RU2217742C2 - Method of prediction of residual life of metal of mining equipment - Google Patents

Abstract

FIELD: mining industry. SUBSTANCE: technique establishing residual life of metal structures, method of prediction of residual life of metal of mining equipment by nondestructive testing includes entry of radiation into tested medium and measurement of amplitude-frequency spectrum with its subsequent narrow-band filtration for isolation and analysis of components of emission spectrum. Reference cyclic crack resistance and degraded cyclic crack resistance are found by physical and mechanical properties of initial metal as well as longitudinal speed of sound corresponding to them. Intermediate crack resistance and longitudinal speed of sound corresponding to it are also computed at moment of measurement of shift of frequency resonance in six ranges. Predicted value of residual life is calculated by longitudinal speed of sound. Relations between three friction angles in structural no uniformities of natural roughness reflecting corresponding relaxation frequencies at moment of measurement of shift of frequency resonance can identify most pronounced causes of degradation of metal. Measurements are taken with spacing of 0.1 m. EFFECT: increased accuracy, authenticity and speed of evaluation of predicted value of residual life in process of nondestructive testing. 2 cl

Description

 The invention relates to the field of non-destructive testing and can be used in quality control, changes in structural-phase states and physico-mechanical parameters of materials and structural elements. However, the invention is mainly intended to predict the residual resource of a metal, such as mining equipment, based on the determination of not only its qualitative and quantitative composition, but also its mechanical properties.

 A known method for predicting the residual resource of metal of mining equipment by non-destructive testing of the acoustical emission radiation response, including introducing radiation into the test medium and taking an amplitude-frequency spectrum with its subsequent narrow-band filtering to isolate and analyze the maximum dynamic range amplitudes in octaves (RF patent 2141654, G 01 N 29 / 14, Bull. 32, 1999). The disadvantage of this method is the low noise immunity of the amplitudes of the dynamic range.

 Closest to the invention is a method for predicting the residual resource of metal of mining equipment by non-destructive testing of the response of acoustic emission radiation, including inputting radiation into the test medium and taking an amplitude-frequency spectrum followed by narrow-band filtering to isolate and analyze from the spectrum components the emission range of the shift-separation and displacement frequencies in resonance (RF patent 2112235, G 01 N 29/14, Bull. 15, 1998). The disadvantage of this method is, for example, the blurring of the amplitude and frequency of degradation of shear-separation, which significantly reduces the accuracy of prediction of the residual life. In other words, despite the high technical level of the mentioned method, its accuracy and reliability for predicting the residual life are insufficient, since for this it is necessary to know the boundaries of all ranges of the frequency spectrum of acoustic emission radiation to establish the magnitude of the frequency resonance shift in them.

 The objective of the invention is to improve the accuracy, reliability and speed of assessment of the forecast of residual life with non-destructive testing.

где ∂n $\genfrac{}{}{0ex}{}{\text{*}}{\text{i}}$ - ширина зоны пластического стеснения при плоском напряженном состоянии на момент замера;
ρ_оп - объемная плотность металла;
f_сд-о.i - резонансная частота сдвига-отрыва диапазона 1,901-2,674 кГц, определяемая на момент замера Т_i;
l_пн-i - периметр поверхностного натяжения при плоской деформации;
Т^* _э.90-i - вектор интенсивности тензора разрушающего напряжения из эллипсоида интенсивности напряжений, отражающий совокупность вектора шарового тензора гидростатического давления и вектора девиатора напряжений на момент замера Т_i;
∂V $\genfrac{}{}{0ex}{}{\text{*}}{\text{i}}$ - коэффициент скорости деформации на момент замера Т_i, а прогноз остаточного ресурса определяют из соотношения
ΔT_п=T_i(K_1c-f.i-K_1c-f.д)/(K_1c-f.э-K_1c-f.i). (2)
При этом устанавливают соотношения между тремя углами трения структурных неоднородностей естественных шероховатостей: ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{мр}}$ , ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{мс}}$ и ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{мв}}$ , отражающих соответствующие релаксационные частоты: f_мр, f_мс и f_мв на момент замера смещения частотных резонансов в Т_i, определяя наиболее выраженные причины деградации металла, а именно:
- при ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{мр-i}}$ >ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{мс-i}}$ >ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{мв-i}}$ - из-за жесткого нагружения;
- при ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{мр-i}}$ <ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{мс-i}}$ <ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{мв-i}}$ - из-за малоцикловой усталости;
- при прочих соотношениях: из-за коррозии под нагрузкой.This problem is solved by predicting the residual resource of the metal of mining equipment by non-destructive testing of the forced response of acoustic emission radiation, including introducing radiation into the test medium and taking the amplitude-frequency spectrum followed by narrow-band filtering to isolate and analyze the components of the emission spectrum, in which, according to the invention, according to the physical the mechanical properties of the source metal determine the reference cyclic crack resistance K _1s-f.e , degraded cyclic crack resistance K _1c-f.d including the corresponding longitudinal sound velocities, and at the time T _{i of} measuring the frequency resonance bias in six ranges f _mv = 4.205-4.513 Hz, f _ms = 17.846-50.200 Hz, f _mr = 81.953- 433.890 Hz, f _sd-o = 1.901-2.674 kHz, f _narrow-sz = 19.069-62.745 kHz and f _microwave-m = 1.532-1.978 GHz calculate the intermediate cyclic crack resistance K _lc-fi and the corresponding longitudinal sound speed C ^* _Li , which is determined from the relation

