Multi-objective optimization of different dome reinforcement methods for composite cases

A multi-objective optimization method was proposed for different dome reinforcement methods of a filament-wound solid rocket motor composite case based on a Radial Basis Function (RBF) model. Progressive damage of the composite case was considered in a simulation based on Hashin failure criteria, and simulation results were validated by hydraulic burst tests to precisely predict the failure mode, failure position, and burst pressure. An RBF surrogate model was established and evaluated by Relative Average Absolute Error (RAAE), Relative Maximum Absolute Error (RMAE), Root Mean Squared Error (RMSE), and R² methods to improve the optimization efficient of dome reinforcement. In addition, the Non-dominated Sorting Genetic Algorithm (NSGA-II) was employed to establish multi-objective optimization models of variable-angle and variable-polar-radius dome reinforcements to investigate the coupling effect of the reinforcement angle, reinforcement layers, and reinforcement range on the case performance. Optimal reinforcement parameters were obtained and used to establish a progressive damage model of the composite case with dome reinforcement. In accordance with progressive damage analysis, the burst pressure and performance factor were obtained. Results illustrated that variable-angle dome reinforcement was the optimal reinforcement method compared with variable-polar-radius dome reinforcement as it could not only ensure the reinforcement angle’s continuous changing but also decrease the mass of composite materials. Compared with the unreinforced case, the reinforced case exhibited an increase in the burst pressure and performance factor of 36.1% and 23.5%, respectively.     

Short term topological changes of coronal holes associated with prominence eruptions and subsequent CMEs

We study the short-term topological changes of equatorial and polar coronal hole (CH) boundaries, such as a variation of their area and disintegration, associated to reconnection with nearby (within 15° distance) quiescent prominence magnetic fields leading to eruptions and subsequent Coronal Mass Ejections (CMEs). The examples presented here correspond to the recent solar minimum years 2008 and 2009. We consider a temporal window of one day between the CH topological changes and the start and end times of prominence eruptions and onset of CMEs. To establish this association we took into account observational conditions related to the instability of prominence/filaments, the occurrence of a CME, as well as the subsequent evolution after the CME. We found an association between short-term local topological changes in CH boundaries and the formation/disappearance of bright points near them, as well as, between short-term topological changes within the whole CH and eruptions of nearby quiescent prominences followed by the appearance of one or more CMEs.     

纤维缠绕壳体封头厚度的计算方法

纤维缠绕固体发动机壳体的厚度是不均匀的,壳体的封头形状、纱带宽度及两端开口均影响它的厚度.本文利用纤维叠带几何关系推导了一种计算纤维缠绕壳体封头厚度的公式.使用这一公式计算的壳体封头厚度,经与实测值比较表明,计算精度较高,可供纤维缠绕发动机壳体设计、工艺人员使用.     

缠绕角度对碳/环氧厚壁管件轴压性能影响的实验研究

文摘采用缠绕工艺制备了20°、30°和40°三种缠绕角度的碳/环氧厚壁管件,通过轴压实验研究了缠绕角度对厚壁管件的轴压模量和轴压强度的影响,并对轴压破坏模式进行了分析。实验测得轴向模量值比有限元模型计算值偏小,破坏模式为纤维层向外崩裂破坏与有限元分析结果一致。     

纤维缠绕封头结构的一般性方程及其解

本文在壳体理论和均衡型网络分析的基础上,建立了纤维缠绕结构封头问题的一般性整化方程,可以用来求解封头曲面形状,纤维缠绕角和壳体厚度、纤维应力和应变、封头位移值、容积及其改变率、纱线长度和滑移系数等。对于等张力封头,给出了解析解;对于平面缠绕封头,用Rung-Kutta方法和Simpson方法给出了数值解,从而实现了表格化。     

固体发动机纤维缠绕壳体设计准则判别式

给出了固体火箭发动机纤维缠绕复合材料壳体设计准则判别式。依据这一准则，当用于制造壳体的纤维材料特征值时，则该材料按刚度准则设计固体火箭发动机壳壁厚度，否则，按强度准则设计壳体厚度。以及机纤维和碳纤维为增强材料，给出两例分别按强度和刚度准则设计的实例，通过另两例强度相近但刚度不同的设计尘实例的比较。文中提出在设计固体火箭发动机壳体时，应合理选用纤维的最佳值，并建议发展纤维材料时，应注重强度与刚度的     

弯管制造过程中三坐标纤维缠绕机运动分析

在确定弯管及其连接段稳定缠绕线型分布的基础上，利用绕丝嘴与芯模之间相对运动关系，建立纱线的悬纱方程，可进一步解出缠绕机运动轨迹方程。文中研究绕丝嘴作平动时缠绕机的三坐标运动方程，即绕丝嘴的平动方程和芯模转角方程，为计算机控制纤维缠绕机奠定了基础。     

多轴联动多功能微机控制纤维缠绕机控制系统的设计

本文根据纤维缠绕理论，设计了多轴联动多功能纤维缠绕机的控制系统，给出了控制参数的数学描述，叙述了系统的工作原理。经过工程实践的检验，证明该系统性能稳定、工作可靠、功能完善。     

复合材料壳体缠绕芯轴设计分析

讨论了空心芯轴的优越性,得到了芯轴内、外直径的确定方法,给出了芯轴强度和结构稳定性校核方法。当芯轴外直径一定时,空心轴与实心轴相比,芯轴挠度和芯模质量都减小了。算例表明,文中给出的计算方法可用于空心芯轴的设计。     

复合材料布带缠绕纠偏控制系统设计

针对复合材料缠绕过程中的布带跑偏问题,在分析纠偏工作原理和影响纠偏控制精度关键因素的基础上,以线阵CCD( Charge Coupled Device)图像传感器为检测元件,以步进电机、蜗轮蜗杆、纠偏辊等为执行机构,采用FUZZY-PID复合控制策略,建立了布带缠绕纠偏控制系统.经纠偏试验验证,该纠偏控制系统的纠偏精度完全满足缠绕工艺要求,使缠绕过程的纠偏自动化得以实现.