upsetting operation and at the same time To protect high-speed testing device from overloading, as a control-technical shutdown of the test device would react too slowly to achieve an effective limitation of the compression force.

From DE 692 16 592 T2 a high-speed pressure testing device for performing compression tests on material samples is known, which has two upsetting punches acting on a compression sample. A power transmission and stop unit is provided in order to prevent movement of a first upsetting punch in the form of an anvil after successful End compression of a specimen when the specimen has been compressed by a predetermined amount. However, DE 692 16 592 T2 does not provide any possibilities for limiting an upsetting force and protecting the testing machine against impermissibly high forces.

The present invention has for its object to provide a compression stamper comprehensive testing device for a conventional, not necessarily designed specifically for compression tests high-speed train-pressure testing machine and a method for performing compression tests with simple means and cost so that the compression force variably limited can be performed so that stopped, that is limited to a defined compression force or a desired degree of deformation compression tests can be performed and overload protection of the high-speed train pressure testing machine and the tester is guaranteed.

This object is achieved by a test device designed according to the features of patent claim 1 for a high-speed tension-compression testing machine.

Advantageous developments of the invention are the subject of the dependent claims.

The basic idea of the invention is that one of the two upsetting punches (an upsetting die arranged stationarily or movably on the testing device) comprises a cutting punch which is supported on a shear plate individually used for a compression test, wherein the shear plate is designed such that it is formed during the An upsetting test is abruptly interrupted by the action of the cutting punch when a certain force exerted on the compression test sample is exceeded. After severing the shear plate of the power flow is interrupted in the tester, and the cutting punch can - possibly freely slidably mounted on guide means - leak. The limitation of the forces acting on the testing device and the compression test force, which can be individually adjusted as a function of the respective shear plate, prevents "on-block driving" and overloading of the testing device and testing machine. The maximum force acting on the swage sample is limited by the force that the shear plate is able to support. If this force is exceeded, the shear plate is severed by the action of the cutting punch and the force flow in the testing device is thus interrupted. The control of the testing machine then remains enough time to safely stop the working organ, ie the hydraulic piston. In an embodiment of the invention, the shear plate is annular and supported on a die, which is arranged, for example, the end face on a cutting punch in the movement receiving discharge cylinder of the associated compression punch. The die advantageously corresponds to a cutting ring provided on the cutting punch.

The shear plate may e.g. be fixed by means of a releasably attached to the discharge cylinder blank holder on the associated (second) upsetting punch by the shear plate is pressed by the hold-down against the die, so that the shear plate is clamped between the hold-down and the die. In this case, the die is arranged behind the shear plate along an impact direction in which the first punch approximates the second punch in a compression test, so that the shear plate is pressed against the die by the force effect occurring during a collision test. The pressing of the shear plate to the die of the discharge cylinder can e.g. take place via a formed on the hold-down, continuous hold-down collar. As a guide means for the advantageously designed as a downwardly open hollow body cutting punch serve e.g. the hollow cylindrical holding-down device and / or a collection mandrel arranged in the outlet cylinder.

In a further embodiment of the invention, a corresponding with an outer surface of the cutting punch first sliding bush and an inner surface of the hollow-shaped cutting punch are provided with an Au ßenfläche of the collecting mandrel corresponding second sliding bush for exact guidance of the cutting punch on the hold-down.

In an advantageous embodiment of the invention, the cutting punch in the ready state (ie before performing a compression test) facing the end of the collecting mandrel is conical to ensure reliable sliding of the cutting punch on the collecting mandrel after shearing the shear plate in a compression test. In addition, e.g. on an Au ßenumfang the collecting mandrel be a support collar for the sheared off from the cutting part of the shear plate, so that it is intercepted and supported after shearing the collecting mandrel.

In a further embodiment of the invention, the collecting mandrel forms a stop, for example, arranged on the face side for the cutting punch, wherein the cutting punch has a damping element at the end-side abutment point with the collecting mandrel. The collecting mandrel thus limits the movement path of the cutting punch in a compression test after shearing the shear plate such that the cutting punch is intercepted in a reliable manner and is braked by the effect of the damping element in a damping manner, after he has severed the shear plate.

In a further embodiment, vent holes may be formed on a wall of the discharge cylinder, which allow easy movement of the cutting punch in the discharge cylinder by allowing escape of air from the interior of the hollow cylindrical discharge cylinder during movement of the cutting punch in the discharge cylinder.

