PSI- Issue 9

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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. © 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. IGF Workshop “Fracture and Structural Integrity” Mode II fracture toughness for non-planar frictional cracks Andrea SPAGNOLI a, ∗ , Andrea CARPINTERI a , Michele TERZANO a a Department of Civil-Environmental Engineering & Architecture, University of Parma, Parco Area delle Scienze 181 / A, 43124 Parma, Italy Abstract Traction-free and planar cracks represent a rather idealized picture of the physical reality, commonly used in fracture mechanics problems. In the present paper, the influence of roughness and friction of crack surfaces is examined in relation to both the resulting near-tip stress field and the fracture resistance under monotonic mixed-mode loading. A two-dimensional model is presented where an elastic-plastic-like constitutive interface law is adopted to describe the Mode I / II coupling between displacements and tractions along the crack surfaces. The solution is obtained using the Distributed Dislocation T chnique (DDT). By considering a linear piecewise periodic profile of the crack, the present model is empl yed to quantify the mode II fracture toughness of di ff erent types of natural stones under varying mode I compressive load. c 2018 The Authors. Published by Elsevier B.V. eer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. Keywords: friction, crack roughness, distributed dislocation technique, crack shielding. 1. Introduction Observ tions on th failur of brittl materials, such s concrete, rocks and gla s, reveal that crack growth of pre- xisting microcracks does not proceed collinearly; on the contrary, cracks tend to kink. T is behaviour may be ascribed to the combination of di ff erent factors, such as the presence of far field multi-axial stresses, residual stresses, microstructural inhomogeneities, material properties dispersion. As was recognised by several authors (Kitagawa et al., 1975; Evans and Hutchinson, 1989; Gates and Fatemi, 2016), the fracture strength and the crack propagation are strongly influenced by such e ff ects. Traction-free and planar cracks represent a rather idealized model of the physical reality, commonly used in fracture mechanics problems. For instance, in order to account for the actual features of crack surfaces, the first two authors have recently explored the influence of crack path meandering on fatigue propagation, by modelling the crack profile as a piecewise linear curve in two dimensions (Spagnoli et al., 2015; Brighenti et al., 2014) (the same type of model was initially conceived in the realm of fractal geometry, Carpinteri et al. (2008)). Many attempts have been made to analytically study the behaviour of cracks in real materials, and here we mention just a few of them, which are consistent with the purpose of our study. The case of a rough and frictional crack in IGF Workshop “Fracture and Structural Integrity” ode II fracture toughness for non-planar frictional cracks Andrea SPAGNOLI a, ∗ , Andrea CARPINTERI a , Michele TERZANO a a Department of Civil-Environmental Engineering & Architecture, University of Parma, Parco Area delle Scienze 181 / A, 43124 Parma, Italy Abstract Traction-free and planar cracks represent a rather idealized picture of the physical reality, commonly used in fracture mechanics problems. In the present paper, the influence of roughness and friction of crack surfaces is examined in relation to both the resulting near-tip stress field and the fracture resistance under monotonic mixed-mode loading. A two-dimensional model is presented where an elastic-plastic-like constitutive interface law is adopted to describe the Mode I / II coupling between displacements and tractions along the crack surfaces. The solution is obtained using the Distributed Dislocation Technique (DDT). By considering a linear piecewise periodic profile of the crack, the present model is employed to qua tify the mode II fracture toughness of di ff erent types of natural stones under varying mode I compressive load. c 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. Keywords: fricti n, crack roughness, distributed dislocation technique, cr ck shielding. 1. Introduction Observations on the failure of brittle materials, such as concrete, rocks and glass, reveal that crack growth of pre-existing microcracks d es not proceed collinearly; on the contrary, cracks tend to kink. This behaviour may be ascribed to the combination of di ff erent factors, such as the presence of far field multi-axial stresses, residual stresses, microstructural inhomogeneities, material properties dispersion. As was recognised by several authors (Kitagawa et al., 1975; Evans and Hutchinson, 1989; Gates and Fatemi, 2016), the fracture strength and the crack propagation are strongly influenced by such e ff ects. Traction-free and planar cracks represent a rather idealized model of the physical reality, commonly used in fracture mechanics problems. For instance, in order to account for the actual features of crack surfaces, the first two authors have recently explored the influence of crack path meandering on fatigue propagation, by modelling the crack profile as a piecewise linear curve in two dimensions (Spagnoli et al., 2015; Brighenti et al., 2014) (the same type of model was initially conceived in the realm of fractal geometry, Carpinteri et al. (2008)). Many attempts have been made to analytically study the behaviour of cracks in real materials, and here we mention just a few of them, which are consistent with the purpose of our study. The case of a rough and frictional crack in © 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. 2452-3216  2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. 10.1016/j.prostr.2018.06.024 ∗ Corresponding author. Tel.: + 39-0521-905927; fax: + 39-0521-905924. E-mail address: spagnoli@unipr.it 2210-7843 c 2018 The Authors. Published by Elsevier B.V. Peer-revi w under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. ∗ Corresponding author. Tel.: + 39-0521-905927; fax: + 39-0521-905924. E-mail address: spagnoli@unipr.it 2210-7843 c 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. * Corresponding author. Tel.: +351 218419991. E-mail address: amd@tecnico.ulisboa.pt