RU2552601C2 - Part state estimation method - Google Patents

Abstract

FIELD: instrumentation.

SUBSTANCE: invention is used for estimation of technical state of details by means of X-ray diffraction inspection. The essence of the invention consists in making of X-ray diffraction image of a detail using which the residual compression stresses are determined, the controlling criterion is identified and compared with the limit value, and at the low-cyclic fatigue for the detail with n stress concentrators as a controlling criterion the average value of the stressed state parameter is used, then the average value of the stressed state parameter of the detail with n stress concentrators is compared with minimum and maximum limit values, the detail is returned into service if the average value of the stressed state parameter of the detail with n stress concentrators is greater than the maximum limit value, or the detail is withdrawn from service if the average value of the stressed state parameter is less than the minimum limit value, because the detail is in a limit state at the stage of formation of defect, or the detail is sent for repair in case the average value of the stressed state parameter of the detail is between the minimum and maximum limit values or is close to these values, in other words, if the detail is in a "pre-defective" state.

EFFECT: possibility of estimation of technical state of details in tress concentrators or on surfaces close to stress concentrators located in the plane along the direction of distribution of supposed defect inside metal, and also improvement of accuracy of the obtained results for direct stress concentrators.

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Description

The invention relates to non-destructive methods of X-ray diffraction control and can be used to assess the technical condition of parts of aviation equipment, for example, blades, gears, disks, with low-cycle fatigue using X-ray diffraction analysis both at the stage of manufacturing the part and in the process of repairing it.

A known theoretical method for determining the concentration coefficient of stresses on the details of gas turbine engines (GTE), which is understood as the ratio of the maximum radial voltage to the circumferential voltage (G.S. Skubachevsky. "Aircraft gas turbine engines. Design and calculation of parts", M., Engineering, 1981. , 550 p., P. 211).

The disadvantage of this method is that the method is approximate, not taking into account the physical state of the material of the surface of the part, and the data obtained by this method require verification.

A known method for determining the service life of a metal is that the method of x-ray diffraction analysis determines the value of the structurally sensitive parameter, which is used as the width of the x-ray line in the initial and post-deformation state, determine the deformation-strength characteristics of the metal, namely, the dependence of the true stresses and width x-ray line from the degree of relative residual deformation, and compare the deformation-strength characteristics with allowable values, thereby determining the performance of the metal (RU 2261436 from 06/28/2004, IPC G01N 23/00, G01N 33/20, publ. 09/27/2005, Bull. No. 27).

The disadvantage of this method is that the method allows to determine the service life of the part only provided that the measurement results in the initial state are known, and in order to obtain objective values of the X-ray line width, it is necessary to use the same X-ray modes and apply reference samples.

Closest to the claimed one is a method for assessing the technical condition of parts having stress concentrators, including taking an x-ray from the part, which determines the residual compressive stresses, determining the control criterion and comparing it with the limit value (US 5625664 from 04.29.1997, IPC G01N 23/20 )

The disadvantage of this method is that the method provides an assessment of the technical condition only in the immediate area of the stress concentrator, while the use of this method for metal parts is limited due to the fact that the deformation is non-linear in the areas of stress concentration. There is also the difficulty of applying the method to parts of complex construction, where stress concentrators are located in a remote place.

The technical result, which the method aims to achieve, is to evaluate the technical condition of parts in stress concentrators or on surfaces close to stress concentrators located in a plane along the direction of propagation of the alleged defect deep into the metal at any stage, both manufacturing and repair of the part, and also increasing the accuracy of the results obtained for direct stress concentrators, where the deformation does not change according to a linear law.

