Biological load carriers such as trees, bones etc do self optimize their design by adaptive growth The mechanism used IS simple material is only attached by growth at overloaded places until a homogeneous stress state at the surface of the component is attained this mechanism can be copied by clever use of the Finite Element Method (FEM) Two 2D-examples are analyzed before and after optimization and In every case a striking reduction of notch stresses can be shown The success of this new method, called CAO (Computer Aided Optimization), IS verified experimentally by fatigue testing of non-optimized and optimized T-Joints which have been manufactured by CAM Under the same fatigue conditions the optimized design could endure much more cycles until breakage occurred. The method IS recommended especially to the engineer In the Industrial environment who IS looking for a straight forward method leading to a design with minimum weight and maximum fatigue resistance
It IS well known that biological load carriers are subject to a hard competition for energy and living space Therefore only the best mechanical construction has a chance to survive This optimum IS characterized by minimized weight and sufficient mechanical strength A large number of preliminary studies by Mattheck (1990a, b) have shown that biological structures adapting their growth with respect to external loads Will always grow Into a state of constant mechanical stress at their surface. This leads to a situation where no point of the biological structure IS either under- or overloaded.
Nature has had ample time to optimize biological structures In the context of this paper an "optimized" design shall Imply structural Optimization, I e reducing or even eliminating stress concentrations for a given geometry and loading situation