【作者】 陈强；

【导师】 费庆国；

【作者基本信息】 东南大学 ， 工程力学， 2020， 博士

【摘要】 高速飞行器在服役时会面临由高温、振动、噪声等载荷组成的复杂力学环境,宽频和高强的噪声载荷使得结构动响应呈现出明显的宽频特性。准确地宽频动响应预示是指导飞行器结构设计、地面试验方案与试验条件制定的重要依据。由于薄壁结构在高频段的模态密集、其高频响应对不确定性因素较为敏感等原因,结构高频段动响应大多采用统计化的平均能量进行表征,常用的分析方法为统计能量分析。现阶段有关统计能量分析的研究大多针对常温环境下带有确定性统计能量分析参数的系统,但工程实际中的热环境、时变特性、不确定性等因素对结构高频动响应的影响不可忽视。因此,研究热噪环境下结构的高频能量响应预示方法对高速飞行器的发展具有重要意义。本文针对该主题,主要开展了以下五个方面的研究工作:首先,针对热噪环境下结构的频域能量响应预示问题,基于功率输入法和功率流模型,提出了一种热环境下结构统计能量分析参数获取方法,开展了热噪环境下结构的统计能量分析,探讨了热效应和载荷温度对结构统计能量分析参数和高频能量响应的影响规律。研究结果表明:对于本文所研究的结构,当同时考虑热效应引起的材料力学性能变化和热应力引起的附加刚度效应时,热应力对耦合损耗因子、阻尼损耗因子和结构高频能量响应的影响占主导地位,耦合损耗因子和阻尼损耗因子均随温度的升高而减小。其次,针对宽频冲击载荷下结构的时域响应预示问题,基于瞬态统计能量分析方法和瞬态局部能量分析方法开展了冲击载荷下结构瞬态能量响应预示研究,分析了耦合强度对峰值时间、峰值能量及计算精度的影响。进而与热环境下的统计能量分析参数获取方法结合,分析了热环境下结构的瞬态能量响应特征。研究结果表明:瞬态局部能量分析方法能够精确地预示不同耦合强度下结构的瞬态能量响应;子系统瞬态能量响应的峰值时间和峰值能量均随着耦合强度的增加而降低;高温会导致子系统间耦合损耗因子的降低,进而降低了子系统瞬态能量响应的峰值能量。再次,针对计及时变特征结构的时域响应预示问题,考虑时变统计能量分析参数和功率流平衡方程中时变阻尼引起的瞬态项,推导了计及时变特征结构的功率流平衡方程,发展了计及时变特征结构的瞬态能量响应预示方法,分析了时变参数对结构瞬态能量响应的影响规律。结合热环境下的统计能量分析参数获取方法,预示了变温环境下结构的时域能量响应。研究结果表明:所提出的统计能量分析方法能够快速有效地预示计及时变特征结构的瞬态能量响应。对于变温环境下受脉冲载荷作用的结构而言,子系统的能量在较短时间内达到峰值,随后能量以较快的速率耗散。然后,针对含有区间不确定性统计能量分析系统的频域和时域能量响应预示问题,分别提出了一种仿射区间摄动统计能量分析方法和基于区间模型的瞬态局部能量分析方法,通过引入子区间分解技术进一步地提高了预示方法的准确性。研究结果表明:本文提出的区间响应预示方法具有比传统分析方法更高的计算精度;通过将子区间分解技术引入这两种方法中,可以高效准确地预示含有较大不确定度区间参数的统计能量分析系统的频域和时域能量响应。最后,针对含有模糊不确定性统计能量分析系统的频域能量响应预示问题,基于水平截断法、区间摄动法、Sherman-Morrison-Woodbury公式和统计能量分析,提出了一种基于模糊不确定性模型的频域能量响应预示方法,通过引入子区间分解技术进一步地提高了分析方法的预示精度。研究结果表明:本文提出的改进摄动统计能量分析方法具有比传统摄动统计能量分析方法更高的计算精度;通过引入子区间分解技术,可以进一步地提高改进摄动统计能量分析方法的计算精度,最终实现快速精确地预示含有较大不确定度模糊参数的统计能量分析系统的频域能量响应。更多还原

