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Shu Guo - One of the best experts on this subject based on the ideXlab platform.

  • nano indentation investigation on the local softening of equiaxed zone in 2060 t8 2099 t83 aluminum lithium Alloys t joints welded by double sided laser beam welding
    Journal of Alloys and Compounds, 2018
    Co-Authors: Bing Han, Yanbin Chen, Wang Tao, Zhenglong Lei, Shu Guo
    Abstract:

    Abstract Double-sided laser beam welding of 2-mm-thick 2060-T8 and 2099-T83 Aluminum-Lithium Alloys T-joint was performed with AlSi12 wire. Microstructure and nano-indentation hardness characteristics were studied especially in nondendritic equiaxed zone (EQZ). In comparison with the precipitates of LiAlSi, Mg2Si and Al2Cu in weld zone except for the EQZ, an AlCuFeMn icosahedral quasicrystal was detected in the EQZ and Al3Zr particle could be the heteromorphic core of this quasicrystal phase. Local softening problem was confirmed in the EQZ's localized enrichment regions by nano-indentation tests. The cross sections of different indents in and out of the EQZ's local softening area prepared by focused ion beam (FIB) were examined by using transmission electron microscopy (TEM). For the first time, it was directly observed that an intergranular tiny hot crack was formed right underneath the indent tip in the EQZ's local softening area, and mainly thin Al2Cu precipitates were generated and sparsely distributed in equiaxed grains and their boundaries. However, thick and continuous Al2Cu intergranular precipitates with no microcrack defect were observed below the indent in the other area in the EQZ without softening. Obviously, local softening in the EQZ was most likely to be induced by a combined action of the formation of microcrack and the absence of abundant Al2Cu precipitates in equiaxed grain boundaries. Since the quantity and size of Al3Zr particle were both much smaller than those of Al2Cu, it had more limited impact on the EQZ's local softening than Al2Cu particle in equiaxed grain.

Bing Han - One of the best experts on this subject based on the ideXlab platform.

  • nano indentation investigation on the local softening of equiaxed zone in 2060 t8 2099 t83 aluminum lithium Alloys t joints welded by double sided laser beam welding
    Journal of Alloys and Compounds, 2018
    Co-Authors: Bing Han, Yanbin Chen, Wang Tao, Zhenglong Lei, Shu Guo
    Abstract:

    Abstract Double-sided laser beam welding of 2-mm-thick 2060-T8 and 2099-T83 Aluminum-Lithium Alloys T-joint was performed with AlSi12 wire. Microstructure and nano-indentation hardness characteristics were studied especially in nondendritic equiaxed zone (EQZ). In comparison with the precipitates of LiAlSi, Mg2Si and Al2Cu in weld zone except for the EQZ, an AlCuFeMn icosahedral quasicrystal was detected in the EQZ and Al3Zr particle could be the heteromorphic core of this quasicrystal phase. Local softening problem was confirmed in the EQZ's localized enrichment regions by nano-indentation tests. The cross sections of different indents in and out of the EQZ's local softening area prepared by focused ion beam (FIB) were examined by using transmission electron microscopy (TEM). For the first time, it was directly observed that an intergranular tiny hot crack was formed right underneath the indent tip in the EQZ's local softening area, and mainly thin Al2Cu precipitates were generated and sparsely distributed in equiaxed grains and their boundaries. However, thick and continuous Al2Cu intergranular precipitates with no microcrack defect were observed below the indent in the other area in the EQZ without softening. Obviously, local softening in the EQZ was most likely to be induced by a combined action of the formation of microcrack and the absence of abundant Al2Cu precipitates in equiaxed grain boundaries. Since the quantity and size of Al3Zr particle were both much smaller than those of Al2Cu, it had more limited impact on the EQZ's local softening than Al2Cu particle in equiaxed grain.

