DE2422872A1 - LOADING DEVICE FOR DYNAMIC TENSION TESTING - Google Patents

Description

Loader for dynamic tensile specimens

The invention relates to a loading device for tensile specimens of material with a high rate of deformation.

Devices and devices for dynamic pressure tests of material are known. However, there are structural breaks almost always occur due to tensile deformation, a dynamic tensile test for determination becomes more general Behaviors required.

The so-called "block bar" device is known consists of two slide rails on which a projectile operated by means of explosives and springs runs. the The front of the projectile pushes the pedestal of two solid, cylindrical buffers into the other pedestal by means of a lower beam, on the cross section of which the solid specimen with a central rod and parallel attached to the rails.

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However, this method has the disadvantage that a large part the energy is absorbed by the cylinders. In addition, the repetition of the sample depends on the perfect parallelism of the cylinders, which is not always constant.

Are also known. Devices consisting of a measuring system with Hopkinson 'sch.er Doppel & ange and from a charging device exist, which in one case consist of an explosive and in another lall of a shock tube .

However, these bodies showed. Limitations; the explosive device could only be used to withstand high loads within 100 - 200 / uSec. and caused a pressure wave with relatively long rise times of about 40 Ai s, so that the deformation rate changed during the sample.

The device with shock tubes, which requires a rise time of about 30 Ai s, ie. is fairly, high, moreover, has the disadvantage of a fairly long time for the push tube to be ready for loading.

The invention is based on the object of providing a charging device while avoiding the aforementioned disadvantages for developing dynamic tensile specimens of simple composition, with short rise times and substantially, higher total impulse duration works.

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In order to achieve this object, "the inventive ■ Device for dynamic tensile tests of a mechanical accumulator, which is loaded at one end by means of a charging device is attached to a solid base. The other end, by means of a small spacer is rigidly connected to the accumulator, sits in the notch of the small intermediate piece in a first Rod continued, which is connected to a second rod by means of a test piece. The end of this second Bar, opposite to the specimen, is attached to a second fixed pedestal by a yorloader firmly connected.

An embodiment of the invention is shown in the drawing and is described in more detail below. Show it:

Fig. 1 the device for the sample, Fig. 2 the loading device,

Fig. 3 and 4 two different block systems with small Intermediate pieces.

In FIG. 1, 1 is the mechanical accumulator which is attached to the wall 2 or to another fixed base by the charging device 3. The accumulator 1 is connected to the measuring system by a small intermediate piece 4-, which consists of the Hopkins on ¹ rod, consisting of a first rod 5, a second rod 6,

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connected to the test piece 7, composed. The rod 6 is at the other end with another, fixed base 8 by, a Vorladervorriclitung 9 tied together.

Fig. 2 shows the loading device 3 in vertical section, which is attached to the wall 2. It consists of a differential screw, which consists of a screw nut 10 and consists of two screws 11 and 12 with slightly different threads and opposite directions of rotation; the screw 12 is connected to a further screw nut which is connected to the threaded head 14- the represents one end of the mechanical accumulator 1 or the rod. The other end of the accumulator is the same by means of a small intermediate piece 4 with, for example, a rather predetermined breaking point by means of a press 15 opposite a bearing 16 CFig. 3d and 3t>) blocked. In the Depression of the bearing 16 extends the accumulator and forms the first rod 5> which is mechanically connected to the second rod 6 by the test piece 7. The other end of this second rod is attached to the fixed base 8 by a preloading device 9.

The pre-loading device 9 'is similar to the loading device 3' serves to give the rods 5 and 6 and the specimen 7 the desired preload or around the rods well to position.

After the stress in the accumulator 1 by the charging device 3 is reached, the small intermediate piece 4-

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according to the known methods e.g. Push or Overload smashed. A tensile stress is then transmitted to the rods 5 and 6, with the test piece 7 leads to rapid deformation and therefore to breakage.

As with the previously mentioned devices with Hopkinson ¹ shear rod, two force values in relation to time, which can be carried out on the two half rods by means of an electrical extensometer, obtain all force and deformation parameters and therefore determine the dynamic force and deformation diagram.

4- is another embodiment of the invention shown in connection with the fracture system of the small spacer. The accumulator 1 is in the Near the small intermediate piece connected to a claw 17, which with the tip 18 against the small intermediate piece 4- presses. After the desired stress has been reached without external intervention, the tip 18 breaks the small intermediate piece 4-, and the pulling wave is transmitted to the rods 5 and 6, whereby the specimen 7 is caused to be deformed rapidly and broken.

As can be seen, this device is very simply put together compared to the previous devices and results in a very low cost.

Furthermore, various deformation speeds

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or you can optionally achieve a long pulse duration, since it is proportional to the length of the accumulator rod and equal to twice the frequency of a sound wave in the rod itself.

In the solution described, the length of the accumulator 1 of the first rod 5 and the second rod 6 is the same. Other different lengths can be selected without departing from the scope of the invention.

Claims;

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Claims (2)

_ η _ Pat ent to spray 1.jLoading device for dynamic tensile tests of material - with high deformation rate, consisting of a test piece, which is mechanically between two measuring rods held ", characterized in that that it is provided with a mechanical accumulator (1), which at one end by a loading device (J) and a fixed base (2) is attached, the other end by a small Intermediate piece (4) is rigidly connected to the accumulator and is located in a notch of the small intermediate piece in a first rod (5), which continues with a second rod (6) by means of a test piece to be measured (7) is connected, the end of this second rod, opposite to the specimen, with a second, fixed base (8) is connected by means of a preloading device (9). 2. Device for dynamic tensile specimens of material with high deformation rate according to claim. 1, characterized in that the mechanical accumulator (1) consisting of a number of rods that are tensioned by means of a loading device, consists. -8th- 409849/0311 J. Apparatus for dynamic tensile testing of material with high deformation rate according to claim 1 and 2, characterized in that that the loading device (j) is differential. 4-. Device for dynamic tensile testing of material with high deformation rate according to claim 1, characterized in that the mechanical accumulator (1) is discharged by breaking a small intermediate piece (4-). 5 · Device for dynamic tensile tests of material with high deformation rate according to claim 1 and characterized in that the small intermediate piece (4-) has a predetermined breaking point. Be / MP - 25 607 409849/0311