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Structure and corrosion resistance of Co-Cr-Mo alloy used in Birmingham Hip Resurfacing system

Dobruchowska E., Paziewska M., Przybyl K., Reszka K.

Acta of Bioengineering and Biomechanics

2017

Vol. 19, no. 2

31--39

The endoprostheses made of cobalt-chromium-molybdenum (Co-Cr-Mo) alloys belong to the group of the most popular metallic implants used for hip joints reconstruction. For such biomaterials, the primary goal is correct and long-term functioning in the aggressive environment of body fluids. Therefore, the purpose of this study was to examine both the morphology and the corrosion resistance of implants made of the cobalt alloy used in Birmingham Hip Resurfacing (BHR) system (Smith & Nephew). For comparative purposes, the electrochemical studies were done for the nitrided stainless steel – Orthinox. Methods: Observations of the microstructure of the investigated material were performed by means of the optical metallographic microscope and the scanning electron microscope. Furthermore, Energy Dispersive X-ray Spectroscopy was used to analyse the chemical composition of the endoprosthesis. Characterisation and evaluation of electrochemical corrosion resistance of the selected alloys were performed by potentiodynamic polarisation tests. Results: The structural studies confirmed that Co-Cr-Mo (BHR system) is characterised by a typical dendritic microstructure with carbide precipitates, mainly M23C6, within the interdendritic areas. Results of the polarisation measurements showed that the investigated cobalt alloy exhibits lower corrosion potential than Orthinox in the utilised environments (3% NaCl, simulated body fluid – Hank’s Body Fluid). Conclusions: However, the high passivation ability of the Co-Cr-Mo alloy, as well as its resistance to the initiation and propagation of localised corrosion processes, indicate that this material is significantly more appropriate for long-term implants.

Numerical Investigations Application for Assessment of the Influence of the Spinning Zone Geometry of a Ring Spinning Machine on the Dynamics of Yarn in the Manufacturing Process

Przybyl K, Jańczyk R, Kluka A, Kossowski Z

Fibres & Textiles in Eastern Europe

2013

Vol. 21, no. 1 (97)

41--46

Results of simulation investigations of the influence of changes in the spinning zone geometry of a ring spinning machine on the tension and quality of the yarn manufactured are presented in this study. Changes in the geometry resulted from modification of the conventional drafting system into a compact drafting system. For the investigations, construction parameters of the machine and the technological process of spinning were taken into consideration. Numerical investigations were based on the mathematical model for the dynamics of yarn motion through the twisting-winding unit. Experimental tests were performed on the Polish ring spinning machine type PJ 35, equipped with a conventional drafting system and the author’s compact drafting system. It was shown that changes in the spinning zone geometry on the spinning machine caused by modification of the conventional drafting system into a compact system had no effect on the mean tension value of the yarn. Instead it diminished the amplitude of tension during the revolution around the spindle.

W pracy przedstawiono wyniki badań symulacyjnych wpływu zmiany geometrii strefy przędzenia na przędzarce obrączkowej, na napięcie i jakość tworzonej przędzy. Zmiana geometrii była wywołana modyfikacją klasycznego aparatu rozciągowego w kompaktowy aparat rozciągowy. W badaniach uwzględniono parametry konstrukcje maszyny i technologiczne procesu przędzenia. Eksperymenty numeryczne przeprowadzono w oparciu o model matematyczny dynamiki przędzy przemieszczającej się przez zespół skrętowo-nawojowy. Badania doświadczalne wykonano na polskiej przędzarce obrączkowej, wyposażonej w klasyczny oraz autorski kompaktowy aparat rozciągowy. Wykazano, iż zmiana w geometrii strefy przędzenia przędzarki wywołana modyfikacją klasycznego aparatu do postaci kompaktowej, nie wpłynęła na zmianę średniej wartości napięcia przędzy. Spowodowała zaś zmniejszenie amplitudy zmian chwilowego napięcia przędzy w czasie jej jednego obiegu wokół osi wrzeciona.