SU1359706A1 - Method of determining crack resistance of materials - Google Patents

Abstract

The invention relates to a testing technique and can be used to determine the crack resistance of a material. In order to improve the accuracy of the moment of crack opening under static loading of sample 1 with notch 2 and with fatigue crack 3 pointed from the top of notch 2, load diagram P-displacement parameter and displacement diagram f of the point of load - displacement v of the notch sides are recorded. As a displacement parameter, either f or V is recorded. The loading is carried out before the crack propagates and spreads. The magnitude of the displacement parameter corresponding to the moment of crack opening is determined by the v (f) diagram. For this, find the inflection point A of the dependence v (f) and take one of its coordinates v or f p as the transfer parameter. The value of the displacement parameter determines the value of i corresponding to the moment of the crack opening, which is rather accurate. What is more, the crack resistance of the material is determined. 2 Il. /// x /////// oo from CO o Cn v / xyx /// сrig.1

Description

ten

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1359706

The invention relates to a test technique and can be used to determine the crack resistance of a material.

The purpose of the invention is to improve the accuracy of determining the moment of cracking of a crack.

On .fig. 1 shows the load test circuit; in fig. 2 - combined load diagrams P - displacement f of the point of application of the load and displacement v of the crack faces - deflection of the sample.

The method is carried out as follows.

Sample 1 with notch 2 and with a fatigue crack 3 induced from the tip of notch 2 are statically loaded and the load pattern P is recorded - displacement parameter.

As a displacement parameter, the displacement f of the point of application of the load (Fig. 2) or the offset V of the notch sides are recorded. At the same time, the displacement f and the displacement V are also measured and the dependence V (t) between them is established. Measurement of f and v optics using strain gauges 4 and 5, loading is carried out before cracking and propagation of the crack. The moment of crack opening and the value of the displacement parameter corresponding to this moment are determined as follows. On the graphical dependence of v (f), the inflection point A is found and one of its coordinates is taken as the displacement parameter. Wherein

20

25

thirty

35

use either the coordinate or the coordinate v. If the P-f dependence was recorded during loading (Fig. 2), then the coordinate is used, and if the P-lg dependence is registered, then the y coordinate is used, -. According to the value of the displacement parameter, the value corresponding to the moment of crack initiation is determined, and with its consideration the crack resistance of the material is determined. The use of the graphical dependence v (f) and the selection of the inflection point on it allows you to

but determine the value of P,

cr

F O R m ula invention

The method for determining the crack resistance of materials by which a specimen with a notch and, with a crack induced from the top of the incision, is statically loaded, the load diagram is recorded, the displacement parameter is determined, the crack opening moment and the value corresponding to this moment are determined. The displacement parameter and with its consideration determine the crack resistance, which is due to the fact that, in order to improve the accuracy of determining the moment of cracking, the displacement f of the point of application of the load and the displacement v of the notch sides are measured, and the coordinate of the inflection point (f) is taken as the displacement parameter.

VNIIPI Order 6149 / A6 Circulation 7.76 Subscription Prod. Polygr. , g, Uzhgorod, st. Project, 4

Claims (2)

Claim 2θ A method for determining the fracture toughness of materials by which a specimen with a notch and a crack induced from a crack tip is statically loaded * crack resistance, due to the fact that, in order to increase the accuracy of determining the moment of crack cracking, simultaneously measure the displacements f of the point of application of the load and the displacement v of the edges of the notch a, a coordinate of the point of inflection 35 in the plot of v (f) is taken as the parameter movement. VNIIIPI Order 6149/46 ____ Circulation 7.76 _____ Subscription Custom polygr. ave, city of Uzhhorod, st. Project, 4