On the finite displacement problem of a hollow cylinder under internal and external pressures

Using the method of successive approximations we find of this boundary-value problem the first-and second-order solutions. And then we obtain the formulae in the second approximation for the displacement, strain, and stress fields. Also, our results show that after deformation (i) a cross-section of the cylinder must be displaced into a plane section perpendicular to the central axis of the cylinder; and (ii) neither the sum of the strain components E _RR ⁽²⁾ and E ⁽²⁾ nor the sum of the stress components E _RR ⁽¹⁾ and E ⁽¹⁾ maintains contant throughout the cylinder. The latter effect, which is absent from classical elasticity, bears respensibility for the presence of the E _ZZ ⁽¹⁾ . Moreover, there exhibits a linear relation between E _ZZ ⁽¹⁾ and (E _RR ⁽²⁾ +E _OO ⁽¹⁾ ), with the proportionality coefficients depending only on the material of the cylinder.     

Oscillatory correlations between external force and damping

In this paper we shall examine the correlations among the external froce, variable damping and variable restoring force. Some new results are obtained.     

基于拓扑与尺寸优化的风力机叶片轻量化设计

为有效减轻风力机叶片质量, 进一步实现降本增效, 对叶片内部结构进行拓扑优化与尺寸优化设计. 首先以叶片内部单元密度为设计变量, 将叶片柔顺度最小作为目标, 并以结构体积为约束条件, 考虑3种极限荷载工况, 利用ANSYS软件对叶片内部实体结构进行拓扑优化; 然后根据拓扑优化结果结合实际叶片内部材料铺层情况建立叶片壳体模型, 以关键结构参数为设计变量, 以叶片质量最轻为目标, 叶片强度、刚度、振动性能及稳定性等为约束, 采用MATLAB和ANSYS软件对叶片内部结构进行尺寸优化. 拓扑优化结果表明, 对叶片传统结构形式进行适当改进, 可有效改善叶片结构性能; 尺寸优化结果表明, 基于拓扑优化结果的改进结构优化方案与初始方案相比质量减轻了12.4%, 与传统结构优化方案相比质量减轻了2.6%, 较好地实现了叶片轻量化.     

基于CFD/Kirchhoff方法的直升机旋翼高速脉冲噪声模拟分析

将三阶迎风格式(MUSCL)与通量差分裂方法相结合,以改进二阶中心差分格式导致较大尾迹数值耗散的不足,建立了基于N-S方程和嵌套网格技术的旋翼流场求解方法,提高了CFD/Kirchhoff方法中流场信息计算的准确性.在流场求解的基础上,提出了一种谐波展开分析方法,基于该方法,Kirchhoff公式中的被积函数可解析表达,从而简化了获得Kirchhoff公式中被积函数的插值方法,提高了插值效率和精度.用上述方法对旋翼跨音速流场的高速脉冲(HSI)噪声进行了预测,计算结果与实验数据一致;同时对高速脉冲噪声在不同桨尖马赫数时和不同方向观测点上的特点进行了计算和分析.结果表明:旋翼高速脉冲噪声具有很强的指向性,在桨盘平面内噪声最大,在桨盘下方,随着与桨盘平面的夹角增加,噪声的脉冲迅速减弱.     

水平轴风力机叶片气动性能研究

以动量-叶素理论为基础建立了水平轴风力机叶片气动计算模型,同时考虑叶尖损失、叶根损失及失速状态下动量理论的失效对动量-叶素理论进行修正,通过对NREL10 m风力机叶片进行气动性能计算,通过与实验数据的对比,探讨模型的准确性.     

Dynamic stiffness characteristics of aero-engine elastic support structure and its effects on rotor systems: mechanism and numerical and experimental studies

The support structure of a rotor system is subject to vibration excitation,which results in the stiffness of the support structure varying with the excitation frequency(i.e., the dynamic stiffness). However, the dynamic stiffness and its effect mechanism have been rarely incorporated in open studies of the rotor system. Therefore, this study theoretically reveals the effect mechanism of dynamic stiffness on the rotor system. Then,the numerical study and experimental verification are conducted on...