  • double sided laser beam welded t joints for aluminum lithium alloy aircraft fuselage panels effects of filler elements on microstructure and mechanical properties
    Optics and Laser Technology, 2017
    Co-Authors: Bing Han, Wang Tao, Yanbin Chen
    Abstract:

    Abstract In the current work, T-joints consisting of 2.0 mm thick 2060-T8/2099-T83 Aluminum-Lithium Alloys for aircraft fuselage panels have been fabricated by double-sided fiber laser beam welding with different filler wires. A new type wire CW3 (Al-6.2Cu-5.4Si) was studied and compared with conventional wire AA4047 (Al-12Si) mainly on microstructure and mechanical properties. It was found that the main combined function of Al-6.2%Cu-5.4%Si in CW3 resulted in considerable improvements especially on intergranular strength, hot cracking susceptibility and hoop tensile properties. Typical non-dendritic equiaxed zone (EQZ) was observed along welds’ fusion boundary. Hot cracks and fractures during the load were always located within the EQZ, however, this typical zone could be restrained by CW3, effectively. Furthermore, changing of the main intergranular precipitated phase within the EQZ from T phase by AA4047 to T2 phase by CW3 also resulted in developments on microscopic intergranular reinforcement and macroscopic hoop tensile properties. In addition, bridging caused by richer substructure dendrites within CW3 weld’s columnar zone resulted in much lower hot cracking susceptibility of the whole weld than AA4047.

Cano Miguel - One of the best experts on this subject based on the ideXlab platform.

  • Contribution à l'étude du comportement mécanique d'un ruban de préimprégné dans le procédé de placement de fibres : analyse expérimentale et modélisation
    2010
    Co-Authors: Cano Miguel
    Abstract:

    Une grande partie de la structure des avions modernes est fabriquée à partir des dernières générations de matériaux composites. Le principal défi des constructeurs d’avions réside dans la taille importante des pièces en composites. D’où la nécessité de développer de nouvelles technologies de fabrication telle que la dépose automatique de préimprégné. La qualité des pièces fabriquées dépend de nombreux facteurs dont notamment la maîtrise de la rhéologie de la résine du préimprégné. Cette dernière évolue fortement avec les conditions environnementales et les conditions de fabrication. Elle détermine pour partie, les instabilités de la matière particulièrement le long des trajectoires curvilignes. Ces instabilités, qui se présentent sous forme de cloques, engendrent après cuisson des pièces avec des défauts de repliement des couches dans les stratifiés. L’objectif principal de cette thèse de doctorat est l’étude du comportement mécanique d’un ruban de préimprégné prenant en compte la rhéologie de la matière ainsi que sa pégosité dans le but de mieux comprendre les conditions d’apparition des cloques en trajectoire curviligne. Une partie de mes travaux est consacrée à la caractérisation des propriétés physico-chimiques et mécaniques de la matière. Une seconde partie, complémentaire à la première, est dédiée au développement d’un modèle de comportement mécanique d’une plaque sur fondation élastique représentant le ruban de préimprégné et soumise à une rotation imposée. La méthode de Ritz a été utilisée pour l'obtention de solutions explicites des charges critiques de flambement. Il a été montré que les plus faibles rayons de courbure sans formation de cloques en trajectoire curviligne dans le plan sont obtenus avec un faible écrasement du rouleau et un niveau de collant élevé.The evolution of composite materials in aerospace has been spectacular over the last thirty years. The main advantage provided by composites is weight gain compared to other materials. However, new aluminum lithium Alloys may slow this trend because of their specific properties and exceptional manufacturing costs lower than those of composites. Much parts of the structure of the A380 are made from the latest generation of composite materials with organic matrix. The Airbus A380 is the first plane of the manufacturer composed by a center wing box made by composite reinforced with carbon fibers and organic matrix. And like the devices that preceded it, the center wing box, rudder, horizontal stabilizer and the elevators were designed with composites reinforced with carbon fibers and organic matrix. But the main challenge with the new aircraft is the size of parts ; the size of the horizontal stabilizer of the A380 for example, is similar to the wing of the A310. Hence the need to develop the intensive use of automatic prepreg lay up technology. The use of semi-finished prepregs for the manufacture of parts allows standardizing production. Indeed, these products exhibit with the desired rate of reinforcement on the final parts, all the delicate operations of pumping excess resin during the implementation of parts, as the case in the RTM process (Resin Transfer Molding) are eliminated. The quality of parts produced using automatic lay up depends on many factors including the accuracy of trajectory lay up, the control of rheology of the resin contained in the prepreg and behavior at the interface of the material and tooling. The rheology of the resin is changing considerably with environmental conditions (temperature, humidity) and processing conditions (speed of removal, compaction strength). It determines in part and in combination with the tackiness of the prepreg, the instabilities of the material particularly along curved trajectories. In curvilinear lay up, the rotation of the tow placement head imposes to this portion of slit tape, a curvature generating a circular bending phenomenon.The outer portion of the tape is then stretched while the inside is compressed. When the radius of curvature of the tow placement head is low, the result is a phenomenon of local buckling of the slit tape. The corresponding layer waviness (See figure 1) is visible after the passage of the roller so instantly or delayed, depending on the conditions of lay up (speed lay up,compaction strength, temperature, humidity) and the tackiness of the material. Thus, the formation of the layer waviness is a local phenomenon that appears in the material between the tow placement head and tools. It is this area of the material defined by the form of plate, and the extent of which depends on the compaction strength and flexibility of the roller which will be the model proposed in this communication. It is supposed that this plate is based on elastic foundation in order to reflect the tack of the material. The formation mechanism of ply waviness is very few studied and remains unclear since these defects appear at different steps in the manufacturing process. Some studies recommend, without justification, to not exceed some radius of curvature to avoid buckling [1]. Interactions between tooling and material in relation with lay up conditions were studied [2]. In this paper we study the mechanical behavior of a slit tape taking into account the rheology of the material so that his tack in order to better understand the conditions of appearance of layer waviness during circular trajectories. At first, we will present some results from the identification of physico-chemical and mechanical properties of prepreg carbon / epoxy and then we will explain the evolutions observed. A second part, complements the first,will be dedicated to the development of a model of mechanical behavior of a plate based onelastic foundation, representing the slit tape which is subjected to a rotation imposed. The mechanical model of the slit tape will be based on the theory of plate under the hypotheses of Kirchhoff-Love and Von-Karman. Determining the critical buckling load is carried by the Ritz method. The simulation results using different boundary conditions will be analyzed and compared to real cases

