碳纤维复合材料/钛合金叠层钻孔工艺优化

在不同的工艺参数下用硬质合金麻花钻分别对碳纤维复合材料板和碳纤维复合材料板/钛合金叠层板进行钻孔,对钻孔过程用Abaqus有限元软件进行三维仿真,对比仿真和试验结果的轴向力和制孔效果。结果表明,在保证制孔的质量的前提下,选取合理的工艺参数,得到叠层材料制孔的工艺参数的优化结论。     

Experimental,analytical and numerical investigation on tensile behavior of twisted fiber yarns

Stitched composite materials are emerging as a promising material due to their high interlaminar strength, combined performance and light weight. The mechanical properties of stitch yarns are very essential for stitched composite structures. In this study, the tensile behaviors of the twisted fiber yarn in stitched composites were investigated experimentally, analytically and numerically. Two kinds of cross-sectional area of twisted yarn are proposed and discussed. The paper presents an intersecting circle model to describe the cross-section of twisted fiber yarns, and a physics-based theoretical model to predict the effective tensile moduli. The numerical models take into account the cross-sectional characteristic and the twist architecture. The investigation shows that: the sum of each fiber area should be used for experimental analysis; and the cross-sectional area surrounded by the yarn profile should be used for theoretical predictions and finite element (FE) simulations. The relative errors of the prediction method and the FE simulation are less than 2% and 1%, respectively. The friction between the fibers is derived, and the effect of friction on mechanical properties is discussed. The investigation method will serve as a fundamental component of twisted fiber bundle/yarn analysis.     

Aerodynamic investigation of twist angle variation based on wing smarting for a flying wing

In this paper, the effects of twist angle variation on aerodynamic coefficients and flow field on the wing with wing smarting approach are studied using numerical simulation. The simulation was performed using incompressible Reynolds-Averaged Navier-Stokes (RANS) equations based on the two-equation k-ω Shear Stress Transport (SST) turbulent model for flow speed 30 m/s and a Reynolds number of 69000. Investigations have been carried out for several twist angles and at a specific range of angles of attack. The twist applied is the type of geometric twist (wash-out), which is linearly distributed along the span. The test case is a lambda-shaped tailless aircraft with a wing fracture on the trailing edge, and a sweep angle 56°. The results show that with increasing twist angle, the aerodynamic efficiency improves over a wide range of angles of attack, but at 0° angle of attack it will decrease significantly. By increasing the angle of attack, the effect of twist on the flow field and aerodynamic coefficients will gradually decrease; hence, at a certain amount of angle of attack, the effect of twist will stop, that angle is called the neutral brink angle. Longitudinal stability analysis shows that by growing the twist angle, the conditions required for longitudinal stability are satisfied, and the pitch-up phenomenon will be delayed.     

轴向磁场对去偏陀螺消偏器的影响

分析了磁场对陀螺影响的机理。运用琼斯矩阵，基于单色光，导出了与消偏器绕向平行的轴向磁场，仍能对去偏光纤陀螺中理想的消偏器产生影响，从而给陀螺带来Faraday非互易相位差的具体公式，并给出了此相位差随保偏光纤扭转率变化的仿真结果和加磁场后的实验结果。仿真结果表明：具有扭转的消偏器能产生Faraday非互易相位差；实验结果表明：作用在消偏器上的轴向磁场影响去偏陀螺零偏精度。提出了减小作用在消偏器上的轴向磁场影响陀螺精度的主要方法：使构成两个消偏器的每段保偏光纤的扭转率φ→0。     

Optimization of aerodynamic efficiency for twist morphing MAV wing

Twist morphing(TM) is a practical control technique in micro air vehicle(MAV) flight.However, TM wing has a lower aerodynamic efficiency(CL/CD) compared to membrane and rigid wing. This is due to massive drag penalty created on TM wing, which had overwhelmed the successive increase in its lift generation. Therefore, further CL/CDmaxoptimization on TM wing is needed to obtain the optimal condition for the morphing wing configuration. In this paper, two-way fluid–structure interaction(FSI) simulation and wind tunnel testing method are used to solve and study the basic wing aerodynamic performance over(non-optimal) TM, membrane and rigid wings. Then,a multifidelity data metamodel based design optimization(MBDO) process is adopted based on the Ansys-DesignXplorer frameworks. In the adaptive MBDO process, Kriging metamodel is used to construct the final multifidelity CL/CDresponses by utilizing 23 multi-fidelity sample points from the FSI simulation and experimental data. The optimization results show that the optimal TM wing configuration is able to produce better CL/CDmaxmagnitude by at least 2% than the non-optimal TM wings. The flow structure formation reveals that low TV strength on the optimal TM wing induces low CDgeneration which in turn improves its overall CL/CDmaxperformance.     

玻璃纤维复合材料钻削轴向力与分层分析

为研究玻璃纤维复合材料钻削轴向力与分层特征,以电镀金刚石钻头和硬质合金麻花钻为钻削工具,对玻璃纤维复合材料进行正交钻削实验,研究钻头的几何形状、刀具材质以及钻削工艺参数对玻璃纤维复合材料钻削轴向力和钻削质量的影响.结果表明,钻削工艺参数直接影响玻璃纤维复合材料的钻削轴向力和钻削质量,高转速、低进给速度和合适的刀具结构、...