The technical result is achieved by the fact that in the method for assessing the technical condition of parts having stress concentrators, including taking an X-ray from the part, which determines the residual compressive stresses, determining the control criterion and comparing it with the limiting value, new is that with low-cycle fatigue for the part with n number of stress concentrators, the average value of the stress state parameter is used as a control criterion $$\overline{K_n^{\sigma }}=\frac{{\displaystyle \sum _{i=\mathrm{one}}^n\left(\raisebox{1ex}{${\sigma }_s^{\text{'}\text{'}}$}\!\left/ \!\raisebox{-1ex}{${\sigma }_s^{\text{'}\text{'}\text{'}\text{'}}$}\right.\right)}}{n}$$

- остаточные напряжения сжатия в точке с большей интенсивностью изменения остаточных напряжений i-го концентратора напряжений;Where $${\sigma }_s^{\text{'}\text{'}}$$

- residual compressive stresses at a point with a greater intensity of change in the residual stresses of the i-th stress concentrator;

- остаточные напряжения сжатия в точке с меньшей интенсивностью изменения остаточных напряжений сжатия i-го концентратора напряжений, далее среднее значение параметра напряженного состояния $$\overline{K_n^{\sigma }}$$

детали с n количеством концентраторов напряжений сравнивают с минимальным $${\left[K_n^{\sigma }\right]}_{\min }$$

и максимальным $${\left[\overline{K_n^{\sigma }}\right]}_{\max }$$

предельными значениями, деталь возвращают в эксплуатацию, если среднее значение параметра напряженного состояния $$\overline{K_n^{\sigma }}$$

детали с n количеством концентраторов напряжений больше максимального предельного значения $${\overline{K}}_n^{\sigma }>{\left[\overline{K_n^{\sigma }}\right]}_{\max }$$

, или деталь снимают с эксплуатации, если среднее значение параметра напряженного состояния $$\overline{K_n^{\sigma }}$$

меньше минимального предельного значения $${\overline{K}}_n^{\sigma }<{\left[\overline{K_n^{\sigma }}\right]}_{\min }$$

, так как деталь находится в предельном состоянии на стадии образования дефекта, или деталь направляют на ремонт в случае, если среднее значение параметра напряженного состояния $$\overline{K_n^{\sigma }}$$

детали находится между минимальным и максимальным предельными значениями или принимает эти значения $${\left[\overline{K_n^{\sigma }}\right]}_{\min }\le {\overline{K}}_n^{\sigma }\le {\left[\overline{K_n^{\sigma }}\right]}_{\max }$$

, то есть если деталь находится в «преддефектном» состоянии, на m поверхностях, расположенных в плоскости вдоль направления распространения предполагаемого дефекта вглубь металла вблизи n концентраторов напряжений, среднее значение параметра напряженного состояния определяется как $$\overline{K_m^{\sigma }}=\frac{{\displaystyle \sum _{j=1}^m\left(\raisebox{1ex}{${\sigma }_{в}^{\text{'}}$}\!\left/ \!\raisebox{-1ex}{${\sigma }_{в}^{\text{'}\text{'}}$}\right.\right)}}{m}$$

$${\sigma }_s^{\text{'}\text{'}\text{'}\text{'}}$$

- residual compression stresses at a point with a lower rate of change in residual compression stresses of the i-th stress concentrator, then the average value of the stress state parameter $$\overline{K_n^{\sigma }}$$

parts with n number of stress concentrators are compared with a minimum $${\left[K_n^{\sigma }\right]}_{\min }$$

and maximum $${\left[\overline{K_n^{\sigma }}\right]}_{\max }$$

limit values, the part is returned to operation if the average value of the stress state parameter $$\overline{K_n^{\sigma }}$$

parts with n number of stress concentrators greater than the maximum limit value $${\overline{K}}_n^{\sigma }>{\left[\overline{K_n^{\sigma }}\right]}_{\max }$$

, or the part is taken out of service if the average value of the stress state parameter $$\overline{K_n^{\sigma }}$$

less than the minimum limit value $${\overline{K}}_n^{\sigma }<{\left[\overline{K_n^{\sigma }}\right]}_{\min }$$

