Advanced Materials Research Vols. 816-817

Abstract: Indirect method combined with homotopy approach is used to solve low-thrust fuel-optimal problem. To start the homotopy progress, pseudospectral method is used to solve energy-optimal problem to generate the initial guess. The proposed approach is applied to Earth to a near earth asteroid rendezvous mission. The performance of such approach is demonstrated through simulation.

Abstract: In order to solve the heavy mass problem of the commercial vehicle drive axle housing, the structure of axle housing is optimized with finite element method. At first, the parametric finite element model of axle housing is built by using ANSYS software, and the dynamic response characteristics of axle housing are obtained with transient dynamics analysis. The dynamic analysis results show that strength and stiffness of axle housing can satisfy design criteria very well. Then the fatigue life of axle housing are predicted based on the dynamics analysis, and results show that the fatigue dangerous regions occur on the spring seats. Finally, the structure optimization of axle housing is done aimed at lightweight with goal drive optimization method, and the fatigue life of optimized axle housing are verified with FEA and bench test. The results of verification by both FEA and test show that the optimized axle housing has apparent lightweight effects with its fatigue life meeting design requirements.

Abstract: Geometric analyses and mechanical analytical method are used to study a kind of D-type driving mechanism. The theoretical formulae of computing angular velocities of the connecting rod and the rocker are given, and the linear velocity of the driving point C is obtained, and the finite differential numerical method for computing the angular velocities of the connecting rod and the rocker is also introduced. The results of the given numerical example show the feasibility of the theoretical conclusions here.

Abstract: In the rubber mixing production line, because of the traditional design method, the stiffness of the small arm of feed mechanism is usually not enough and the reserve of strength and weight is surplus. To solve the above problems, we optimized the arm structure with the optimization design module of the finite element analysis software. Based on the structure theory and optimization design theory, the three-dimensional model and the proper optimization model been established with the three-dimensional software and finite element analysis software. The total weight of the small arm is used as the objective of optimization and the dimensions of each parts is used as the design variables. Under the precondition of requirements of strength and stiffness, the optimal solution of these dimensions is figured out. Analysis shows that the method of structure optimization is feasible. This method provides an important reference for the optimization design of feed mechanism's small arm and similar parts.

Abstract: Thermo-mechanical failure is the main factor to impact the microelectronic packaging reliability. Under thermal loads, the microelectronic packaging is easy to produce cracks, delamination, voids, and other defects, which can emerge and grow under thermo-mechanical stresse caused by the different coefficients of thermal expansion (CTE). Firstly, a geometric model of Plastic Leaded Chip Carrier (PLCC) packaging was established and the thermo-mechanical property of PLCC packaging was analyzed using finite element analysis (FEA) software ANSYS. Then, the thermal cycling test on a set of PLCC packaging was conducted according to the MIL-STD-883H Microcircuits Test Method Standard with temperature range from-65°C to 150°C, and the crack growth rate of PLCC packaging was studied experimentally using Scanning Acoustic Microscopy (SAM). Finally, the Anand model was adopted to predict thermal fatigue life, which was consistent with the experimental results. With these researches, the thermo-mechanical reliability evaluation of the PLCC packaging was investigated using finite element analysis (FEA) combined with analytical methods.

Abstract: A two-level method is presented to improve dynamic characteristic of a truss and let it out of the resonance region. The does is as follow: selected the desired design variable by sensitivity analysis, used the optimum solution of the subproblem approximation method as initial solution of the simplex method, and improved the simplex method by introducing golden section method. While ensuring requirement of strength, stiffness and stability, the two-level method makes the truss less weight and avoids the resonance region. The improved simplex method searches the better point further by introducing golden section method on the path of the extending principle and the shrinking principle and reduces searching times.

Abstract: Nowadays, a complicated and expensive conformation jig is needed to inspect the nonrigid parts. In a free-state condition, these parts may have a significant different shape than their nominal model (CAD) due to gravity loads and residual stress. In this paper, we present a new method for automatic fixtureless inspection of nonrigid parts. The inspection in our case is limited to the profile deviation as required by ASME Y14.5 standard and the defects are dent shapes. Our method combines the curvature estimation, one of the intrinsic properties of the geometry, with the Thomson statistical test in order to identify the defects due to the inherent variations of the manufacturing process from the deformations due to the flexibility of the part. The method is tested and validated on a simulated flexible part representing a typical sheet metal from the transport industry.

Abstract: In this article, the fault problem of power system is investigated with an adaptive immune genetic algorithm (AIGA) for the complications of fault. By introducing new crossover rate and mutation rate, considering the general characteristics of population, vaccines are extracted with dynamic self-adaption approach, thus avoiding the disadvantage of standard genetic algorithm. On the other hand, with the idea of survival of the fittest, the antibody population with low fitness is replaced by parts of new antibody generated randomly, which allows the variety of population. A general power system is employed to show the efficiency of the new method.

Abstract: The output performance of piezoelectric double mode energy harvester is studied, which is provided with a dynamic magnifier consisting of a spring-mass system placed between the piezoelectric element and the moving base. The theory governing the operation of the energy harvester with dynamic magnifier is developed using the Lagrangian dynamic approach, Numerical examples are presented to illustrate the output performance of the energy harvester in comparison with the conventional energy harvester, the results show that with proper selection of the design parameters of the magnifier, the harvested power can be dramatically enhanced and the effective bandwidth of the harvester can be improved.

Abstract: Kinematic analysis plays an important role in the research of parallel kinematic mechanism. This paper addresses a novel forward kinematic solution based on RBF neural network for a novel 2PRRR-PPRR redundantly actuated parallel mechanism. Simulation results illustrate the validity and feasibility of the kinematic analysis method.