PSI - Issue 16

Zinovij Nazarchuk et al. / Procedia Structural Integrity 16 (2019) 169–175 175 Zinovij Nazarchuk, Olexandr Andreykiv, Valentyn Skalskyi, Denys Rudavskyi / Structural Integrity Procedia 00 (2019) 000 – 000 7

The constant B 4 in formula (18) is defined as follows. For some high values , the high-temperature creep crack growth rate V will be significant, so that its visible growth will take place at short time intervals t i  . For these values of ( ) i In K we find i n  . Then we determine the constant B 4 by the formula         k i i i i l t B k h n 1 1 1 1 1 4 ( ) ( )  . (19) CC i In K K  ( )

3  k . In other words, at least three length changes of low-temperature creep

In formula (19) the value k must be

crack have to be fixed when measuring the values of l i  , t i  , i n  . Thus, using the formulas (18) and (19), relatively easily accessible kinetic diagram

In n K ~  can be translated into

an experimentally hard-to-reach diagram V ~ K I .

6. Conclusions

A new method for the investigation of the materials delayed fracture and determination of the structural elements residual life under the influence of the mechanical and physico-chemical factors is proposed. This method is based on the author's previously developed energy approach to the investigation of cracks subcritical growth in materials and on the known from the literature correlation between the new-formed defects area and acoustic emission parameters. The method application is demonstrated on the example of the residual life determination of the structural elements operating under long-term static load and high temperature. With the help of this method an effective methodology was developed for kinetic diagrams constructing of high-temperature creep cracks growth in metallic materials.

Acknowledgements

The investigation has been supported by the budget Program “ Support of development of scientific research priority directions ” ( KPKVK-6541230).

References

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