船舶涡旋流堵漏桨叶位置与涡旋流形成效果的关系研究

船舶涡旋流堵漏方法是为克服现有堵漏手段存在的不足而提出的一种新技术思想。在自行设计制作了专门实验装置的基础上,分别利用柔性桨叶和刚性桨叶进行了一系列涡旋流堵漏实验,定量研究了桨叶工作位置对破口进水量的影响规律,进而揭示了桨叶位置与涡旋流形成效果的关系。实验结果发现：当桨叶与破口处于同一高度且距离破口越近时,对降低破口进水量的效果越明显,使用于堵漏的时间可延长300%以上。这一结论可为船舶涡旋流堵漏方法的完善提供必要的理论基础和实验依据。     

Stress analysis and damage evolution in individual plies of notched composite laminates subjected to in-plane loads

This work aims to investigate local stress distribution, damage evolution and failure of notched composite laminates under in-plane loads. An analytic method containing uniformed boundary equations using a complex variable approach is developed to present layer-by-layer stresses around the notch. The uniformed boundary equations established in series together with conformal mapping functions are capable of dealing with irregular boundary issues around the notch and at infinity. Stress results are employed to evaluate the damage initiation and propagation of notched composites by progressive damage analysis(PDA). A user-defined subroutine is developed in the finite element(FE) model based on coupling theories for mixed failure criteria and damage mechanics to efficiently investigate damage evolution as well as failure modes. Carbon/epoxy laminates with a stacking sequence of [45°/0°/ 60°/90°]sare used to investigate surface strains, in-plane load capacity and microstructure of failure zones to provide analytic and FE methods with strong validation. Good agreement is observed between the analytic method, the FE model and experiments in terms of the stress(strain) distributions, damage evaluation and ultimate strength, and the layerby-layer stress components vary according to a combination effect of fiber orientation and loading type, causing diverse failure modes in individuals.     

Analysis of reaction torque-based control of a redundant free-floating space robot

Owing to the dynamics coupling between a free-floating base and a manipulator,the non-stationary base of a space robot will face the issue of base disturbance due to a manipulator's motion.The reaction torque acted on the satellite base's centroid is an important index to measure the satellite base's disturbance.In this paper,a comprehensive analysis of the reaction torque is made,and a novel way to derive the analytical form of the reaction torque is proposed.In addition,the reaction torque null-space is derived,in which the manipulator's joint motion is dynamically decoupled from the motion of the satellite base,and its novel expression demonstrates the equivalence between the reaction torque null-space and the reaction null-space.Furthermore,the reaction torque acted as an optimization index can be utilized to achieve satellite base disturbance minimization in the generalized Jacobian-based end-effector Cartesian path tracking task.Besides,supposing that the redundant degrees of freedom are abundant to achieve reaction torque-based active control,the reaction torque can be used to realize satellite base attitude control,that is,base attitude adjustment or maintenance.Moreover,because reaction torque-based control is a second-order control scheme,joint torque minimization can be regarded as the optimization task in reaction torque-based active or in-active control.A real-time simulation system of a 7-DOF space robot under Linux/RTAI is developed to verify and test the feasibility and reliability of the proposed ideas.Our extensive empirical results demonstrate that the corresponding analysis about the reaction torque is correct and the proposed methods are feasible.     

Structural Design and Control Strategy Analysis of Micro/Nano Transmission Platform

A fully flexure micro/nano transmission platform(MNTP)which has five degrees of freedom is designed on the basis of bridge type amplification mechanism.According to the kinematic theory and the elastic beam theory,the theoretical output displacement equation of the platform is derived,and then piezoelectric actuator(PZT)is calibrated.Meanwhile,a full closed-loop control strategy of the platform is established using the feedforward proportional-integral-derivative(PID)compound control algorithm based on the Preisach model.Moreover,the total transfer function of the micro positioning system is derived,and the calculation method of output signal is acquired.Finally,the theoretical output displacement is verified by finite element analysis(FEA)and positioning experiments.     

风力机翼型的多学科设计优化

为了解决优化计算和流场分析耦合求解的难题,并实现优化流程的自动化运行,采用多学科优化设计框架软件,针对风力机专用翼型运行工况,对低雷诺数航空翼型NACA 4412的气动性能进行优化设计。软件集成了翼型生成、网格划分、流场分析、优化计算4个模块。其中,流场计算采用N-S方程求解;优化方法为多岛遗传算法。优化结果表明,优化后翼型有较高的升力系数和相对大的升阻比,其升阻比提高了15.9%。该方法可以实现多学科领域的精确分析和整个优化循环过程的自动化运行,也能为其他气动外形的优化设计提供参考。     

飞行器气动外形的正交设计与分析

结合飞行器总体快速设计需求,研究基于正交试验设计的气动外形分析方法。通过正交试验设计,获得飞行器气动特性数据,再根据试验结果的极差分析和方差分析,快速明确飞行器外形参数与阻力系数的影响程度,辨识关键参数,指导飞行器外形设计。以某飞行器为应用对象开展了实例验证,结果表明该方法能够快速获得满足要求的气动外形,提高分析效率,满足总体方案快速设计需求。     

一种惯组外场标定振动干扰的分离方法

惯组在外场进行标定时常会受到地基振动的干扰,这种干扰会对惯组的测试精度造成极大的影响.为解决这一问题,根据工程实际需要,提出了一种基于经验模态分解和数字信号滤波技术相结合的惯组输出振动干扰分离方法.首先利用经验模态分解将受振动干扰的惯组输出分解成若干本征模态分量,然后采用低通滤波器对高频分量进行滤波,对低频分量相应区段做幅值修正,最后将处理过的各分量叠加,即重构出消除振动干扰的信号.相对于传统的剔除野值后的平滑滤波方法,新方法保证了数据信息的完整性,有效降低了振动干扰的不利影响,提高数据信息的可靠性和真实性.仿真实验和工程实践表明,该方法对外场的瞬时振动干扰有较强地分离能力.     

凸曲面的离散求交算法及其在飞机设计上的应用

构建精确的目标外形是飞机设计的必要条件。本文给出了凸曲面离散求交的算法，在飞机设计中采用此方法，能够得到机身机翼交线的准确位置。     

25Cr3MoA合金棒材组织与性能的研究

研究了25Cr3MoA合金棒材热处理对组织和性能的影响。结果表明:电弧炉加电渣重熔冶炼的25Cr3MoA钢组织均匀、纯净度高;艾氏冲击功与夏比冲击功没有对应关系;WS9-6001组别低温冲击韧性最好;在600℃以下仍保持较好的高温性能;400℃时仍具有较高的高温疲劳强度。