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On the thermocyclic tests of corset shape samples as a promising method for studying thermal fatigue
https://doi.org/10.22349/1994-6716-2020-103-3-61-69
Abstract
The dynamics of deformation and fracture of the corset shape flat samples under cyclic heating was analyzed. These tests allow us to trace metallographic changes in the substructure of the material that is a result of its plastic deformation. The cracks appear in the first test cycles, regardless of the length of their thermal cycle mode. It means that the material is currently in a state favorable for cracking, according to the commonly accepted terminology. The damage accumulation specific for the development of thermal fatigue was completed in the first few cycles, and possibly in the zero half-cycle of tests. Test results could be explained by an excessively large plastic deformation in the cycle and confirmed by the evaluation calculation. We believe that deformation under cyclic heating in the central part of the corset shape samples is of a different mechanism if compared with cylindrical Coffin samples. Deformation occurs as a result of “external force”, which is created by the shoulders of the sample itself. The analysis showed that the range of plastic deformation changes on corset shape samples is more considerable than in the Coffin method, and it is more consistent with what is happening. It seems that thermocyclic tests of corset shape samples are promising for studying the destruction in real products subjected to cyclic heating, so it is necessary to identify dangerous zones and simulate them in corset samples. Published results of thermocyclic tests of the ZhS32 alloy were used to demonstrate the features of fracture development in corset shape samples. For a visual representation of the process in semi-cycle tests, a deformation diagram has been developed, which is useful when planning the thermocyclic tests.
About the Author
S. P. Degtyareva
Polzunov Scientific and Development Association on Research and Design of Power Equipment
Russian Federation
3/6 Atamanskaya St, 191167, St Petersburg
Russian Federation
3/6 Atamanskaya St, 191167, St Petersburg
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For citations:
Degtyareva S.P. On the thermocyclic tests of corset shape samples as a promising method for studying thermal fatigue. Voprosy Materialovedeniya. 2020;(3(103)):61-69. (In Russ.) https://doi.org/10.22349/1994-6716-2020-103-3-61-69
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