Use of loading-unloading compression curves in medical device design

• Published in: IOP conference series. Materials Science and Engineering 2017-08, Vol.227 (1), p.12026
• Main Authors: Ciornei, M C, Alaci, S, Ciornei, F C, Romanu, I C
• Format: Article
• Language: English
• Subjects: Compression loads; Interpolation; Mathematical analysis; Mechanical properties; Mechanical tests; Moving loads; Prostheses; Tissues
• ISSN: 1757-8981; 1757-899X
• DOI: 10.1088/1757-899X/227/1/012026

The paper presents a method and experimental results regarding mechanical testing of soft materials. In order to characterize the mechanical behaviour of technological materials used in prosthesis, a large number of material constants are required, as well as the comparison to the original. The present paper proposes as methodology the comparison between compression loading-unloading curves corresponding to a soft biological tissue and to a synthetic material. To this purpose, a device was designed based on the principle of the dynamic harness test. A moving load is considered and the force upon the indenter is controlled for loading-unloading phases. The load and specimen deformation are simultaneously recorded. A significant contribution of this paper is the interpolation of experimental data by power law functions, a difficult task because of the instability of the system of equations to be optimized. Finding the interpolation function was simplified, from solving a system of transcendental equations to solving a unique equation. The characteristic parameters of the experimentally curves must be compared to the ones corresponding to actual tissue. The tests were performed for two cases: first, using a spherical punch, and second, for a flat-ended cylindrical punch.