, since the part is in the ultimate state at the stage of defect formation, or the part is sent for repair if the average value of the stress state parameter $$\overline{K_n^{\sigma }}$$

the part is between the minimum and maximum limit values or accepts these values $${\left[\overline{K_n^{\sigma }}\right]}_{\min }\le {\overline{K}}_n^{\sigma }\le {\left[\overline{K_n^{\sigma }}\right]}_{\max }$$

that is, if the part is in a “pre-defective” state, on m surfaces located in a plane along the direction of propagation of the alleged defect deep into the metal near n stress concentrators, the average value of the stress state parameter is defined as $$\overline{K_m^{\sigma }}=\frac{{\displaystyle \sum _{j=\mathrm{one}}^m\left(\raisebox{1ex}{${\sigma }_{\mathrm{at}}^{\text{'}\text{'}}$}\!\left/ \!\raisebox{-1ex}{${\sigma }_{\mathrm{at}}^{\text{'}\text{'}\text{'}\text{'}}$}\right.\right)}}{m}$$

- остаточные напряжения сжатия в точке с большей интенсивностью изменения остаточных напряжений сжатия на j-й поверхности вблизи i-го концентратора напряжений;Where $${\sigma }_{\mathrm{at}}^{\text{'}\text{'}}$$

- residual compressive stresses at a point with a greater intensity of change in residual compressive stresses on the j-th surface near the i-th stress concentrator;

- остаточные напряжения сжатия в точке с меньшей интенсивностью изменения остаточных напряжений сжатия на j-й поверхности вблизи i-го концентратора напряжений, далее сравнивают среднее значение параметра напряженного состояния $$\overline{K_m^{\sigma }}$$

на поверхности вблизи концентраторов напряжений с минимальным $${\left[\overline{K_m^{\sigma }}\right]}_{\min }$$

и максимальным $${\left[\overline{K_m^{\sigma }}\right]}_{\max }$$

предельными значениями и деталь возвращают в эксплуатацию, если среднее значение параметра напряженного состояния $$\overline{K_m^{\sigma }}$$

на поверхности вблизи концентраторов напряжений меньше минимального предельного значения $${\overline{K}}_m^{\sigma }<{\left[\overline{K_m^{\sigma }}\right]}_{\min }$$

, или отправляют на ремонт, в случае если деталь находится в «преддефектном» состоянии, то есть среднее значение параметра напряженного состояния $$\overline{K_m^{\sigma }}$$

на поверхностях вблизи концентраторов напряжений находится между минимальным и максимальным предельными значениями или принимает эти значения $${\left[\overline{K_m^{\sigma }}\right]}_{\min }\le {\overline{K}}_m^{\sigma }\le {\left[\overline{K_m^{\sigma }}\right]}_{\max }$$

, или деталь снимают с эксплуатации, когда среднее значение параметра напряженного состояния $$\overline{K_m^{\sigma }}$$

на поверхностях вблизи концентраторов напряжений больше максимального предельного значения $${\overline{K}}_m^{\sigma }>{\left[\overline{K_m^{\sigma }}\right]}_{\min }$$

. $${\sigma }_{\mathrm{at}}^{\text{'}\text{'}\text{'}\text{'}}$$

- residual compressive stresses at a point with a lower rate of change in residual compressive stresses on the j-th surface near the i-th stress concentrator, then compare the average value of the stress state parameter $$\overline{K_m^{\sigma }}$$

on the surface near stress concentrators with minimal $${\left[\overline{K_m^{\sigma }}\right]}_{\min }$$

and maximum $${\left[\overline{K_m^{\sigma }}\right]}_{\max }$$

limit values and the part is returned to operation if the average value of the stress state parameter $$\overline{K_m^{\sigma }}$$

on the surface near stress concentrators is less than the minimum limit value $${\overline{K}}_m^{\sigma }<{\left[\overline{K_m^{\sigma }}\right]}_{\min }$$

, or sent for repair if the part is in a “pre-defective” state, that is, the average value of the stress state parameter $$\overline{K_m^{\sigma }}$$

on surfaces near stress concentrators is between the minimum and maximum limit values or takes these values $${\left[\overline{K_m^{\sigma }}\right]}_{\min }\le {\overline{K}}_m^{\sigma }\le {\left[\overline{K_m^{\sigma }}\right]}_{\max }$$

or the part is taken out of service when the average value of the stress state parameter $$\overline{K_m^{\sigma }}$$

on surfaces near stress concentrators greater than the maximum limit value $${\overline{K}}_m^{\sigma }>{\left[\overline{K_m^{\sigma }}\right]}_{\min }$$

.

