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  • 1
    In: International Journal of Structural Integrity, Emerald, Vol. 5, No. 3 ( 2014-8-12), p. 187-201
    Abstract: – The purpose of this paper is to assess the quality of adhesively bonded joints using an alternative artificial neural networks (ANN) approach. Design/methodology/approach – Following the necessary surface pre-treatment and bonding process, the coupons were investigated for possible defects using C-scan ultrasonic inspection. Afterwards, the damage severity factor (DSF) theory was applied in order to quantify the existing damage state. A series of G IC mechanical tests was then conducted so as to assess the fracture toughness behavior of the bonded samples. Finally, the data derived both from the NDT tests (DSF) and the mechanical tests (fracture toughness energy) were combined and used to train the ANN which was developed within the present work. Findings – Using the developed neural network (NN) the bonding quality, in terms not only of defects but also of fracture toughness behavior, can be accessed through NDT testing, minimizing the need for mechanical tests only in the initial material characterization phase. Originality/value – The innovation of the paper stands on the feasibility of an alternative approach for assessing the quality of adhesively bonded joints using and ANNs, thus minimizing the necessary testing effort.
    Type of Medium: Online Resource
    ISSN: 1757-9864
    Language: English
    Publisher: Emerald
    Publication Date: 2014
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  • 2
    Online Resource
    Online Resource
    Emerald ; 2013
    In:  International Journal of Structural Integrity Vol. 4, No. 1 ( 2013-03-01), p. 108-120
    In: International Journal of Structural Integrity, Emerald, Vol. 4, No. 1 ( 2013-03-01), p. 108-120
    Abstract: To investigate the effect of different welding configurations on the mechanical properties of friction stir welding (FSW) overlap joints. The application of FSW in an overlap configuration could be an attractive replacement to the riveting process for assembly of fuselage primary structures due to the similarity in tolerance management. However, the mechanical properties of welded overlap joints are often inferior to the respective riveted lap‐joint properties. Design/methodology/approach In order to quantify the static and fatigue strength of FSW overlap joints, numerical and experimental investigation on overlap welds were performed in the current work. Several single shear overlap joints welding configurations were investigated, including single and multiple pass friction stir welds. The static and fatigue behaviour of these joints was assessed through tensile and fatigue tests. Findings Static and fatigue behaviour were found to strongly depend on the welding process parameters and configuration. With respect to the static behaviour, it was found that values close to base material can be achieved. However, depending on configuration and process parameters, static properties can be as low as about 30% of the base material properties. As for the fatigue behaviour, the fatigue limit for all configurations tested was found to be unrealistic for structural applications. Originality/value The distance between the outermost welds in multiple pass welds were found to influence the mechanical properties, although no direct relationship can be derived. Indications have been found but no clear conclusion has been reached with respect to the optimum configuration. In some cases, specimens with superior tensile properties exhibited reduced fatigue properties whereas the exact opposite effect was observed for other configurations.
    Type of Medium: Online Resource
    ISSN: 1757-9864
    Language: English
    Publisher: Emerald
    Publication Date: 2013
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  • 3
    In: MATEC Web of Conferences, EDP Sciences, Vol. 233 ( 2018), p. 00029-
    Abstract: In the present work, a numerical model is developed to predict the mechanical properties of nanocrystalline materials using a Finite Element Analysis. The model is based on Representative Volume Elements (RVE) in which the microstructure of the material is described using the Voronoi tessellation algorithm. The use of the Voronoi particles was based on the observation of the morphology of nanocrystalline materials by Scanning Electron and Transmission Electron Microscopy. In each RVE, three-dimensional modelling of the grain and grain boundaries as randomlyshaped sub-volumes is performed. The developed model has been applied to pure nanocrystallline copper taking into account the parameters of grain size and grain boundary thickness. The mechanical properties of nanocrystalline copper have been computed by loading the RVE in tension. The numerical results gave a clear evidence of grain size effect and the Hall-Petch relationship, which is a consequence of macroscopic strain being preferentially accumulated at grain boundaries. On the other hand, for a given grain volume fraction, the results for elastic moduli showed no effect of the grain size. The model predictions have been validated successfully against numerical results from the literature and predictions of the Rule of Mixtures and the Mori-Tanaka analytical model.
