A method to determine the equivalent static load of aircraft impact load

Abstract

It is significant to determine the equivalent static load of impact load for the strength design and verifica-tion of aircraft structures. The formula to calculate shock load dynamic effect coefficient is established based on ter-minal peak saw-tooth shock pulse describing the time history of shock load, single freedom dynamic response mod-el and the equivalent principle of model displacement. Then the function relationship between dynamic effect coeffi-cient and the product of shock load duration and model natural frequency is deduced from trigonometric function in-equality. The flow chart to determine equivalent static load of shock load is drawn according to the above theory. Fi-nally this method is used to verify the equivalent static load of arresting hook system and aircraft model ditching pro-cess. The comparative results show that the maximal relative error of dynamic effect coefficient of arresting impact load is below 4% between theoretic estimated values and numerical simulated values by FEM, the relative error of equivalent static pressure during model ditching test is below 0.9% between theoretic estimated value and deter-mined design value. It shows that the theoretical calculation formula of the established dynamic effect coefficient has a high accuracy, and the proposed method has certain engineering application value.

Keywords

• shock load
• equivalent static load
• terminal peak saw-tooth shock
• displacement equivalent
• dynamic effect coefficient
• structural strength design