抄録
Living bones have the adaptive function to change the shape and the structure to outer forces exerting on the bones. The function interests even engineers because the order of the whole system is reformed and maintained properly by the way that each element of bone senses the mechanical states produced by outer forces at each position and adjust its material strength by itself. It is a kind of Autonomous Distributed Systems.
This paper describes a computational method to generate mechanical structures based on the adaptive function of bone. The original idea was proposed as the Growing-Reforming method. But the application of a three-dimensional problem has not yet been examined.
We examined the possibility of application to the three-dimensional problem by changing Young's modulus of the elements referring to the Growing-Reforming method. A three-dimensional cantilever on which terminal outer forces are exerting was set for this study. First, we used a methematical model that the target stress value was constant for Young's modulus. The computer simulation showed that the model did not converge to the desirable mechanical condition.
Next, we discussed the reason why the model diverged using basic equations of the finite element method. And we pointed out that the target stress value should be changed for the present Young's modulus of each element because the target stress value reflects the material strength of each element. We settled that the target stress value has a linear relationship to Young's modulus. The computer simulation showed that the new model generated an appropriate distribution of Young's modulus which can support the force efficiently.
We also examined a case of non-linear relationship between the target stress value and Young' modulus. The simulation result showed that the model generates a clearer three-dimensional structure.