where ∂n $\genfrac{}{}{0ex}{}{\text{*}}{\text{i}}$ - the width of the zone of plastic constraint in a plane stress state at the time of measurement;
ρ _op - bulk density of the metal;
f _sd-o.i is the resonance shift-separation frequency of the range 1.901-2.674 kHz, determined at the time of measurement T _i ;
l _Mon-i - the perimeter of surface tension during plane deformation;
T ^* _e.90-i is the intensity vector of the _tensile stress tensor from the stress intensity ellipsoid, which reflects the combination of the hydrostatic pressure ball tensor vector and the stress deviator vector at the time of measurement T _i ;
∂V $\genfrac{}{}{0ex}{}{\text{*}}{\text{i}}$ - the coefficient of strain rate at the time of measurement T _i , and the forecast of residual life is determined from the ratio
ΔT _p = T _i (K _1c-fi -K _1c-f.d ) / (K _1c-f.e -K _1c-fi ). (2)
At the same time, the relations between the three friction angles of structural inhomogeneities of natural roughnesses are established: ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{mr}}$ , ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{ms}}$ and ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{mv}}$ reflecting the corresponding relaxation frequencies: f _Mr , f _ms and f _mV at the time of measuring the shift of the frequency resonances in T _i , determining the most pronounced causes of metal degradation, namely:
- at ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{mr-i}}$ > ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{ms-i}}$ > ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{mv-i}}$ - due to hard loading;
- at ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{mr-i}}$ <ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{ms-i}}$ <ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{mv-i}}$ - due to low-cycle fatigue;
- other ratios: due to corrosion under load.

 Measurements according to the proposed method are made in increments of 0.1 m.

 The essence of the proposed method is as follows.

Based on the certificate of quality of the metal, take reference values of its physical and mechanical properties:
σ _B - temporary tensile strength;
σ _T - yield strength;
δ _beats - elongation;
Ψ _su - relative narrowing;
E _d - the modulus of dynamic elasticity;
P _op - bulk density.

Using the well-known relations, all other standard physical and mechanical properties are determined, including the spectral density of the released energy at the mouth of the fatigue crack: I _1c-f , crack resistance K _1c-f , and also the six most informative resonant frequencies: f _mv in the range: 4.205- 4.513 Hz; f _ms in the range of 17.846-50.2 Hz; f _Mr in the range of 81.953-433.89 Hz; f _cd-0 in the range of 1.901-7.674 kHz; f _narrow-ss in the range 19.069-62.745 kHz; and f _{microwave m} in the range 1.53275-1.97882 GHz. Using the relations of G.M. Avchyan to determine the transverse speed of sound C ^* _S-e = 0.637 • C ^* _L-e due to the fact that at the time of complete degradation of the metal, the longitudinal reference speed of sound C ^* _L-e becomes equal to the transverse speed of sound, that is, C ^* _{L -d} = C ^* _S-e , the same physical and mechanical properties are determined only for completely degraded metal. In this case, it is taken into account that the angle of friction of structural inhomogeneities of natural roughness ρ ^* is 45 ^o when a quasi-brittle separated flow arises according to A. Nadoi.

 Measurements of the values of the shift of the resonant frequencies in the six most informative frequency ranges of the radiation of the acoustic emission response allow, without laborious processes requiring special surface preparation for synchronous measurements of the actual longitudinal speed of sound, to determine the indicated speed from relation (1).

When predicting the residual resource of metal in mining equipment by non-destructive testing of the response of acoustic emission radiation, the values of the shift of the resonant frequencies to lower resonant frequencies at relatively maximum amplitudes are analyzed. Namely: in the range of microwave oscillations modulated by the relaxation slip frequency of edge dislocations f _mp , which determine the rigidity of the load; in the ultrasonic range of oscillations modulated by the relaxation slip frequency of screw dislocations f _ms , which determines the corrosion damage; as well as in the range of accumulation of fatigue deformations (i.e., shear-separation frequencies modulated by the relaxation infrared frequency f _mv and determining a quasi-brittle vortex flow during low-cycle fatigue.

