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Virtual testing, strain correlation for loads optimization of composite fuselage structure

Knaap, Bart van der (2017) Virtual testing, strain correlation for loads optimization of composite fuselage structure.

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Abstract:In this study load identification methods will be investigated on two different finite element models, with the goal to enhance and understand a load determination procedure for a complex and full scale virtual test of large composited fuselage panels. With proper load identification methods full scale tests of a complete fuselage barrel can be simplified to a large fuselage panel tests. This will have major time and cost benefits in the validation of fuselage structures. The focus of the investigations was on the strain correlation of the end result and the load identification method, the development of the efficient virtual testing modelling and analysis process and the enhancement of accurate strain extraction methods and element selection. The goal of the study was to perform a correct load identification on the DFEM. The method used for the load identification is based on a linear least squares procedure that determines the linear combination of load factors that yields the best approximation of a set of reference strains from the barrel test. Before the analyses are carried out and the results are presented, first the two finite element models are presented. Then the method is further explained and also the error calculation which are the root means square of the relative error and the relative root mean square of the error. One of the two finite element models represents a simplified aluminium panel (SFEM), the other is a detailed model of the fuselage panel (DFEM). The SFEM is used for the quick calculation and to create understanding of the method. This is done by carrying out linear analyses and then nonlinear analyses. Then changes are made to the number of loads used in the analysis. With the aspects found in the results of SFEM, the choices are made for the linear and nonlinear analyses of the DFEM. The different aspects of the analyses that have an effect on the result of the load identification are the neglecting of lower strain values, the increase in loads on a model introduces more insecurity, the influence to the choice of the sensor position and number of sensor elements. These aspects are found back in the DFEM analyses. Potentially there are also numerical issues like the singularity of the unit load matrix. The load identification of the linearly analysed FE models can be performed with excellent results. For the nonlinear analyses of SFEM also yield good results, but for the nonlinear analyses of the DFEM an accurate reproduction of the strain field was not possible, at this moment. Aspects as sensor position and choice of magnitude of forces play an important role in the quality of the results.
Item Type:Internship Report (Master)
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Mechanical Engineering MSc (60439)
Keywords:fuselage panels, finite element models, strain gauges, static test, Abaqus
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