    Type of Medium: Online Resource
    ISSN: 2261-236X
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2018
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  • 4
    Online Resource
    Online Resource
    EDP Sciences ; 2018
    In:  MATEC Web of Conferences Vol. 188 ( 2018), p. 00001-
    In: MATEC Web of Conferences, EDP Sciences, Vol. 188 ( 2018), p. 00001-
    Type of Medium: Online Resource
    ISSN: 2261-236X
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2018
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  • 5
    In: MATEC Web of Conferences, EDP Sciences, Vol. 188 ( 2018), p. 01020-
    Abstract: In the present work, Life Cycle analysis (LCA) and Life cycle costing (LCC) models were developed in order to quantify the environmental footprint and cost and thus compare different manufacturing scenarios associated with the production of aeronautical structural components. To validate the models developed, they were implemented for the case of a helicopter's canopy processed by two techniques commonly used in aeronautics, namely the autoclave and the Resin Transfer moulding (RTM). The canopy was assumed to be made of a carbon fiber reinforced thermosetting material. Using the models developed the expected environmental and cost benefits by involving the RTM technique have been quantified.
    Type of Medium: Online Resource
    ISSN: 2261-236X
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2018
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  • 6
    Online Resource
    Online Resource
    EDP Sciences ; 2018
    In:  MATEC Web of Conferences Vol. 188 ( 2018), p. 02011-
    In: MATEC Web of Conferences, EDP Sciences, Vol. 188 ( 2018), p. 02011-
    Abstract: The precipitation hardenable and non-toxic Cu-Ni-Si alloys are good alternatives to Cu-Be and Cu-Co-Ni-Be alloys due to their high strength and high conductivity that can be attained by not only alloying but also thermo-mechanical routes. In this study, the fractographic analysis was carried out to understand the fatigue failure of aged 2.55Ni-0.55Si-0.25Zr-0.25Cr (wt-%) alloy which is a member of Corson family. In fatigue tests, a constant amplitude loading was applied at a stress ratio (R = σ min /σ max ) of -1 and different stress levels (400, 350, 200 and 175 MPa) were used. The fracture response of the alloy was discussed depending on the applied stress levels and microstructural features. It was concluded that (i) Ni,Zr-rich precipitates and Cr-rich precipitates at the grain boundaries caused crack nucleation at all stress levels and (ii) the interaction between Ni-rich silicides and dislocations at lower stress level resulted in localized shearing and fine striations.
    Type of Medium: Online Resource
    ISSN: 2261-236X
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2018
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  • 7
    In: MATEC Web of Conferences, EDP Sciences, Vol. 188 ( 2018), p. 02006-
    Abstract: In the present work, a numerical model is developed to predict the Young’s modulus and shear modulus of nanocrystalline materials using a Finite Element Analysis. The model is based on Representative Volume Elements (RVE) in which the microstructure of the material is described using the Voronoi tessellation algorithm. The use of the Voronoi particles was based on the observation of the morphology of nanocrystalline materials by Scanning Electron and Transmission Electron Microscopy. In each RVE, three-dimensional modelling of the grain and grain boundaries as randomly-shaped sub-volumes is performed. The developed model has been applied to pure nanocrystallline copper at grain volume fractions of 80%, 90% and 95% taking also into account the parameters of grain size and grain boundary thickness. The elastic moduli of nanocrystalline copper have been computed by loading the RVE in tension. The numerical results reveal that the elastic moduli of nanocrystalline copper increase with increasing the grain volume fraction. On the other hand, for a given grain volume fraction, the results showed no effect of the grain size. The model predictions have been validated successfully against numerical results from the literature and predictions of the Rule of Mixtures and the Mori-Tanaka analytical model.
