Advanced Software for Integrated Probabilistic Damage Tolerance Analysis Including Residual Stress Effects

New analysis methods and software tools are being developed for improved accuracy and efficiency in performing damage tolerance analyses of critical aerospace components.  This presentation provides an overview of recent advances that automate and streamline the process of fracture mechanics (FM) model development and life analysis, including direct integration of finite element (FE) models that simulate the manufacturing process and the service usage.  Stress analysis results from the FE models are directly incorporated into the life analysis through a powerful graphical user interface.  Residual stresses can be included in this analysis, including bulk residual stresses arising from forging and heat treating as well as localized residual stresses from peening or other surface engineering processes.  The effect of these residual stresses on fatigue crack growth life and component reliability can be automatically computed using algorithms that include advanced weight function stress intensity factor solutions to accommodate arbitrary stress gradients accurately.  A novel scheme has been developed that automatically determines (without user input) the orientation, size, and stress input for a FM model that will produce accurate life results, given only a 2D model of the crack plane and an initial crack location, and taking into account the actual component boundaries and stress fields.  This capability is then exercised to construct life contours that visualize the fatigue life response over an entire component.  The life calculation capabilities are combined with probabilistic descriptions of key input variables and tailored probabilistic methods to calculate the probability of fracture of the component.  Long-range goals include performing this reliability calculation in a similar automated fashion with minimal user intervention, as well as optimizing the manufacturing and inspection plans through the integrated software system in order to maximize the reliability.