  • Contribution à l'étude du comportement mécanique d'un ruban de préimprégné dans le procédé de placement de fibres (analyse expérimentale et modélisation)
    2010
    Co-Authors: Cano Miguel, Beakou Alexis
    Abstract:

    Une grande partie de la structure des avions modernes est fabriquée à partir des dernières générations de matériaux composites. Le principal défi des constructeurs d avions réside dans la taille importante des pièces en composites. D où la nécessité de développer de nouvelles technologies de fabrication telle que la dépose automatique de préimprégné. La qualité des pièces fabriquées dépend de nombreux facteurs dont notamment la maîtrise de la rhéologie de la résine du préimprégné. Cette dernière évolue fortement avec les conditions environnementales et les conditions de fabrication. Elle détermine pour partie, les instabilités de la matière particulièrement le long des trajectoires curvilignes. Ces instabilités, qui se présentent sous forme de cloques, engendrent après cuisson des pièces avec des défauts de repliement des couches dans les stratifiés. L objectif principal de cette thèse de doctorat est l étude du comportement mécanique d un ruban de préimprégné prenant en compte la rhéologie de la matière ainsi que sa pégosité dans le but de mieux comprendre les conditions d apparition des cloques en trajectoire curviligne. Une partie de mes travaux est consacrée à la caractérisation des propriétés physico-chimiques et mécaniques de la matière. Une seconde partie, complémentaire à la première, est dédiée au développement d un modèle de comportement mécanique d une plaque sur fondation élastique représentant le ruban de préimprégné et soumise à une rotation imposée. La méthode de Ritz a été utilisée pour l'obtention de solutions explicites des charges critiques de flambement. Il a été montré que les plus faibles rayons de courbure sans formation de cloques en trajectoire curviligne dans le plan sont obtenus avec un faible écrasement du rouleau et un niveau de collant élevé.The evolution of composite materials in aerospace has been spectacular over the last thirty years. The main advantage provided by composites is weight gain compared to other materials. However, new aluminum lithium Alloys may slow this trend because of their specific properties and exceptional manufacturing costs lower than those of composites. Much parts of the structure of the A380 are made from the latest generation of composite materials with organic matrix. The Airbus A380 is the first plane of the manufacturer composed by a center wing box made by composite reinforced with carbon fibers and organic matrix. And like the devices that preceded it, the center wing box, rudder, horizontal stabilizer and the elevators were designed with composites reinforced with carbon fibers and organic matrix. But the main challenge with the new aircraft is the size of parts ; the size of the horizontal stabilizer of the A380 for example, is similar to the wing of the A310. Hence the need to develop the intensive use of automatic prepreg lay up technology. The use of semi-finished prepregs for the manufacture of parts allows standardizing production. Indeed, these products exhibit with the desired rate of reinforcement on the final parts, all the delicate operations of pumping excess resin during the implementation of parts, as the case in the RTM process (Resin Transfer Molding) are eliminated. The quality of parts produced using automatic lay up depends on many factors including the accuracy of trajectory lay up, the control of rheology of the resin contained in the prepreg and behavior at the interface of the material and tooling. The rheology of the resin is changing considerably with environmental conditions (temperature, humidity) and processing conditions (speed of removal, compaction strength). It determines in part and in combination with the tackiness of the prepreg, the instabilities of the material particularly along curved trajectories. In curvilinear lay up, the rotation of the tow placement head imposes to this portion of slit tape, a curvature generating a circular bending phenomenon.The outer portion of the tape is then stretched while the inside is compressed. When the radius of curvature of the tow placement head is low, the result is a phenomenon of local buckling of the slit tape. The corresponding layer waviness (See figure 1) is visible after the passage of the roller so instantly or delayed, depending on the conditions of lay up (speed lay up,compaction strength, temperature, humidity) and the tackiness of the material. Thus, the formation of the layer waviness is a local phenomenon that appears in the material between the tow placement head and tools. It is this area of the material defined by the form of plate, and the extent of which depends on the compaction strength and flexibility of the roller which will be the model proposed in this communication. It is supposed that this plate is based on elastic foundation in order to reflect the tack of the material. The formation mechanism of ply waviness is very few studied and remains unclear since these defects appear at different steps in the manufacturing process. Some studies recommend, without justification, to not exceed some radius of curvature to avoid buckling [1]. Interactions between tooling and material in relation with lay up conditions were studied [2]. In this paper we study the mechanical behavior of a slit tape taking into account the rheology of the material so that his tack in order to better understand the conditions of appearance of layer waviness during circular trajectories. At first, we will present some results from the identification of physico-chemical and mechanical properties of prepreg carbon / epoxy and then we will explain the evolutions observed. A second part, complements the first,will be dedicated to the development of a model of mechanical behavior of a plate based onelastic foundation, representing the slit tape which is subjected to a rotation imposed. The mechanical model of the slit tape will be based on the theory of plate under the hypotheses of Kirchhoff-Love and Von-Karman. Determining the critical buckling load is carried by the Ritz method. The simulation results using different boundary conditions will be analyzed and compared to real cases.CLERMONT FD-Bib.électronique (631139902) / SudocSudocFranceF

