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本研究是为获得SAM-D ED(工程研制)飞行器设计中涉及的随机振动响应载荷。认为此响应载荷是飞行中随机气动压力激励下,飞行器诸小阻尼横向弯曲振动模态单个响应的总和。 横向弯曲振动模态是飞行器结构刚度和质量分布的函数。飞行器质量较小时,横向响应加速度较高,因此主要研究发动机燃料耗尽的情况。随机载荷计算中包括了十一个模态,其特征频率高达500赫。 飞行中作用在飞行器外表面的激励力与随机气动压力分布有关,系由SAM-DCTV(控制试验飞行器)飞行试验所得数据计算得到。假设此外力谱密度的幅频特性与每一试验飞行器上的几个加速度计所实测的分布特性相似且成正比;假设实测横向加速度0—2000赫频带中所含的能量对于0—1000赫频带依旧有效,这样就得到了输入力的保守值,据之确定结构模态的随机响应。 利用上述飞行器特性和气动力数据,即可得到作用在飞行器结构上的随机响应载荷。这些设计数据是:沿飞行器长度上的横向弯矩、剪力和横向加速度。
This study was conducted to obtain random vibration response loads involved in SAM-D ED (Engineering Development) aircraft design. The response load is considered to be the sum of the individual responses of small damped transverse flexural vibration modes of the aircraft under random aerodynamic pressure in flight. The transverse flexural vibration mode is a function of the stiffness and mass distribution of the aircraft structure. When the mass of the aircraft is small, the lateral response acceleration is high, so the main concern is the exhaustion of the engine. Eleven modalities are included in the stochastic load calculation, with characteristic frequencies up to 500 Hz. The excitation force acting on the outer surface of the aircraft in flight is related to the distribution of random aerodynamic pressure and is calculated from the data obtained from the SAM-DCTV (Controlled Experiment Aircraft) flight test. It is assumed that the amplitude-frequency characteristics of the force spectrum density are also similar to and proportional to the measured distribution characteristics of several accelerometers on each experimental aircraft; it is assumed that the energy contained in the measured transverse acceleration 0-2000 Hz band is proportional to 0-1000 Hz band Still valid, so you get the conservative value of the input force, according to which to determine the random response of the structure modal. Using these aircraft characteristics and aerodynamic data, a random response load acting on the structure of the aircraft is obtained. These design data are: transverse moments along the length of the aircraft, shear forces and lateral accelerations.