Wear of piston in an engine and

 

   Wear of piston in an internal combustion engine and industrial machinerydepend on many factors such as load,
running time, reciprocating velocity, composition
of piston material, temperature, the effectiveness
of lubrication etc. The design of piston
in an engine and reciprocating machinery
is a very complicated task and much
attention required to find the influence
of each factor on the responses wear and
friction characteristics.Several
wear studies related to these applications have been conducted during the past
decade. Almost all of them were performed using either pin-on-disc or block-on-ring
testing machines where the Al-Si alloy material experienced only unidirectional
sliding wear 2–5.However, very few
of these tests were reported under reciprocal sliding conditions where the same
material may behave differently compared to that under unidirectional wear
conditions 25,68,71. High wear rate has been reported
under reciprocating condition than unidirectional sliding 2572. It is therefore important to
understand the reciprocal sliding wear behaviour of these composites
considering the fact that a number of industrial applications, such as engine
cylinders, pistons, etc., involve reciprocal sliding wear. Moreover, many
tribological components are used under dry sliding conditions that influence
the stress distribution between the sliding surfaces, and even alter the
surface behaviour during the sliding motion. Studies on wear performance under
the dry reciprocating condition is therefore of practical significance and not
enough investigations concerning the influence of combined effect of wear
parameters on the reciprocating wear of the Al-Si alloys have been reported in
the literature.

 

The Design of Experiments (DOE) is a statistical method to determine
the effect of factors on a process and its
responses qualitatively. A full factorial design approach under the design
of experiment consists of two or more factors, each with discrete possible
values or levels, and whose experimental units take on all possible
combinations of these levels across all such factors. Many studies have
been conducted to study the effect of load, sliding distance, velocity,
material composition and temperature on the responses wear loss and coefficient
of friction of alloys and composites by using Full Factorial Design (FFD) 737475.But if the model shows the presence of
curvature effect and insignificant lack of fit,it requires higher order
optimization to fit the model7677.A central composite design
(CCD) is a higher order experimental design under in response surface
methodology, for building a second order (quadratic) model for the response
variable without needing to use a complete three-level factorial experiment. The Central composite design explores the
significance of factors in a quadratic level on the wear characteristics of
alloys and composites78–81.

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Further,
research into the wear of piston alloys has usually investigated the effect of
a single factor, such as sliding distance, sliding speed or contact pressure,
on the wear performance. The interaction effects of these factors have been
given little consideration. Such studies provide information regarding the wear
performance of piston alloys, but not the comprehensive information that
reflects the combined effects of such factors on the wear performance,
especially for the wear under dry condition. In fact, the interactions of the
factors have certain degree of effects, sometime strong effects, upon the wear
of piston alloys. Hence a fundamental and comprehensive understanding of the
effects of such factors and their interaction on the wear performance of piston
alloys is needed.

Although some investigations had been conducted on the experimental
design and optimization modelling
approach for reciprocating wear characteristics of alloys and composites, very few
studies were focused on the dry reciprocating wear loss and friction
characteristics of Al-12.6Si-3Cu-(2–2.6) wt.% Ni piston alloys in respect of a wide range of wear and friction test parameters.
Hence attempts were made to investigate the effect of load, sliding distance,
reciprocating velocity and the weight
percentage of nickel in a wider range of wear and friction test parameters on
the response wear loss and coefficient of friction ofAl-12.6Si-3Cu-(2–2.6) wt.% Ni
piston alloys under dry reciprocating sliding condition using FFD followed by
FCCCD.

 

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