Yanbin Chen - One of the best experts on this subject based on the ideXlab platform.

  • nano indentation investigation on the local softening of equiaxed zone in 2060 t8 2099 t83 aluminum lithium Alloys t joints welded by double sided laser beam welding
    Journal of Alloys and Compounds, 2018
    Co-Authors: Bing Han, Yanbin Chen, Wang Tao, Zhenglong Lei, Shu Guo
    Abstract:

    Abstract Double-sided laser beam welding of 2-mm-thick 2060-T8 and 2099-T83 Aluminum-Lithium Alloys T-joint was performed with AlSi12 wire. Microstructure and nano-indentation hardness characteristics were studied especially in nondendritic equiaxed zone (EQZ). In comparison with the precipitates of LiAlSi, Mg2Si and Al2Cu in weld zone except for the EQZ, an AlCuFeMn icosahedral quasicrystal was detected in the EQZ and Al3Zr particle could be the heteromorphic core of this quasicrystal phase. Local softening problem was confirmed in the EQZ's localized enrichment regions by nano-indentation tests. The cross sections of different indents in and out of the EQZ's local softening area prepared by focused ion beam (FIB) were examined by using transmission electron microscopy (TEM). For the first time, it was directly observed that an intergranular tiny hot crack was formed right underneath the indent tip in the EQZ's local softening area, and mainly thin Al2Cu precipitates were generated and sparsely distributed in equiaxed grains and their boundaries. However, thick and continuous Al2Cu intergranular precipitates with no microcrack defect were observed below the indent in the other area in the EQZ without softening. Obviously, local softening in the EQZ was most likely to be induced by a combined action of the formation of microcrack and the absence of abundant Al2Cu precipitates in equiaxed grain boundaries. Since the quantity and size of Al3Zr particle were both much smaller than those of Al2Cu, it had more limited impact on the EQZ's local softening than Al2Cu particle in equiaxed grain.

