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Qin H.,Hangzhou Dianzi University | Cai Z.,Zhejiang University | Hu H.,Hangzhou Dianzi University | Wang J.,Shanghai Institute of Aerospace Systems Engineering | And 2 more authors.
Marine Georesources and Geotechnology | Year: 2016

The shortcomings of gravity corers in sampling marine sediments have been observed extensively in various field tests. In order to optimize the coring, this article provides an alternative numerical way to model the gravity coring and analyze the sampling effect. Based on this analysis, a new hydraulic hammer corer is devised. A coupled Eulerian-Lagrangian method with capability of simulating the problem involving extreme deformation, penetration is used to simulate the coring process. The results show that the hydrostatic pressure and deviator stress increase and reach their peak when the pile tip is slightly above or at the level of the observation point and then drop rapidly when the pile tip slides below the observation point. In addition, the stress path indicates that the soil element sustains plastic compression before yielding and then expands until recovering to the original state. The obvious “under-sampling” phenomenon is also well-captured by the finite element model. 2016 Copyright © Taylor & Francis Group, LLC

Qin H.,Hangzhou Dianzi University | Hu H.,Hangzhou Dianzi University | Ye W.,University of Wolverhampton | Wang J.,Shanghai Institute of Aerospace Systems Engineering | And 2 more authors.
Journal of Pressure Vessel Technology, Transactions of the ASME | Year: 2014

The hydrostatic corer is designed for sampling sediment from the seafloor. Its operation relies on a water distributing valve which converts the potential pressure difference between ambient seawater and a built-in chamber with atmospheric pressure to the dynamic energy as the driving power. As the valve is exposed to the ambient water, the deformation of its components may exceed their fitting tolerance under the high pressure and low temperature on seafloor, and thus cause the failure of the valve. Three possible failure modes have been taken into account, representing the positions where interference of fitting tolerance is likely to occur. Corresponding models are then created considering the coupled effects of pressure and temperature on the valve. Based on the model results and the reliability requirement of the corer, one failure mode is selected to calculate the reliability of the valve and is used as guidance for the future improvement of the design. Copyright © 2014 by ASME.

Chen J.,Nanjing University of Aeronautics and Astronautics | Nie H.,Nanjing University of Aeronautics and Astronautics | Bo W.,Shanghai Institute of Aerospace Systems Engineering
Journal of Vibroengineering | Year: 2013

In the overall study of the design and performance of the lunar Lander, analysis of touchdown dynamics of the landing stage is an important part. In this paper, the influence of the lunar Lander's body deformation on the landing performance is studied. First, the equations with the flexible part are derived from the subsystem method and deducing a multi-mass model by comparing and analyzing the mode of the body in Lander. Second, based on the existing aluminum honeycomb buffering and the model used in the landing-impact tests for the soft-landing system, a finite element model for the cantilever-type landing gear with four legs is established in MSC.Patran and submitted to MSC.Dytran to conduct a simulation analysis. Finally, the flexibility of lander's body to the performance in landing is studied. Results show that the deformation of the body has considerable effect on the overloading of the lunar Lander system though the deforming can absorb litter energy during landing. © VIBROENGINEERING.

Chen J.,Nanjing University of Aeronautics and Astronautics | Nie H.,Nanjing University of Aeronautics and Astronautics | Zhang Z.,Shanghai Institute of Satellite Engineering | Li L.,Shanghai Institute of Aerospace Systems Engineering
Journal of Vibroengineering | Year: 2014

Lunar exploration is one of the most important projects in the world. A primary objective of the probe in lunar is to soft-land a manned spacecraft on lunar surface. The soft-landing system is the key composition of the lunar lander. In the overall design of lunar lander, the analysis of touchdown dynamics during landing stage is an important work. In this paper, firstly, based on the mechanical theory, a finite element model for the lunar lander is established. Secondly, the linear static structural analysis under particular conditions is performed to determine the nodal stress and displacement distributions and the modal analysis is conducted to obtain the frequencies and their corresponding vibration shapes. Finally, the weakness parts of the structure and the behavior of the system are obtained by analyzing the simulating results, which are beneficial to the optimizing design for the lunar Lander. © JVE INTERNATIONAL LTD.

Gu Q.-W.,Harbin Institute of Technology | Zhang S.-J.,Harbin Institute of Technology | Zeng Z.-K.,Harbin Institute of Technology | Zeng Z.-K.,Shanghai Institute of Aerospace Systems Engineering | Ning M.-F.,Harbin Institute of Technology
Yuhang Xuebao/Journal of Astronautics | Year: 2016

Aiming at pose (relative attitude and position) estimation of non-cooperative spacecraft, an algorithm is developed based on monocular vision and some natural feature points. Considering the increasing estimated error caused by using the natural features, this paper introduces an iterative solution based on convex relaxation optimization and LMI algorithm to solve this problem. The optimization model in this paper is built on adverse projection. First, using relaxation algorithm, turn the non-convex and equality constrained attitude matrix to a convex and inequality constrained matrix. Then, this paper can prove that the convex problem is equal to the original problem. That is, when the convex problem gets extremum, the attitude matrix still satisfies the original equality and non-convex constrain. To further simplify this problem, we can express the convex and unequal constrain as linear matrix inequalities. At last, we can solve it with the developed interior point method and prove convergence of this algorithm. Finally, in the background of on-orbit servicing, the simulation experiment shows that this algorithm can converge within 7 iterations. Compared with SVD, this algorithm nearly doubles accuracy when noise increases gradually. And the results show that this algorithm is robust and efficient. © 2016, Editorial Dept. of JA. All right reserved.

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