The figures show:

Figure 1 - detail with stress concentrators (from 1 to n) and with surfaces near stress concentrators (from 1 'to m).

Figure 2 - i-th stress concentrator on the part.

Figure 3 - the j-th surface near the i-th stress concentrator, located in a plane along the direction of propagation of the alleged defect deep into the metal.

The method is as follows.

A part with n number of stress concentrators and with m number of surfaces near stress concentrators (FIG. 1) is subjected to x-ray radiation. Then take the x-ray for stress concentrators (Figure 2) and for surfaces near stress concentrators (Figure 3) located in a plane along the direction of propagation of the alleged defect deep into the metal.

The surface near the stress concentrator (Figure 3), located in a plane along the direction of propagation of the alleged defect deep into the metal, is characterized by a simpler profile geometry, different patterns of change in the stress state in contrast to the surface with the stress concentrator.

The X-ray diffraction pattern determines the residual compressive stress for these characteristic zones.

Fatigue is the accumulation of a certain amount of damage in cycles of plastic deformation. With low-cycle fatigue, accumulation occurs in the entire volume of the sample. (Stremel MA On unity in diverse processes of fatigue, “Deformation and destruction of materials”, No. 6 - 2011. Pages 1-12).

, которое определяется по формуле (1):To assess the technical condition of the part with low-cycle fatigue of the part with n number of stress concentrators, the average value of the stress state parameter is used as a control criterion $$\overline{K_n^{\sigma }}$$

, which is determined by the formula (1):

$$\overline{K_n^{\sigma }}=\frac{{\displaystyle \sum _{i=\mathrm{one}}^n\left(\raisebox{1ex}{${\sigma }_s^{\text{'}\text{'}}$}\!\left/ \!\raisebox{-1ex}{${\sigma }_s^{\text{'}\text{'}\text{'}\text{'}}$}\right.\right)}}{n},\left(\mathrm{one}\right)$$

where n is the total number of stress concentrators on the investigated part;

- остаточное напряжение сжатия в точке с большей интенсивностью изменения остаточных напряжений на i-м концентраторе напряжений; $${\sigma }_s^{\text{'}\text{'}}$$

- residual compressive stress at a point with a higher intensity of change in residual stresses at the ith stress concentrator;

- остаточное напряжение сжатия в точке с меньшей интенсивностью изменения остаточных напряжений сжатия на i-м концентраторе напряжений. $${\sigma }_s^{\text{'}\text{'}\text{'}\text{'}}$$

- residual compression stress at a point with a lower intensity of change in residual compression stresses at the ith stress concentrator.

с предельными минимальным $${\left[K_n^{\sigma }\right]}_{\min }$$

и максимальным $${\left[\overline{K_n^{\sigma }}\right]}_{\max }$$

значениями данного параметра. Данные предельные значения получены экспериментальным путем в зависимости от работы детали.Next, the obtained average value of the stress state parameter is compared. $$\overline{K_n^{\sigma }}$$

with extreme minimum $${\left[K_n^{\sigma }\right]}_{\min }$$

and maximum $${\left[\overline{K_n^{\sigma }}\right]}_{\max }$$

values of this parameter. These limit values are obtained experimentally, depending on the operation of the part.

детали с n количеством концентраторов напряжений больше максимального предельного значения $${\overline{K}}_n^{\sigma }>{\left[\overline{K_n^{\sigma }}\right]}_{\max }$$

, то деталь возвращают в эксплуатацию.If the average value of the stress state parameter $$\overline{K_n^{\sigma }}$$

parts with n number of stress concentrators greater than the maximum limit value $${\overline{K}}_n^{\sigma }>{\left[\overline{K_n^{\sigma }}\right]}_{\max }$$

, then the item is returned to operation.

