SU1670493A1 - Method of testing thin-wall structure members for stability - Google Patents

Abstract

The invention relates to a testing technique and can be used to test the stability of thin-walled structures. The purpose of the invention is to improve accuracy. The structural element in the form of a rod or shell is loaded with a static compressive load, the load value and radius of curvature are measured, the curve of the radius of curvature versus load is plotted, and the critical load value is determined by the intersection of the extended linear dependence with the load axis. Measuring the radius of curvature as a deformation characteristic and the linear nature of the dependence as the curve approaches the axis of the load, the critical load is determined by the intersection point of the dependence with the axis of the loads, which improves the accuracy of the test. 2 Il.

Description

The invention relates to a testing technique, and specifically to methods for testing the stability of thin-walled structures.

The purpose of the invention is to improve accuracy.

FIG. 1 shows the dependence of compressive loads on the radius of curvature when testing for the stability of a glass-plastic rod; in fig. 2 shows the dependence of the external pressure on the radius of curvature for a fiberglass cylindrical shell.

The method is carried out as follows.

The structural element in the form of a rod or shell is subjected to static compressive loading. Then, the load value and the radius of curvature are measured, and a curve of the dependence of the radius of curvature on

loads and the intersection of the continued linear relationship with the axis of the loads determine the magnitude of the critical load.

Example. The critical load of the fiberglass rod under the action of axial compressive forces, as well as the critical load of the fiberglass cylindrical shell under the action of external pressure were determined.

The radius of curvature of a fiberglass rod 168 mm long with a width of 15 mm and a thickness of 2.6 mm was measured in the middle part. One end of the rod was rigidly clamped, the second was connected to the piston. A static uniformly distributed load was applied to the piston using pressure through a rubber casing.

FIG. 1 shows the dependence of compressive loads on the radius of curvature. The ordinate axis is compressed

Vi o

4 YO

load P-10 (N), on the abscissa axis radius R of curvature (m). Racing marked the results of measurements. The curve, starting with some values, goes to the straight line, which crosses the axis of loads. The point of intersection of the direct with the load axis is the critical load value of the P-600 N. The rod loses stability under the load of 594 N. The critical load determination error is about 1%.

A similar dependence of the external pressure on the radius of curvature was obtained for a fiberglass cylindrical shell (Fig. 2).

The shell with a diameter of 120 mm and a length of 300 mm is made by winding seven layers of fiberglass with a thickness of 0.1 mm. The radius of curvature is measured by the arc coordinate in the middle part of the shell. The load was carried out by pumping air from the shell. The shell loses stability under load equal to 5.8 105 Pa. The critical load value obtained by the claimed method is 5.93 105 Pa. In this case, the error in determining the critical load is less than 3%.

The curves in FIG. 1 and 2 show that the dependences obtained when approaching the axis of loads have a pronounced linear character.

Thus, measuring as a deformation characteristic the radius of curvature of the tested structural element and the linear nature of the dependence of the radius of curvature on the load as the curve approaches the axis of the load when building this dependence allows you to determine by the intersection of the extended linear dependence with the axis of the load

critical load value, which provides improved test accuracy.

Claims (1)

Invention Formula The method of testing the stability of the elements of thin-walled structures, according to which the sample is loaded with a static compressive load, the load and the deformation characteristic are measured the curve of the load on the deformation characteristic and on the intensity of the growth of the characteristic determine the magnitude of the critical load, characterized in that, in order to increase accuracy, as the deformation characteristic of the sample, the radius of curvature is measured, and the critical load is determined by the point of intersection with the load axis of the linear dependence of the load on radius of curvature. R , -2 P- 10 6 (Hcf} 6 5 4 J 2 one R (M) fig 2