Driven by requirements of five-axis numerical control (NC) machine for its executive mechanism, this paper creatively proposes a flow path to synthesize a novel class of n-degree-of-freedom (n-DoF, 4 ≤ n ≤ 6) parallel manipulators (PMs) resorting to four steps, and takes a patented 5-DoF PM, named T5, for example to demonstrate the flow path in depth. Comparing with existing five-axis executive mechanisms, this novel class of the PMs has some advantages of light end-effector, good static, dynamic performance, and so on. Upon the underlying architecture of T5, the kinematic analysis and optimal design are carried out for the first time, in which two essential procedures are involved, one is the kinematic performance index by means of the reciprocal product associated with the wrench screw and twist screw with specific physical meaning, the other is the design method adopted to perform the multi-objective dimensional synthesis using an artificial intelligence approach, that is nondominated sorting genetic algorithm II (NSGA-II). This paper is aimed at laying a solid theoretical and technical foundation for the prototype design and manufacture of T5 PM.
Driven by the increasing demands of the aircraft assemblage for the pose-adjustment equipment in the large-scale component docking, this paper carries out the topology synthesis of a 1-translational and 3-rotational (1T3R) four degrees of freedom (DoF) parallel manipulator with an articulated traveling plate. First, the articulated traveling plate is defined as that includes more than one rigid body articulated by one or more kinematic joints. Then, the relationship among the DoFs of the parallel manipulator and the articulated traveling plate and the number of the in-parts are proposed. According to the agreement of the arrangement way between the open-loop limbs and the in-parts, the topology synthesis procedure of the 1T3R 4-DoF parallel manipulator with an articulated traveling plate is proposed. Finally, their topology structures are obtained by discussing those of four types in terms of 1D-H, 1D-V type with opposite layout and 1D-H, 1D-V type with adjacent layout, in which the topology structures exist only for 1D-H and 1D-V type with opposite layout.
The abnormal growth of Ag 3 Sn intermetallic compounds in eutectic Sn-3.5% Ag solder was investigated through high-temperature aging treatment. Microstructural evolutions of this solder before and after the aging treatment were observed by optical microscopy and scanning electron microscopy. Precise differential thermal analysis was made to study the changes in enthalpies of the solder under different conditions. The results reveal that the water-cooled solder is in metastable thermodynamic state due to the high free energy of Ag 3 Sn nanoparticles, which sporadically distribute in the matrix as second-phase. The second-phase Ag 3 Sn nanoparticles aggregate rapidly and grow to form bulk intermetallic compounds due to the migration of grain boundary between primary Sn-rich phase and the Ag 3 Sn nanoparticles during high temperature aging treatment.
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