WEAR TESTING MACHINE BY LASER BEAM ABLATION

ABSTRACT
Wear testing machine by laser ablation has been considered as a new machine for
wear measurement. It overcomes the problems generated by old machines and
systems. In this case, wear rate has occurred due to ablation by laser beam and test
sample transformed from solid state to gas state directly (sublimation) and avoid
relative movement and loss of material between sample and disk or plate. The
different operation conditions such as temperature, chemicals, environmental
conditions and different types of stresses have been considered. The new machine
consists of two main parts; optical and mechanical parts. The optical parts includes
ultraviolet laser source, optical filter, lenses to concentrate the beam and manhole of
laser beam to the tested sample in the control room. The mechanical parts include
the insulated chamber, dead weight, variable speed motor, sample holder,
temperature and pressure sensors and ph meter. Mechanism of operation depends
mainly on ablation process which is removal of material from the surface of a tested
object by vaporization. Ultraviolet laser beam is used as source of energy required
for ablation process. The new technique is suitable for all kinds of materials such as
metals, alloys polymers, ceramics and composites in any shape and size. The main
factors affecting the new technique are divided into: i) factors related to the laser
beam characteristics and ii) factors related to material properties such as surface
roughness, thermal conductivity, specific heat, density and mainly latent heat of
sublimation.