热效应对高频声振响应与疲劳寿命影响研究

发布时间：2018-01-02 14:00

本文关键词：热效应对高频声振响应与疲劳寿命影响研究　出处：《中国科学技术大学》2017年硕士论文　论文类型：学位论文

【摘要】：高超声速飞行器在其巡航和再入阶段将会面临噪声载荷、热载荷、和机械载荷等复杂的力学环境。噪声载荷主要是由激波振荡和湍流边界层引起的,该噪声不仅分布的频段比较宽,而且含有丰富的高频成份,会影响飞行器重要仪器设备的工作精度和可靠性;热载荷会导致飞行器的承载力下降,对结构的固有特性、动态响应均会产生很大的影响。在热声载荷的联合作用下会引起结构剧烈声振响应,而且可能在快速地交变应力作用下,引发裂纹的萌生、扩展,最终导致壁板、蒙皮等结构疲劳破坏。因此考虑热-声-振疲劳失效是飞行器设计阶段必须关注的问题。本文研究的主要内容为典型结构的热-声-振耦合及疲劳失效问题。首先采用有限元法探究如何获取较高精度的耦合损耗因子。接着采用有限元法、统计能量分析分别研究了热效应对铝合金壁板低频、高频声振响应以及疲劳寿命的影响。具体内容如下:1.典型结构耦合损耗因子计算及误差分析采用有限元方法计算耦合损耗因子并和波法结果对比给出有限元方法误差存在的原因。研究了L型板的边长、厚度、内损耗因子、集中质量以及边界条件对耦合损耗因子计算精度的影响,为采用有限元方法计算出精确耦合损耗因子给出指导。最后研究了预应力对Y型板耦合损耗因子的影响。2.热效应对结构低频声振响应及疲劳寿命的影响采用有限元法分别考察了温度变化导致结构的刚度(弹性模量和热应力)、材料S-N曲线变化对铝合金壁板低频疲劳寿命的影响规律,进而分析了非均匀温度场作用下结构的疲劳寿命。3.热效应对高频声振响应及疲劳寿命的影响基于统计能量分析研究了在不同温度条件下飞行器铝合金壁板的高频声振响应及均方应力,采用零阶矩应力谱法获得危险点的简化应力功率谱,然后结合频域疲劳寿命预报方法计算铝合金壁板的高频疲劳寿命。分别研究温度变化导致结构的刚度、材料S-N曲线变化对铝合金壁板高频疲劳寿命的影响规律。
[Abstract]:Hypersonic vehicles will face complex mechanical environments such as noise load thermal load and mechanical load during their cruise and reentry. The noise load is mainly caused by shock oscillation and turbulent boundary layer. The noise not only has a wide frequency range, but also contains rich high-frequency components, which will affect the working accuracy and reliability of the important instrument and equipment of the aircraft. The thermal load will lead to the reduction of the bearing capacity of the aircraft, which will have a great impact on the natural characteristics of the structure and the dynamic response, and the combination of the thermoacoustic load will cause the violent acoustic-vibration response of the structure. And it is possible to initiate crack initiation and propagation under the action of fast alternating stress and eventually lead to the wall plate. Therefore, it is necessary to pay attention to the thermal acoustic vibration fatigue failure in the design stage of aircraft. The main contents of this paper are the thermoacoustic vibration coupling and fatigue failure of typical structures. First, the finite element method is used to explore how to obtain the coupling loss factor with high precision. Then, the finite element method is used. The effect of thermal effect on the low frequency of aluminum alloy panel was studied by statistical energy analysis. Effects of high frequency acoustic vibration response and fatigue life. Details are as follows:. 1. The calculation and error analysis of coupling loss factor of typical structures using the finite element method to calculate the coupling loss factor and comparing with the results of the wave method, the reason of the error of the finite element method is given, and the side length of the L-shaped plate is studied. The influence of thickness, internal loss factor, lumped mass and boundary condition on the accuracy of coupling loss factor. Finally, the influence of prestress on coupling loss factor of Y plate is studied. 2. The influence of thermal effect on the low frequency acoustic vibration response and fatigue life of structure is studied. The stiffness of the structure caused by temperature change is investigated by finite element method. Elastic modulus and thermal stress). Influence of material S-N curve change on low frequency fatigue life of aluminum alloy panel. Furthermore, the fatigue life of the structure under the action of inhomogeneous temperature field is analyzed. 3. The effect of thermal effect on the high frequency acoustic vibration response and fatigue life of aircraft aluminum alloy panels under different temperature conditions is studied based on statistical energy analysis. High frequency acoustic vibration response and mean square stress. The simplified stress power spectrum of the dangerous point is obtained by using the zero-order moment stress spectrum method, and then the high-frequency fatigue life of the aluminum alloy panel is calculated by using the frequency-domain fatigue life prediction method. The stiffness of the structure caused by the temperature change is studied respectively. Influence of material S-N curve change on high frequency fatigue life of aluminum alloy panel.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：V215;O346.2

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