PSI - Issue 13

ScienceDirect Available online at www.sciencedirect.com Available o line at www.sciencedirect.com ienceDirect Structural Integrity Procedia 00 (2016) 000 – 000 Procedia Structural Integrity 13 (2018) 1141–1147 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2018) 000 – 000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2018) 000 – 000

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XV Portuguese Conference on Fracture, PCF 2016, 10-12 February 2016, Paço de Arcos, Portugal Thermo-mechanical modeling of a high pressure turbine blade of an airplane gas turbine engine P. Brandão a , V. Infante b , A.M. Deus c * a Department of Mechanical Engineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001 Lisboa, Portugal b IDMEC, Department of Mechanical Engineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001 Lisboa, Portugal c CeFEMA, Department of Mechanical Engineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001 Lisboa, Portugal Abstract During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data. ECF22 - Loading and Environmental effects on Structural Integrity Features of the Hydrogen-Assisted Cracking Mechanism in the Low-Carbon Steel at Ex- and In-situ Hydrogen Charging E.D. Merson a , P.N. Myagkikh a , V.A. Poluyanov a , D.L. Merson a , A. Vinogradov b a Institute of Advanced Technologies, Togliatti State University, Belorusskaya str. 14, Togliatti 445667, Russian Federation b Department of Mechanical and Industrial Engineering, Norwegian University of Science and Technology – NTNU, N-7491 Trondheim, Norway Hydrogen embrittlement has been intensively studied in the past. However, its governing mechanism is still under debate. Particularly, the details of the formation of specific cleavage-like or quasi-cleavage fracture surfaces related to hydrogen embrittled steels are unclear yet. Recently it has been found that the fracture surface of the hydrogen charged and tensile tested low-ca bon steel exhibits quasi-cleavage facets having specific smoothly curved surface, which is completely different from common flat cleavage facets. In the present contribution we endeavor to shed light on the origin of such facets. For this purpose the notched flat s cimens of the commercial low carbon st el we tensile t sted using ex- and in-situ hydr g n charging. It is found th t in the ex-situ hydrogen charged specimens the racks riginate primarily inside the specim n bulk and expand radially form the origin to the spe imen surface. This process r sults in formation of “fisheyes” – th round-shape areas with the surface composed of curved quasi-cleavage facets. In contrast, during tensile testing with in-situ hydrogen charging, the cracks initiate from the surface and propagate to the bulk. This process results in the formation of the completely brittle fracture surface with the quasi-cleavage morphology - the same as that in fisheyes. The examination of the side surface of the in-situ hydrogen charged specimens revealed the straight and S-shaped sharp cracks which path is visually independent of the microstructure and crystallography but is strongly affected by the local stress fields. Nano-voids are readily found at the tips of these cracks. It is concluded that the growth of such cracks occurs by the nano-void coalescence mechanism and is responsible for the formation of fisheyes and smoothly curved quasi-cleavage facets in hydrogen charged low-carbon steel. ECF22 - Loading and Environmental effects on Structural Integrity Features of the Hydrogen-Assisted Cracking Mechanism in the Low-Carbon Steel t Ex- and In-situ Hydrogen Charging E.D. Merson a , P.N. Myagkikh a , V.A. Poluyanov a , D.L. Merson a , A. Vinogradov b a Institute of Advanced Technologies, Togliatti State University, Belorusskaya str. 14, Togliatti 445667, Russian Federation b Department of Mechanical and Industrial Engineering, Norwegian University of Science and Technology – NTNU, N-7491 Trondheim, Norway Abstract Hydrogen embrittle ent has been intensively studied in the past. However, its governing mechanism is still under debate. Particularly, the d tails of the formation of specific cleavage-like or quasi-cleavag fracture surfaces related to hy rogen embrittled steels ar unclear yet. Recently it has been found that the fracture surface of the hydrogen charged an tensile test d low-carbon st el exhibits quasi-cleavage facets having specific smoothly curved surface, which is compl tely different from common flat cl avage facets. In th pres nt ontribution we endeavor to shed light on the origin of su h facets. For this purp se the notched flat specimens of the commercial low carbon steel were tensile tested using ex- and in-situ hydrogen charging. It is found that in the ex-situ hydrogen charged specimens the cracks originate primarily inside the speci en bulk and exp nd radially f rm the origin to the specimen surface. This process results in f rmation of “fisheyes” – t round-shape areas with the surface c posed of curved quasi-cl avage facets. In c ntrast, during tensile testing with in-situ hydr gen charging, the cracks initiat from the surfa e an propagate to the bulk. This process results in the formation of the completely brittle fracture surf e with th quasi-cleavage morphology - the same as that in fisheyes. The examination f the side surface of the in-situ hydrogen charged specimens revealed the straig t and S-shaped sharp cracks which path is visually independent of the microstructure and crystallography but is strongly affected by th local stress fields. Nano-void are readily found at the tips of these cracks. It is concluded that the growth of such cracks occurs by the nano-void co lescence mechanism and is responsible for the formation of fisheyes and smoothly curved quasi-cleavage facets in hydrogen charged low-carbon steel. Abstract

© 2016 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of PCF 2016. © 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ECF22 organizers. © 2018 The Authors. Published by Elsevier B.V. Peer-revi w under responsibility of the ECF22 organizers. © 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ECF22 organizers. Keywords: High Pressure Turbine Blade; Creep; Finite Element Method; 3D Model; Simulation. Keywords: hydrogen embrittlement; fracture surface; quasi-cleavage; Keywords: hydrogen embrittlement; fracture surface; quasi-cleavage;

* Corresponding author. Tel.: +351 218419991. E-mail address: amd@tecnico.ulisboa.pt 2452-3216 © 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ECF22 organizers. 2452-3216 © 2018 The Authors. Published by Elsevier B.V. Peer review under r sponsibility of the ECF22 organizers.

2452-3216 © 2016 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of PCF 2016.

2452-3216  2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ECF22 organizers. 10.1016/j.prostr.2018.12.238