PSI - Issue 2_B

ScienceDirect Available online at www.sciencedirect.com Av ilable o line at www.sciencedire t.com cienceDirect Structural Integrity Procedia 00 (2016) 000 – 000 Procedia Struc ural Integrity 2 (2016) 1055–1062 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2016) 000–000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2016) 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. 21st European Conference on Fracture, ECF21, 20-24 June 2016, Catania, Italy The influenc of the alpha grain size on internal fatigue crack initiation in drawn Ti-6Al-4V wires Joris Everaerts*, Bert Verlinden, Martine Wevers Department of Materials Engineering, KU Leuven, Kasteelpark Arenberg 44 bus 2450, 3001 Leuven, Belgium Abstract In the very high cycle fatigue regime, the location of crack initiation in titanium alloys is known to shift from the surface towards the bulk of the m terial. This intern l fatigu crack initiation results in faceted features on the fracture surface. These facets are in fact alpha grains that have been broken in a planar manner. Typically, a cluster of many facets is observed either just below the surface or deeper inside the bulk. In this study, uniaxial tension-tension fatigue tests are performed on Ti-6Al-4V wires which have been subjected to different heat treatments in order to vary the alpha grain size. Four different microstructures are obtained, with average alpha grain sizes of approximately 1, 2, 5 and 10 µm. The fatigue life is found to decrease with increasing grain size. Electrochemical polishing of the wires prior to fatigue testing is applied in order to promote internal crack initiation at higher stresses and consequently shorter testing durations. Four samples broke due to an internal crack: three samples with average alpha grain size 5 µm, which failed after 2.6 x 10 7 , 5.7 x 10 7 and 9.6 x 10 7 cycles, and one sample with average alpha grain size 10 µm, which failed after only 7.6 x 10 6 cycles. The threshold stress intensity factor range, which is calculated from the size of the facet containing area, is between 5 and 6 MPa.m 1/2 for all four samples. Fractographic examination of the facets reveals that they are not smooth, but show roughness at the nanoscale. This roughness has a linear appearance for nearly all facets, except for one anomalous facet in the sample with the largest grain size, which shows a fan-shaped pattern. From electron backscatter diffraction measurements on cross-sections of the fracture surfaces obtained by focused ion beam milling, it is also found that nearly all the facets coincide with a prismatic plane, and the linear markings are parallel to the prismatic slip direction. Only the anomalous facet has a n ar-basal orientation. These observations suggest the possibility that facets are formed by either a slip-based mechanism or a cleavage-based mechanism, and that the alpha grain size is one of the parameters that controls which mechanism occurs. © 2016 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of ECF21. 21st European Conference on Fracture, ECF21, 20-24 June 2016, Catania, Italy The influence of the alpha grain size on internal fatigue crack initiation in drawn Ti-6Al-4V wires Joris Everaerts*, Bert Verlinden, Martine Wevers Department of Materials Engineering, KU Leuven, Kasteelpark Arenberg 44 bus 2450, 3001 Leuven, Belgium Abstract In the very high cycle fatigue regime, the location of crack initiation in titanium alloys is known to shift from the surface towards the bulk of the material. This internal fatigue crack initiation results in faceted features on the fracture surface. These face s are in fact alpha grains that have bee broken n a pl nar manner. Typically, cluster of many facets is observed ither just b low the surface or deeper inside the ulk. In this study, u iaxial tension-tension f tig e tests are per ormed on Ti-6Al-4V wires which hav been subject d to different heat trea men s in order to vary the alpha gr in size. Fou different microstructures are obtained, with av rage alpha grain siz s of pp oxi ately 1, 2, 5 and 10 µm. T e fatigue life is found to decrease with increasing grain size. El ctrochemical poli hing of the wires prior to fatigue testing is applied in order t promote internal crack initiation at high r str sses and consequently shorter testing durati ns. Four samples broke due to an internal crack: three samples w h aver ge alpha grain size 5 µm, which failed after 2.6 x 10 7 , 5.7 x 10 7 and 9.6 x 10 7 cycles, an one sample with average alpha grain size 10 µm, wh ch failed after only 7.6 x 10 6 cycles. The threshold stress intensity factor range, which is calculated from the size of the facet containing area, is between 5 and 6 MPa. 1/2 fo all four samples. Fractographic examination of the facets reveals that they are not smooth, but show roughn ss at the nanoscale. This roughness has a linear appearance for nearly all facets, except for one anomalous facet in the sample with the largest grain size, which shows a f n-shaped patte . From electron backscatter diffraction measurements on cross-sections of the fracture surfaces obtained by focused ion beam milling, it is also found tha nearly ll the facets coincide with a prismatic plane, and the linear markings are parallel to the prismatic s p direction. Only the anom lous facet h s a near-basal orientat on. These observations suggest the possibility that fac ts are formed by either a slip-based mechanism or a cleavage- ased m chanism, and that the alpha grain ize is one of the p rameters that controls which mechani m occurs. © 2016 The Authors. Published by Elsevier B.V. Peer-review under espons bility of the Scientific Committee of ECF21. Keywords: very high cycle fatigue; subsurface crack initiation; fish-eye fracture; quasi-cleavage facets; titanium; Ti-6Al-4V Copyright © 2016 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 ECF21. © 2016 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of PCF 2016.

Keywords: High Pressure Turbine Blade; Creep; Finite Element Method; 3D Model; Simulation. Keywords: very high cycle fatigue; subsurface crack i itiation; fish-eye fracture; quasi-cleavage facets; titanium; Ti-6Al-4V

* Corresponding author. Tel.: +351 218419991. E-mail address: amd@tecnico.ulisboa.pt 2452-3216 © 2016 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of ECF21. 2452-3216 © 2016 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of ECF21. * Corresponding author. Tel.: +32 16 321234; fax: + 32 16 321990. E-mail address: joris.everaerts@mtm.kuleuven.be * Corresponding author. Tel.: +32 16 321234; fax: + 32 16 321990. E-mail address: joris.everaerts@mtm.kuleuven.be

2452-3216 © 2016 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of PCF 2016. Copyright © 2016 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 ECF21. 10.1016/j.prostr.2016.06.135