引張りと捩りの複合荷重下のカテーテルの降伏応力

（降伏応力に及ぼす含水の影響について）

抄録

The purpose of this study is to investigate the mechanical property of catheter made of soft nylon resin reinforced with thin stainless wires. In our previous study, the yield stresses under combined loads for tension and torsion have been examined with changing those ratios and with two types of different deformation speeds. As the way to determine the yield stress, the method that the point where a curve obtained in the viscoelastic region and a curve in plastic region intersects will be regarded as the yield stress is adopted. Since not only Young's modulus reduces for containing water but also stainless wires are peeled from matrix with an increase of load, it is predicted that the value of yield stress decrease. In the present study, the yield phenomenon is examined by using the test pieces, which have already been contained water, in consideration of actual usage. Then, the relation between the occurrence region of yield stress in water content condition and the occurrence region of yield stress in non-water content condition is revealed by performing the combined loading tests with various directions in the stress space.