Characteristic Stress and Strain Optimization of Cardiovascular Catheters with Laser-Cut Hypotubes using Finite Element Analysis

Author

• Kyle E. Hirth, California Polytechnic State University, San Luis ObispoFollow

Available at: https://digitalcommons.calpoly.edu/theses/3385

Date of Award

6-2026

Degree Name

MS in Mechanical Engineering

Department/Program

Mechanical Engineering

College

College of Engineering

Advisor

Scott Hazelwood

Advisor Department

Biomedical Engineering

Advisor College

College of Engineering

Abstract

Cardiovascular catheter systems rely on laser-cut hypotubes to balance flexibility and structural integrity required for minimally invasive surgical procedures.  Optimizing these mechanical characteristics remains a significant challenge.  This study aims to investigate the influence of key laser-cut geometric parameters on the mechanical performance of hypotubes through finite element analysis.

Commercially representative laser-cut hypotubes were modeled and a finite element model was developed.   Geometric design parameters were varied across a design space consisting of pitch values ranging from 0.006 in. to 0.018 in. and cuts per revolution (CPR) ranging from 2.5 – 4.5.  For each pitch and CPR combination, loading stiffness was calculated and normalized to facilitate comparison between designs.  Stress distribution contour plots were examined to identify stress propagation and regions where high stress concentrations occurred.

Results demonstrated that laser-cut geometry strongly influenced the mechanical response of the hypotubes.  Increasing pitch and CPR resulted in a higher force needed to initiate plastic deformation and increased the stiffness of hypotube samples.  Distinct trends in stiffness and stress propagation were observed between tensile, bending, and torsional loading cases, showing that bending behavior dominates the global stress response of the hypotube during deformation.

The findings presented in this study provide a framework for tailoring the mechanical performance of laser-cut hypotubes through geometric optimization.  Results can be used to help design laser-cut hypotubes that reduce stress concentrations and reduce development time, ultimately providing physicians with confidence in medical devices during surgery.