A novel finite element for modeling a fastener in a lap joint assembly
This work documents the development of a novel finite element. This element introduces parameters that allow more accurate modeling for the specific application of mechanically fastened lap joints. The research here bridges the gap between two traditional methods commonly used in industry today. The novel element is more accurate than the first traditional method, by using a single-beam element to join plate elements with a linear solution. It is also more computationally compact than the second traditional method, which consists of an assembly of solid, three-dimensional elements with a non-linear solution. The case studies used are specifically limited to mechanically fastened lap joints pulled in tension, also referred to as "secondary bending." The plates joined together with these fasteners are loaded up to a fraction of a yielding load of the plate material in order to maintain linearity. Isotropic materials are used exclusively for both the plates and fasteners. Ultimately, the fastening element created in this study is intended strictly for a linear calculation. The calculation contains a one-dimensional beam element with two nodes that connects two, two-dimensional plate elements together. To match the problem more accurately, this research introduces the principle of finite element Hertzian contact mechanics, which is specifically applied to mechanically fastened lap joints. This addition to the existing beam finite element allows for a more accurate simulation while holding to the simplicity of a linear solution of a single element with two nodes in a plate/beam/plate element modeling scheme. Transverse deflections resulting from the applied loading in this new finite element are first compared to the two baseline finite element models that the new element is intended to bridge. The new model is also compared to the deflections calculated from empirically formulated stiffness values generated for the neutral line model.
Thesis (Ph.D.)-- Wichita State University, College of Engineering, Dept. of Aerospace Engineering