PSI - Issue 22

S.V. Belodedenko et al. / Procedia Structural Integrity 22 (2019) 51–58 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

54

4

10 * - this data is used for calculations for Eq. (2) and (3).

Individual SD (Table 1) are obtained for the coefficient of variation of the resource v Tik = 0.5 as S lgTik = ( v Tik / 2,3 ). Then, for Eq. (5) or Eq. (6), find the safety indices β ΣP for the systems. The graph of the reliability function is constructed for certain values of P and T P = 10 βΣР . It is believed that the exponential function of reliability P EXP is inherent in failure of the sudden type. The current development of technical diagnostics makes it possible to transform the failure of a sudden type into a failure of a gradual type. This is one way to improve reliability. Therefore, the algorithms for constructing the reliability functions of the system, the LDF of which elements obey the laws of Lindley (LND) and Weibull (W) (Table 2, PLND, PW curves, Fig.1) are involved to analysis. Table 2. To constructing of the system reliability function for failures of a gradual type. ik LND W 1-3 0.1  3.9

(1 3) (1 0.1 ) t t P 

P

 

t

exp 0.9         4         10 exp 0.9 5 t

(1 3) 

LND

EXP

P

(1 3) 

W

0.2 (4 6) (1 0.2 ) t t P  

P

 

4-6

P

(4 6) 

LND

EXP

(4 6) 

W

4

0.3 (7 10) (1 0.3 ) t t P  

P

 

t

 

  

7-10

exp 0.9

P

  

(7 10) 

LND

EXP

(7 10) 

W

3.3

Σ=1 -10

3 4 (1 3) (4 6) (7 10) P P P P      3

The desired system reliability function based on the principle P Σ → P ikmin has the form P Σ = P (7-10) EXP = exp (- 0.3t) (curve P (7-10) exp, Fig. 1).

Fig.1. System reliability functions obtained on the basis of Eq. (2) (PI), Eq. (3) (PVI=P LND ), Eq. (5) and Eq. (6 ) for 10 elements (βΣexp10, βΣLND10) and for 3 elements (βΣexp3, βΣLND3), as well as general LDF ( 7) (LDFΣ). Optimal models for determining the reliability of systems must meet at least two requirements. On the one hand, they should provide sensitivity to the reliability index (for example, PS) to the operative time. This requirement does not conform to the rules based on the distribution of Weibull (PW, Fig. 1) and the method of general LDF (LDF Σ , Fig. 1). Moreover, this applies to responsible systems: their PS should not fall below 0.8, and in this area, the graph P(t) is not changing significantly. On the other hand, it is necessary to get rid of excessive conservatism when amalgamating (which, in fact, is explored in this work). In this aspect, the RSI method, as well as the P Σ LND