SU1649377A1 - Method for determining hardness - Google Patents

Abstract

The invention relates to mechanical testing of materials, to methods for determining the hardness of materials. The purpose of the invention is to improve the accuracy of hardness determination by taking into account the elastic properties of the materials of the sample and the indenter. A conical indenter is inserted into the surface of the test material, the depth of its penetration from the initial surface under load, the residual indentation depth, the dynamic hardness coefficient of the test material, the elastic constants of the test material and the indenter are measured, the half angle at the apex of the residual indentation and the average pressure at the surface of the imprint, which is judged on the hardness of the known dependence. i

Description

The invention relates to mechanical testing of materials, in particular, to methods for determining the hardness of materials during the introduction of an indenter.

"

The aim of the invention is to improve the accuracy of hardness determination due to the elastic properties of the materials of the sample and the indenter.

The method is implemented as follows.

The elastic constants of the test material of the sample (E, jtlf) and the indenter (E2, | K2) are measured. If the materials of the sample and the indenter are known in advance, then the moduli of normal elasticity E and E and the Poisson's coefficients | U (and (Uz. Can be determined from the reference table. "

The dynamic coefficient of hardness / test material is determined. With static indentation of the indenter, the coefficient of dynamic hardness is equal to one.

A conical indenter is inserted into the surface of the test material and the depth of intrusion of the indenter under load and the depth of the residual imprint are measured (from the level of this surface). This operation can be carried out on any stationary hardness tester (press) or with the aid of portable hardness testers of the type VPI, additionally equipped with a device for measuring bH and he.

The half angle at the tip of the residual print is determined.

with

W)

| -vj

arccos

cos y

G31i1

H and the average pressure H on the surface

imprint

2 1

 2r5 „

 C | 2.1 l / 1

,

h

E

 Z.

tg

H pr

where the tangent of the given half angle is

tlf 15

20

25

tstfnptgCf0

The standard static Kickers hardness of the test material is determined from a known relationship

HV H-Kq ,, where KQ.- coefficient describing

  the dependence of the ratio HV / H on the angle of the cone 2 (0 at the tip of the indenter,

In the particular case when 2C 136 (an indenter with such an angle is most often used to measure hardness) Cr sinu sin 68, the formula takes the form

HV H-sinCp H "sin68 ° .30

Example. The hardness was determined on parts made of various materials: steels, titanium f brass, aluminum.

The 35 indenter used was a cone with a vertex angle of 2 (0 136 made of a hard alloy. The elastic constants of the test materials (K, L) and the material of the indenter (E2, (U2) were determined by reference. 40

The dynamic hardness coefficient of the sample material was determined from the tables.

Claims (1)

The introduction of a conical indenter was carried out with a static loading on a Brinell press or a Rockwell device, and with a shock load using (a portable VPI hardness meter, additionally equipped with a device for measuring HC and h0. The depth of insertion h H and he was measured with an accuracy of 1 µm. Definition of H, and tg ({op wire, silt and by the formulas. Formula of the invention The method of determining the hardness, which is charged to the current, is introduced , ten 45 50. 15 20 649377.4 indenter into the surface of the test material and measure the depth of its introduction under load, which is due to the fact that, in order to increase accuracy, materials with known moduli of normal elasticity and coefficient of test material are used as the test material 10 by Poisson’s test, the depth of the residual print from the initial surface of the test material is measured, the dynamic hardness coefficient of the test material and the half angle at the tip of the residual print are determined 2 "cos RS . arccos 1 + hjL hA and the average pressure on the surface of the print 25 H -2l5 (l. HHH where Ср is the half angle at the vertex of the conic indenter; Pe R t & ff-, - ts tRtfo the tangent of the reduced half angle at the contact of the conic surfaces of the indenter and Hni h. E 0 - respectively, the depth of indentation of the indenter under load and the depth of the residual indentation, measured from the level of the initial surface of the material; H is the average pressure on the surface, 2, of the footprint; - the modulus of normal elasticity and Poisson's ratio (indices 1 and 2 refer to the material under test and the indenter, respectively), P is the dynamic coefficient the hardness of the test material which is judged on the hardness of the known dependence | And "