Corrosion study of single crystal Ni–Mn–Ga alloy and Tb<Subscript>0.27</Subscript>Dy<Subscript>0.73</Subscript>Fe<Subscript>1.95</Subscript> alloy for the design of new medical microdevices

Once placed in a magnetic field, smart magnetic materials (SMM) change their shape, which could be use for the development of smaller minimally invasive surgery devices activated by magnetic field. However, the potential degradation and release of cytotoxic ions by SMM corrosion has to be determined. This paper evaluates the corrosion resistance of two SMM: a single crystal Ni–Mn–Ga alloy and Tb_0.27Dy_0.73Fe_1.95 alloy. Ni–Mn–Ga alloy displayed a corrosion potential (E _corr) of −0.58 V/SCE and a corrosion current density (i _corr) of 0.43 μA/cm². During the corrosion assay, Ni–Mn–Ga sample surface was partially protected; local pits were formed on 20% of the surface and nickel ions were mainly found in the electrolyte. Tb_0.27Dy_0.73Fe_1.95 alloy exhibited poor corrosion properties such as E _corr of −0.87 V/SCE and i _corr of 5.90 μA/cm². During the corrosion test, this alloy was continuously degraded, its surface was impaired by pits and cracks extensively and a high amount of iron ions was measured in the electrolyte. These alloys exhibited low corrosion parameters and a selective degradation in the electrolyte. They could only be used for medical applications if they are coated with high strain biocompatible materials or embedded in composites to prevent direct contact with physiological fluids.     

Performance of CF/PA12 composite femoral stems

This study presents the microstructural and mechanical behavior of the CF/PA12 composite material developed as well as its biomechanical performance when used for the fabrication of femoral stems. The static tests were performed to evaluate the compressive and flexural modulus as well as the ultimate compressive and bending strength. It was found that CF/PA12 composite had bone-matching properties in the same order of magnitude as cortical bone in the femur. Density and void content measurements were also done to assess the consolidation quality. Dynamic fatigue testing was conducted on both CF/PA12 cylinders and femoral stems to evaluate the long term durability and mechanical reliability of the composite. Compression–compression cyclic loading was used at a frequency of 6 Hz with loads varying between 17 kN and 22 kN for the composite cylinders while a frequency of 10 Hz and load of 2300 N was employed for the femoral stems. Results indicate that the fatigue performance of CF/PA12 composite surpasses by far the required fatigue performance for total hip prosthesis (THP) stems. The overall performance of the CF/PA12 femoral stems confirms that this composite is an excellent candidate material for orthopedic applications such as THP stems.     

Reliability Analysis of Type III Gas Storage Vessel Under Pressure Loading

Journal of Failure Analysis and Prevention - This work presents the suggestion of a model for the prediction of the reliability of type III gas storage vessel under pressure, considering the...