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Chen Y.,Harbin Institute of Technology | Yang Z.,Harbin Institute of Technology | Tao W.,Harbin Institute of Technology | Chen J.,National Engineering Research Center for Commercial Aircraft Manufacturing | And 3 more authors.
Zhongguo Jiguang/Chinese Journal of Lasers | Year: 2013

The microstructure characteristics and mechanical properties of double-sided laser beam welded aluminum alloy T-joints for aircraft fuselage panels are systematically analyed. The experimental results show that five distinct zones are identified between the fusion zone center and the base material which consists cellular dendrite zone, parallel dendrite zone, partially melted zone, over-aged zone, and base material. The heat affected zone of the skin side is the weakest area. The tensile strength depends on the weld penetration, and the failure originates at the weld toe on the skin side. The average transverse and axial tensile strengths reach 87.8% and 53.1% of the base materials and the fracture mechanisms of the transverse and axial tensile tests are found to be ductile and brittle fracture, respectively. The average longitudinal tensile strength reaches 90.8% of the base materials, and the average elongation is 8.4% of the original test specimens. The dimples are small and shallow, the fracture is a mixture of ductile and brittle fracture, and a tearing trace near the fusion line appears. Fatigue failure is found to originate at the weld toe on the skin side and finally crack on the skin, and the conditioned fatigue strength is 80.7 MPa. The fracture at the weld toe is a mixture of ductile and brittle fracture, and the skin panel fracture appears brittle fracture feature. Source


Yang Z.,Harbin Institute of Technology | Tao W.,Harbin Institute of Technology | Liu S.,Harbin Institute of Technology | Chen J.,National Engineering Research Center for Commercial Aircraft Manufacturing | And 3 more authors.
Zhongguo Jiguang/Chinese Journal of Lasers | Year: 2013

With the development of double-sided laser beam welding technique of aluminum alloy T-joints for domestic aircraft fuselage panels as the ground, the effects of welding parameters and laser posture on the welding seam formation quality are studied in details, and the microstructure characteristics of the T-joints are also preliminarily discussed. The experimental results show that it can realize the welding of T-joints for aircraft fuselage panels by double-sided laser beam welding and can obtain good welding appearance. In order to get adequate weld, the heat input will be controlled between 25 J/mm and 35 J/mm by matching laser power to suitable welding speed. Moreover, the wire feeding speed must be reasonable matched to guarantee the smooth transition of the weld surface. It is better to adopt low incident beam angle under the requests of weld penetration and fusion area, which is good for reducing the heat effects of the heat input. The optimal incident beam position is determined to be 0.2 mm on the stringer yielding a 45°-50° seam angle, and the maximum tensile strength reaches a maximum value. In order to keep the double-sided weld symmetry and improve the mechanical properties of T-joints, the beam separation distances must be strictly controlled to realize the double-sided welds fused in a common molten. Five distinct zones are identified which consist of the cellular dendrite zone, parallel dendrite zone, partially melted zone, over-aged zone, and base material. The partially melted zone become narrower further from the fusion zone center and which on the skin side is obviously than that on the stringer side. Source


Zhang Y.,Harbin Institute of Technology | Tao W.,Harbin Institute of Technology | Chen Y.,Harbin Institute of Technology | Chen J.,National Engineering Research Center for Commercial Aircraft Manufacturing | And 2 more authors.
Zhongguo Jiguang/Chinese Journal of Lasers | Year: 2013

Double-sided fiber laser beam welding is used to synchronously weld T-section of fuselage panels (skins and stringers) for aluminum-lithium alloy 2060/2099 and shaping control is analyzed as well as long transverse (LT) tensile performance. The results indicate that a good fusion between skins and stringers can be obtained by using incident beam angle as small as possible in an adjustable range. The LT tensile strength reaches the maximum when the incident beam position is 0.1 mm on the stringer yielding a 45°~50° weld beam angle. To ensure weld microstructure uniformity and improve the T-joints' mechanical properties, beam separation distance must be strictly controlled to achieve the fusion of the double-sided welds in a common molten. In order to realize smooth transition of the weld surface, the ratio of wire feeding speed to welding speed should be matched with a reasonable value. For welds with a fully fusion and uniform microstructure, the key factor restricting the LT tensile strength is weld penetration. The average LT tensile strength reaches 80.1% of that of the base materials and the maximum rises up to 82.1%, when weld penetration is controlled in 1 mm. Source


Liu H.,National Engineering Research Center for Commercial Aircraft Manufacturing | Tao W.,Harbin Institute of Technology | Chen J.,National Engineering Research Center for Commercial Aircraft Manufacturing | Yang Z.,Harbin Institute of Technology | And 3 more authors.
Hanjie Xuebao/Transactions of the China Welding Institution | Year: 2013

The behavior characteristics of wire melting and fiber laser beam welding process of aluminum alloys with filler wire were carried out by using high-speed camera and experimental tests. The filler wire melting behavior and its main influencing factors were analyzed. The effect of wire feeding mode and wire feeding angle on weld formation and welding process stability were also studied. The results show that the melting behavior, which mainly depends on the distance between laser incident position and filler wire, can be divided into three types: the spreading transfer, the liquid bridge transfer and the globular transfer, and the liquid bridge transfer is the ideal type. The mode of pre-wire has higher efficiency and wider process window. The level of laser energy absorption by wire and the impact force of liquid wires on the liquid weld pool are affected by the wire feeding angle. The back weld width increases obviously with increase of wire feeding angle, while the weld penetration keeps essentially invariable. Source

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