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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“As the United States Air Force continues to extend the service life of their aircraft the Aircraft Structural Integrity Program (ASIP) has had to refine the methods it uses to analyze and predict fatigue crack growth. Through the use StressCheck®, coupled with AFGROW, we in A-10 ASIP have been able to more accurately model, predict and analyze critical aircraft structure for the A-10 and other types of structure for non-A-10 system managers. This also allows us within the A-10 to more accurately assess risk for decision makers, streamline aircraft inductions into scheduled maintenance and reduce cost for total life cycle management.”
A-10 ASIP Manager