SU1305596A1 - Acoustical method of determining parameters of crack brittle jump - Google Patents

Abstract

The invention relates to a technique for controlling the strength properties of materials, in particular, to methods for measuring the parameters of brittle shocks in a propagating crack. The purpose of the invention is to improve the accuracy by controlling the cracks located inside and the sample material being examined. Two electroacoustic transducers are placed on the sample on opposite sides of the crack tip on the line of its intended spread, load the sample until the crack starts, and each transmitter transmits acoustic emission signals corresponding to the start and stop points of the crack, and fix the time of their transfer to the transducers. According to the data obtained, the magnitude of the brittle crack in a crack, the duration of the shock, the velocity of the movement of the crack during the shock, and the length of the crack at the start time are determined. 2 Il. (A L O Eat 00 Ot)

Description

The invention relates to a technique for controlling the strength properties of materials, in particular, to methods for measuring the parameters of brittle shocks in a propagating crack, and can be applied in the development of new structural materials, in particular in the study of their cyclic and dynamic crack resistance.

The purpose of the invention is to enhance the functionality and increase accuracy by controlling the cracks located inside the material sample under investigation.

Figure 1 shows a sample of a material With a controlled crack and electroacoustic transducers; figure 2 - characteristic plots of signals from the outputs of the first and second electroacoustic transducers.

The proposed method consists in that sample 1 with a crack 2 is loaded with a load P prior to the start of the crack and a crack jump is recorded, so that with two electro-electrical transducers 3 and 4 located on the surface of sample 1 on opposite sides of the crack tip 2 the lines of its intended propagation receive acoustic emission signals emitted by a crack at the moments of start and stop. In this case, at the output of the first electroacoustic converter 3 (the first control channel), pulses 5 and 6 are received (FIG. 2), and at the output of the second electroacoustic converter (the second control channel) - pulses 7 and 8, respectively, in MO2 L WITH HELP

h,, timelines t,, t torye record meters.

The parameters and F, t, v and brittle crack jump are calculated by the formulas

 WITH,

U g

 )

- l / s;

 A2 / t;

 a - c-C2) / 2,

DE is the magnitude of the crack jump; - the duration of the crack jump;

the rate of movement of the crack during the shock; initial value (length) of the crack; the speed of sound in the sample material;

.

 t

one

H t, -, t. one

m

L is the distance between electroacoustic transducers.

The calculation of the desired parameters &, t. ,, V and can be carried out by NO,.

mediocre in the process of loading the sample using a measuring-calculating casting complex, for example, IVK-7

in which the values of c and L are preliminarily entered.

The proposed method ensures the operative control of the parameters of a brittle crack jump (including

cracks that have not penetrated to the surface), an increase in the measurement accuracy due to the elimination of uncertainty in determining the start and stop moments of the crack and the position uncertainty

the tip of the crack under static, cyclic and dynamic loads, the ability to automate measurements.

40

35

Claims (1)

Invention Formula An acoustic method for determining the parameters of a brittle crack in a crack, consisting in loading the sample before the crack starts and registering a crack in the crack, which differs in its functional capabilities and accuracy by controlling the cracks located inside the sample under investigation using two electroacoustic transducers located on the surface of the sample along different sides. from the top of the crack on the line of its intended spread. wounds, receive acoustic emission signals emitted by a crack at the moments of starting and stopping, register the time of their arrival at the electroacoustic transducers, according to which the parameters of a brittle crack jump are measured. i Editor A. Kozoriz Compiled by I. Ardasheva Tehred M. Khodanych 1423/42 Circulation 777 Subscription VNIIPI USSR State Committee for inventions and discoveries 413035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, Projecto st., 4 Channel 7 .five FIG. 2 Proofreader L. Pilipenko