The collecting mandrel is formed in an advantageous embodiment of the invention as an open hollow body. In the outlet cylinder can be connected to a source of compressed air, up to the collecting mandrel ranging compressed air supply channel can be formed. Compressed air can be fed into the collecting mandrel via the compressed air supply channel, which acts on the cutting punch when the punch is driven onto the collecting mandrel and moves it in the outfeed cylinder to remove the cutting punch from the outfeed cylinder and assemble it with a new shear plate for another upsetting test to be able to.

The object is also achieved by a method for performing upsetting tests for material testing by means of a high-speed pressure testing device for a high-speed testing machine, in which a first upsetting punch and a second upsetting punch act on an upsetting sample. It is provided that the second upsetting punches for limiting the forces acting on the compression sample and the test apparatus and the high-speed testing machine includes a supported on a shear plate cutting punch, the shear plate is severed during the compression test when a predetermined force action is exceeded abruptly from the cutting punch. The advantages and advantageous embodiments described above for the device are analogously also applied to the method.

The invention will be explained in more detail with reference to the embodiment shown in the figures. Show it:

1 is a partially sectional side view of the two upsets of a high-speed pressure tester during the compression test with a still undeformed, located between two printing plates cy- cylindrical compression test;

FIG. 2 shows a side view of the testing device in the region of the two upsetting punches according to FIG. 1, but with a compression test sample deformed until reaching a predetermined limited compression force in the compression test;

3 is a side view of the two upsets in a lowered position of a cutting punch after exceeding the predetermined compression force. and

Fig. 4 is a side view of the two upsets at the end of the compression test in the final position of the cutting punch. The reproduced in Fig. 1 to 4 high-speed pressure tester comprises two in the load line of a high-speed testing machine (not shown) upset dies 1, 3. The two upsets 1 and 3 either on the rigid part (crosshead or table) or be mounted on the movable part (piston rod) of the high-speed testing machine. The attached on the piston rod movable upsetting punch (here the second upsetting punch 3) can be with any, in high-speed servo-hydraulic tension-compression testing machines z.Z. to about 25m / s speed to the fixed upsetting punch (here the first punch 1) to move. A pressure plate 4, 5 made of a high-strength and wear-resistant material is in each case attached to the sides of the two compression punches 1, 3 facing one another.

To perform an upsetting test, an upsetting specimen 6 (FIG. 1) is centered on the one - in the present exemplary embodiment on the pressure plate 4 attached to the movable (second) upset die 3 - positioned as shown in FIGS. 2 to 4 under the effect the force exerted on this high-speed force of the other - in the present exemplary embodiment stationary (first) - compression punch 1 is deformed (compressed). The deformation and force measurement performed during the upsetting process is used to characterize the deformation and damage behavior of the sample material. The force measurement is carried out by the force measuring device accommodated in the stationary stamper 1 here. The movable (second) upsetting punch 3 comprises a cutting punch 7, on whose free end face the pressure plate 4 is attached, an outlet cylinder 8 for the cutting punch 7, one on the open side of the discharge cylinder 8 entrable hold-down 9 for resting on a front-side die 10 of the discharge cylinder 8 annular shear plate 1 1 (Stauchkraftbegrenzungsplatte) and a centrally arranged in the outlet cylinder 8 collecting mandrel 12. The cutting punch 7 is as the discharge cylinder 8 out formed open hollow body and has on the open end side cooperating with the die 10 cutting ring 13. On the cylindrical inner surface of the cutting punch 7, a first sliding bush 14 is formed, while at its inner end face a damping element 15 is located. A second slide bushing 16 is arranged on an inner peripheral surface of the hold-down 9, which is designed as a union nut and can be screwed to the outlet cylinder 8, specifically above a circumferential hold-down collar 17.