меньше минимального предельного значения $${\overline{K}}_n^{\sigma }>{\left[\overline{K_n^{\sigma }}\right]}_{\min }$$

, то деталь снимают с эксплуатации, так как деталь находится в предельном состоянии на стадии образования дефекта.If the average value of the stress state parameter $$\overline{K_n^{\sigma }}$$

less than the minimum limit value $${\overline{K}}_n^{\sigma }>{\left[\overline{K_n^{\sigma }}\right]}_{\min }$$

, then the part is taken out of service, since the part is in a limiting state at the stage of defect formation.

детали находится между минимальным и максимальным предельными значениями или принимает эти значения $${\left[\overline{K_n^{\sigma }}\right]}_{\min }\le {\overline{K}}_n^{\sigma }\le {\left[\overline{K_n^{\sigma }}\right]}_{\max }$$

, то деталь находится в «преддефектном» состоянии и ее направляют на ремонт.If the average value of the stress state parameter $$\overline{K_n^{\sigma }}$$

the part is between the minimum and maximum limit values or accepts these values $${\left[\overline{K_n^{\sigma }}\right]}_{\min }\le {\overline{K}}_n^{\sigma }\le {\left[\overline{K_n^{\sigma }}\right]}_{\max }$$

, then the part is in a “pre-defective” state and it is sent for repair.

The “defect” state of the part represents the beginning of irreversible processes of plastic deformation and the formation of microcracks in the surface layer in the zones of stress concentrators, which are recorded by structural analysis methods, but cannot be determined by flaw detection methods (ultrasonic testing, eddy current, LC, etc.). The “pre-defective” state of the metal occurs when irreversible changes at the level of the structure have occurred, and damage due to fatigue can develop suddenly (A. A. Durov, prof., Doctor of technical sciences, prof., “The problem of assessing the residual life of an aging equipment ”, appeal date: 02/09/12, http://www.energodiagnostika.ru/en/about_mmm/article/about_mmm _old_equipment.aspx).

по формуле (2):To assess the technical condition of the part with low-cycle fatigue on m surfaces located in a plane along the propagation direction of the alleged defect near n stress concentrators, determine the average value of the stress state parameter $$\overline{K_m^{\sigma }}$$

by the formula (2):

$$\overline{K_m^{\sigma }}=\frac{{\displaystyle \sum _{j=\mathrm{one}}^m\left(\raisebox{1ex}{${\sigma }_{\mathrm{at}}^{\text{'}\text{'}}$}\!\left/ \!\raisebox{-1ex}{${\sigma }_{\mathrm{at}}^{\text{'}\text{'}\text{'}\text{'}}$}\right.\right)}}{m},\left(2\right)$$

where m is the total number of surfaces located in a plane along the direction of propagation of the alleged defect into the metal near n stress concentrators;

, $${\sigma }_{в}^{\text{'}\text{'}}$$

- остаточные напряжения сжатия в точке с большей интенсивностью изменения остаточных напряжений сжатия и в точке с меньшей интенсивностью изменения остаточных напряжений сжатия на j-й поверхности вблизи i-го концентратора напряжений соответственно. $${\sigma }_{\mathrm{at}}^{\text{'}\text{'}}$$

, $${\sigma }_{\mathrm{at}}^{\text{'}\text{'}\text{'}\text{'}}$$

- residual compressive stresses at a point with a higher intensity of change in residual compressive stresses and at a point with a lower intensity of change in residual compressive stresses on the j-th surface near the i-th stress concentrator, respectively.

на поверхности вблизи концентраторов напряжений с минимальным и максимальным $${\left[\overline{K_m^{\sigma }}\right]}_{\max }$$

предельными значениями среднего параметра напряженного состояния $$\overline{K_m^{\sigma }}$$

.Next, the average value of the stress state parameter is compared. $$\overline{K_m^{\sigma }}$$

on the surface near stress concentrators with minimum and maximum $${\left[\overline{K_m^{\sigma }}\right]}_{\max }$$

limit values of the average stress parameter $$\overline{K_m^{\sigma }}$$

.

