SU1350482A1 - Method of determining normal and tangential stresses along preset direction at check points of object made of sheet anisotropic material - Google Patents

Abstract

The method relates to the technique of measuring stress and strain, and can be used to determine the normal to tangential stresses in a given direction at the control points of an object from an anisotropic sheet material. The purpose of the invention is to reduce the laboriousness of testing fiber materials in multipoint applications due to a reduction in the number of strain gages and electronic equipment channels used. This is achieved by carrying out preliminary studies of the position of the special axes, for which the deformations from the force acting perpendicular to the given direction are minimal, on specimens of the same material. On the sample and on the object, but in a given direction 1 relative to the direction of the 2 fibers of the upper marking line. A sample is applied at different angles of the strain gauge and carried out, c), w) - wives 1 special ocei i - two strain gauges in the directions of these axes and enima 1 calibration curves of the specimen under the action of the cuts and moment. According to the 1-right angle, the axial resistors 3 and 4 are glued to the object on the object, and they are shown taking into account the previously obtained calibration characteristics. The method saves up to 30% of the required number of strain gauges and measurement channels. 1 il. S (L, oo 01 o 4 00 y.

Description

The invention relates to a technique for measuring strain and stress, and is intended for use in experimental studies of the strength of machines of various kinds and other engineering objects.

The purpose of the invention is to reduce the laboriousness of testing fiber materials in multi-strap measurements by reducing the number of strain gages and electronic channels used.

The drawing shows a diagram of the installation of strain gauges on the object of study.

Line 1 markings (direction in which it is necessary to find tangential stresses normal and perpendicular to it) and direction 2 fibers of the upper layer of the material are specified in the diagram. Two strain gauges 3 and 4 are fixed at the object at angles a | Ji and i |) 2 to the direction specified by the marking.

The method is carried out as follows.

Before testing on a sample of the same material as the object, at different angles (with a shag 10-20 °) to the direction of the fibers of the upper layer, strain gauges are installed. An angle equal to the angle P between the marking line on the object and the direction of the fibers of the upper material layer is applied to the sample, as shown in the drawing. A force perpendicular to the marking line is then applied to the sample.

According to the indications of strain gages, when loading the sample, they approximate it by the least squares method or another method. They find the angular position of special axes for which the deformations from the applied load are minimal. Note the angles and i | 52 composed by special axes with the direction defined by the marking line. Next, two strain gauges with axes parallel to the special axis are installed on the sample. A force is applied to the sample in the direction of the marking line and a pair of forces creating shear stresses, and the coefficients included in the analytical expressions of the calibration characteristics are determined:

e, / ji, ax + fei2Tx ,,.;

B2 Y2 | SGH | -,

where 81 and 62 are the relative elongations measured by both strain gages;

Oj: and t: xy are the normal and tangential stresses during graduation;

k, fel2, k.2,

/ 222 - proportionality coefficients.

In the main experiment on the object, two strain gages 3 and 4 are installed at each control point at the detected angles ij5i and r | 2) to the marking line 1, they are tested and the desired normal and tangential stresses are determined using the calibration characteristics found: and 1 xy by the formulas

  2- & 2ki2)

ten

ZZiL iEl k ik: 2- / e12 / g2

where EI and 82 are relative elongations measured by strain gauges 3 and 4. Using the proposed method to determine normal and tangential stresses in a given direction at the control points of an object made from sheet anisotropic material reduces the number of strain gauges and associated sensors used on the object by 30%. using them channels of electronic equipment, which significantly facilitates measurements in places where the possibilities of placing strain gauges and supplying the cable network to them are limited according to the conditions of Yeni tests.

Claims (1)

Invention Formula 0 The method of determining normal and tangential stresses by a given direction in the control points of an object made of sheet anisotropic material, consisting in that the object is fixed at different angles to the resistance strain gages and, according to their indications, In order to reduce the operational capacity of fiber testing of materials with multipoint measurements by reducing the number of strain gauges and electronic channels used, the angle between the specified unwind on the object is determined By directing and directing the fibers of the upper layer of the material, a sample is made from the same material, a marking line is laid on it at this angle, the sample is glued at different angles to the strain-relief line, the sample is loaded with a force, perpendicular to the resistance line, according to strain gauges relative to the marking line, the angular positions of the special axes, for which the deformations from this force are minimal, are glued to the sample and to the object along the directions of the special axes by two strain gauges per Each point of the object and the sample are consistently applied to the sample in the direction of the marking line and a couple of forces creating shear stresses, the calibration characteristics of the strain gauges are measured in both cases of loading the sample and the resulting calibration characteristics are determined.