In the article, the low‐cycle fatigue life durability of thin‐plate auxetic cellular structures is compared with the thin‐plate specimens of standard shape. Both the re‐entrant auxetic cellular structures and the standard specimens were cut from a 2‐mm‐thick strip of aluminium alloy 7075‐T651. First, a fatigue life curve and a cyclic curve were determined for the standard specimens. A special antibuckling device was applied to prevent the bending of the specimens. The same experimental arrangement was then applied to determine the low‐cycle fatigue life of auxetic structures. In the continuation, the most appropriate method was selected to calculate the fatigue life on the basis of the measured fatigue life curves. Abaqus and SIMULIA fe‐safe software were applied for this purpose. The best predictions for the standard specimens were obtained with the Brown‐Miller method. Finally, the selected method was applied to predict the low‐cycle fatigue life of re‐entrant auxetic cellular specimens.
The static and low-cycle durability of three planar cellular structures, hexagonal, auxetic and auxetic-chiral, have been compared. The three structures have the same critical cross-section and are made from an aluminium alloy Al7075-T651. The reference region of each structure is represented by a matrix of nine elementary shaped cells (3 rows by 3 columns). For each structure static and low-cycle fatigue experiments at different loading amplitudes were made. Numerical simulations were then performed for the same boundary conditions to predict the static and low-cycle fatigue durability. For this purpose a continuum damage mechanics approach with element removal was used in explicit dynamic simulations. The results of static simulations were also checked using the eXtended Finite Element Method (XFEM). All the numerical simulations were carried out using Abaqus. Good agreement was observed between the simulated and measured results for each of the three cellular structures.
Most of the published research work related to the fatigue life of porous, high-pressure, die-cast structures is limited to a consideration of individual isolated pores. The focus of this article is on calculating the fatigue life of high-pressure, die-cast, AlSi9Cu3 parts with many clustered macro pores. The core of the presented methodology is a geometric parameterisation of the pores using a vector-segmentation technique. The input for the vector segmentation is a μ-CT scan of the porous material. After the pores are localised, they are parameterised as 3D ellipsoids with the corresponding orientations in the Euclidian space. The extracted ellipsoids together with the outer contour are then used to build a finite-element mesh of the porous structure. The stress–strain distribution is calculated using Abaqus and the fatigue life is predicted using SIMULIA fe-safe. The numerical results are compared to the experimentally determined fatigue lives to prove the applicability of the proposed approach. The outcome of this research is a usable tool for estimating the limiting quantity of a structure’s porosity that still allows for the functional performance and required durability of a product.
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