PSI - Issue 7

ScienceDirect Available online at www.sciencedirect.com Av ilable o line at www.sciencedire t.com Sci ceDirect Structural Integrity Procedia 00 (2016) 000 – 000 Procedia Structu al Integrity 7 (2017) 368–375 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2017) 000–000 Available online at www.sciencedirect.com Scie ceDirect Structural Integrity Procedia 00 (2017) 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. Copyright © 2017 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of the 3rd International Symposium on Fatigue Design and Material Defects. 3rd International Symposium on Fatigue Design and Material Defects, FDMD 2017, 19-22 September 2017, Lecco, Italy Evaluation of Size Effect in Low Cycle Fatigue for Q&T rotor steel S.P. Zhu a, b, *, S. Foletti b , S. Beretta b a School of Mechatro ics Engineering, Univ rsity of Electronic Science and Technology of China, Chengdu 611731, China b Department of Mechanical Engineering, Politecnico di Milano, Via La Masa 1, 20156 Milan, Italy Abstract This study presents a probabilistic modeling of size effect of 30NiCrMoV12 steel in a low cycle fatigue (LCF) regime. Three types of fatigue tests have been conducted on three geometrical specimens. Results indicate that nearly all of the LCF lifetime of 30NiCrMoV12 consists of the development of multiple surface short cracks, which has shown statistical aspects of their mutual interactions and coalescence. This gives rise to an approach of LCF damage based on statistical physics. A statistical Weibull’s weakest link model has been verified and a procedure for surface multiple fracture simulation is then established by including the random processes of initiation, propagation and coalescence of dispersed surface cracks. Using this procedure, the life of a component can be predicted fr m the criterion of critical cracks formation by coalescence of dispersed defects. © 2017 The Authors. Published by Elsevier B.V. Peer-re ie er res si ilit f t e cie tific ittee f t e r I ter ati al si ati e esi a aterial efects. Keywords: size effect; low cycle fatigue; crack growth; statistics of extremes; crack coalescence 1. Introduction Fatigue and fracture tests are normally conducted on small test specimens of structural materials used for aircrafts and high speed trains. In predicting the fatigue life of full scale components or structures, such as high speed train railway axles, the specimen size effect is critical when utilizing the laboratory testing of small standard specimens as the reference basis. In other words, fatigue testing on large specimens for those structures is not always possible due to financial considerations. Therefore, characterizing the effect of specimen size on fatigue life is needed and corresponding methods are lacking, especially a robust probabilistic method for quantifying the effect of specimen size on fatigue life. According to the German FKM guideline launched for the strength assessment of structures under different loading conditions, the treatment of size effect is purely empirical, which is determined from empirical design curves or formulae [1-3]. The application of this size effect to other cross-sectional shapes and stress distributions is often not explained as well as the robustness of the low cycle fatigue (LCF) resistance against specimen size [4]. One of the commonly-used way to characterize the size effect by means of the weakest-link theory and the statistics of extremes. Therefore, to explain the specimen size effect toward increasing reliability of fatigue critical components, metallurgical and mechanical details must be considered in fatigue modelling and lifing procedure. Note from [5, 6] that LCF life of ductile steels is generally dominated by crack propagation life rather than crack initiation life. Namely, the effect of specimen size on the fatigue propagation rate, particularly on the scatter in small fatigue crack growth, has been viewed as the main factor influencing the fatigue life. The challenge will be to use not only the governing factors, such as 3rd International Sy posiu on Fatigue esign and Material Defects, FDMD 2017, 19-22 September 2017, Lecco, Italy al ati f ize ffect i cle ati e f r r t r steel S.P. hu a, b, *, S. Foletti b , S. eretta b a School of Mechatronics Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China b Department of Mechanical Engineering, Politecnico di Milano, Via La Masa 1, 20156 Milan, Italy Abstract This study presents a probabilistic modeling of size effect of 30NiCr oV12 steel in a low cycle fatigue (LCF) regime. Three types of fatigue tests have been conducted on three geometrical specimens. Results indica e that nearly all of the LCF lifetime of 30NiCr oV12 consists of the development of multiple surfac short cracks, which has hown statistical aspe ts of th ir mutual interactions and coalescence. This gives r e to an approach of LCF damage based on statistical physics. A statistical eib ll’s weakest link model has been verified and a procedure for surface multiple fracture simulation is then established by including the random processes of initiation, propagation and c alescence of dispersed surface cracks. Using this procedure, the life of a component can be predicted fr m the criterion of critical cracks formation by coalescence of dispersed defects. © 2017 The Authors. Published by Elsevier B.V. r-re ie er res si ilit f t e cie tific ittee f t e r I ter ati al si ati e esi a aterial efects. Keywords: size effect; low cycle fatigue; crack growth; statistics of extremes; crack coalescence 1. Introduction Fatigue and fracture tests are normally con ucted on small test specimens of structural materials sed for aircrafts and high speed trains. In predicting the fatigue lif of full scale components or structures, such as high speed train railway axl s, the specimen size ffect is cri ical when utilizing the laboratory testing of small standard specimens as the reference basis. In other wo ds, fatigue testing on larg sp cimens for those st uctures is not always possible due to financial considerations. Therefore, characterizing the effect of specimen size on fatigue life is needed and corresponding methods are lacking, especially a robust probabilistic method for quantifying the effect of specimen size on fatigue life. According to th German FK guideline launched for the strength assessment of structures under different loading conditions, the treatment of size effect is purely empirical, which is determined from empirical design curves or formulae [1-3]. The application of this size effect to other cross-sectional shapes and stress distributions is often not explained as well as the robustness of the low cycle fatigue (LCF) resistance against specimen size [4]. One of the commonly-used way to characterize the size effect by means of the weakest-link theory and the statistics of extremes. Therefore, to explain the specimen size effect toward increasing reliability of fatigue critical components, metallurgical and mechanical details must be considered in fatigue modelling and lifing procedure. Note from [5, 6] that LCF life of ductile steels is generally dominated by crack propagation life rather than crack initiation life. Namely, the effect of specimen size on the fatigue propagation rate, particularly on the scatter in small fatigue crack growth, has been viewed as the main factor influencing the fatigue life. The challenge will be to use not only the governing factors, such as © 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.

* Corresponding author. Tel.: +351 218419991. E-mail address: amd@tecnico.ulisboa.pt * Corresponding author. E-mail address: zspeng2007@uestc.edu.cn * Corresponding author. E-mail address: zspeng2007@uestc.edu.cn

2452-3216 © 2016 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of PCF 2016. 2452-3216 © 2017 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of the 3rd International Symposium on Fatigue Design and Material Defects. 2452-3216 © 2017 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientifi Committee of the 3rd International Symposium on Fatigue Design and aterial Defects. 2452-3216 Copyright  2017 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of the 3rd International Symposium on Fatigue Design and Material Defects. 10.1016/j.prostr.2017.11.101