PSI - Issue 13

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 Structural Integrity 13 (2018) 2261–2266 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2018) 000–000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2018) 000–000 Available online at www.sciencedirect.com Sci nceD rect Structural Integrity Procedia 00 (2018) 000–000 Available online at www.sciencedirect.com Sci nceDir t Structural Integrity Procedia 00 (2018) 000–000

www.elsevier.com/locate/procedia

www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia

www.elsevier.com/locate/procedia ECF22 - Loading and Environmental effects on Structural Integrity Fatigue crack initiation and propagation in auxetic porous structures B. Nečemer a , * , J. Kramberger a , S. Glodež a a University of Maribor, Faculty of Mechanical Engineering, Smetanova 17, 2000 Maribor, Slovenia Abstract The investigation of fatigue behavior of auxetic porous structure made of Al-alloy 7075-T651 is presented in this study. The complete fatigue process of analyzed porous structure is divided into the crack initiation (Ni) and crack propagation (Np) period w re the ot l fatigue life (Nt) is defined s: N = Ni + Np. The c ack initiation peri d, Ni, is determined using strain life approach in the framework of FE-Safe computational code where elastic-pl stic numerical analysis is performed to obtain the total st ain amplitud in the critical cross section of the porous structure. The number of stress cycles, Np, requ re for the crack pro agation from initial to the critical crack length is lso numerically determined using finite element model in the framework f Abaqus computation FEM code. The Maximum T nsile Stress (MTS) criterion is considered when analyzing the crack path inside the p rous s ruc ure. 1. Introduction Auxetic porous structures are modern metamaterials which exhibit some typical features (e.g. negative Poisson’s ratio, counter-intuitive deformation behavior, etc.), which are useful in various engineering applications, such as aerospace engineering, a tomobile industry, c nstructions, etc. (Liu, 2006). As described in Novak et al. (2016), the n g tive Poisson’s ratio is a consequence of rotating cel s i the g ome ry of the auxetic structure when an exter al l ad is ap lied. In general, auxetic porous mat rials can be divided into the three main groups (Ren, 2017): auxetic honeycombs, auxetic micr porous polymers and auxetic composites. In the present study only the honeycomb auxsetic structures are address d. Conventional 2D auxetic porous structures are the most common typ s which have been investigated ov r the last few decades. Most studies on these field were only inv stigated in the relation to the theoretical behavior of po ous structures. In the articles of Gibson et all (1997) and Choi et all (1992) the fracture havior of conventional nd re-entr nt foam are d cribed. Th oretical studies of the fractur tough ess of conv tional oneyc mb str cture and re-entrant auxetic p rous structure are described by Liu et all (2006) and Choi et all (1996). Huang et all (2001) investigated the theoretical behavior of the honeycombs structures under in- plane multiaxial loads. This paper inv stigates the fatigue behavior of the re-entrant and rotated re- ntrant auxetic porous structures. Th performed numerical analysis is di ided into the crack initiation and crack propagation phase u ing the Simulia softw re packages Fe-safe and Abaqus. From that resp ct, the total fatigu lif of treated porous str cture, , can be d fined as: 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 ECF22 organizers. ECF22 - Loading and Environmental effects on Structural Integrity Fatigue crack initiation and propagation in auxetic porous structures B. Nečemer a , * , J. Kramberger a , S. Glodež a a University of Maribor, Faculty of Mechanical Engineering, Smetanova 17, 2000 Maribor, Slovenia Abstract The investigation of fatigue behavior of auxetic porous structure made of Al-alloy 7075-T651 is presented in this study. The complete fatigu process of analyzed porous struc ure is divided into the c ack initiation (Ni) and crack propagation (Np) period where the total fatigue life (Nt) is defined as: Nt = Ni + Np. The crack initiation period, Ni, is determined using strain life approach in the framework of FE-Safe computational code where elastic-plastic numerical analysis is performed to obtain the total strain amplitude in the critical cross section of the porous structure. The number of stress cycles, Np, required for the crack propagation from initial to the critical crack length is also numerically determined using finite element model in the framework