SU729485A1 - Method of evaluating the tendency of materials to brittle failure - Google Patents

Description

The invention relates to tests of materials for fracture toughness.

There is a method for assessing the tendency of materials to brittle fracture, which includes dynamically loading the specimen with a notch and using a pendulum and with a fatigue crack induced from the notch top of the notch to complete fracture (11.

However, this method does not allow to quantitatively determine the work spent on crack cracking under conditions of plane deformation, which leads to significant errors in evaluating the quality of the material.

In order to obtain a quantitative assessment of the tendency of materials to brittle fracture, the samples are subjected to repeated dynamic loading with a constant energy supply, the pendulum, after each impact, the fatigue crack is increased by an amount exceeding the size of the distortion zone until the growth of the pendulum bounce from the sample stops.

The essence of the method is as follows.

where is gig

And zap

A rebound

In the notched specimen, the initial fatigue crack is induced in length, after which the specimen is subjected to impact tests using a pendulum ram. After each impact, the value of the stored energy of the pendulum (constant value) and the value of the rebound are recorded. Then the fatigue crack is increased in the sample to a new length of the DC, which is

1.1-2.5 magnitude of the distortion zone. The process is repeated until the moment the pendulum bounces off of the sample, which corresponds to impact loading, leading to crack compression.

The tendency of the material to brittle fracture is judged by the ratio:

'- A> dap ~ Aqtck - fracture toughness, kgm / cm * - stored energy of the pendulum, kgm;

- energy returned to the pendulum during the rebound, kgm:

B is the thickness of the sample, cm;

W is the width of the sample, cm;

- critical crack length, cm The proposed method allows to quantitatively evaluate the work spent on crack cracking, and, thus, to most reliably judge the tendency of materials to brittle fracture under dynamic loading.

Claims (1)

This invention relates to the testing of material viscosity of fracture. There is a method for estimating the tendency of materials to brittle fracture, which includes the loading of a specimen with a notch and with a fatigue crack induced from the top of the notch by means of a tiller until complete destruction 1. However, this method does not allow to quantify the work expended on striking cracks under plane deformation conditions, which leads to significant errors in the assessment of the quality of the material. To obtain a quantitative assessment of the material brittleness to brittle fracture, the samples are subjected to multiple dynamic loading with a constant energy supply, the master, after each impact, increases the fatigue crack by an amount greater than the size of the distortion zone of the tandem sample. The essence of the method is as follows. In a notched specimen, an initial fatigue crack is applied in length, after which the specimen is subjected to impact tests with an erecting copra. After each blow, the turnips {erase the magnitude of the stored energy of the tambourine (constant value) and the magnitude of the rebound. Then, a fatigue crack is built into the formation by a certain length of Ali, amounting to 1.1-2.5 values of the distortion zone. The process is repeated until the moment of stopping the increment of the rebound of the specimen from the sample, which corresponds to the shock load, leading to a shrinkage of the cracking of the material bent for brittle fracture is judged by the ratio of: - Arpt B (- fracture rate, kgm / cm where GIC - energy stored, A - energy returned to the character during a rebound, kgm: 3 V - sample thickness, cm; W - sample width, cm; with a critical crack length, cm The proposed method allows to quantify the work expended on cracking , and, thus, most reliably judge the tendency of materials to brittle fracture under dynamic loading. Formula before complete destruction of the sample, characterized in that, in order to quantify the propensity of materials to brittle failure, the samples are subjected to multiple dynamic loading with constant the reserve energy of the tombstone, equal to 0.3-0.9 of the specific work of destruction, after each impact, increases the fatigue crack by the relation: G - Bty / - € c determines the propensity of materials to brittle, Mu fracture, where GH; - fracture viscosity, kgm / cm; AOHSK, respectively, stored energy and energy, returned to the staff during a rebound, kgm; B is the sample thickness, cm; W is the sample width, cm; fic - critical crack length, see Sources of information taken into account during the examination 1. Drozdovsky B. А., Fridman L. B. The effect of a crack on the mechanical properties of structural steel. M. Metallurgizdat, 1960, p. 202-211.