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influences of an operating time on character of change of residual voltages in a blanket

One of key parametres, detail hardening, residual voltages in a blanket are characterising. As it has already been established, for definition of parametres IT to the full approaches magnitoshumovoj a quality monitoring (item 1.4 and item 2.5 see), however within the limits of the flowing

103 operations during the analysis of ways of the control also have been used rentgenostrukturnyj and ultrasonic methods.

For research of influence of preliminary hardening on magnitude of residual voltages in a blanket at various level of an operating time, has been made experiment, in which course of a detail (cylindrical samples of 018 mm with a neck of 0 8 mm [43]) from a type steel 30ХГСН2А, preliminary strengthened to different level of residual voltages, exposed fatigue nagruzheniju. After each of stages nagruzhenija samples it was spent rentgenostrukturnyj the analysis of residual voltages in a blanket on which foundation magnitude of relative change of voltages in comparison with ishodnymipo to results of experiment was evaluated it is received

regressionnaja model (4.5) and graphic dependence (fig. 4.12) changes of voltages from longevity at various levels preliminary nagruzhenija. The model is informative with criterion inofrmativnosti Fm φ. = 2,3 also it is adequate to experimental data at level of a fiducial probability of 95 % [45].

Fig. 4.12. Dependence of change of residual voltages in blankets from an operating time of samples at various initial voltages: 1 - σucx. = 0; 2 - σucx. =-20 MPa, 3 - σucx. =-40 MPa, 4 - σucx. =-60 MPa.

The similar shape of curves allows to judge the fatigue processes occurring in a blanket of a material. From the moment nagruzhenija to magnitude of a relative operating time z, xx =0,2происходит lowering of level of residual compressing voltages (a stage razuprochnenija); in a range zonm, =0,2 ∙∙∙ 0,6происходит growth IT caused by ageing of a material at cyclic loadings (a hardening stage); the range is characterised by sharp lowering of magnitude of compressing residual voltages in a blanket of samples that speaks the common razuprochneniem and explicated processes of fatigue failure [45]. Thus, the given dependence has confirmed conjectures of character

Distributions of fatigue failures to surfaces of the details stated before (item 4.2).

Considering dynamics of change of magnitude of residual voltages in a blanket at various levels of preliminary hardening, it is possible to mark, that the first stage - a stage razuprochnenija - becomes less expressed, at simultaneous increase in a role of a stage of cyclic hardening.

The given remark allows to draw an output according to which the big magnitude of residual voltages in a blanket promotes heightening uprochnjaemosti a material [45].

For the purpose of prediction of a resource of operation of articles and definition of level of an operating time, optimum for substitution or repair, the accurate estimation of degree of the fatigue damages arising in a detail under effect «cyclically varying voltages (lower, than strength)» [101] is necessary. Being grounded on the above-stated recommendations for choice an optimum condition of handling of details, experiment has been made, in which course samples from a type steel 30ХГСН2А exposed to hardening in fraction by manufacture and further nagruzheniju (rotational curving) with magnitude of the affixed loading σa = 0,9 GPa. At each level nagruzhenija trial sequentially in some stages to certain number of cycles was conducted. Monitoring of a condition of a material was carried out by means of an ultrasonic method, by means of gear ДУК-66. The method of ultrasonic oscillations is grounded on acoustics organic laws according to which the elastic wave of an acoustic signal at transiting through a crystalline lattice of a material, refracts fractionally and reflected that affects level of an output signal [92]. For holding of an estimation of degree of accumulation of fatigue damages of a material comparison of the magnitudes of amplitude of ultrasonic signal amsja received as a result of the control was spent. With
ishodnymipo to results of experiment it is received

regressionnaja model (4.6):

The model is enough informative (F ιι n φ = 1,12) and is adequate to experimental data at level of a fiducial probability of 95 %.

The model study has allowed to construct graphic dependence of changes amlitudy an ultrasonic signal from level of a relative operating time (fig. 4.13).

Considering the received dependence of a variance of amplitudes of an acoustic signal on an operating time, it is necessary to mark the similar distribution of curves consisting in ascending character of lines up to level of operating time Zonm. = 0,4 - i.e. heightening of amplitude of an ultrasonic signal. It testifies to ordering of domain structure of a material during maintenance after hardening process as at hardening there is "seal" of a crystalline lattice in a material blanket. It is necessary to mark separately, that less strengthened details are characterised by much more intensive «the ordering period» material structures (Zonm. = 0... 0,4). The given phenomenon speaks smaller influence of surface plastic deformation on density and quality of structure of a blanket. Further nagruzhenie samples (a site of curves in range Z, ^... = 0,4. . 1) leads to occurrence in a material of defective sites, amount and which sizes steadily grow - as causes lowering of amplitude of ultrasonic oscillations [45].

Fig. 4.13. Dependence of change of amplitude of ultrasonic oscillations on an operating time at various initial amplitudes: 1 - А0 = 46 db, 2 - D = 44 db, 3 - D = 42 db, 4 - D = 40 db, 5 - D = 38 db.

The obtained data closely correlate with the results received in a course magnitoshumovogo of the control and rentgenostrukturnogo of the analysis.

Generalising all aforesaid, it is possible to draw an output on high cyclic hardening of the details made of a steel of type 30ХГСН2А at relative preliminary operating time Zonm. = 0,25... 0,4 and also to mark influence of preliminary hardening by shock methods of surface plastic deformation - their application raises degree of cyclic hardening of a steel. "Ageing" of samples

Ensures heightening of residual longevity of samples on on 70-75 % [44]. The given effect is called first of all by formation and development dislokatsionnoj structures in a material at handling by methods Ш1Д and during further nagruzhenija. Besides it, at the big amplitudes of breaking points there is an intensive relaxation of residual compressing voltages in a blanket, and at the big preliminary operating time occurs cyclic razuprochnenie steels [44] ∙

4.3.

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A source: Zyk Evgenie Nikolaevich. HEIGHTENING of FATIGUE DURABILITY of DETAILS FROM HIGH-RESISTANCE STEELS BY MANUFACTURE And RESTORATION by SHOCK METHODS PPD. The thesis on competition of a scientific degree of a Cand.Tech.Sci. Moscow - 2018. 2018

More on topic influences of an operating time on character of change of residual voltages in a blanket:

  1. residual voltages in a blanket of details at PPD
  2. 3.2. Residual voltages as a result of surface deformation
  3. residual voltages as a result of surface heat
  4. an estimation of exactitude of the forecast of theoretical model of shaping of residual voltages
  5. THEORETICAL DEFINITION OF RESIDUAL VOLTAGES
  6. INFLUENCE OF STRENGTHENING HANDLING IN FRACTION ON PROPERTIES OF THE BLANKET AND OPERATING PERFORMANCES OF DETAILS BY MANUFACTURE AND RESTORATION
  7. influences of preliminary hardening and repair on character of curves nagruzhenija
  8. 2.1. Working out of a design procedure of tolerances at the direct control taking into account an operating time of vehicles and influence of a variation of the mean error of measurement.
  9. the regulated character, compulsion and presence of time limits as discriminating lines of consultations
  10. APPLICATION 4 CRITERION FUNCTIONS OF THE DROP OF POWER EXPENDITURES FOR VARIOUS OPERATING MODES OF INSTALLATION AT USE OF BEST VALUES OF OPERATING PARAMETERS
  11. the Poljarizatsionno-optical analysis of interior voltages and structure of dislocations
  12. the Control of interior voltages
  13. the Blanket description
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