The shift of the resonances in the indicated pairs to their degradation levels at the time of the measurements is determined by the packages of cyclic effects on the metal of the mining equipment. Assuming the repetition of similar packages of cyclic effects, based on the reference and degraded physical and mechanical parameters, the aforementioned forecast of the residual life (ΔT _p ) is made using the above formula at each scanning point, since from relation (1) simultaneously when scanning in 0.1 m increments the value of the actual longitudinal sound velocity at a given point of the metal structure is determined at the time of measuring the response of the acoustic emission spectrum of radiation.

 When predicting the residual life, the intensity of the shift of the resonant frequencies between the indicated pairs through the corresponding friction angles of structural inhomogeneities of the natural roughness is also analyzed, which allows not only to predict the residual life, but also to determine the most pronounced cause of metal degradation: hard loading, corrosion under load, or low-cycle fatigue .

For clarification, a table of frequency relationships in six informative ranges with the main calculated coefficients, including the angle (ρ ^* ) of friction of structural inhomogeneities of natural roughnesses, is attached.

 The method allows to obtain the correct forecast of the residual resource for all elements of metal structures.

Claims (3)

1. A method for predicting the residual resource of metal of mining equipment by non-destructive testing of the response of acoustic emission radiation, including inputting radiation into the test medium and taking an amplitude-frequency spectrum with subsequent narrow-band filtering to isolate and analyze the components of the emission spectrum, characterized in that by the physicomechanical properties of the source metal determine the reference cyclic crack resistance To _1c-f.e. degraded cyclic crack resistance K _1c-f.d. , including the corresponding longitudinal speed of sound, and at the time T _i measuring the offset of the frequency resonances in six ranges f _mv = 4.205-4.513 Hz; f _ms = 17.846-50.2 Hz; f = _mr 81,953-433,890 Hz; f _sd-o = 1.901-2.674 kHz; f _narrow-sz = 19.069-62.745 kHz and f _{microwave m} = 1.532-1.978 GHz and calculate the intermediate cyclic crack resistance K _1c-fi and the corresponding longitudinal sound speed C $\genfrac{}{}{0ex}{}{\text{*}}{\text{Li}}$ which is determined from the relationship C $\genfrac{}{}{0ex}{}{\text{*}}{\text{Li}}$ = [143,192K $\genfrac{}{}{0ex}{}{\text{2}}{\text{1c-fi ∂}}$ n $\genfrac{}{}{0ex}{}{\text{*}}{\text{i}}$ / ρ $\genfrac{}{}{0ex}{}{\text{2}}{\text{on ·}}$ f _{cd-oi ·} l _{nn-i ·} T $\genfrac{}{}{0ex}{}{\text{*}}{\text{S.90-i}}$ TO $\genfrac{}{}{0ex}{}{\text{*}}{\text{mm-i}}$ V $\genfrac{}{}{0ex}{}{\text{*}}{\text{i}}$ ] ^1/2 (m / s), where ∂n $\genfrac{}{}{0ex}{}{\text{*}}{\text{i}}$ - the width of the zone of plastic constraint in a plane stress state at the time of measurement; ρ _on is the bulk density of the metal; f _cd-oi is the resonance shift-separation frequency of the range 1,901-2,674 kHz, determined at the time of measurement T; l _nn-i is the perimeter of surface tension during plane deformation; T $\genfrac{}{}{0ex}{}{\text{*}}{\text{z.90-i}}$ - the intensity vector of the tensile stress tensor from the stress intensity ellipsoid, reflecting the combination of the vector of the ball hydrostatic pressure tensor and the stress deviator vector at the time of measurement T _i ; ∂V $\genfrac{}{}{0ex}{}{\text{*}}{\text{i}}$ - the coefficient of strain rate at the time of measurement T _i , and the forecast of residual life is determined from the ratio _Δ T _n = T _i (K _1c-fi -K _1c-f.d ) / (K _1c-f.e -K _1c-fi ). 2. The method according to claim 1, characterized in that according to the ratio between the three friction angles of the structural inhomogeneities of the natural roughness ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{mr}}$ , ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{ms}}$ , ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{mv}}$ , reflecting the corresponding relaxation frequencies f _mp , f _ms , f _mv at the time T _{i of} measuring the frequency resonance bias, establish the most pronounced causes of metal degradation, namely: at ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{mr-i}}$ > ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{ms-i}}$ > ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{mv-i}}$ due to hard loading, - at ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{mr-i}}$ <ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{ms-i}}$ <ρ $\genfrac{}{}{0ex}{}{\text{*}}{\text{mv-i}}$ due to low-cycle fatigue, other ratios due to corrosion under load. 3. The method according to claim 1, characterized in that the measurements are made in increments of 0.1 m

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