на поверхности детали вблизи концентраторов напряжений меньше минимального предельного значения $${\overline{K}}_m^{\sigma }<{\left[\overline{K_m^{\sigma }}\right]}_{\min }$$

, то деталь возвращают в эксплуатацию.If the average value of the stress parameter $$\overline{K_m^{\sigma }}$$

on the part surface near stress concentrators is less than the minimum limit value $${\overline{K}}_m^{\sigma }<{\left[\overline{K_m^{\sigma }}\right]}_{\min }$$

, then the item is returned to operation.

на поверхности вблизи концентраторов напряжений находится между минимальным и максимальным предельными значениями или принимает эти значения $${\left[\overline{K_m^{\sigma }}\right]}_{\min }\le {\overline{K}}_m^{\sigma }\le {\left[\overline{K_m^{\sigma }}\right]}_{\max }$$

, то деталь находится в «преддефектном» состоянии.If the average value of the stress parameter $$\overline{K_m^{\sigma }}$$

on the surface near stress concentrators is between the minimum and maximum limit values or takes these values $${\left[\overline{K_m^{\sigma }}\right]}_{\min }\le {\overline{K}}_m^{\sigma }\le {\left[\overline{K_m^{\sigma }}\right]}_{\max }$$

, then the part is in a “pre-defective” state.

на поверхности вблизи концентраторов напряжений больше максимального предельного значения $${\overline{K}}_n^{\sigma }>{\left[\overline{K_n^{\sigma }}\right]}_{\min }$$

, то деталь снимают с эксплуатации.If the average value of the stress parameter $$\overline{K_m^{\sigma }}$$

on the surface near stress concentrators is greater than the maximum limit value $${\overline{K}}_n^{\sigma }>{\left[\overline{K_n^{\sigma }}\right]}_{\min }$$

then the part is taken out of service.

Evaluation of the technical condition of parts using this method will determine the technical condition of the part both in direct stress concentrators and on surfaces close to stress concentrators located in a plane along the direction of propagation of the alleged defect deep into the metal, at any stage, both manufacturing and repair of the part, this increases the accuracy of the results obtained for direct stress concentrators, where the deformation does not change according to a linear law.

Example

Assessment of the technical condition of KND disks with low-cycle fatigue

The compressor disk of low pressure (KND) is a critical part of a gas turbine engine (GTE). On KND disks, in places of maximum load of parts in operation (in hazardous areas of stress concentrations), the type and level of stress state are known. It was experimentally established that at the ends of the rim of the KND disks the level of residual stresses differs by no more than 1.5 times. With an increase in the operating time of the disk and the degree of damage to the disk, the stress state is redistributed and stresses are relaxed (at the stage of defect formation) at the ends of the disk rim. The greatest change in the stress state parameters on the KND disks occurs in the zones of stress concentrators, namely, at the rear end of the disk rim on the right side of the groove.

To assess the technical condition of two KND disks, the parts were subjected to x-ray radiation. To record the X-ray spectrum, a ψ-modified diffractometer was used under the following X-ray modes: the radiation used was Ti-Kα titanium radiation with an α-Ti phase and a voltage of 25 kV, a current of 6 mA, the diffraction angle (Wulf-Bragg angle) 2θ _(11.0) = 139 °, the oscillation of the angle between the incident x-ray and the normal to the surface of the study Δψ = ± 4 °. To measure the reflection coefficient from the atomic plane (11.0) of the α-Ti hexagonal phase crystal lattice and residual compressive stresses, a goniometer arc of 75 mm and a collimator of 5 mm and an X-ray elastic constant E / (1 + ν) = 83 GPa were used with the Pearson peak processing function 7 with a parabolic background subtraction function.