    Type of Medium: Online Resource
    ISSN: 2261-236X
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2018
    detail.hit.zdb_id: 2673602-0
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  • 8
    In: Metals, MDPI AG, Vol. 9, No. 2 ( 2019-02-08), p. 202-
    Abstract: Nanocrystalline metals have been the cause of substantial intrigue over the past two decades due to their high strength, which is highly sensitive to their microstructure. The aim of the present project is to develop a finite element two-phase model that is able to predict the elastic moduli and the yield strength of nanostructured material as functions of their microstructure. The numerical methodology uses representative volume elements (RVEs) in which the material microstructure, i.e., the grains and grain boundaries, is presented utilizing the three-dimensional (3D) Voronoi algorithm. The implementation of the 3D Voronoi particles was performed on the nanostructure investigation of ultrafine materials by SEM and TEM. Proper material properties for the grain interiors (GI) and grain boundaries (GB) were computed using the Hall-Petch equation and a dislocation-based analytical approach, respectively. The numerical outcomes show that the Young’s Modulus of nanostructured copper increased by increasing the crystallite volume fraction, while the yield strength increased by decreasing the grain size. The numerical predictions were strongly confirmed in opposition to finite element outcomes, experimental results from the open literature, and predictions from the rule of mixtures and the Mori-Tanaka analytical models.
    Type of Medium: Online Resource
    ISSN: 2075-4701
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
    detail.hit.zdb_id: 2662252-X
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  • 9
    Online Resource
    Online Resource
    Emerald ; 2015
    In:  International Journal of Structural Integrity Vol. 6, No. 5 ( 2015-10-5), p. 567-577
    In: International Journal of Structural Integrity, Emerald, Vol. 6, No. 5 ( 2015-10-5), p. 567-577
    Abstract: – The purpose of this paper is to investigate the fracture of grade X42 microalloyed steel used as pipe material after tensile test at room temperature and impact tests at 0, −20 and −40°C, respectively. Design/methodology/approach – In the first stage of the study, X42 steels in the form of sheet and pipe materials were selected and etched samples were characterized using light microscope. In the second stage, mechanical properties of steels were obtained by microhardness measurements, static tensile and impact tests and all the broken surfaces were examined by scanning electron microscope to determine the fracture type as a function of both microstructure and loading. Findings – The examinations revealed that: first, the sheet material had a typical ferritic-pearlitic matrix, second, the transverse section of the sheet steel exhibited a matrix consisting of polygonal ferrite-aligned pearlite colonies and the longitudinal one had elongated ferrite phase and pearlite colonies in the direction of rolling, third, ferrite and pearlite distribution was different from the sheet material due to multiaxial deformation in the pipe material, fourth, tensile fracture surfaces of the steels had typical dimple fracture induced by microvoid coalescence, fifth, impact fracture surfaces of the steels changed as a function of the test temperature and cleavage fracture mode of ferritic-pearlitic matrix became more dominant as the temperature decreased, and sixth, grain morphology had an effect on the fracture behavior of the steels. Originality/value – The paper explains the fracture behaviour of X42 microalloyed pipeline steel and its fractographical analysis.
    Type of Medium: Online Resource
    ISSN: 1757-9864
    Language: English
    Publisher: Emerald
    Publication Date: 2015
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  • 10
    Online Resource
    Online Resource
    Emerald ; 2011
    In:  International Journal of Structural Integrity Vol. 2, No. 4 ( 2011-11-22)
    In: International Journal of Structural Integrity, Emerald, Vol. 2, No. 4 ( 2011-11-22)
    Type of Medium: Online Resource
    ISSN: 1757-9864
    Language: English
    Publisher: Emerald
    Publication Date: 2011
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