An evaluation method for stiffness of origami folding is proposed. As a simple idea to evaluate the stiffness, we may consider a sheet of paper as a rectangular board, and evaluate its elastic deformation. However, when we apply this simple idea to folding of a folded sheet of paper, it contradicts the results of a questionnaire survey. We investigate more details of folding motion of origami, and give a hypothesis that the stiffness of folding motion comes from the intersection points of crease lines, where is the toughest points to fold. Our proposed evaluation method is consistent with the questionnaire survey, and hence useful to evaluate the stiffness of folding.

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In this paper, 3-axial knee joint torques given by compression sports tights were performed by numerical simulations using 3-dimensional computer graphics of a human model. Running motions of the human model were represented as the 3-dimensional computer graphics, and the running motions were determined by the motion capturing system of human subjects. Strain distribution on the surface of the 3-dimentional computer graphics of the human model was applied to the boundary conditions of the numerical simulations. An anisotropic hyperelastic model considering stress softening of fabric materials was implemented to reproduce the mechanical characteristics of the compression sports tights. Based on the strain-time relationships, knee joint torques in 3-dimentional coordinates given by the compression sports tights were calculated. As a result, the three types of knee joint torque generated by the compression sports tights in running motions were calculated. From the calculated results, the maximum value of flexion/extension, varus/valgus, and internal/external knee joint torques were given as 2.52, 0.59, and 0.31 Nm, respectively. The effect of compression sports tights on the knee joint was investigated.