Research On Key Techniques In The Simulation And Testing System Of Braided Non-vascular Stents

With the development of interventional radiology, stent dilation is used more and more widely in the treatment of lumen stenosis due to various diseases. Stents can be used to expand the esophagus, urethra, trachea, bile duct, intestine and other non-vascular lumen. They also can be used to extend the various vascular lumens. Various stents, as implants in the body, is bound to be continuously influenced by the environment, such as acid and alkali environment, periodic or aperiodic stress function, the special state of the human lumen and so on. In order to evaluate the safety of the products, the numerical simulation and related experiment in vitro must be done on the mechanical properties of the stents. Therefore, the research in this area will be further and further. Based on the above background, major achievements and conclusions are as follows:(1)The numerical simulation on the jet process of mechanical property testing device of stents was developed. The simulation scheme was completed based on the basic theory of fluid mechanics and the demand of testing device. According to the scheme, the numerical simulation was accomplished. One scheme, under the same jet distance, the effect of the inlet pressure of the annular loading device on the pressure applying on the stents is researched. Scheme two, under the same inlet pressure, the effect of the jet distance on the pressure applying on the stents is researched. Based on that, the relationship between inlet pressure value of annular loading device and the pressure applying on the stents is researched, the relation curve is fitted out and the mathematical formula is addressed.(2) The fatigue performance of stents with different end shapes is analyzed. The parameterized models of the braided esophagus stents with a variety of end shapes are built. According to the actual working conditions of the esophageal stents, the finite element mechanical models of the stents in actual working conditions are established. The reasonable boundary conditions, including the radial compression simulation and the esophageal peristalsis load, are set up. The fatigue analysis of the multiple end shapes stents with the optimum structure parameters is completed. The results show that the fatigue life of the stents with different end shapes can meet the clinical demand.(3)The research designed the control module and the monitoring module of the test system. According to the control requirements of the test system, the overall scheme design of the control module and the monitoring module is completed. According to the control scheme, the selection of the devices is finished. The hardware design and software programming for the control of stepper motor at the end of digital valve, the control of DC motor at the end of the lead screw and the communication between the upper computer and the lower computer are realized. Based on software of LabVIEW, the communication and data acquisition interface design and program design are completed.(4) Experimental test and the result analysis. By selecting reasonable test material, after obtaining the relevant mechanical parameters of the material, the radial pressure test of the stents is completed. Test data are analyzed and compared to the theoretical simulation results. Finally, the fatigue life test of the stents with Cup-Sphere end shape is done, whose structural parameters are consistent with the model in the numerical simulation. Experiment results show that the fatigue life of the stents can meet the clinical demands.