как напряжения с большей интенсивностью изменения остаточных напряжений и определяем остаточные напряжения сжатия на переднем торце обода со стороны паза $${\sigma }_{в}^{\text{'}\text{'}}={\sigma }_{nj}$$

как напряжения с меньшей интенсивностью изменения остаточных напряжений сжатия. При этом передний и задний торец обода формируют общую j-ю поверхность вблизи i-го концентратора напряжений (то есть лопаточного паза).Using the sin ² ψ method, we determine the residual compression stresses on the j-th surface near the i-th stress concentrator (Figure 3). In this case, both disks have the same number of grooves - 31. We determine the residual compression stresses at the rear end of the rim from the groove side $${\sigma }_{\mathrm{at}}^{\text{'}\text{'}}={\sigma }_{sj}$$

as stresses with a higher rate of change in residual stresses and determine the residual compression stresses at the front end of the rim from the groove side $${\sigma }_{\mathrm{at}}^{\text{'}\text{'}\text{'}\text{'}}={\sigma }_{nj}$$

as stresses with a lower rate of change in residual compressive stresses. In this case, the front and rear ends of the rim form a common j-th surface near the i-th stress concentrator (i.e., the blade groove).

на m поверхностях вблизи n концентраторов напряжений по формуле (2). С учетом того что $${\sigma }_{в}^{\text{'}}={\sigma }_{зj}$$

и $${\sigma }_{в}^{\text{'}\text{'}}={\sigma }_{nj}$$

, среднее значение параметра напряженного состояния определяется:During the study of two disks, the average value of the stress state parameter was determined $$\overline{K_m^{\sigma }}$$

on m surfaces near n stress concentrators according to formula (2). Given the fact that $${\sigma }_{\mathrm{at}}^{\text{'}\text{'}}={\sigma }_{sj}$$

and $${\sigma }_{\mathrm{at}}^{\text{'}\text{'}\text{'}\text{'}}={\sigma }_{nj}$$

, the average value of the stress state parameter is determined by:

. $$\overline{K_m^{\sigma }}=\frac{{\displaystyle \sum _{j=\mathrm{one}}^m\left(\raisebox{1ex}{${\sigma }_{sj}^{\text{'}\text{'}}$}\!\left/ \!\raisebox{-1ex}{${\sigma }_{nj}^{\text{'}\text{'}\text{'}\text{'}}$}\right.\right)}}{m}$$

.

и максимальное $${\left[\overline{K_n^{\sigma }}\right]}_{\max }=1.6$$

для среднего значения параметра напряженного состояния $$\overline{K_m^{\sigma }}$$

при малоцикловой усталости.Moreover, in the course of experimental studies, the minimum values were established $${\left[\overline{K_m^{\sigma }}\right]}_{\min }=1.2$$

and maximum $${\left[\overline{K_n^{\sigma }}\right]}_{\max }=1.6$$

for the average value of the stress state parameter $$\overline{K_m^{\sigma }}$$

with low-cycle fatigue.

, то есть деталь находится в «преддефектном» состоянии и требует ремонта.During the study of the first disk, the average value of the stress state parameter $$\overline{K_m^{\sigma }}=1.4$$

, that is, the part is in a “pre-defective” state and needs repair.

, то есть деталь находится в предельном состоянии и ее снимают с эксплуатации.During the study of the second disk, the average value of the stress state parameter $$\overline{K_m^{\sigma }}=2.1$$

, that is, the part is in extreme condition and is being decommissioned.

Claims (1)

A method for assessing the technical condition of parts having stress concentrators, including taking an x-ray from a part, which determines the residual compressive stresses, determining a control criterion and comparing it with a limit value, characterized in that for low-cycle fatigue for a part with n number of stress concentrators as a control criteria use the average value of the stress state parameter $$\overline{K_n^{\sigma }}=\frac{{\displaystyle \sum _{i=\mathrm{one}}^n\left(\raisebox{1ex}{${\sigma }_s^{\text{'}\text{'}}$}\!\left/ \!\raisebox{-1ex}{${\sigma }_s^{\text{'}\text{'}\text{'}\text{'}}$}\right.\right)}}{n}$$

