PSI - Issue 35

Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2021) 000 – 000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2021) 000 – 000

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Procedia Structural Integrity 35 (2022) 141–149

© 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of IWPDF 2021 Chair, Tuncay Yalçinkaya Abstract Ti-6Al-4V alloy turbine components for aeronautical applications operate at a steady state after reaching the maximum stress during each duty cycle. The load holds combined with the fatigue process causes a phenomenon called the dwell effect. The dwell periods reduce the fatigue strength of disks and blades of aeronautical turbine engines made of titanium alloys. In this work, trapezoidal dwell-fatigue and triangular fatigue tests were performed with a fatigue ratio of 0.1 at room temperature. The trapezoidal waveforms (dwell-fatigue tests) had a 10-second dwell period and 1-second loading and unloading rates for each fatigue cycle. The triangular waveforms (fatigue tests) were equivalent to trapezoidal waveforms with zero seconds at the maximum stress. The Weibull distribution was used to analyze the dwell-fatigue data statistically. The experimental results showed that the dwell-fatigue life debits for dwell periods of 10 seconds at stress levels of 1.0, 0.975, and 0.95 of the material yield strength were 10.2, 10.0, and 4.5, respectively. The results suggest that the dwell sensitivity of Ti-6Al-4V alloy increases at high-stress levels. The fracture of dwell fatigue specimens occurred at a high-cumulated plastic strain and after a significantly lower fatigue life than at pure fatigue tests, indicating a substantial dwell-life debit of the Ti-6Al-4V alloy. The damage mechanism responsible for reducing the fatigue life when the dwell time was introduced was the plastic deformation accumulation observed in dwell-fatigue tests, possibly as a result of the stress redistribution mechanism in the α phase grains that leads to slip of dislocations and, consequently, early plas tic deformation processes that instigate crack nucleation. © 2021 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) 2nd International Workshop on Plasticity, Damage and Fracture of Engineering Materials Investigation of the damage and fracture of Ti-6Al-4V titanium alloy under dwell-fatigue loadings Martin Ferreira Fernandes a, *, Verônica Mara de Oliveira Velloso a and Herman Jacobus Cornelis Voorwald a a Fatigue and Aeronautical Materials Research Group, Department of Materials and Technology, Sao Paulo State University (Unesp), School of Engineering, Guaratingueta, Sao Paulo, 12516-410, Brazil. Abstract Ti-6Al-4V alloy turbine components for aeronautical applications operate at a steady state after reaching the maximum stress during each duty cycle. The load holds combined with the fatigue proce s causes phenomenon called the dwell ffect. The dw ll periods reduce he fatigue strengt f disks and blades of aeronautical turbine ngines made f titanium alloys. In this work, trapezoidal dwell-fatigue and triangular fatigue tests were per ormed with a fatigue ratio of 0.1 t ro m emperature. The trapezoidal w v f rms (d e l-fatigue tests) had a 10-second dwell period and 1-second loading and unlo ding rat s for each fatigue cycle. The triangular wav forms (fa igue tests) wer equival nt to trapezoidal wavef rms with zer seconds at th maximum stress. The Weibull distribution w s s d to analyze the dw ll-fatigue data statistically. The experimental re ul s showed that the dwell-fatigu life ebits for dwell periods of 10 seconds at stress lev ls of 1.0, 0.975, and 0.95 of the material yield strength were 10.2, 10.0, and 4.5, r spectively. The results suggest that the dwell s nsitivity of Ti-6Al-4V alloy increases at high-stress levels. The fracture of dwell fatigue specimens occurred at a high-cumulated plastic strain and after sign fi antly lower fatigue life than at pure fatigue tests, indicating a substantial dwell-life debit of the Ti-6Al-4V lloy. The dama e mechanism r sponsible or reducing the fatigue life when he dwell time was introduce was the plastic deformation accumul tion observed in dwell-fatigue t sts, possibly s a result of the stress red stributio mechanism in the α phase grains th t leads to slip of dislocations and, consequently, early pla tic deforma ion processes hat instig te crack nucleation. © 2021 The Author . Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review u der re ponsibility of IWPDF 2021 hair, Tuncay Yalçinkay K ywords: Dwell-fatigue, fatigue, titanium alloys, Ti-6Al-4V, turbine engines. 2nd International Workshop on Plasticity, Damage and Fracture of Engineering Materials Investigation of the damage and fracture of Ti-6Al-4V titanium alloy under dwell-fatigue loadings Martin Ferreira Fernandes a, *, Verônica Mara de Oliveira Velloso a and Herman Jacobus Cornelis Voorwald a a Fatigue and Aeronautical Materials Research Group, Department of Materials and Technology, Sao Paulo State University (Unesp), School of Engineering, Guaratingueta, Sao Paulo, 12516-410, Brazil. Peer-review under responsibility of IWPDF 2021 Chair, Tuncay Yalçinkaya Keywords: Dwell-fatigue, fatigue, titanium alloys, Ti-6Al-4V, turbine engines.

* Corresponding author. Tel.: +55-012-98867-3133. E-mail address: martin.fernandes@unesp.br * Corresponding author. Tel.: +55-012-98867-3133. E-mail address: martin.f rnandes@unesp.br

2452-3216 © 2021 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of IWPDF 2021 Chair, Tuncay Yalçinkaya 2452-3216 © 2021 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review u der responsibility of IWPDF 2021 hair, Tuncay Yalçinkay

2452-3216 © 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of IWPDF 2021 Chair, Tuncay Yal ç inkaya 10.1016/j.prostr.2021.12.058