The Numerical Simulation Research Of Stress And Strain Of Sea Urchin Spines And The Biomimetic Structure

In this study, the relationship between the structure and mechanical property for sea urchin spines, a potential artificial bone substitute, was investigated. Scanning electron microscope (SEM), energy dispersive spectra (EDS) and Micro-CT (Micro-CT) results revealed that the urchin spines mainly comprised of calcium carbonate with sequential dense growth rings and porous structures, which is likely suitable for bone substitution. The porous structure is suitable for ingrowth of new bone, whereas the dense ring may improve the load-bearing capacity. It is difficult to study the relationship between mechanical property and the complex microstructures for sea urchin spines using traditional mechanical tests and microstructure study. Thus, finite element models of microstructures of sea urchin spines were established, which was imported into ANSYS for numerical analysis of stress distribution in the structures. By this method, the relationship between microstructure and mechanical property for sea urchin spines as well as that for a novel biomimetic structures designed using SolidWorks was studied, including:(1) Finite element models:The three-dimensional structures of sea urchin spines were scanned and reconstructed using Micro-CT, which were further converted into finite element models using the Avizo software. Furthermore, the cell type and data format of the above finite element models were processed using Hypermesh before further numerical analysis.(2) The relationship between the microstructure and mechanical property for sea urchin spines:The parameters for material property were probably chosen for sea urchin spines based on literature. The boundary conditions and certain mechanical loads were applied to the above finite element model, and the characteristics of stress and strain in the model were analyzed. Obvious stress concentration was observedfor the junction portion of the dense growth ring and the porous structure, while the static compressive load was applied. The maximum stress was approximately 802.3 MPa and the maximum strain was 1%, when the compressive load was 50 MPa.(3) The relationship between the microstructure and mechanical property of the biomimetic structure:A biomimetic structure with sequential dense ring and porous structure like that of sea urchin spines was designed using SolidWorks. The numerical analysis of this novel structure using ANSYS revealed that there was stress concentration along the junction portions of the dense ring and the porous structure, which was consistent with the result from numerical analysis for sea urchin spines. The maximum stress was 405.8 MPa when the compressive load was 50 MPa, which is much smaller than that for sea urchin spines, suggesting that the newly designed structure is more suitable for load bearing compared to sea urchin spines.Our results show that the unique microstructures with sequential dense ring and porous structure of sea urchin spine and the biomimetic structure not only allow ingrowth of new bone, but also render the capability of load bearing to such structures, and therefore are suitable as bone substitute grafts. These findings will shed light on design of novel structures for bone substitutes (i.e. biomimetic structures like sea urchin spines).