PSI - Issue 2_B

ScienceDirect Available online at www.sciencedirect.com Av ilable o line at ww.sciencedire t.com cienceDirect Structural Integrity Procedia 00 (2016) 000 – 000 Procedia Structu al Integrity 2 (2016) 557–564 ScienceDire t Structural Integrity Procedia 00 (2016) 000–000 ScienceDirect Structural Integrity Procedia 00 (2016) 000–000 Available online at www.sciencedirect.com Available online at www.sciencedirect.com

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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 On the mechanism of dynamic embrittlement and its effect on fatigue crack propagation in IN718 at 650°C Hans-Jürgen Christ a, *, Ken Wackerman b , Ulrich Krupp c a Institut für Werkstofftechnik, Universität Siegen, 57068 Siegen, Germany b Fraunhofer-Institut für Werkstoffmechanik, Wöhlerstraße 11, 79108 Freiburg im Breisgau, Germany c Fakultät für Ingenieurwissenschaften und Informatik, Hochschule Osnabrück, 49009 Osnabrück, Germany IN718 is a commonly used nickel-base alloy for high temperature applications, e.g., in gas and steam turbines. At elevated temperatures, this and other superalloys are prone to the failure mechanism "dynamic embrittlement". Dynamic embrittlement can be considered as a kind of stress corrosion cracking, driven by tensile-stress-controlled oxygen grain boundary diffusion. Oxygen embrittles the grain boundaries by weakening the grain boundary cohesion resulting in fast and brittle intercrystalline crack propagation. In order to reveal the mechan sm of dynamic embrittlement, high-temperature fatigue crack ropagation tests were carried out at 650°C applying various dwell times and testing frequ nci . Most of the tests were performed in laboratory air, but some exp riments were run in vacuum as well, i order to eliminate environmental ffects a d, h nce, to define the reference fatigue crack propagation behaviour. The observations show that at low stress intensity factor ranges  K I , continuous crack growth occurs. At intermediate values of  K I , no crack propagation takes place during the dwell part of the cycle. Rather, the crack extends during unloading and reloading between subsequent hold times. The time necessary to grow the crack under sustained load during the dwell time was found to decrease with increasing stress intensity factor. Therefore, at high values of  K I , there is a contribution of the crack propagation at constant stress, since the incubation time is shorter than the dwell time. A mechanism-based model was developed for the range of test parameters, where intergranular and transgranular areas exist side by side in the fracture surface. The total crack growth per cycle is calculated by a linear combination of the intergranular and the transgranular contribution using the corresponding area fractions as weighting factors. It is shown that simulation calculations based on this model approach correspond very reasonably to the experimental observations. Hence, the model provides a quantitative mechanismen-related description of the effect of dynamic embrittlement on fatigue crack propagation rate. © 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 On the mechanism of dynamic embrittlement and its effect on fatigue crack propagation in IN718 at 650°C Hans-Jürgen Christ a, *, Ken Wackerman b , Ulrich Krupp c a Institut für Werkstofftechnik, Universität Siegen, 57068 Siegen, Germany b Fraunhofer-Institut für Werkstoffmechanik, Wöhlerstraße 11, 791 8 Freiburg im Breisgau, Germany c Fakultät für Ingenieurwissenschaften und Informatik, Hochschule Osnabrück, 49009 Osnabrück, Germany Abstract IN718 is a commonly used nickel-base alloy for high temperature applications, e.g., in gas and steam turbines. At elevated temperatures, this a d oth r superalloys re prone to t e failu e m chanism "dynamic embrittlemen ". Dynamic embrittl ment can be considered as a kind of stress corrosion cracking, driv n by te sile-stress-controlled oxyg grain boundary diffusio . Oxygen embrittles the grain boundaries by weakening the grai boundary coh ion resu ting in fast and brittle intercrystalli e crack propagation. In order to reveal the mechanism of dynamic embrittlement, high-t mperature tigue crack propagation tests were carried out at 650°C applying va ious dwell times a d testing frequen i s. Most of the tests were pe form d in lab ratory air, but some experiment were ru in vacuum as w ll, in order to limi at environme tal effects and, hence, to d fine the reference fatigue crack propagation behavio r. The observations show tha low stress intensity factor rang s  K I , conti uous crack growth occu s. At intermediate values of  K I , no ack propagati n akes pla e during the dwell part of the cy le. Rather, the crack extends during unloading and reloading between subsequen hol times. The time necessary to grow the rack under sustained load during the dwell time was f und to decr ase with increasing stress intensity factor. Therefo e, at high val es of  K I , th re is a contribution of the crack propagati n at constant stress, since the incubation time is shorter than the dwell time. A mechanism-b sed model was developed for the ra ge of test parameters, where intergra ular and transgranular areas exist side by side n the fracture surface. Th t tal crack growth per cycle is calculated by a linea combination of the inte granular and th transgranular contribution using the corresponding area fraction as weighting factors. It is shown that simulation calculations b sed o this model approach correspond very re sonably to the experiment l b ervations. Hence, the model provides a quantitative mechanismen-related description of the effect of dynamic embrittlement on fatigue crack propagation rate. © 2016 Th Aut ors. Published by Elsevier B.V. Peer-review under espons bility of the Scientific Committee of ECF21. Keywords: IN718; Dynamic embrittlement; Intergranular fatigue crack propagation; Oxygen diffusion; Damage zone formation; Fatigue lifetime 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. Abstract Keywords: IN718; Dynamic embrittlement; Intergranular fatigue crack propagation; Oxygen diffusion; Damage zone formation; Fatigue lifetime

* 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.  Corresponding author. Tel.: +49-(0)271-740-4658; fax: +49-(0)271-740-2545. E-mail address: hans-juergen.christ@uni-siegen.de 2452-3216 © 2016 The Authors. Published by Elsevier B.V. Peer-review under r sponsibility of the Scientific Committee of ECF21.  Corresponding author. Tel.: +49-(0)271-740-4658; fax: +49-(0)271-740-2545. E-mail address: hans-juergen.christ@uni-siegen.de

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.2016.06.072