SU1303902A2 - Method of testing materials for corrosion cracking - Google Patents

Abstract

The invention relates to corrosion tests and is an improvement on the basic invention in the author. St. No. 1241108. The purpose of the additional invention is to improve test accuracy by ensuring that all the initial load on the sample is fixed. A sample with a stress concentrator and a fatigue crack induced on its tips is stretched in a direction perpendicular to the crack propagation plane. The sample is kept under load until the creep process of the material at the crack tip ceases, which ensures further fixation of the entire load on the sample, and then fix the load on the sample by partially filling the cavity with TpemjiHH and the concentrator with a chemically inert hardening mass and holding the sample under load until it hardens. masses. Then, the external load is removed, and the sample is placed in the medium and, based on the change in the length of the crack, corrosion cracking is judged. (L with about with with about 14)

Description

ten

The invention relates to corrosion tests, namely to methods for testing materials for corrosion cracking, and is an improvement of the basic invention according to the author. St. No. 1241108.

The purpose of the invention is to improve the accuracy of the test by ensuring that all the initial load on the sample is fixed.

The method is implemented as follows.

In a sample with a concentrator and a fatigue crack induced from its top by a distance from the top 15

A hub smaller than the crack length is drilled, the axis of which lies in the plane of the crack and parallel to its front, and its diameter and distance from the axis to the crack tip are chosen in such a way as to eliminate the effect of the hole on the top of the hole: . The smaller the diameter of the hole, the closer it may be to the crack.

The sample is then loaded on a testing machine to the desired load level, which is kept constant, and the crack opening is monitored. An increase in crack opening under constant load indicates a creep process of the material at the tip of the crack. Upon completion of the creep process, as indicated by the stabilization of the crack opening level, the concentrator and the TpemjiHbi cavity from

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with the corrosion level stopped, it is removed from the corrosive environment and is loaded on a testing machine, fixing the load at which the opening of the crack faces begins to increase. By the magnitude of this load and length

the centralizer to the hole is filled

chemically inert hardening mass, corrosion crack 0, for example using epoxy resin without plasticizer. In the case of high mass flow or large crack opening, which corresponds to a large load level, in order to avoid mass falling into the hole when the concentrator is filled and the treptine cavity, the hole is plugged with a stopper, for example, rubber. Then, the sample is continued to be maintained under the load of complete solidification of the mass, if there is a plug in the hole, it is removed, and the sample is unloaded, registering the change to open the cracks. complete solidification of the mass between the banks of the crack, when the external load is removed, the banks of the crack are fixed in the open state -

known dependencies determine the current value of the stress intensity factor Kj or Kjscc

Example. Experienced hardened and tempered at 600 ° C steel 50X. Beam samples of rectangular cross section (length 80 mm height 18 mm, width 12 mm) with a previously created one-sided crack 9 mm long were used. A 1 mm diameter hole was made in the sample at a distance of 4 mm from the top of the traverse. Distilled water was used as a corrosive medium. The samples were loaded according to the three-point bend scheme up to the level of the intensity factor eg

Research Institute due to the wedge effect frozen

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neck mass, which de-energizes the fixation of the stress state at the top of cracks at the required level. The constancy of the level of opening of the requirement for removal of the load is evidence of the complete solidification of the mass and its ability to fix the shores of the victims in a position corresponding to the initially loaded sample. Since the mass is very tight to the walls of the crack, the load applied to the sample is fixed with high accuracy.

The sample is placed in a corrosive environment, which gets to the top both from the side surfaces of the sample and from the volume bounded by the aperture. The growth rate of treshlny and the threshold level Kjggp, respectively, by which the resistance of the material to corrosion cracking is evaluated, is determined by the length of the corrosion crack growth, the time of testing and the load perceived by the solidified mass at each specific growth stage and after the crack growth ceases. Dp determining the perceived hardened mass of the load at a particular stage of growth of a corrosion crack or after its growth stops

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with the corrosion level stopped, it is removed from the corrosive environment and is loaded on a testing machine, fixing the load at which the opening of the crack faces begins to increase. By the magnitude of this load and length

corrosion crack using

corrosion crack using

known dependencies determine the current value of the stress intensity factor Kj or Kjscc

Example. Experienced hardened and tempered at 600 ° C steel 50X. Beam samples of rectangular cross section (length 80 mm height 18 mm, width 12 mm) with a previously created one-sided crack 9 mm long were used. A 1 mm diameter hole was made in the sample at a distance of 4 mm from the top of the traverse. Distilled water was used as a corrosive medium. The samples were loaded according to the three-point bending scheme to the level of the intensity factor for example

zhenny KI 0,9.5 Kj ;. where K - short-term crack resistance of the material.

Samples before filling the crack cavity with hardening mass (for example, epoxy resin without plasticizer) were kept under constant load (0.95 Kj.) Until the creep process of the material in the vicinity of the crack tip was terminated and only then the load was filled, the hole and cracks filled with epoxy resin. At the same time, there was no shift of the banks of the fissure due to the removal of the load from the sample

served as proof of complete fixation - 5 corrosion cracking on the auto,

the initial stress state at the crack tip. The specimens were then exposed to a corrosive environment for 1000 hours and destroyed, fixing the load at which the crack faces began to shift. Analysis of the fracture surfaces of the samples revealed the presence of corrosion

Editor A.Dolinich

Compiled by E. Karpilovska

Tehred M. Khodanich Proofreader M, Pojo

Order 1300/43 Circulation 777 Subscription

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab, d, 4/5

Production and printing company, Uzhgorod, st. Design, 4.

th growing crack. From the measured crack length, taking into account its corrosive growth and the fixed load at which the crack faces began to shift during the reloading of the specimen that passed the corrosion cracking test, the K rscc value was determined, which for the batch of specimens varied within (0.7-0 , 75) Kje ,.

Claims (1)

Claim method Testing materials on 124P08, characterized in that, in order to test the accuracy of the test, before filling the cavity and the crack with the hardening mass, the specimen is held under load until the creep process stops in the crack crack.