Global/local stress analysis of composite panels

Abstract

A method for pcrforming a global/local stress analysis is described and its capabilities are demonstrated. The method employs spline interpolation functions which satisfy the linear plate bending equation to determine displacements and rotations from a global model which are used as "boundary conditions" for the local model. Then, the local model is analyzed independent of the global model of the structure. This approach can be used to determine local, detailed stress states for specific structural regions using independent, refined local models which exploit information from less-refined global models. The method presented is not restricted to having a priori knowledge of the location of the regions requiring local detailed stress analysis. This approach also reduces the computational effort necessary to obtain the detailed stress state. Criteria for applying the method are developed. The effectiveness of the method is demonstrated using a classical stress concentration problem and a graphite-epoxy blade-stiffened panel with a discontinuous stiffener. NomenclatureVector of unknown spline coefficients of the interpolation function Polynomial coefficients of the interpolation function, i = 0,1,.

NASA Airframe Structural Integrity Program

“…Greater efficiency can be achieved by exploiting a global/local strategy where local details that produce stress gradients can be treated in a companion analysis to the global structural analysis. Figure 5 shows an example stress analysis of a circular cutout in a blade-stiffened panel where quite accurate results were obtained by the global/local analysis methodology [6]. To accurately predict the behavior of a growing crack in a stiffened shell structure, the global/local methodology must be extended to include an adaptive mesh concept so that the local refined mesh can change in a manner dictated by the growing crack.…”

Pollution Error in the h-Version of the Finite Element Method and the Local Quality of A-Posteriori Error Estimators

“…An example of this type of analysis is given in [6]: In that work a methodology is outlined in which a relatively coarse global mesh is used to analyze a complex structure. The critical regions requiring a more detailed analysis are subsequently identified and interpolation regions are then defined around these regions and an interpolation procedure is employed to determine the boundary conditions for the local meshes.…”

Improvement of plane stress solutions using adaptive finite elements

“…This problem was previously analyzed using the global/local finite element modeling technique described in Ref. [4]. The technique divides the panel into two regions with coarse mesh (global model) and fine mesh (local model) as shown in Fig.…”