SU1462124A1 - Method of measuring residual stresses in rod specimens made from composite materials - Google Patents

Abstract

The invention relates to a measuring technique and can be used in laboratory studies of core samples of composite materials. The aim of the invention is to improve the performance of residual stress measurements. The method for determining residual stresses is that the core sample of composite material under investigation is fixed in the oscillatory system of a torsion instrument, oscillate independently and measure the amplitude of the dependence of internal friction (AFT) at frequencies of 1 Hz and relative deformations. 510 -5 l6 3. On the amplitude dependence, the maximum of the internal friction is observed, the position of which shifts towards lower values of the relative deformations with increasing stresses. Using this pattern, the residual stresses are determined by the position of the AFT mechanism and the calibration characteristics. 3 il. (L

Description

one- .

The invention relates to a measurement technique and can be used in laboratory studies of core samples of composite materials.

The purpose of the invention is to increase the productivity of residual stress measurements.

The method of determining the residual stresses in the core samples is that the core sample under investigation, fixed in the oscillating system of a spinning magnet, excites natural oscillations

and measuring the amplitude dependence of the internal friction (AFT) at frequencies of 1/1 Hz and relative deformations of 5 -10 -5 10-.

For composite materials, the maximum of internal friction is observed on the amplitude dependence, the position of which shifts towards lower values of the relative deformation with increasing stresses. Using this pattern in the position of the maximum of the AZVT of the composite under study and graded characteristic -. stress - relative strain

qi is used to determine the residual for example. The calibration characteristic is set based on the aggregate of the ASAT data for a number of specified voltages.

As a measure of loss, the value of internal friction is used, defined by the expression:

-I In L, / Ats4., -

where A is the amplitude of 1-gb and N-ro

hesitation; N is the number of oscillations.

FIG. 1 shows the dependence of the internal friction on the amplitude of the relative deformation for a given composite; in fig. 2 - graduation characteristic 6 in FIG. 3 - AZVT for samples of the studied composite with eliminated residual stresses.

Having determined the curve in FIG. 1 deformation value V, corresponding to the maximum amplitude dependence of the internal friction, according to the calibration characteristic for this material

1462124

(Fig. 2). It was obtained on the basis of the ASTT (Fig. 3) for the samples of the composite under investigation with initially eliminated residual stresses at various tensile loads.

Claims (1)

Formula invented and five five The method of determining residual stresses in rod samples of composite materials in, consisting in the excitation of the own torsional vibrations of the sample and establishing the magnitude of the residual stresses along the calibration curve, so that with the aim of increasing productivity During the excitation process, the amplitude dependence of the internal friction of the sample at a frequency of 1 Hz in the strain interval is measured. The relative deformation, corresponding to the maximum of internal friction, is found and w last determined magnitude of residual stress. 50. 10 10 Fig.T 6. MT and 50 W 30 20 Yu O 5 10 15 20 Figure 2. 50 /ten . ten -h ten -3