【Abstract】 For a high-speed aircraft under service,it will encounter a complex mechanical environment composed of loads such as thermal,vibration,and acoustic load.The high-level and broadband acoustic excitation could lead to the broadband dynamic response of the system,which is an important basis for guiding the structural design of the aircraft,the formulation of ground test plans and test conditions.Due to the high-level modal density of thin-walled structures under the high-frequency excitation and the sensitivity of high-frequency response to uncertainty,the high-frequency dynamic response is normally characterized by the statistical averaged energy.Statistical energy analysis(SEA)is the most commonly used method for the high-frequency dynamic response analysis of structures.Most of the existing researches about SEA only focus on systems with deterministic SEA parameters under normal temperature environment.However,in engineering practice,the influence of the thermal environment,timevarying characteristics,and uncertain SEA parameters on the high-frequency dynamic response of systems cannot be neglected.Therefore,the research of predicting the high-frequency dynamic response of systems under thermal and acoustic load is essential for the development of high-speed aircraft.This thesis aims at solving these problems.The main contributions of this work are performed as follows.First,an algorithm is presented to predict the high-frequency dynamic response of structures under thermal and acoustic load.The SEA parameters considering thermal effects are obtained by using the energy flow model and power injection method.The high-frequency dynamic analysis for structures under thermal and acoustic load is subsequently conducted.The influence of thermal effect and temperature load on SEA parameters and energy response is investigated.For the simulation case used in this chapter,when both the effects of temperaturedependent material properties and additional stiffness due to thermal stresses are taken into account,the influence of thermal stresses on the damping loss factor,coupling loss factor,and energy response is dominant.Both the damping loss factor and coupling loss factor decrease with the increase of temperature.Secondly,to predict the dynamic behavior of systems under broadband impact loads,the transient statistical energy analysis(TSEA)and the transient local energy approach(TLEA)are adopted to quantify the transient response of systems under impulse load.The influence of coupling strength on the peak time,peak energy,and computational accuracy is investigated.Subsequently,the transient response of systems under impulse excitation and thermal load is predicted by using the SEA parameters considering thermal effects.Results indicate that the transient local energy approach achieves better performance than the transient statistical energy analysis for systems with different coupling strengths.With the increasing coupling ratio between subsystems,the rise time and peak energy of the transient energy response of subsystems decrease gradually.The increase of temperature load leads to the decrease of coupling loss factors between subsystems and subsequently results in the decrease of the peak energy of the transient energy response.Thirdly,SEA is developed to predict the transient energy response of structures with timevarying parameters.The power balance equations of systems with time-varying parameters are derived by considering time-varying SEA parameters and energy flow item caused by the timevarying damping loss factor.The influence of time-varying parameters on the transient energy response of systems is investigated.Subsequently,the transient response of systems under timevarying thermal load is predicted by using the SEA parameters considering thermal effects.Results show that the proposed SEA method for systems with time-varying parameters is capable of predicting the transient energy response of structures with time-varying parameters,accurately and efficiently.For structures subjected to impulse load in a temperature-varying environment,the energy dissipates quickly after reaching its peak in a short time.Fourthly,to quantify the uncertain energy response of SEA systems considering interval parameters in the frequency domain and the time domain,an affine interval perturbation statistical energy analysis and an interval-based transient local energy approach are proposed,respectively.The sub-interval technique is introduced in the proposed methods to improve their computational accuracy.Results indicate that the proposed methods achieve better performance than the traditional methods in the high-frequency analysis of the system with interval parameters.By employing the sub-interval technique,the computational accuracy of the proposed methods is significantly improved.The proposed methods are capable of predicting the interval energy response in the case that high levels of uncertain parameters exist in systems.Finally,to investigate the high-frequency energy response of SEA systems with fuzzy parameters,a modified perturbation statistical energy analysis is proposed by combining the level-cut strategy,perturbation method,Sherman-Morrison-Woodbury formula,and SEA.The sub-interval technique is further introduced in the proposed method to improve its accuracy.Results indicate that the proposed method has better performance than the traditional method for the high-frequency analysis of systems with fuzzy parameters.The proposed method with a suitable number of sub-intervals is capable of predicting the energy response of systems with large fuzzy parameters,accurately and efficiently.更多还原