  • double sided laser beam welded t joints for aluminum lithium alloy aircraft fuselage panels effects of filler elements on microstructure and mechanical properties
    Optics and Laser Technology, 2017
    Co-Authors: Bing Han, Wang Tao, Yanbin Chen
    Abstract:

    Abstract In the current work, T-joints consisting of 2.0 mm thick 2060-T8/2099-T83 Aluminum-Lithium Alloys for aircraft fuselage panels have been fabricated by double-sided fiber laser beam welding with different filler wires. A new type wire CW3 (Al-6.2Cu-5.4Si) was studied and compared with conventional wire AA4047 (Al-12Si) mainly on microstructure and mechanical properties. It was found that the main combined function of Al-6.2%Cu-5.4%Si in CW3 resulted in considerable improvements especially on intergranular strength, hot cracking susceptibility and hoop tensile properties. Typical non-dendritic equiaxed zone (EQZ) was observed along welds’ fusion boundary. Hot cracks and fractures during the load were always located within the EQZ, however, this typical zone could be restrained by CW3, effectively. Furthermore, changing of the main intergranular precipitated phase within the EQZ from T phase by AA4047 to T2 phase by CW3 also resulted in developments on microscopic intergranular reinforcement and macroscopic hoop tensile properties. In addition, bridging caused by richer substructure dendrites within CW3 weld’s columnar zone resulted in much lower hot cracking susceptibility of the whole weld than AA4047.

Wang Tao - One of the best experts on this subject based on the ideXlab platform.

  • nano indentation investigation on the local softening of equiaxed zone in 2060 t8 2099 t83 aluminum lithium Alloys t joints welded by double sided laser beam welding
    Journal of Alloys and Compounds, 2018
    Co-Authors: Bing Han, Yanbin Chen, Wang Tao, Zhenglong Lei, Shu Guo
    Abstract:

    Abstract Double-sided laser beam welding of 2-mm-thick 2060-T8 and 2099-T83 Aluminum-Lithium Alloys T-joint was performed with AlSi12 wire. Microstructure and nano-indentation hardness characteristics were studied especially in nondendritic equiaxed zone (EQZ). In comparison with the precipitates of LiAlSi, Mg2Si and Al2Cu in weld zone except for the EQZ, an AlCuFeMn icosahedral quasicrystal was detected in the EQZ and Al3Zr particle could be the heteromorphic core of this quasicrystal phase. Local softening problem was confirmed in the EQZ's localized enrichment regions by nano-indentation tests. The cross sections of different indents in and out of the EQZ's local softening area prepared by focused ion beam (FIB) were examined by using transmission electron microscopy (TEM). For the first time, it was directly observed that an intergranular tiny hot crack was formed right underneath the indent tip in the EQZ's local softening area, and mainly thin Al2Cu precipitates were generated and sparsely distributed in equiaxed grains and their boundaries. However, thick and continuous Al2Cu intergranular precipitates with no microcrack defect were observed below the indent in the other area in the EQZ without softening. Obviously, local softening in the EQZ was most likely to be induced by a combined action of the formation of microcrack and the absence of abundant Al2Cu precipitates in equiaxed grain boundaries. Since the quantity and size of Al3Zr particle were both much smaller than those of Al2Cu, it had more limited impact on the EQZ's local softening than Al2Cu particle in equiaxed grain.

  • double sided laser beam welded t joints for aluminum lithium alloy aircraft fuselage panels effects of filler elements on microstructure and mechanical properties
    Optics and Laser Technology, 2017
    Co-Authors: Bing Han, Wang Tao, Yanbin Chen
    Abstract:

    Abstract In the current work, T-joints consisting of 2.0 mm thick 2060-T8/2099-T83 Aluminum-Lithium Alloys for aircraft fuselage panels have been fabricated by double-sided fiber laser beam welding with different filler wires. A new type wire CW3 (Al-6.2Cu-5.4Si) was studied and compared with conventional wire AA4047 (Al-12Si) mainly on microstructure and mechanical properties. It was found that the main combined function of Al-6.2%Cu-5.4%Si in CW3 resulted in considerable improvements especially on intergranular strength, hot cracking susceptibility and hoop tensile properties. Typical non-dendritic equiaxed zone (EQZ) was observed along welds’ fusion boundary. Hot cracks and fractures during the load were always located within the EQZ, however, this typical zone could be restrained by CW3, effectively. Furthermore, changing of the main intergranular precipitated phase within the EQZ from T phase by AA4047 to T2 phase by CW3 also resulted in developments on microscopic intergranular reinforcement and macroscopic hoop tensile properties. In addition, bridging caused by richer substructure dendrites within CW3 weld’s columnar zone resulted in much lower hot cracking susceptibility of the whole weld than AA4047.