引張りと捩りの複合荷重下のカテーテルの降伏応力について

（降伏応力に及ぼす変形速度の影響について）

抄録

This paper describes the occurrence region of the yield stress of catheter, which is made of soft nylon resin reinforced with thin stainless wires. In our previous study, the occurrence region of the flattening phenomenon in the cross section of catheter due to the torsional buckling has ever been examined by using the method for the visco-elasticity theory. In consideration of the shape of cross section gradually changing into the elliptical shape during the process of applying the torsional moment, the experimental equation for the torsional moment has been derived based on the shear flow theory for determining the occurrence region of the flattening phenomenon. Moreover, in this research, in order to confirm the effect of stress relaxation on the yielding phenomenon, the yielding area under combined loads for tension and torsion is examined with the different deformation speeds. As for the determination method of the yield stress, a point where the stress relaxation curves based on the elastic mechanical model and the plastic mechanical model intersect is adopted. The experiments are conducted under conditions that the axial displacement velocity and the angular velocity are variously changed. Then, the occurrence regions of yield stress are estimated on the basis of these experimental results.