On a cylindrical wall of the discharge cylinder 8 are vent holes 18 and extending into the interior of the collecting mandrel 12, to a compressed air source (not shown) connected compressed air supply channel 19. The tapered at the upper end collecting mandrel 12, the outer diameter substantially with the inner diameter the first sliding bush 14 coincides, has at the lower end a support collar 20 for a sheared portion 21 of the annular shear plate 1 1. The Au ßendurchmesser of the cutting punch 7 is smaller than the inner diameter of the discharge cylinder 8. The function of the test device described above in the static state for performing compression tests will be described below with reference to FIGS. 1 to 4:

Before carrying out the experiment, the movable upsetting punch 3 is in a starting position (not shown) at a clear distance from the stationary upset punch 1. The cutting punch 7 and the holding-down device 9 designed as a union nut are located in a position (not shown) that is dismantled by the movable upsetting die 3. In this state, a shear plate 1 1 is placed on the integrated into the end face of the discharge cylinder 8 die 10, and then the cutting punch 7 is centrally positioned on the shear plate 1 1, so that the outer edges of the die 10 and the cutting ring 13 are aligned. Thereafter, the trained as a union nut hold-9 is screwed onto the outlet cylinder 8 to fix the shear plate 1 1 and to create an exact sliding guide for the cutting punch 7 by means of trained in holding down slide bushing 16. The cutting ring 13 now rests on the over the cutting edge of the die 10th projecting area (referred to below as Part 21) of the shear plate 1 1.

With regard to the material and the thickness, the shear plate is selected such that when an upsetting test is carried out when a predetermined compression force is reached, depending on the material and the geometry of the compression sample 6 and the speed difference of the two compression punches 1, 3 and the degree of deformation Cutting ring 13 of the cutting punch 7 is severed suddenly. As a result, the flow of force in the tester is interrupted, the upsetting process is terminated and the high-speed tension-compression testing machine is protected from overloading.

In the present embodiment, the annular shear plate 1 1, whose inner diameter is greater than the outer diameter of the collecting mandrel 12, made of aluminum and has a thickness of 0.5 mm. Of course, the shear plate can also consist of a different material and have a different thickness. By selecting material and thickness of the shear plate, the characteristic of the piercing process is significantly determined. After the movable upsetting punch 3 is mounted with respect to the guided in the hold-down device 9 and resting on the shear plate 1 1 arrangement of the cutting punch 7, the cylindrical compression test 6 is positioned centrally on the pressure plate 4. Subsequently, the upsetting process is carried out by an upward movement of the movable upsetting die 3 with the compression sample 6 arranged on the pressure plate in the direction of the stationary edging stem 1, in order to deform the compression specimen 6 at high speed and thereby both the forces acting on the compression specimen with those in the stationary Upset stamp 1 arranged force measuring device 2 and - to detect the deformation of the compression sample 6 - for example, with a high-speed camera or with a laser extensometer. 1 shows the still undeformed compression test 6 and the two compression punches 1, 3 (as well as the individual components of the compression punch 3) at the time of the first contact of the stationary compression punch 1 on the compression test 6.

FIG. 2 shows the already fully compressed compression test 6 'and the movable upsetting die 3 raised relative to the illustration in FIG. 1 and the still unchanged position of the cutting die 7.

In the illustration shown in Fig. 3, the movable upsetting die 3 has a certain Force effect exceeded, so that the shear plate 1 1 is pierced abruptly and no further force on the already deformed compression sample 6 ', the cutting punch 7 and ultimately the testing device and the testing machine can be exercised. In other words, the compression force is variably limited in the desired manner by the selection of the respective shear plate 1 1. A compression test is abruptly interrupted as soon as the compression force exceeds the predetermined, predetermined by the selection of the shear plate 1 1 maximum compression force. An overload of the tester with the two compression dies 1, 3 and the testing machine can be effectively prevented in this way.

Fig. 3 shows the cutting punch 7 in the downward movement shortly after the shearing of the part 21 of the shear plate 1 1, which, as shown in FIG. 4, falls on a support collar 20 of the collecting mandrel 12. The cutting punch 7 with the deformed compression test 6 'slides with its sliding bush 14 along the Au ßenumfangsfläche the collecting mandrel 12 and is at the free end face, and damped by the damping element 15, collected.

During the movement of the cutting punch 7 in the discharge cylinder 8 arranged in the wall of the discharge cylinder 8 vent holes 18 prevent pressure buildup in the discharge cylinder 8, so that the downward movement of the cutting punch 7 can be done within the discharge cylinder 8 in a smooth manner.

In order to be able to remove the cutting punch 7 from the discharge cylinder after a compression test and a shearing of the shear plate 1 1, compressed air is blown into a cavity of the collecting mandrel 12 via the compressed air supply duct 19 so that the cutting punch 7 is moved upwards and then removed can be.

The invention is not limited to the previously described embodiment. Within the scope of the basic concept of the invention numerous modifications are conceivable.

