SU1281976A1 - Method of determining cyclic longetivity of welded joints - Google Patents

Abstract

The invention relates to a testing technique and can be used in determining the cyclic durability of welded joints. In order to determine the accuracy of durability, the welded joint envelopes are loaded in the mode of repeated static action before the residual stresses stabilize, the residual stresses are measured and the constant components b and the variable (5d components of the residual stresses after their stabilization are measured. Then the small-sized stresses are cyclically loaded specimens made from the welded zone, or from the heat-affected zone, or from the base material with –h l voltage xb din ,,, b, c Q gdeb „, for components corresponding to the nominal for design stress. Small-sized samples are loaded until failure and, according to their durability, the cyclic durability of the welded joint is judged.

Description

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The invention relates to the study of the strength of materials and structures, and in particular to methods for determining the cyclic durability of welded joints.

The aim of the invention is to reduce material and labor intensity and improve the accuracy of determining the cyclic durability of a welded joint by stabilizing the properties of the joint when testing small-sized samples.

The method is carried out as follows.

A welded joint sample is subjected to several re-static loads at given levels of external load until the residual stresses at each load level stabilize. Measure 20 (the shape of residual stresses, for example, by an ultrasonic non-destructive method. A constant is determined (5 and G are the components of the cycle stresses in the area under investigation after they are stabilized at each level of loading. At the same time, they are loaded first with a smaller load , the transition then to the next higher level.

Then, to determine the cyclic durability of the welded joint at nominal design stress, compact specimens made from the material of the heat-affected zone or from the base metal subjected to thermal cycling according to the welding mode of the joint are loaded cyclically until failure. Cyclic loading is carried out under stress

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The cyclic durability of a welded joint is judged by the number of cycles before the destruction of small-sized samples.

Example. Test butt weld of steel 20K with a sheet thickness of 36 mm.

Characteristics of the base material: yield strength 6f 28 MPa, tensile strength Gy, 430 MPa, elongation at break S 34.1%, narrowing at break (f 53.7.

The size of the butt joint section is 500-36 mm. Nominal eg G

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Verbal notion and measurement of residuals and times (2Gq

Well X 10 lychees eg max after

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For a long time, taking into account the registration of welding seams of the infl uence of ni5 ni nical scars into the bilge lining of the metallic image of the metal

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206 MPa with the cycle asymmetry factor R 0.

The weld sample is exposed to 3 cycles of design load of 206 MPa. Using a non-destructive ultrasound monitor. L and low-base strain gauges measure stable residual stresses, 64 MPa and the magnitude of alternating voltages (2Gq 267 MPa). From them, the values of the constant and variable components of the cycle are determined: (3,198 MPa,

134 MPa. . .

Then a small-sized sample of the base material with a cross section of 10 x X 10 mm is subjected to cyclic loads until destruction at cycle voltages (R, n 64 MPa and max MPa. The sample is destroyed after 0.676-10 cycles.

The results of cyclic tests of a large-size welded butt specimen (cross-section 500.36 mm) on an MP-800 machine show its durability of 0, cycles, which is close to the results of using a small-sized specimen.

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Claims (1)

Invention Formula G five 0 The method of determining the cyclic durability of welded joints, according to which residual stresses are measured in a joint sample and the durability of a welded joint is determined taking into account, in order to reduce material and labor intensity and increase accuracy by stabilizing the properties of the joint when testing small-sized samples, the residual stresses are measured after static loading of the sample of the compound at various increasing levels of external load, a constant is determined (j and a variable (jg c after their stabilization during several re-static loads at each load level, the stress cycles that remain are loaded cyclically until destruction of small-sized specimens made of the material of the near-weld zone or of the base metal subjected to thermal cycling under the joint groom's 0 five  (Jm - (a and b Max  sg m 312819764 4b and by the number of cycles to section about the cyclic durability of the weld of small-sized samples of a large compound.