The advanced development of additive technologies over the past years led to the fact that parts made by these technologies have been increasingly used in the most diverse engineering applications. One of the most famous and the most applied additive technology is 3D printing. In this paper the influence of the material type on the operational characteristics of spur gears manufactured by the 3D printing technology is analyzed, after the experimental testing performed on a back to back gear test rig, in the predefined laboratory conditions.
One of the most important factors influencing ball bearings service life is
its internal radial clearance. However, this parameter is also very complex
because it depends on applied radial load and ball bearings dimensions,
surface finish and manufacturing materials. Thermal condition of ball
bearings also significantly affects internal radial clearance. Despite many
researches performed in order to find out relevant facts about different
aspects of ball bearings thermal behaviour, only few of them are dealing with
the real working conditions, where high concentration of solid contaminant
particles is present. That?s why the main goal of research presented in this
paper was to establish statistically significant correlation between ball
bearings temperatures, their working time and concentration of contaminant
particles in their grease. Because of especially difficult working
conditions, the typical conveyor idlers bearings were selected as
representative test samples and appropriate solid particles from open pit
coal mines were used as artificial contaminants. Applied experimental
methodology included thermographic inspection, as well as usage of custom
designed test rig for ball bearings service life testing. Finally, by
obtained experimental data processing in advanced software, statistically
significant mathematical correlation between mentioned bearings
characteristics was determined and applied in commonly used internal radial
clearance equation. That is the most important contribution of performed
research - the new equation and methodology for ball bearings internal
clearance determination which could be used for eventual improvement of
existing bearings service life equations. [Projekat Ministarstva nauke
Republike Srbije, br. TR35029 i br. TR14033]
Corrosion effects on structural integrity and life of oil rig welded pipes
are analysed by experimental, analytical, and numerical methods. Experiments
were performed using standard tensile specimens and CT specimens for static
loading, Charpy specimens for impact loading, and 3 Point Bending specimens
for fatigue crack growth with amplitude loading. In each case new and old
pipes were used to evaluate corrosion effects. Results indicated negligible
corrosion effects in the case of tensile properties and impact toughness,
and strong effects in the case of fracture toughness and especially fatigue
crack growth rates, increasing the risk of static failure and reducing
significantly structural life. Analytical expressions are used for oil rig
pipe structural integrity and life assessment to quantify these effects.
Recently introduced risk-based approach is applied to analyse oil rig drill
pipe with a corrosion defect treated as a surface crack.
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