Fractured Metallic Tracheostomy Tube: Report of a Fractographic Study

Objective: To investigate the cause of a broken metallic tracheostomy tube.Material and Methods: In this study, we performed a fractographic investigation of a broken tracheostomy tube from an elderly patient using surface visualization, scanning electron microscopy, energy dispersive X-ray spectroscopy, and chemical composition analysis using X-ray fluorescent and metallographic testing.Results: Surface visualization revealed multiple corrosive pits which were confirmed by liquid penetrant testing. Scanning electron microscopy and energy dispersive X-ray spectroscopy revealed the chemical composition of the tube to be an austenitic chromium-nickel-manganese stainless steel alloy. Metallographic analysis suggested that the fracture site originated from the inner surface from intergranular corrosion.Conclusion: The evidence suggests that the corrosion resistance properties of this material might not be suitable for long term use in the human trachea. Higher grade stainless steel or more frequent device change is recommended.

Learning geometry through surface creation from the hypocycloid curves expansion with derivative operators for ornaments

Geometry is one of the particular problems for students. Therefore, several methods have been developed to attract students to learn geometry. For undergraduate students, learning geometry through surface visualization is introduced. One topic is studying parametric curves called the hypocycloid curve. This paper presents the generalization of the hypocycloid curve. The curve is known in calculus and usually is not studied further. Therefore, the research's novelty is introducing the spherical coordinate to the equation to obtain new surfaces. Initially, two parameters are indicating the radius of 2 circles governing the curves in the hypocycloid equations. The generalization idea here means that the physical meaning of parameters is not considered allowing any real numbers, including negative values. Hence, many new curves are observed infinitely. After implementing the spherical coordinates to the equations and varying the parameters, various surfaces had been obtained. Additionally, the differential operator was also implemented to have several other new curves and surfaces. The obtained surfaces are useful for learning by creating ornaments. Some examples of ornaments are presented in this paper.