Where $${\sigma }_s^{\text{'}\text{'}}$$

- residual compressive stresses at a point with a greater intensity of change in the residual stresses of the i-th stress concentrator;
$${\sigma }_s^{\text{'}\text{'}\text{'}\text{'}}$$

- residual compression stresses at a point with a lower rate of change in residual compression stresses of the i-th stress concentrator, then the average value of the stress state parameter $$\overline{K_n^{\sigma }}$$

parts with n number of stress concentrators are compared with a minimum $${\left[K_n^{\sigma }\right]}_{\min }$$

and maximum $${\left[\overline{K_n^{\sigma }}\right]}_{\max }$$

limit values, the part is returned to operation if the average value of the stress state parameter $$\overline{K_n^{\sigma }}$$

parts with n number of stress concentrators greater than the maximum limit value $${\overline{K}}_n^{\sigma }>{\left[\overline{K_n^{\sigma }}\right]}_{\max }$$

, or the part is taken out of service if the average value of the stress state parameter $$\overline{K_n^{\sigma }}$$

less than the minimum limit value $${\overline{K}}_n^{\sigma }<{\left[\overline{K_n^{\sigma }}\right]}_{\min }$$

, since the part is in the ultimate state at the stage of defect formation, or the part is sent for repair if the average value of the stress state parameter $$\overline{K_n^{\sigma }}$$

the part is between the minimum and maximum limit values or accepts these values $${\left[\overline{K_n^{\sigma }}\right]}_{\min }\le {\overline{K}}_n^{\sigma }\le {\left[\overline{K_n^{\sigma }}\right]}_{\max }$$

that is, if the part is in a “pre-defective” state, on m surfaces located in a plane along the direction of propagation of the alleged defect deep into the metal near n stress concentrators, the average value of the stress state parameter is defined as $$\overline{K_m^{\sigma }}=\frac{{\displaystyle \sum _{j=\mathrm{one}}^m\left(\raisebox{1ex}{${\sigma }_{\mathrm{at}}^{\text{'}\text{'}}$}\!\left/ \!\raisebox{-1ex}{${\sigma }_{\mathrm{at}}^{\text{'}\text{'}\text{'}\text{'}}$}\right.\right)}}{m}$$

Where $${\sigma }_{\mathrm{at}}^{\text{'}\text{'}}$$

- residual compressive stresses at a point with a greater intensity of change in residual compressive stresses on the j-th surface near the i-th stress concentrator;
$${\sigma }_{\mathrm{at}}^{\text{'}\text{'}\text{'}\text{'}}$$

- residual compressive stresses at a point with a lower rate of change in residual compressive stresses on the j-th surface near the i-th stress concentrator, then compare the average value of the stress state parameter $$\overline{K_m^{\sigma }}$$

on the surface near stress concentrators with minimal $${\left[\overline{K_m^{\sigma }}\right]}_{\min }$$

and maximum $${\left[\overline{K_m^{\sigma }}\right]}_{\max }$$

limit values and the part is returned to operation if the average value of the stress state parameter $$\overline{K_m^{\sigma }}$$

on the surface near stress concentrators is less than the minimum limit value $${\overline{K}}_m^{\sigma }<{\left[\overline{K_m^{\sigma }}\right]}_{\min }$$

, or sent for repair if the part is in a “pre-defective” state, that is, the average value of the stress state parameter $$\overline{K_m^{\sigma }}$$

on surfaces near stress concentrators is between the minimum and maximum limit values or takes these values $${\left[\overline{K_m^{\sigma }}\right]}_{\min }\le {\overline{K}}_m^{\sigma }\le {\left[\overline{K_m^{\sigma }}\right]}_{\max }$$

or the part is taken out of service when the average value of the stress state parameter $$\overline{K_m^{\sigma }}$$

on surfaces near stress concentrators greater than the maximum limit value $${\overline{K}}_m^{\sigma }>{\left[\overline{K_m^{\sigma }}\right]}_{\min }$$

.

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