The effect of phase angle on crack growth mechanisms under thermo-mechanical fatigue loading

Abstract

Link to publication on Research at Birmingham portal General rightsUnless a licence is specified above, all rights (including copyright and moral rights) in this document are retained by the authors and/or the copyright holders. The express permission of the copyright holder must be obtained for any use of this material other than for purposes permitted by law.• Users may freely distribute the URL that is used to identify this publication.• Users may download and/or print one copy of the publication from the University of Birmingham research portal for the purpose of private study or non-commercial research.• User may use extracts from the document in line with the concept of 'fair dealing' under the Copyright, Designs and Patents Act 1988 (?) • Users may not further distribute the material nor use it for the purposes of commercial gain.Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document.When citing, please reference the published version. Take down policyWhile the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.

The prediction of crack propagation in coarse grain RR1000 using a unified modelling approach

“…Test TC026 shows the highest, TC010 the lowest crack growth rates under the same IP TMF test conditions [25] (see Figure 13). It is clear from Figure 11 that the number of tertiary ' is significantly higher than the number of secondary ' for the investigated microstructures.…”

“…The current state of the model is just able to capture the lower boundary region of the conducted IP tests. Microstructural evaluation conducted by John et al [25] showed a relationship between decreasing secondary ' size distribution and increasing crack growth rate under IP-TMF loading for RR1000. In addition, Li et al [27] showed the influence of the microstructure, especially tertiary ' for isothermal crack growth tests with different hold times.…”

“…During pre-cracking and TMF testing, crack growth was measured using direct current potential drop (DCPD) signals. Further information about the experimental setup can be found in [25].…”

“…As a first approach the current model shown in Figure 9 was used and the parameter added as multiplier to the total crack growth value. A new optimization procedure was carried out, in order to determine for every crack growth test with the correlated average tertiary ' size taken from [25]. Proceeding the results of the optimization, a power law function was fitted for the correlation between average tertiary ' size and as Figure 12 demonstrates.…”

Fatigue crack growth mechanisms in powder metallurgy Ni-based superalloys—A review

“…Although the high stress state at the crack tip with high ΔK level can promote the occurrence of creep damage as seen in RR1000, the creep damage may not have time to fully develop if the crack tip advances quickly enough at a high ΔK level as seen in Udimet 720Li. Ni-based superalloys [119][120][121], which is supported by the higher FCG rates associated with intergranular fractography under the in-phase (IP) loading conditions compared with out-of-phase (OP) testing associated with transgranular fractography, due to the increased temperature at peak stress and therefore increased time-dependent FCG. A few reviews of the interaction between environmental damage and fatigue in Ni-based superalloys can be found in [4,21,109].…”