of Abaqus computation FEM code. The Maximum Tensile Stress (MTS) criterion is considered when analyzing the crack path inside the porous structure. © 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ECF22 organizers. Keywords: Auxetic porous structures; fatigue crack initiation; fatigue crack propagation, numerical analysis 1. Introduc ion Auxetic porous structures are modern metamaterials which exhibit some typical features (e.g. negative Poisson’s ratio, counter-intuitive deformation behavior, etc.), which are useful in various engineering applications, such as aerospace engineering, automobile industry, constructions, etc. (Liu, 2006). As described in Novak et al. (2016), the negative Poisson’s ratio is a consequence of rotating cells in the geometry of the auxetic structure when an external load is applied. In general, auxetic porous materials can be divided into the three main groups (Ren, 2017): auxetic honeycombs, auxetic microporous polymers and auxetic composites. In the presented study only the honeycomb auxsetic structures are addressed. Conventional 2D auxetic porous structures are the most common types which have been investigated over the last few decades. Most studies on these field were only investigated in the relation to the theoretical behavior of porous structures. In the articles of Gibson et all (1997) and Choi et all (1992) the fracture behavior of conventional and re-entrant foams are described. Theoretical studies of the fracture toughness of conventional honeycomb structure and re-entrant auxetic porous structure are described by Liu et all (2006) and Choi et all (1996). Huang et all (2001) investigated the theoretical behavior of the honeycombs structures under in- plane multiaxial loads. This paper investigates the fatigue behavior of the re-entrant and rotated re-entrant auxetic porous structures. The performed numerical analysis is divided into the crack initiation and crack propagation phase using the Simulia software packages Fe-safe and Abaqus. From that respect, the total fatigue life of treated porous structure, , can be defined as: ECF22 - Loading and Environmental effects on Structural Integrity Fatigue crack initiation and propagation in auxetic porous structures B. Nečemer a , * , J. Kramberger a , S. Glodež a a University of Maribor, Faculty of Mechanical Engineering, Smetanova 17, 2000 Maribor, Slovenia Abstract The investigation of fatigue behavior of auxetic porous structure made of Al-alloy 7075-T651 is presented in this study. The complete fatigue process of analyzed porous structure is divided into the crack initiation (Ni) and crack propagation (Np) period where the total fatigue life (Nt) is defined as: Nt = Ni + Np. The crack initiation period, Ni, is determined using strain life approach in the framework of FE-Safe computational code where elastic-plastic numerical analysis is performed to obtain the total strain amplitude in the critical cross section of the porous structure. The number of stress cycles, Np, required for the crack propagation from initial to the critical crack length is also numerically determined using finite element model in the framework of Abaqus computation FEM code. The Maximum Tensile Stress (MTS) criterion is considered when analyzing the crack path inside the porous structure. © 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ECF22 organizers. Keywords: Auxetic porous structures; fatigue crack initiation; fatigue crack propagation, numerical analysis 1. Introduction Auxetic porous structures are modern metamaterials which exhibit some typical features (e.g. negative Poisson’s ratio, counter-intuitive deformation behavior, etc.), which are useful in various engineering applications, such as aerospace engineering, automobile industry, constructions, etc. (Liu, 2006). As described in Novak et al. (2016), the negative Poisson’s ratio is a consequence of rotating cells in the geometry of the auxetic structure when an external load is applied. In general, auxetic porous materials can be divided into the three main groups (Ren, 2017): auxetic honeycombs, auxetic microporous polymers and aux tic composites. In the presented study only the honeycomb auxsetic structures are addressed. Conventional 2D auxetic porous structures are the most common types which have been investigated over the last few decades. Most studies on these field were only investigated in the relation to the theoretical behavior of porous structures. In the articles of Gibson et all (1997) and Choi et all (1992) the fracture behavior of conventional and re-entrant foams are described. Theoretical studies of the fracture toughness of conventional