SU939996A1 - Method of checking material fatigue - Google Patents

Description

(54) METHOD OF CONTROL OF FATIGUE MATERIAL

one

The invention relates to the testing of materials and construction elements, in particular to methods for controlling material fatigue.

The closest to the proposed technical entity is a method of controlling the fatigue of a material, by which the intensity of specular reflection of the test area of the surface of the test object is measured by changing the intensity of the specular reflection of the material fatigue state fl

A disadvantage of the known method is its low accuracy, since it does not allow fixing fatigue cracks with a length of less than 0.2 mm and makes it impossible to monitor and estimate the accumulation of fatigue damage & ..

The purpose of the invention is to increase the accuracy of the control.

This goal is achieved by the fact that, simultaneously with the intensity of specular reflection, the intensity of diffuse reflection of the same surface area is also measured, measurements are made at wavelengths comparable to the size of the initial fatigue defects to be recorded and by the ratio of the intensities of specular and diffuse reflections judged fatigue material condition.

The drawing shows a diagram of the control of material fatigue.

The method is carried out as follows.

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Claims (1)

In a controlled area of the test object, a surface is prepared to measure its optical properties. In the process of loading the object, the intensity J of specular reflection and the intensity of diffuse reflection are measured. Measurements are made in the ultra-violet or close to it range of LENGTH waves of monochromatic rays coupled with heme, that when the dimensions of the microscopic irregularities of the reflecting surface are small compared to the wavelength of the incident light, there is a ghostly reflection. When the dimensions of asperities are commensurate with the wavelength or exceed it, then the reflection of light is diffuse. In the intermediate situation there is a mixed reflection of the rays, in which part of the incident radiation is reflected in a mirror, and part is in an diffuse manner. In this connection, in order to increase the number of points, the control is carried out on daty waves, which provide registration on the basis of minor shallow roughness in the form of extrusions, intrusions, block shifts, etc., associated with the accumulation of fatigue damage in the surface layers. To predict the residual workability of the material during its operation, first measure the intensity of the specular and diffuse reflection on the reference sample, and then compare their parameters with the reflection parameters of the test specimen. Since for the reference sample the diagrams were constructed: changes in intensity, on the number of loading cycles, it is possible to determine the number of loading cycles that the test sample sustained, and the number of loading cycles remaining before destruction, by the values of intensities. Measurements are made using a device containing a light source 1, connected to a stabilized power source 2, focusing systems including an optical unit 3 with a filter 4, and a recording system consisting of two valve photo cells 5 and microammeters 6. For increasing the system sensitivity registration, instead of valve photocells, photomultiplier tubes powered by high-voltage stabilized sources are used. 7. To automatically output the {3,) difference or O / LoIS ratio, use to 8 comparison of signals. The coefficients of specular and diffuse reflections using the proposed device are measured by the following 3CJM: on the next sample 9 at a certain angle f a focused or parallel beam of light with intensity 3 is directed. After reflection from the sample, the light enters the photo cells 5 located at an angle of% f and f × that convert light to signal1 into electrical. Micro-1 diameters 6 register the intensity of the reflected signal. By preliminarily measuring the intensity of the incident light, the coefficients of specular and diffuse reflections are calculated: li-,%:) n de jjK intensity, respectively, specular and di ({fuzzy components of the light reflected from the surface, intensity of light incident on the surface). either the difference (.) or the ratio f. .2l V With an increase in the number of fatigue loading cycles, the intensity of the specular component of the reflection 3j decreases and the intensity of the diffuse reflection U (j, increases. These changes are greater with smaller e initial roughness of the surface to cyclic loads. Based on the ratio of CT, and Discussing the fatigue state of the material. The proposed method allows us to predict the beginning of the destruction of machine parts in operation and to replace in time the parts that have run out of performance. in which the intensity of the specular reflection of the test surface area of the test object is measured, characterized in that, in order to increase the control accuracy, with the intensity of specular reflection is also measured intensity of the diffuse reflectance of the same surface area, measurements are made at wavelengths t commensurate with the size of initial fatigue defects to be registered, and sootnoscheshpo intensiviestey specular and diffuse reflections judged state of fatigue of the material. Source of information taken into account during the examination 1. L. M. Shkolnik. Crack growth rate and metal survivability. M., Metallurgists, 1973, p. 26 (prototype).