PSI - Issue 1

ScienceDirect Procedia Structural Integrity 1 (2016) 158–165 Available online at www.sciencedirect.com Av ilable online at ww.sciencedire t.com ScienceDirect Structural Integrity Procedia 00 (2016) 000 – 000 Available online at www.sciencedirect.com Structural Integrity Procedia 00 (2016) 000–000 Available online at www.sciencedirect.com Structural Integrity Procedia 00 (2016) 000–000 Available online at www.sciencedirect.com 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. XV Portuguese Conference on Fracture, PCF 2016, 10-12 February 2016, Pac¸o de Arcos, Portugal Fatigue crack growth in low cycle fatigue: an analysis of crack closure based on image correlation S. Rabbolini a, ∗ , S. Beretta a , S. Foletti a a Politecnico di Milano, Department of Mechanical Engineeri g, Via La Masa 1, Milan 20156, Italy Abstract In this paper, the e ff ects of crack closure on the propagation of short cracks is investigated. An experimental campaign, performed in the low cycle fatigue regime, was performed on specimens with micro-defects, considering two di ff erent strain ratios: initially, tests were performed under fully reversed straining, whereas the e ff ect of an applied mean strain were studied by considering a strain ratio equal to 0.5. Crack closure was characterized with an innovative technique based on digital image correlation: crack opening and closing levels were measured starting from the experimental crack tip displacement fields. Finally, experimental results were compared to those computed with the analytical model proposed by Newman. c 2016 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of PCF 2016. Keywords: Low cycle fatigue; Fatigue crack closure; Digital image correlation; Short crack propagation; Fatigue crack growth. 1. Introduction Modern aviation and energy industry requirements have necessitated the adoption of design techniques based on damage tolerant approaches. In this frame, residual life of components, such as turbine disks and combustors, is eval uated considering a crack propagation problem, in which it is assumed that a crack propagates from the first fatigue cycle, starting from an initial defect present in the component most stressed region (Miller and Murakami (2005)). Accordingly, crack growth rates r calculated with mod ls that take into accou t low cycle fatigue (LCF) conditions, since cracks usually grow in regions where high plastic strains are present. The natural scatter of the external ap plied loads is introduced by considering a series of safety factors, calculated following semi-probabilistic approaches (Beretta et al. (2016)). A further improvement in fatigue life assessment can be implemented by considering the pres ence of small shallow cracks, whose depth is set equal to the detection limit of non-destructive techniques (NDT), as proposed by Cristea et al. (2012). XV Portuguese Conference on Fracture, PCF 2016, 10-12 February 2016, Pac¸o de Arcos, Portugal Fatigue crack growth in low cycle fatigue: an analysis of c ack closure based on image correlation S. Rabbolini a, ∗ , S. Beretta a , S. Foletti a a Politecnico di Milano, Department of Mechanical Engineering, Via La Masa 1, Milan 20156, Italy Abstract In this paper, the e ff ects f crack closure o the propagation of short racks is investigated. An experimental campaign, performed in the low cycle fatigue regime, was performed on specimens with micro-defects, considering two di ff erent strain ratios: initially, tests were performed under fully reversed straining, whereas the e ff ect of an applied mean strain were studied by considering a strain ratio equal to 0.5. Crack closure was characterized with an innovative technique based on digital image correlation: crack opening and closing levels were measured starting from the experimental crack tip displacement fields. Finally, experimental results were compared to those computed with the analytical model proposed by Newman. c 2016 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of PCF 2016. Keywords: Low cycle fatigue; Fatigue crack closure; Digital image correlation; Short crack propagation; Fatigue crack growth. 