honeycomb structure and re-entrant auxetic porous structure are described by Liu et all (2006) and Choi et all (1996). Huang et all (2001) investigated the theoretical behavior of the honeycombs structures under in- plane multiaxial loads. This paper investigates the fatigue behavior of the re-entrant and rotated re-entrant auxetic porous structures. The performed numerical analysis is divided into the crack initiation and crack propagation phase using the Simulia software packages Fe-safe and Abaqus. From that respect, the total fatigue life of treated porous structure, , can be defined as: ECF22 - Loading and Environmental effects on Structural Integrity Fatigue crack initiation and propagation in auxetic porous structures B. Nečemer a , * J. Kramberger a , S. Glodež a a University of Maribor, Faculty of Mechanical Engineering, Smetanova 17, 2000 Maribor, Slovenia Abstract The investigation of fatigue behavior of auxetic porous structure made of Al-alloy 7075-T651 is presented in this study. The complete fatigue process of analyzed porous structure is divided into the crack initiation (Ni) and crack propagation (Np) period where the total fatigue life (Nt) is defined as: Nt = Ni + Np. The crack initiation period, Ni, is determined using strain life approach in the framework of FE-Safe computational code where elastic-plastic numerical analysis is performed to obtain the total strain amplitude in the critical cross section of the porous structure. The number of stress cycles, Np, required for the crack propagation from initial to the critical crack length is also numerically determined using finite element model in the framework of Abaqus computation FEM code. The Maximum Tensile Stress (MTS) criterion is considered when analyzing the crack path inside the porous structure. © 2018 The Authors. Published by Elsevier B.V. Peer-review unde responsibilit of the ECF22 organizers. Keywords: Auxetic porous structures; fatigue crack initiation; fatigue crack propagation, numerical analysis 1. Introduction Auxetic porous structures are modern metamaterials which exhibit some typical features (e.g. negative Poisson’s ratio, counter-intuitive deformation behavior, etc.), which are useful in various engineering applications, such as aerospace engine ring, automobile industry, constructions, tc. (Liu, 2006). As described in Novak et al. (2016), the negative Poisson’s ratio is a c nsequence of rotating cells in the geometry of the auxetic structure when an external load is applied. In general, auxetic porous materials can be divided into the three main groups (Ren, 2017): auxetic honeycombs, auxetic microporous polymers and auxetic composites. In the presented study only the honeycomb auxsetic structures are addressed. Conventional 2D auxetic porous structures are the most common types which have been investigated over the last few decades. Most studies on these field were only investigated in the relation to the theoretical behavior of porous structures. In the articles of Gibson et all (1997) and Choi et all (1992) the fracture behavior of conventional and re-entrant foams are described. Theoretical studies of the fracture toughness of conventional honeycomb structure and re-entrant auxetic porous structure are described by Liu et all (2006) and Choi et all (1996). Huang et all (2001) investigated the theoretical behavior of the honeycombs structures under in- plane multiaxial loads. This paper investigates the fatigue behavior of the re-entrant and rotated re-entrant auxetic porous structures. The performed numerical analysis is divided into the crack initiation and crack propagation phase using the Simulia software packages Fe-safe and Abaqus. From that respect, the total fatigue life of treated porous structure, , can be defined as: © 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ECF22 organizers. K ywords: Auxetic porous structures; fatigue crack initiation; fatigue crack propagation, numerical analysis © 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

2452-3216 © 2016 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Scientific Committee of PCF 2016. * Corresponding author. Tel.: +386-2-220-7853; fax: +386-2-220-7994. E-mail address: brank .necemer@um.si * Corresponding author. Tel.: +386-2-220-7853; fax: +386-2-220-7994. E mail address: branko.necemer@um.si * Corresponding author. Tel.: +386-2-220-7853; fax: +386-2-220-7994. E-mail address: branko.necemer@um.si 2452-3216  2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ECF22 organizers. 10.1016/j.prostr.2018.12.130 * Corresponding author. Tel.: +386-2-220-7853; fax: +386-2-220-7994. E-mail address: branko.necemer@um.si