Load Case Characterization for the Aircraft Structural Design Process

Abstract

Because aircraft undergo countless ground and flight scenarios during their service life, a large volume of global load cases must be analyzed in a global finite element model to identify the structural load paths and internal load distributions. Analyzing all load cases is not possible due to computational constraints, so that substantial engineering judgment in load case downselection is required. An approach is proposed to reduce the number of load cases analyzed by using singular-value decomposition to derive a smaller set of characteristic loads that approximates all the global load distributions. Herein, robust error quantification methods are also proposed to allow the definition of the characteristic loads to a targeted accuracy level, so that the calculation of structural failure can also be evaluated with a known precision. The major downstream benefit of the process is that the analysis results for this set of characteristic loads can be superimposed to create the internal load distributions resulting from all the original load cases, with known accuracy. For realistic design and load data, internal loads need to only be calculated for a few tens of characteristic loads rather than thousands of real load cases.