SU1455275A1 - Method of determining ultimate strength of material - Google Patents

Abstract

The invention relates to the testing of materials for strength under alternating loads and can be used to determine the endurance limit of a metal under test: a batch of samples. The purpose of the invention is to improve the accuracy of determining the noTekJ-cial physical limit of metal endurance and reduce the labor intensity when testing a batch of image-: csgv. This is achieved by processing the samples by cutting in a mode corresponding to the mutual compensation of the change in the surface structure from the force and temperature effects of the cutting process, stabilizing the annealing of one part of the sample lot. determining, at alternating loading, the endurance limit for one of the annealed samples, for which the temperature coefficient of electrical resistivity is equal to the ordered ™ state of the material, under axial load, its yield strength, and the yield strength for compression for one half is unannealed. specimens and yield strengths for the other half. The annealed sample is used to determine the proportionality coefficient between the yield strength and the ultimate strength, modulo the difference between the average yield strengths for stretching and compression of the unannealed specimens — the level of internal stresses that are added to the yield strength of the annealed sample. The potential physical limit of the metal carrying capacity is determined by multiplying this sum by the proportionality coefficient. The method improves accuracy by reducing the variation in test results and reduces labor intensity, since only one sample from a batch is tested for endurance. with y

Description

one

but - .

The invention relates to the strength testing of materials under alternating loads and can be used to determine the endurance limit of metallic structural materials when testing a batch of specimens.

The purpose of the invention is to increase the accuracy of determining the potential physical limit of the metal and reduce the labor intensity during the testing of a batch of samples, which is achieved by processing the Samples by cutting in a mode corresponding to mutual

compensating for changes in the surface structure from power and temperature of the impact of the cutting process, by stabilizing the annealing of one part of a batch of samples, determining, with alternating load, the endurance limit for one of the annealed samples, for which the temperature coefficient of electrical resistance is constant for the given material yield strength, and determining the yield strength for one half

not about the absence of internal stresses in the sample.

The selected sample is subjected to alternating loading of such amplitude that for a given number of loading cycles the endurance limit for this sample is reached but the sample itself does not break. In the event of failure, the alternating load is reduced and the test is repeated for another sample selected for the same sign that the temperature coefficient of electrical energy is equal.

The second part of the batch of specimens under compression раст 15 is the resistance of the constant for the data for the other half — when stretched.

The method is carried out as follows.

All samples from the metal under study are determined to determine its limit. 0 TLA of the tested batch is treated by wearing the endurance limit to the limit “

th material.

The specimen tested for alternating load is subjected to axial load of stretching or compression and

cutting mode, corresponding to the mutual compensation of changes in the surface structure from the force and temperature effects of the process of re ... 3

The required mode is selected as follows. In the sample, longitudinal oscillations are excited at the natural frequency and this frequency is measured. Then, machining is carried out.

at pre-selected speeds and depths of cut and tool feed. After processing again

Compression and compression for a given material and the difference between them, which characterizes the internal stresses in the material, excites longitudinal axes in the sample. The endurance limit is determined by a bath at its own frequency and changed by the previously determined proportionality coefficient of the yield strength for the annealed sample. internal stresses at 40

ryut this frequency. The processing and measurement of the sample frequency is repeated at different values of the cutting speed or depth of cut or feed. The required values of cutting speed, depth and feed are those for which the -t measured before and after processing frequencies differ by the smallest value in the performed set of experiments.

Then one part of the batch of samples is subjected to stabilizing annealing, the mode of which is selected according to the maximum change in the natural frequency of the sample after annealing, obtained at the lowest annealing temperature for the observed effect. From this batch by measuring the temperature coefficient of resistivity

A sample is taken, for which the value of the indicated coefficient corresponds to the ordered state of this material, which indicates that

that was the proportionality coefficient, and the modulus of the difference between the mean values of the limits. tensile and compression yield for unannealed specimens,

45 The use of the proposed method allows one to reduce the scatter of the measured characteristics of the samples, which indicates an increase in the accuracy of determination of the fineness, and

50 taken as a basis for comparing the endurance and fitness regimens; zts without internal stresses, which eliminates the influence of the spread of the values of internal stresses from

55 of the sample to the sample by the magnitude of the endurance limit, and focus on a more stable value of the potential physical limit of the metal endurance at average values

th material.

The specimen tested for alternating load is subjected to axial load of stretching or compression and

The yield strength characterizes the proportionality coefficient between the specified material characteristics.

25 Then one half of the other part of the batch of samples is subjected to a compressive load, and the other to a tensile load. The yield strengths of each sample are determined at these

30 loads. Calculate the average sign. the yield points at the age of

for the given material and the difference between them, which characterizes the internal stresses in the material, the endurance limit is determined by multiplying the proportionality factor of the yield point for an annealed sample without internal stresses by 0

that was the proportionality coefficient, and the modulus of the difference between the mean values of the limits. tensile and compression yield for unannealed specimens,

The use of the proposed method allows one to reduce the scatter of the measured characteristics of the samples, which indicates an increase in the accuracy of determination of the fineness of the specimen, and

0 taken as a basis for comparing the endurance and fitness regimens; zts without internal stresses, which eliminates the influence of the spread of the values of internal stresses from

5 of the sample to the sample by the magnitude of the endurance limit, and focus on a more stable value of the potential physical limit of the metal endurance with average values of internal

. stresses, not effect of the conditions of the cutting of individual samples from metal.

Using the resulting such. by means of a potential physical limit of the material, it allows one to more accurately predict the reliability of the structures made from the metal under study. The labor consumption of the method is reduced due to the fact that only one sample from the batch is subjected to endurance tests.

of

Claims (1)

Formula of the invention The method for determining the endurance limit of a material, which consists in subjecting a sample from the test material to alternating loads and determining its endurance limit, characterized in that, in order to improve the accuracy and reduce the labor intensity of testing a batch of samples, a batch of samples Editor I. Casard Compiled by N.Timoshenko Tehred M.DidykKorrektor L.Iilipenko Order 7450/51 Circulation 788 VNSHSHI of the State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 4/5, Moscow, Zh-35, Raushsk nab. 113035 0 five 0 5 machined in a mode corresponding to the mutual compensation of changes in the surface structure from the force and temperature effects of the cutting process; one part of the batch is subjected to stabilizing annealing; one of the annealed samples is subjected to alternating load, for which the temperature coefficient of electrical resistance corresponds to the ordered state of this material, and the endurance limit for this sample is subjected to the same sample axial load and its yield strength is determined, one by One half of the other part of the batch of samples is subjected to a compressive load, and the other half is subjected to a tensile load and their yield strength is determined, according to which the endurance strength of the material is judged by the yield strength and endurance of the annealed sample subjected to alternating load. Subscription