Abstract
The development process of the knowledge-based engineering (KBE) system for the structural size optimization of external fixation device is presented in this paper. The system is based on algorithms for generative modeling, finite element model (FEM) analysis, and size optimization. All these algorithms are integrated into the CAD/CAM/CAE system CATIA. The initial CAD/FEM model of external fixation device is verified using experimental verification on the real design. Experimental testing is done for axial pressure. Axial stress and displacements are measured using tensometric analysis equipment. The proximal bone segment displacements were monitored by a displacement transducer, while the loading was controlled by a force transducer. Iterative hybrid optimization algorithm is developed by integration of global algorithm, based on the simulated annealing (SA) method and a local algorithm based on the conjugate gradient (CG) method. The cost function of size optimization is the minimization of the design volume. Constrains are given in a form of clinical interfragmentary displacement constrains, at the point of fracture and maximum allowed stresses for the material of the external fixation device. Optimization variables are chosen as design parameters of the external fixation device. The optimized model of external fixation device has smaller mass, better stress distribution, and smaller interfragmentary displacement, in correlation with the initial model.
Highlights
The flexibility of all steps of product development and design is always desirable
Testing of flexibility and quality of developed computer aided design (CAD) model of external fixation device must be done with the goal to check whether there is any interference between components
In comparison to simulated annealing (SA) method, which is not constrained with the shape of constrains and cost functions, the conjugate gradient (CG) method works with continuous differential functions
Summary
The flexibility of all steps of product development and design is always desirable. To achieve this, automation must be implemented in all possible steps of product development and design. Relationships inside the skeleton model give flexibility to the design to change the shape, place, and orientation of external fixation device components. Relationships reference design parameters and geometrical elements, which are used to place the components of the external fixation device with correlation to the main coordinate system of skeleton model. After the development of the skeleton model of the external fixation device, it is necessary to develop the parametrized model of all components using developed sub algorithms. Testing of flexibility and quality of developed CAD model of external fixation device must be done with the goal to check whether there is any interference between components
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