CAI: Transitioning Advanced Aerospace Technologies Through Cost and Risk Reduction
Abstract: Conventional analysis methods for bonded joints were found to be limited in their capabilities and accuracy. For instance, A4EI, a computer code for bonded joint analysis, is only applicable to adhesive failures in shear-loaded joints and does not account for peel stresses or for potential adherend failures. To date, the only alternative to these limitations has been to develop detailed finite element models of a joint. This approach is time consuming and requires great skill and care by the analyst to ensure stresses and strains in critical locations of the joint are properly quantified. Small errors in modeling can lead to substantial errors in joint performance prediction. To alleviate these problems, the CAI team implemented improvements to the StressCheck® P-version finite element software, including the incorporation of a strain invariant failure theory. The StressCheck® tool handbook function was used to expertly model typical joints, thereby developing reusable joint models including: single lap shear; double lap shear; scarfed lap shear; and step lap joints for in-plane loading; as well as a pi and back-to-back angle joints for out-of-plane loading. These handbooks are parameterized so that similar joints in the future can be modeled by simply updating geometric parameters of the existing model. StressCheck® will then automatically remesh the model, calculate results, check for convergence problems in the new joint configuration, and even post-process the results.
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“The p-type element has been used to great advantage in the finite element system ESRD StressCheck®, . This software provides the engineer with the means to conduct solution verification in an extremely straightforward manner by simply increasing the degree of the element, monitoring convergence and using Richardson extrapolation reliably to estimate the error. This can be conducted automatically by the software thereby enabling the engineer to concentrate on the engineering rather than the simulation. StressCheck® has also been used to develop ESRD’s Handbook and Toolbox applications. The first of these provides engineers with a repository of parameterised standard problems of the type found in texts like Roark’s “Formulas for Stress and Strain”, . The second, Toolbox, is a tool that can be used to parameterise a company’s range of components for rapid and reliable analysis by non-expert analysis. Toolbox then is an exemplary of the way in which the democratisation of simulation can be applied.”
Angus Ramsay, PhDEngineering Director, Ramsay Maunder Associates