Model Updating And Response Analysis Of Aircraft Structure Subject To Engine Imbalance Loads

Imbalanced vibration of the turbofan engine windmilling is essentially the forced vibration suffered by the aircraft during flight.Aeroelastic dynamic response Analysis of airframe is important for the evaluation of the engine windmilling.How to establish the dynamic model of a large passenger aircraft and to establish a reasonable verification scheme is a key issue.In this paper,the compliance methods and the compliance verification techniques recommended by AC 25-24 and AC 25.629-1B are studied.First of all,based on GARTEUR SM-AG19,the modeling method of dynamic response of aircraft structure,ground vibration experiment method and model updating method are studied by numerical simulation and experiments.Secondly,the experimental study of imbalanced vibration response characteristics is conducted to identify key parameters which have the influence on the response of the wing and body.The main work is as follows:The GARTUER aircraft model is designed and manufactured.Using the LMS modal test equipment,the phase resonance/phase separation integrated technology is used to identify the modal parameters of the model.The influence of test boundary conditions(excited position and number)and test methods on the test results is analyzed and compared.The experimental time is greatly shortened and better experimental results are obtained,which verifies the correctness of the experimental method.A parameter updating method is proposed,and the modeling details of the finite element model are adjusted by combining engineering experience,error location and sensitivity analysis techniques.To minimize the frequency and mode shape error of the experimental and simulation results,a multi-island genetic algorithm is used to update the model.In order to evaluate the quality of the model more comprehensively,the three-level quality standard is used to examine the reproducibility and predictability of the model.The predicted accuracy of the model's dynamic characteristics of the structure is equal to that of a foreign research institution,which verifies the correctness of the updating method and its engineering application value.The GARTEUR model is modified by designing the pylon and installing an electronically controlled engine.The model updating and response calculations are performed on the modified model.By changing the engine speed and unbalanced mass to control the unbalanced vibration,the response test experiment is conducted to study the influence on the response level of the airframe(especially the wing and fuselage).The study found that when the rotational speed is fixed,the acceleration responses at different positions show a monotonous increasing trend with the increase of the unbalanced mass.When the unbalanced mass is constant,there will be a large response near the natural frequency of the model,and the size of the response at a specific location is related to the mode shape.The study will not only provide certain reference for the certification work of the Airworthiness Authority,but also provide a reference for the design of new aircraft and derivative aircraft,and provide reference for applicants to demonstrate compliance.