The test device which can be used in the high-speed range up to approx. 25 m / s can also be used, for example, for static compression tests, and likewise the compression force can act not only from bottom to top as described here but also from top to bottom. LIST OF REFERENCE NUMBERS

1 first (stationary) upsetting punch

2 force measuring device

3 second (movable) upsetting punch

4 printing plate of 3

5 printing plate of 1

6 compression test

6 'Deformed compression test

7 cutting punches

8 discharge cylinder

9 hold downs

10 matrix of 8

1 1 annular shear plate

12 collecting spike

13 cut ring from

14 first sliding bush of 7

15 damping element of 7

16 second sliding bush of 9

17 hold-down collar of 9

18 breather hole in 8

19 compressed air supply channel in 8, 12th

20 edition of 12

21 sheared off part of 1 1

Claims

claims

1 . High-speed pressure testing device for a high-speed testing machine for performing upsetting tests for materials testing, with a first upsetting die (1) and a second upsetting die (3) acting on a compression sample (6), characterized in that the second upsetting die (3) for Limiting the forces acting on the compression test (6) and the test apparatus and the high-speed testing machine comprises a on a shear plate (1 1) supported cutting punch (7), wherein the shear plate (1 1) is formed so that it during the compression test when exceeding a predetermined force is abruptly severed by the cutting punch (7).

2. Testing device according to claim 1, characterized in that a maximum of the predetermined, limited force on the compression test (6 ') is exercised.

3. Testing device according to claim 1 or 2, characterized in that the cutting punch (7) after the severing of the shear plate (1 1) on guide means (16, 12) is guided slidably movable.

4. Testing device according to one of claims 1 to 3, characterized in that the shear plate (1 1) is annular.

5. Testing device according to one of the preceding claims, characterized Net, that the shear plate (1 1) is supported on a on a discharge cylinder (8) of the second upsetting die (3) arranged die (10) corresponding to a provided on the cutting punch (7) cutting ring (13).

6. Testing device according to claim 5, characterized in that the shear plate (7) by a at the outlet cylinder (8) releasably secured down device (9) is fixed to the second upsetting die (3).

Has 7. Testing device according to claim 6, characterized in that the cylindrically shaped hold-down (9) acting on the shear plate (7) hold-down collar (17).

8. Testing device according to claim 6 or 7, characterized in that as a guide means for the open hollow body designed punch (7) a downholder (9) associated first slide bushing (16) and / or at the outlet cylinder (8) arranged collecting mandrel (12 ) serve.

9. Testing device according to claim 8, characterized in that on the cutting punch (7) with the collecting mandrel (12) corresponding, second sliding bush (14) is provided.

10. Testing device according to claim 8 or 9, characterized in that the collecting mandrel (12) is at least partially formed conically at one of the cutting punch (7) facing the end.

1 1. Test device according to one of claims 8 to 10, characterized in that on the collecting mandrel (12) a support collar (20) for a from the cutting punch (7) abge- sheared part (21) of the shear plate (1 1) is formed.

12. Test device according to one of claims 8 to 1 1, characterized in that the collecting mandrel (12) forms a stop for the cutting punch (7), wherein the cutting punch (7) at a collecting mandrel (12) associated stop a damping element (15 ) having.

13. Testing device according to one of claims 8 to 12, characterized in that on a wall of the outlet cylinder (8) at least one vent hole (18) is formed.

14. Testing device according to one of claims 8 to 13, characterized in that the collecting mandrel (1, 2) is designed as an open hollow body and on the outlet cylinder (8) connectable to a compressed air source, to the collecting mandrel (12) extending compressed air supply channel (19). is trained.

1 5. Test device according to one of the preceding claims, characterized in that the first and second upsetting punches (1, 3) on the upsetting sample (6) facing the contact side each having a pressure plate (4, 5) made of a material having a particularly high strength, hardness, toughness and impact resistance.

16. A method for performing upsetting tests for material testing by means of a high-speed pressure testing device for a high speed testing machine, in which a first upsetting punch (1) and a second upsetting punch (3) act on a compression sample (6), characterized that the second upsetting punch (3) for limiting the forces acting on the compression sample (6) and the test apparatus and the high-speed testing machine comprises a cutting punch (7) supported on a shear plate (1 1), wherein the shear plate (1 1) during the compression test at Exceeding a predetermined force effect is abruptly cut by the cutting punch (7).