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Liu W.,Inner Mongolia University of Technology | Xue J.,Inner Mongolia University of Technology | Li C.,Inner Mongolia University of Technology | Zhao Y.,The Sixth Academy of CASIC
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2013

When designing the structure of a certain solid propellant rocket motor's rolling ball joint socket nozzle, the maximal swing angle, the excursion of swing center, and the driving moment must be within the design limits permitted, and moreover, system must bear the extreme working loads. Motion state of system components is complicated because of the contact and the collision among the rolling ball, convex sphere, concave sphere and the separator. To solve the key problem of the contact load-bearing property which decides the design of the system structure and functions into play, the elastomeric collision between the ball and the separator in the joint is simulated as a parallel nonlinear spring damper, and the mode flexibility of convex sphere and concave sphere are described by the finite element method model. At the same time, the elastic contact model between the rolling ball and the convex-concave sphere model is established by introducing the calculation result of the elastic-plastic frictional contact deformation. The rigid and flexible coupled multi-body dynamics model of the system is established based on the first kind of Lagrange dynamics equation. The swing disciplinarian, excursion of swing center and driving moment of the system are calculated and analysed. By contrast with the torque measured of the pendulous test and ignition test, the structural design of system, the dynamic modeling method and its result's rationality are examined. © 2013 Journal of Mechanical Engineering. Source


Yang S.,Northwestern Polytechnical University | He G.-Q.,Northwestern Polytechnical University | Li J.,Northwestern Polytechnical University | Liu Y.,Northwestern Polytechnical University | And 3 more authors.
Guti Huojian Jishu/Journal of Solid Rocket Technology | Year: 2011

In this paper, charring layers microstructures of EPDM insulation in different erosion conditions were analyzed, and the charring layers were determined as gas-saturated porous media with dense layer and porous layer. Particle erosion was classified into two groups: mechanical erosion and particle heating increment. Mechanical erosion model was established by analyzing the structure of charring layer under various state parameters of particle erosion, and particle heating increment was obtained by experiment tests. The formation of dense layer inside the charring layer was fit to the theory of CVD. The particle erosion model was coupled with thermo-chemical model considering the porous structure of charring layer. The numerical results for different erosion conditions were found to reasonably agree well with the available experimental data, and the calculate structures of charring layer were almost consistent with the photos of microscope. Source


Liu Y.,Northwestern Polytechnical University | Li J.,Northwestern Polytechnical University | Yang S.,Northwestern Polytechnical University | Chen J.,Northwestern Polytechnical University | And 3 more authors.
Guti Huojian Jishu/Journal of Solid Rocket Technology | Year: 2011

The influence of particle concentration, impacting speed and angle on ablation characteristic of EPDM insulator were investigated based on test facility which can adjust particle concentration, impacting speed and angle. Different ablation rates of insulator material were obtained under different state parameters of particle erosion. Structures of carbonization layers were analyzed by scanning electron microscopy. Base on the structure of cavity, insulator mechanism of EPDM under high acceleration condition was discussed. The results show as follows: (1) By analyzing the influence law of carbonized ablation rates affected by different particle concentrations, impacting velocities and angels, it is found that a critical speed exists. When impacting speed is below the critical value, carbonized ablation rate changes slowly with speed and angle respectively. But if exceeding it, concave pits appear on the surface of carbonized layers. Carbonized ablation rates rise up sharply and the effects of angels cannot be ignored. (2) There are huge discrepancies in the surface and cross section of insulation layer, erosion modes and destroy mechanisms of different particle erosion condition. Compact/loose structures was formed in carburization layer of EPDM insulator. (3) In observing the structures of carbonized layers of basic formula by scanning electron microscope, three typical surface morphologies of the ablation were discovered with the increase of particle erosion speed.(4) The coupling relationship between thermochemistry ablation and parcile erosion is established through analyzing the abalation process of EPDM insulator under different parcile erosion conditions. Source


Liu Y.,Northwestern Polytechnical University | Li J.,Northwestern Polytechnical University | He G.-Q.,Northwestern Polytechnical University | Sun X.-Y.,The Sixth Academy of CASIC | Hu S.-F.,The Sixth Academy of CASIC
Tuijin Jishu/Journal of Propulsion Technology | Year: 2010

Ablation experiments of particle erosion for EPDM basic formulation, overload resistance formulation, no SiO2 formulation and no fiber formulation were performed on ground simulation test motor with high overload. Based on the results of ablation rate and surface characteristic of carburization layer, the formation mechanism of compact structure in carburization layer with both basic formulation and overload resistance formulation was studied. Ablation modes for variety formulation materials were analyzed as well. The results show that: the ablation ratios of different formulation at the same particles impacting conditions rank as follows: overload resistance formulation < basic formulation < no SiO2 formulation < no fiber formulation. It also shows that there are huge discrepancies in the surface and fracture surface profiles of insulation layer, erosion modes and destroy mechanisms of different formulations. Compact and loose structures were formed in carburization layer of both basic formulation and overload resistance formulation during erosion process. While no SiO2 formulation and no fiber formulation materials are destroyed mainly by graininess and sheet shape remove. Finally it shows that the erosion resistance of ablatives is improved by the compact structures on the surface, which are close related to the content of the fiber, SiO2 and the erosion environment. Source


Liu Y.,Northwestern Polytechnical University | Li J.,Northwestern Polytechnical University | He G.-Q.,Northwestern Polytechnical University | Li Q.,Northwestern Polytechnical University | And 2 more authors.
Tuijin Jishu/Journal of Propulsion Technology | Year: 2011

Focusing on the abnormal ablation of certain model solid rocket motor under flight overload condition, insulator material screen experiments were carried out based on the experimental simulation facility of high acceleration condition. Through the screen experiments the maximal carburization ablation rate and mass ablation rate were obtained, and the sort order of three kind of insulator ablation characteristic was achieved. In order to analyze the ablation mechanism of insulator, the surface and cross section configuration of the carburization layer were obtained by using the scanning electron microscope. The results show that: (1) under the same particles impacting conditions, the carburization ablation rate and mass ablation rate of insulator material B is maximal and A1 is minimal than others, and the material A take second place. The anti-particle erosion ability of material A1 is best than others. (2) the appropriate quantity of fiber and SiO2 could intensify the erosion resistance of ablatives because of the formation of the framework structures on carburization layer through the carbonization in situ of aramid fiber; (3) the new type insulator material system reinforced by aramid fiber and asbestos fiber synchronously was proposed. Source

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