1. Introduction Modern aviation and energy industry requirements have necessitated the adoption of design techniques based on damage tolerant approaches. In this frame, residual life of components, such as turbine disks and combustors, is eval uated considering a crack propagation problem, in which it is assumed that a crack propagates from the first fatigue cycle, starting from an initial defect present in the component most stressed region (Miller and Murakami (2005)). Accordingly, crack growth rates are calculated with models that take into account low cycle fatigue (LCF) conditions, since cracks usually grow in regions where high plastic strains are present. The natural scatter of the external ap plied loads is introduced by considering a series of safety factors, calculated following semi-probabilistic approaches (Beretta et al. (2016)). A further improvement in fatigue life assessment can be implemented by considering the pres ence of small shallow cracks, whose depth is set equal to the detection limit of non-destructive techniques (NDT), as proposed by Cristea et al. (2012). XV Portuguese Conference n Fracture, CF 2016, 10-12 February 2016, Pac¸o de Arcos, Portugal Fatigue crack growth in low cycle fatigue: an analysis of crack closure based on image co relation S. Rabboli i a, ∗ , S. Beretta a , S. Foletti a a Politecnico di Milano, Department of Mechanical Engineering, Via La Masa 1, Milan 20156, Italy Abstract I is paper, the e ff ects of crack closure n the propagation of short cracks is investigated. An exper m ntal campaign, performed in he low cycle fatigue regime, was performed o specim n with micro-defects, consid ring two di ff rent strain ratios: init ally, tests were p rformed unde fully reversed straining, whereas the e ff ect of an applied mean strain were studi d by considering a strain ratio equal to 0.5. Crack closure was characterized with an innovative technique bas d on igital imag co relation: crack opening and closing levels were measured st rting from the ex erim ntal crack tip displacement fields. Finally, experimental results were compared o those computed with the analytical model proposed by Newman. c 2016 The Autho s. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of PCF 2016. Keywords: Low cycle fatigue; Fatigue crack closure; Digital image correlation; Short crack propagation; Fatigue crack growth. 1. Introduction Modern aviation and energy indu try equirements have necessitated the adoption of design techniques based on d mage tolerant appro hes. In this frame, residual life of components, such as turbine disks and co bustors, is eval uated considering a crack propagation problem, in which it is assumed that a crack propagates from the first fatigue cycle, starting from an initial defect present in the component most stressed region (Miller and Murakami (2005)). Ac ordingly, crack growth rates are calculated with models that take into account low cycle fatigue (LCF) conditions, since cracks usually grow in regions where high plastic strains are present. The natural scatter of the external ap plied loads is introduced by considering a series of safety factors, calculated following semi-probabilistic approaches (Beretta et l. (2016)). A further improvement in fatigue life assessment can be implemented by considering the pres ence of small shallow cracks, whose depth is set equal to the detection limit of non-destructive techniques (NDT), as proposed by Cristea et al. (2012). Copyright © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecomm n .org/licenses/ y-nc-nd/4.0/). P r-review under responsibility of the Scientifi Committee of PCF 2016. © 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.

2452-3216 © 2016 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of PCF 2016. Copyright © 2015 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 PCF 2016. 10.1016/j.prostr.2016.02.022 ∗ Corresponding author. Tel.: + 39-02-2399-8248 ; fax: + 39-02-2399-8623. E-mail address: silvio.rabbolini@polimi.it 2452-3216 c 2016 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of PCF 2016. ∗ Corresponding author. Tel.: + 39-02-2399-8248 ; fax: + 39-02-2399-8623. E-mail address: silvio.rabbolini@polimi.it 2452-3216 c 2016 The Authors. Published by Els vier B.V. Peer-review under responsibility of the Scientifi Committee of PCF 2016. ∗ Correspon ing author. Tel.: + 39-02-2399-8248 ; fax: + 39-02-2399-8623. E-mail address: silvio.rabbolini@polimi.it 2452-3216 c 2016 The Authors. Publi hed by Elsevier B.V. e r-review under responsibility of the Scientific Committee of PCF 2016. * Corresponding author. Tel.: +351 218419991. E-mail address: amd@tecnico.ulisboa.pt