Damage Tolerance Design of Artificial Mechanical Heart Valve Holder

To study the conservative life of the artificial mechanical heart valve holder,CATIA software was used for modeling,and ABAQUS finite element analysis was used to analyze the stress of the valve holder in the complex environment of the human body and the residual thermal stress during production and processing.The damage tolerance method based on fracture mechanics analyzes the maximum initial crack size that the heart valve holder can tolerate under the premise that the structural safety life is longer than the life of the implanted patient.The results show that the maximum initial crack size is only tens of microns;the traditional S/N life analysis can only obtain non-conservative life,and the damage tolerance method is the basic requirement for analyzing the life and quality control of artificial mechanical heart valves.

Determination of Anisotropic Factors of Pyrolytic Carbon by Electron Diffraction

The preferred orientation of pyrolytic carbon coating is an important performance parameter for the safe use of artificial mechanical heart valve.In this paper,the selected area electron diffraction(SAED)analysis of pyrolytic carbon coating samples of artificial heart valve was carried out by transmission electron microscopy(TEM),and the experimental method of characterizing the preferred orientation of pyrolytic carbon by electron diffraction spectrum,namely bacon anisotropy factor(BAF),was described,and the orientation angle and BAF corresponding to the electron diffraction spectrum were measured.The results show that the BAF value can directly reflect the anisotropy of pyrolytic carbon in the selected area.The BAF value range is from 1 to infinity,and the higher the preferred orientation is,the greater the value is.The BAF value decreases exponentially with the increase of orientation angle.When the pyrolytic carbon tends to be isotropic,the orientation angle tends to 180 and the BAF value tends to 1.