SU1753349A1 - Method of determining the metalwork sheet member bearing capacity - Google Patents

Abstract

The invention relates to a testing technique and can be used to determine the bearing capacity of sheet metal structures. The purpose of the invention is to improve the accuracy of testing. The test element with a thickness t is fixed in the grips of the loading device, the length of the fixed part of the element being assumed to be at least 5t, and the distance L between the axes of the grippers is preselected from the relation: 10t L 20t. After that, the middle part of the element is loaded according to the three-point bending scheme. At the same time, the fixation strength of the test element ensures the localization of the bending deformation zone within the test element, which improves the test accuracy. 2 Il.

Description

The invention relates to a testing technique, in particular, to methods for determining the carrying capacity of sheet metal structures.

There is a known method for determining the bearing capacity of elements of metal structures, according to which samples are cut out from a structure after a predetermined time of operation, loaded under conditions similar to operating conditions at a constant level of stress over time, withstand specimens until failure, and record the time to failure according to which the bearing capacity of structural elements is judged.

The disadvantage of this method is the high laboriousness, due to the necessity of unloading the structure and cutting samples, which leads to local destruction of the structural element.

The closest in technical essence and effect achieved to the proposed is a method of determining the bearing capacity of sheet metal structures, which fix the test element in the grips of the loading device and load the middle part of the element according to the three-point bending scheme.

The disadvantage of the known method is the impossibility of determining the stresses acting in the structure due to the displacement in the process of loading the grips, which reduces the accuracy of the test. .

The purpose of the invention is to improve the accuracy by ensuring the fixation of the test element.

This goal is achieved by the fact that in the method of determining the bearing capacity of sheet metal elements

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The measurements, on which the investigated element is fixed with a thickness t in the grips of the loading device and load the middle part of the element according to the three-point bending scheme, the length of each fixing section of the element is taken at least equal to 5t, and the distance L between the axes of the grips is chosen from the ratio

10t.

Fig. 1 shows a scheme for implementing the described method; figure 2 - section aa in figure 1.

The method is carried out as follows.

To determine the characteristics of the material of the structure in use and the level of the stresses acting therein without cutting the samples (non-destructive method for determining the yield strength of steel), areas with free overhangs of finishing elements (angles, channel bars, I-beams, crossheads, gussets, etc.) are selected. Along the free edge of the sheet 1 with a thickness t, two gripping elements 2 of the loading device are spaced from each other, defined by a ratio of 10t. A bending load in the form of a concentrated force is applied in the middle part 3 of sheet 1 between the gripping elements 2 also near the free edge of the sheet. The bending load is balanced on the gripping elements and the three-point bend test is carried out. The use of such a load application scheme allows only local deformation of the construction site, does not require the creation of rigid additional supports for testing. The assignment of the length of the gripping elements along the free edge of not less than 5 thicknesses of the sheet to be bent makes it possible to reliably pinch this sheet, as well as localize the deformations in the area between the grips.

The test after establishing the grips is carried out in the following sequence. With the help of a powering system, stepwise increases the amount of bending load, followed by unloading to zero level. At the same time, the sheet displacement is measured by the point of application of the bending load. The load corresponding to the violation of proportionality between the magnitude of the measured displacement with the load causing this displacement will correspond to the moment of material flow, and therefore the yield strength of the metal of the structure will be determined. Since the magnitude of the step of increasing the load may be small, the moment of arrival of fluidity can be recorded quite accurately. After the occurrence of the fluidity of the material, the test is stopped, and there will be no noticeable residual deformation of the element in the local part of the structure.

At the specified gripping sizes, the area of the sheet 1 is split within the grips 2, i.e. the possibility of rotation of section 3 in the grippers is excluded. The turn of the grippers themselves is excluded due to the high rigidity of the elements 2.

Thus, displacements in the vertical and horizontal planes of the test element are impossible, which improves the accuracy of the test.

Claims (1)

Claims The method of determining the carrying capacity of sheet metal structures, which fix the test element with thickness t in the grips of the loading device and load the middle part of the element according to the three-point bend scheme, characterized in that, in order to improve the accuracy by ensuring the fixation of the test element, each the fixed section of the element is taken at least equal to 5t; to the distance L between the axes of the grippers is chosen from the ratio 10t L 20t.