SU1698729A1 - Materials physic-mechanic qualities determination method - Google Patents

Abstract

This invention relates to mechanical and electromagnetic testing of materials. The purpose of the invention is to expand the functionality of the method by determining the coercive force of the material under study. The method is as follows. A sample of the material under study in a rod-type is suspended from the sensors and bending vibrations are excited in it in the mode of self-oscillations. The oscillation period is measured using a chronometer frequency meter. Flexible sample harnesses made of thin copper wires are connected to the oscillation nodes of the sample. They are supplied with alternating current of varying strength. By changing the period of natural oscillations depending on the current strength, the coercive force of the sample material is determined, which is proportional to the alternating magnetization current. At the same time, the modulus of elasticity and internal friction in the material, calculated from the natural frequency of the sample and the decrement of their attenuation, are determined. w Ј

Description

The invention relates to mechanical and electromagnetic testing of materials, in particular, to methods for determining the modulus of elasticity, internal friction and coercive force of materials.

The purpose of the invention is to expand the functionality by determining the coercive force.

The method consists in attaching a non-rigid tokovods in the oscillation nodes to the sample of the material under investigation, suspended on thin threads to the sensors, by means of which an alternating electric current is passed through the sample and measured (along with the natural oscillation frequency and the decrement). ) changes in the period of natural oscillations of the sample depending on the current strength. Magnitude change

a period per one amp is proportional to the demagnetization current, which allows the determination of the coercive force.

Example. Samples of 0-8 mm, I 200 mm from the following ferromagnetic materials were made: armco iron, cobalt, steel 70CZ, etc. Samples are suspended on thin threads to two sensors, one of which excites oscillations in the sample, and the other registers them, converts them into an electrical signal (electrical oscillations of the same frequency) and delivers to the amplifier, from where the signal is fed to the measuring instruments. The period of oscillation is measured using a frequency meter-chronometer 05041, which allows you to measure the period with an accuracy of 1 10 μs

ABOUT

h: os

h N: s

in 1 s. This makes it possible to measure the change in the period with a short-term passage of current through the sample rather quickly with high accuracy in order to avoid its heating. With the same purpose, the sample is oscillated in self-oscillation mode, as a result of which the sample immediately oscillates with its own frequency. Measuring the period (or frequency), determine the modulus of normal elasticity by the formula (for a cylindrical sample)

E 1,6388-10-8 (7) 4T (T) 2

(one)

where I is the length of the sample, cm; d is the sample diameter, cm; P is the sample weight, g;

T - t - is the period of natural oscillations,

c (f - frequency, Hz);

Е - modulus of normal elasticity, kgf / mm2.

Internal friction is measured on the same apparatus and sample as the module, with the initial state being the sample oscillating with the natural frequency. Stopping the excitation of oscillations of the sample, simultaneously include a recalculating device that calculates the number of oscillations necessary to calculate the internal friction Cf by the formula

 -

Vj (l / rr

one

AO

(2)

About i | I l about

; JT VnAn where 5 is the damping decrement;

AO is the initial amplitude;

An is the amplitude of the nth oscillation.

To calculate, it is necessary to measure the number of oscillations n, during which the amplitude decreases from A0 to An. Typically, scaling devices use discriminators that establish the ratio

  OG I OL

- 2,7, then PD- 1.

To measure the coercive force on the same unit and sample (for the implementation of the proposed method), non-rigid current leads made of thin copper wires are attached to the flexural vibrations of the sample, through which 50 Hz current is passed through the sample. The current is varied from 0 to 10 A. After measuring the Type without current to determine E, the current of a known force I is switched on briefly and the corresponding oscillation period Tm is measured.

0

five

0

five

0

five

0

five

0

The changes in the period of natural oscillations of the sample A T - Tm are recorded and the A T / 1 is determined.

On the same samples, the magnitude of the magnetization reversal current ip is measured on a CIMF-1 coercimeter, and the coercive force He is calculated by the formula

  p o (

with - g- 3

io and B for the same instrument, the shape and size of the samples, are constant values and are determined by measurements, certification samples. In our case

io, 7.10 5M.

According to experimental data, a regression equation is compiled, the coefficients of which are determined by the least squares method.

Y (240-4 ,, (4)

where Y - j-, μs / A; X ip, mA.

The demagnetization current is found by this formula, the coercive force is determined from the value of the demagnetization current by the formula

AT 240 - 4.3-103 (3, + 2)

(five)

Thus, the proposed method makes it possible to simultaneously measure the modulus of elasticity, internal friction and coercive force, which doubles the productivity of labor.

Claims (1)

Claims The method of determining the physicomechanical properties of materials, including the excitation of bending vibrations in the sample, measuring the period of natural oscillations and the decrement of their attenuation, characterized in that, in order to expand the functionality of the method by determining the coercive force, a variable electric current is passed through the sample under study. current and measure the change in the period of natural oscillations of the sample, determine the coercive force of the material from the following ratio and: AT -five Not + 2-10 -z) five L 240-4.3-103 (3.7-10 where АТ (НС) is the change of the period of natural oscillations of the sample after the passage of electric current through it, I (A); BUT Нс - coercive force of the material, M1