NEW CHARACTERISTICS OF METAL DEGRADATION IN THE COURSE OF OPERATION V.P. Shvets G.S. Pisarenko Institute for Problems of Strength National Academy of Sciences of Ukraine II Hungarian-Ukrainian Joint Conference on SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS Kyiv

Direct methods: – density of volume and surface defects – average defect spacing – average defect proximity – specific weight – other methods Indirect methods: – internal friction – electrical resistivity – acoustic characteristics – X-ray scattering at small angles – other methods II Hungarian-Ukrainian Joint Conference NEW CHARACTERISTICS OF METAL DEGRADATION IN THE COURSE OF OPERATION

The loosening strains are related to the parameters of changes in the chemical composition and to the coefficient of transverse deformation:  l = (1-2  ) , (1) where  is the current strain and  is the coefficient of transverse deformation. The deformation is accompanied by the growth of the defect of the modulus of normal elasticity. The experimental data obtained made it possible to establish that the parameter of loosening,  l, can be determined from the following formula:  l = (E – E )/ E, (2) where E and E are the initial and current values of the modulus of elasticity. II Hungarian-Ukrainian Joint Conference NEW CHARACTERISTICS OF METAL DEGRADATION IN THE COURSE OF OPERATION

The degree of scattering of the characteristics of mechanical properties was determined using the Weibull distribution parameter, which characterizes the degree of the material homogeneity and is calculated from the Gumbel formula:, (3) where parameter d n is determined from the number of measurements, is the value of hardness according to the ith measurement, and is the mean value of the hardness logarithm from the results of n measurements. Special-purpose investigations revealed that sufficiently stable magnitudes of the coefficient m are obtained at n = 30. II Hungarian-Ukrainian Joint Conference NEW CHARACTERISTICS OF METAL DEGRADATION IN THE COURSE OF OPERATION

II Hungarian-Ukrainian Joint Conference

NEW CHARACTERISTICS OF METAL DEGRADATION IN THE COURSE OF OPERATION

II Hungarian-Ukrainian Joint Conference NEW CHARACTERISTICS OF METAL DEGRADATION IN THE COURSE OF OPERATION

II Hungarian-Ukrainian Joint Conference NEW CHARACTERISTICS OF METAL DEGRADATION IN THE COURSE OF OPERATION

II Hungarian-Ukrainian Joint Conference NEW CHARACTERISTICS OF METAL DEGRADATION IN THE COURSE OF OPERATION

II Hungarian-Ukrainian Joint Conference

NEW CHARACTERISTICS OF METAL DEGRADATION IN THE COURSE OF OPERATION II Hungarian-Ukrainian Joint Conference

NEW CHARACTERISTICS OF METAL DEGRADATION IN THE COURSE OF OPERATION II Hungarian-Ukrainian Joint Conference

Conclusions: 1. Presently, there are a large number of nondestructive methods for monitoring the metal state in operation. They include the techniques developed at the G.S. Pisarenko Institute for Problems of Strength, National Ac. Sci. of Ukraine. The experience of applying these methods to practical problems suggests that each of them has its own advantages and disadvantages, which narrows their applicability range in terms of the type of materials and conditions of operation. 2. We propose a new, rather simple, but efficient nondestructive examination method wherein the scattering of the hardness values is employed as a parameter characterizing the material state. 3. Calculations by this method show that the Weibull homogeneity coefficient, which is determined by a technique developed by Gumbell, can be used as a parameter of scattering of the hardness values. 4. The method was used to assess the kinetics of damage accumulation in the material of operated structures, in particular we studied the metal state in railroad switches at different stages of their life. 5. We propose a new characteristic of the amount of damage in a metal, convenient for analyzing its state, which allows monitoring the residual life of operated structures.