SU1486878A1 - Method of determining material hardness - Google Patents

Description

The invention relates to a technique for testing the dynamic properties of structural materials and can be used to measure dynamic hardness at strain rates of ~ 1 O ³ c "'. The purpose of the invention is to improve the accuracy by ensuring that the hardness of materials is directly determined. an elastic one-dimensional wave into the sample, mounted on the base, and at the time of their contact, the hardness is recorded on the indenter reflected and transmitted into the base of the wave and with their allowance taken into account.

The invention relates to a technique for testing the dynamic properties of structural materials and can be used to measure the dynamic hardness at strain rates ~ 1 O ³ s ^- ',

The purpose of the invention is to improve the accuracy by ensuring the determination of the hardness of materials directly.

. The method is implemented as follows.

The sample is placed on the base, an indenter is inserted into the sample, an elastic one-dimensional wave is excited in the latter, and at the moment of contact of the sample and the indenter, the reflected and transmitted waves are recorded on the latter and the 'hardness is determined

_Mr. _____ E ^ AC ^ h ____

Υ '-ίϋ _δ ^ / 2 · s *?} (^ (О-edOMs) ⁵ ·'

about

where E is the Young's modulus of the material of the indenter and base;

And - the cross-sectional area of the base;

С „is the speed of sound waves in the material of the indenter, and the base;

v is the angle at the tip of the indenter; p, (O ~ incident pulse strain;

5 _g (s) is the reflected strain pulse;

£ ^. (С) - the last momentum of deformation.

“Example. The method can be implemented using the installation, in

1486878 A1

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1486878

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composition of which includes: gas gun, a system of rods with an indenter and a sample. The gas gun disperses the firing pin, which excites a compression pulse in the loading rod. The loading and supporting rods (base) with a length of 1 m and a diameter of 20 mm are made of 30 hGHA hardened steel. a cone angle of 136 at the tip, made of steel with a yield strength of 160 kg / mm ² . The sample of the tested material-15 rial is made in the form of a tablet with a diameter of 20 and a height of 20 mm. The impulses of deformations 6 ;, £ _g , in the rods are measured using strain gauges of the type FKP-3-200 with a base of 3 mm, with 20 pulses registered; , carried out by one strain gauge, glued to the loading rod, and the registration of the pulse is carried out by another strain gauge, glued 25 on the support rod. The signals from them are fed to the input of a two-channel oscillo graph "

In order to carry out the separation in time of the pulses, the recording sensor 30 is glued at a distance b from the end that is in contact with the indenter and the sample, determined from the condition b> 0.5 CO ", where C is the ZBuk speed in the rods ·,

's - the maximum duration of the incident pulse. At the same time, the distance to the impact end of the loading rod must be at least 20 diameters of the rod, so that a flat simultaneous elastic compression wave o

To facilitate the registration and processing of pulses, both load cells are located in the middle of the length of the rods. In the experiments record all the parameters of the pulses, including duration, amplitude and their shape. The registration of signals from strain gauges is carried out using oscillographs of type C1-74 or C 9-8,

Claims (1)

Claim The method of determining the hardness of materials, which consists in placing the sample on the base, injects the indenter into the sample and, at the moment of contact between the indenter and the sample, records the parameters by which the hardness of the material is determined, in that, in order to improve the accuracy, elastic one-dimensional wave, as parameters recorded on the indenter reflected and transmitted to the base of the wave and with their account determine the hardness.