Visco-Elastic Properties of Catheter Reinforced with Braids: Stress Relaxation under Two-Stage Step Strain for Different Deformation Paths

Abstract

Generally, as for the material of catheter, a soft characteristic is necessary so as not to damage vascular wall etc. On the other hand, responsivity and enough rigidity are required for the surgical operations such as myocardial infarction or cerebral infarction. Therefore, the catheter, which is made of soft nylon resin and is reinforced with thin stainless wires so called “braid”, is chosen as the subject of this study. The purpose of this study is to reveal the effect of braid on the mechanical property of the catheter by investigating the relationship of the stress relaxation and the relative angle between the braid and the principal axis of stress. Especially, in order to investigate the stress relaxation under combined loading, the experiments of two-stage step strain for tension and torsion are carried out with different deformation paths. Consequentially, the phenomenon of the stress relaxation reduces with the relative angle becomes smaller. Moreover, the numerical model under two-stage step strain is proposed in this paper, and the validity of this model is confirmed by comparing the calculated results with the experimental results.