Abstract
A practical ductile fracture criterion model is developed, which is well suited for the aerospace structure static strength evaluations using detailed finite element analysis. The model is based on the classical Coulomb-Mohr fracture criterion and extended to handle strength anisotropy commonly present in aerospace structural metal materials through the application of stress linear transformation.
The resulting model (TCM: Transformed Coulomb-Mohr model) employs the model parameter identification procedure which utilizes the well-established statistically based material allowable database like MMPDS. Therefore it is relatively easy to establish a MMPDS-compatible TCM model database covering wide range of aerospace structural materials, which makes it usable for the real-world large scale airframe development projects.
To demonstrate the ductile fracture predictive capability of the TCM model, static strength tests for several structural elements are conducted and evaluated. Comparison of TCM model predictions against the ones by two other approaches, namely traditional design chart methods, and naive FE-based evaluation utilizing von Mises stress and Ftu, clearly shows the superior capability of the TCM model approach.
