考虑时变刚度特性的复合材料微结构拓扑优化设计方法

理想的骨折内固定植入物在组织愈合或修复的过程中,其结构性能需要满足不同愈合阶段对生物力学的需求.提出一种对生物可降解复合材料微结构的时变刚度特性进行调控设计的拓扑优化方法,以达到理想的骨折内固定植入物特殊的时变刚度特性需求.使用具有不同降解速率和刚度的两种可降解材料,以相对密度作为设计变量来描述不同材料的分布,以特定降...

TOPOLOGY OPTIMIZATION OF COMPOSITE MATERIAL MICROSTRUCTURE CONSIDERING TIME-CHANGEABLE STIFFNESS

Fracture is a common orthopedic disease, and internal fixation implants are often used in the treatment of fractures. In the process of tissue healing or repair at the fracture, the structure mechanical properties of ideal fracture internal fixation implants need to meet different biomechanical requirements of different fracture healing stages. A microstructure topology optimization design method for regulating and designing the time-changeable stiffness characteristics of the biodegradable composite microstructure is proposed to meet the special time-changeable stiffness characteristics requirements of the ideal fracture internal fixation implant. Two kinds of degradable materials with different degradation rates and stiffness are used, and the relative density is used as the design variable to describe the distribution of different materials. Taking the maximum sum of the stiffness of the intermediate structure in specific degradation steps as the optimization objective, the topology optimization design of microstructure configuration of the composite is carried out to make it have a specific time-changeable characteristic in line with the law of fracture healing.Using the uniform corrosion method, the degradation process of the composite structure is described by material residual rate which is time-dependent, and the finite element model considering material degradation in the time dimension is established. The continuous degradation update formula is proposed by integrating the Heaviside function and Kreisselmeier-Steinhauser function. The mechanical properties of the intermediate structure at different degradation time steps are calculated by homogenization method, and the sensitivity of the optimization objective to the design variables is computed. Compare with the structure using only a single material and the topology optimization structure without timechangeable characteristic regulation, the effectiveness of the proposed topology optimization design method of composite material microstructure considering time-changeable stiffness characteristics is verified. And the effects of different parameters on the optimized configuration of unit cell and time-changeable stiffness characteristics are also studied.