This paper presents a computational strategy for shape change of tensegrity models to achieve the prescribed target coordinates of a set of monitored nodes via forced elongation of cables. Mathematical formulation for incremental equilibrium equations of a tensegrity model during the shape change analysis is derived and presented. An optimization approach in determining forced elongation of cables using sequential quadratic programming with defined inequality constraints is formulated and presented. Four tensegrity models namely the simplex, quadruplex, two-stage tensegrity model and tapered three-stage tensegrity model are tested using the proposed shape change algorithm. Capability of tensegrity models to undergo bending, axial, twisting deformation and combinations of these deformations is also described.
In this paper, results of static loading tests on the stress transfer in mortise-tenon joints are shown. With the investigations of the experimental results, we present key requirements of a mechanical model for stress transfer in tenon joints. The model considers the discontinuity as the results of bi-axial stress state and friction by contact between tenon and mortice. Then the model can be evaluated stress transfer in the directions along fiber and perpendicular to fiber. It is necessary to recognize energy absorbing capacity and strength, inelastic mechanical model should simulate the compressive deformation inclined to the grain, the resistance of cotter and splitting. The mechanical model of main frames should be dealt with geometrically and material non-linearity incorporated with restoring force produced by rocking.
This paper presents a study on form-finding of four-stage class one self-equilibrated spine biotensegrity models. Advantageous features such as slenderness and natural curvature of the human spine, as well as the stabilizing network that consists of the spinal column and muscles, were modeled and incorporated in the mathematical formulation of the spine biotensegrity models. Form-finding analysis, which involved determination of independent self-equilibrium stress modes using generalized inverse and their linear combination, was carried out. Form-finding strategy for searching the self-equilibrated models was studied through two approaches: application of various combinations of (1) twist angles and (2) nodal coordinates. A total of three configurations of the spine biotensegrity models with different sizes of triangular cell were successfully established for the first time in this study. All members in the spine biotensegrity models satisfied the assumption of linear elastic material behavior. With the established spine biotensegrity model, the advantageous characteristics of flexibility and versatility of movement can be further studied for potential application in deployable structures and flexible arm in the robotic industry.
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