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Cold spray (CS) is a rapidly developing solid-state repair and coating process, wherein metal deposition is produced without significant heating or melting of metal powder. Solid state bonding of powder particles is produced by impact of high-velocity powder particles on a substrate. In CS process, metal powder particles typically of Aluminum or Copper are suspended in light weight carrier gas medium. Here high pressure and high temperature carrier gas is expanded through a converging-diverging nozzle to generate supersonic gas velocity at nozzle exit. The CS process typically uses Helium as the carrier gas due to its low molecular weight, but Helium gas is quite expensive. This warrants a need to explore alternate carrier gases to make the CS repair process more economical. Researchers are exploring another viable option of using pure Nitrogen as a carrier gas due to its significant cost benefits over Helium.

Polytetrafluoroethylene (PTFE) is used extensively as the inner tube material in various Aerospace and Industrial hose constructs. The fluoropolymer exhibits various unique mechanical properties from other fluoropolymers including chemical inertness, non-adhesiveness and low friction coefficient making it an attractive solution for hose applications. PTFE material can be modeled using various material modeling approaches including linear-elastic, hyperelastic and viscoplastic depending on the level of accuracy required in predicting material response. Fluoropolymers, like PTFE, are considered viscoelastic-viscoplastic materials. In other words, the material exhibits both viscous and elastic characteristics when undergoing deformation but also possesses behavior in which the deformation of the material also depends on the rate by which loads are applied.

The effect of notches & mean stress in fatigue of materials has been a subject of wider interest. The current study is focused on alpha-beta Titanium alloy (Ti-6Al-4V) which is a common material in aerospace applications. Various mean stress correction approaches are evaluated for notched & un-notched specimens. Life predictions are obtained for a standard test specimen. For the zero mean condition, most approaches predict similar life. However for non-zero mean conditions, significant deviation is observed in life predictions for Titanium alloy (Ti-6Al-4V). Walker mean stress correction approach was found to be in close agreement with published test data. Walker constant is a significant parameter which influences life prediction accuracy. Study has been carried out to find suitable values of constant for different standard shapes/forms of raw material used for manufacturing.