PSI - Issue 3

ScienceDirect Available online at www.sciencedirect.com Av ilable o line at ww.sciencedire t.com ienceDirect Structural Integrity Procedia 00 (2016) 000 – 000 Procedia Structu al Integrity 3 (2017) 411–423 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2017) 000–000

www.elsevier.com/locate/procedia

www.elsevier.com/locate/procedia

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. Copyright © 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the Scientific Committee of IGF Ex-Co. XXIV Italian Group of Fracture Conference, 1-3 March 2017, Urbino, Italy A general model for crack growth from initial defect in Very-High Cycle Fatigue Davide S. Paolino a *, Andrea Tridello a , Giorgio Chiandussi a , Massimo Rossetto a a Politecnico di Torino, Department of Mechanical and Aerospace Engineering, Corso Duca degli Abruzzi 24, Turin 10129, Italy Abstract It is well-known in the literature that internal defects play a major role in the Very-High-Cycle Fatigue (VHCF) response of metallic materials. Generally, VHCF failures nucleate from internal defects characterized by a limited size. Unexpectedly, it has been found that cracks can grow from the initial defect even if the Stress Intensity Factor (SIF) is quite below the characteristic threshold for crack growth. Even though researchers unanimously accept this singular experimental evidence, they still dispute about its physical justification. Different micromechanical explanations have been proposed in the literature: local grain refinement, carbide decohesion, matrix fragmentation, hydrogen embrittlement, numerous cyclic pressure and formation of persistent slip bands are the most f mous proposals. Regardless of the sp cific mi omechanical explanation, i is ge erally acknowledged t at a weakening m chanism occurs around the initial def ct, thu permitting crack growth below the SIF threshol . The present paper prop ses an innovative approach for the quantitative mod ling of the weakening process around the initial defect. The proposed model co siders an additional SIF that reduces the SIF threshold of the material. Starting from a very general formulation for the additional SIF, possible scenarios for crack growth from the initial defect are also identified and described. It is theoretically demonstrated that, depending on the scenario, a VHCF limit may also be present and its final formulation recalls the well-known expression previously proposed by Murakami. © 2017 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of IGF Ex-Co. Dav © l © 2016 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of PCF 2016. Keywords: VHCF limit; SIF threshold; Crack growth

Keywords: High Pressure Turbine Blade; Creep; Finite Element Method; 3D Model; Simulation.

* Corresponding author. Tel.: +39-011-090-5746; fax: +39-011-090-6999. E-mail address: davide.paolino@polito.it

* Corresponding author. Tel.: +351 218419991. E-mail address: amd@tecnico.ulisboa.pt 2452-3216 © 2017 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of IGF Ex-Co.

2452-3216 © 2016 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of PCF 2016. Copyright © 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ). Peer-review under responsibility of the Scientific Committee of IGF Ex-Co. 10.1016/j.prostr.2017.04.069