CS205488B1 - Instrument for strain hardness exponent determination - Google Patents

Description

The present invention relates to a device for determining the exponent of the reinforcement during the tensile test of standardized test bars.

In forming technology, the stress-strain dependence is of paramount importance for assessing the properties of the treated metal. This dependence is most often approximated by a mathematical expression in malleable metals (3 ^ · ^{c, <} Pi where - intensity searched

C - material constant

- intensity of relative logarithmic deformation n - reinforcement exponent

In this expression, the exponent characterizes the tendency of the material to strain hardening and is therefore considered to be an important parameter of the material under test, which is widely used in the field of plasticity theory. The reinforcement exponent is the starting point for calculating the size of the ductile force.

Nowadays ea exponent of reinforcement deceives in several ways. In the intermittent tensile test, it can be determined by varying the tensile force and the geometry of the sample dimensions. However, interruption of the 0 tensile sweep and re-filling of the sample ecreeles the overall measurement results. For that

205 488

205 488 has also established a method of using test bars with graduated cross-section, where the aa exponent determines the fastening only from the change of the geometry of the dimensions after the felting deformation. This method requires the manufacture of special test rods and delays the work of the laboratory during additional measurement of deformation. There are also blasting machines transmitting the value of load and deformation in the form of electrical impulses to an automatic computer, which evaluates the exponent of the fastening. However, such a device is expensive and therefore not very promising for operational measurements.

The above-mentioned drawbacks are eliminated by a device for determining the exponent of the reinforcement according to the present invention, which consists of two mutually displaceable bodies carried by deformation of the test rod, one of which is armed with contact and the other with stops which at the set values test rod contacts close.

By closing the contacts, a light, audible or other signaling device shall be provided in the boat to alert the operator to read the instantaneous tensile force value without interruption of the tensile tester. From the values thus obtained, it is easy to calculate the exponent of the reinforcement without the need to additionally measure the deformation of the test tube. The device can be used for test rods of standard shapes and to determine the exponent of the reinforcement in the normal tensile test, which is also used to determine conventionally mechanical parameters of the material to be comminuted.

Other advantages and features of the invention will be apparent from the non-limiting description and accompanying drawings, in which:

Fig. 1 shows a longitudinal section through the device of FIG. 2 is a cross-sectional view of the A-A device.

The device touches the test rod 1 with two prongs 6 whose mutual distance in the initial position defines a specific length. Tip bodies 2 * 1 relative to ^seb ® sliding pin J.

Connections 6, which are insulated on the left-hand body 2, which close the current circuit from the electric power source J to a bulb, a bell or a filament-like electrical device 8. . With extended ekúšobnej bar 1 closed the contacts periodically stops £ £ eignallzujú and thus obtained the required elongation of the length of the measuring body 2 · J ^and pressed against the bending bar JL spring element, as shown in FIG. Second

The reinforcement exponent is calculated from two tensile strength values F 1 and F g recorded during the signal given by the device when the two selected length extensions are reached.

11 wherein _the F and N are constants of the apparatus odpovedajúee log SV-1 _Mn predlženlam selected two of the measuring rod of length ekúšobnej.

N

A plurality of stops 6, allowing further recording of the evaluation of the tensile force at a known deformation, serves to refine and control the measurement results.

The device according to the invention can also be used for obtaining a hardening curve, i. to determine the dependence of the actual stress on the relative deformation during the homogeneous deformation of the measuring stick length.

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Claims (1)

OBJECT OF THE INVENTION A device for determining the reinforcement exponent, comprising two mutually displaceable bodies carried by deformation of the test rod, characterized in that one of the telle (3) is armed with a contact (6) and the other body (4) of the stops (9) for the set elongation values. of the test rod length / 1 / to the contacts / 6 /.