摘要
面对日益膨胀的能源需求,发展新型的可再生能源已经刻不容缓。风能作为一种取之不尽,用之不竭,没有污染的新型能源得到广泛认可。风力机已经在许多国家迅速发展起来。典型的大型风力机叶片多采用薄壁多闭室复合材料结构形式,并且在新型飞行器设计中薄壁箱型结构应用也十分广泛,因此,对复合材料薄壁结构的研究具有非常重要的价值。形状记忆合金材料(SMA)是二十世纪发展起来的智能材料,它在温度和应力作用下会发生马氏体相变而产生回复作用,能够驱动薄壁结构,使之产生变形,改善结构表面的气动性能,进而对结构动力学特性进行控制和调节。
本文首先研究了具有耦合作用的复合材料薄壁箱型梁的静变形特征,基于变分渐进法导出梁横截面轴向力、扭矩、弯矩与横截面平均位移和转角之间的本构关系方程,并对CUS和CAS两种特殊铺设形式下的拉伸-扭转耦合和弯曲-扭转耦合进行了数值计算,揭示了具有一般铺层角的薄壁梁的拉伸-扭转-弯曲静变形特性的作用规律。其次,介绍了SMA的本构关系和相变动力学方程,并且根据应力-温度之间的关系,将应力引起的马氏体含量转换成温度形式引入马氏体含量函数关系中,通过线性化处理得出不同温度区间线性形式的相变动力学方程。第三,导出了各向同性弹性薄壁箱型外壁粘贴SMA层的复合材料薄壁结构的主动变形模型,针对横向均布载荷作用下的情况进行了数值计算,研究了在温度激励作用下,SMA层对该类结构的驱动作用,分析了温度和基体层厚度的影响。第四,基于变分渐进法、SMA应力应变关系以及线性相变动力模型,提出了具有拉伸-扭转-弯曲变形耦合的、包含SMA主动纤维驱动作用的复合材料薄壁空心梁的截面内力(矩)与位移(转角)本构方程。讨论了CUS构型和CAS构型,并给出了简化的本构方程。通过数值计算揭示了SMA对拉伸-弯曲-扭转变形特性的作用规律,分析了SMA纤维含量和驱动温度与复合材料铺层角的影响。研究表明,在马氏体向奥氏体转变阶段,空心悬臂梁在SMA纤维驱动下的产生较为显著的静变形响应,而且在不同的铺层角下,SMA纤维的驱动作用是不同的,调节SMA纤维的激励温度、改变SMA纤维的含量和SMA的初始应变,都能明显改善SMA的变形驱动性能。
With the growing trend for energy demand, the development of new renewable energy is becoming very urgent. Wind energy as one kind of new sources of energy, which is inexhaustible and no pollution, has been widely recognized. Wind turbine has been developed rapidly in many countries. A typical large wind turbine blades usually use composite materials closed thin-walled structures. And in the design of new generation of flight vehicle, thin-walled box structure is also widely applied. So the research of composite materials thin-walled structures is very important and valuable. Shape memory alloy (SMA) is developed as a smart material in twentieth century. With the change of temperature and stress, martensitic transformation will occur, therefore recovery stress will be produced in the material. The bending and twisting deformations of the structures can be induced by SMA. By controlling the deformations of the structures, the geometry of the structures can be changed, the aerodynamic loads can be modified, and then the aeroelastic behavior of the structures can be controlled.
First, the deformation of the thin-walled laminated composite beams with coupled effect is investigated. The constitutive relationship of the composite thin-walled box structure is derived using an asymptotic variational method. The general form of constitutive relation was applied to the cases of extension-twist coupling, corresponding to Circumferentially Uniform(CUS) and bending-twist coupling, corresponding to Circumferentially Anti-Symmetric(CAS). The static tensile - torsion - bending deformation behavior of thin-walled beam with general ply angle is predicted. Secondly, the constitutive relation of SMA and the phase transformation dynamic equations are described. A linearized phase transformation dynamic equation is obtained by using the linearized approach at different temperature range. Thirdly, a static deformation analytical model of a cantilever box composite beam with shape memory alloy (SMA) layers pasted on the outside surfaces of the isotropy thin-wall beam is developed, and the numerical results of SMA actuated deformations under transverse uniform load is presented. Numerical results show that the transverse deflection is significant due to SMA layer actuation. The effects of thickness of the beam wall and the martensitic residual strain of SMA layers are also very important to the static response of the composite thin-walled beam. Fourth, based on asymptotic variational method, SMA stress-strain relationship, as well as the linearized phase transformation dynamic equation, the constitutive equations relating cross-sectional loads (forces and moments) to cross-sectional displacements (stretching, bending, twisting) of thin-walled laminated beams with integral shape memory alloy (SMA) active fibers was presented. Numerical results shown that significant extension, bending and twisting deflection occur during the phase transformation due to SMA actuation. The effects of temperature on structural response behavior during phase transformation from martensite to austenite are significant. The effects of the volume fraction of the SMA fiber, the martensitic residual strain and ply angle were also addressed.
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