Parametric study of stresses affecting the external and internal fibers of connecting rod small end

Connecting rod is an important element in reciprocating engines which
faces various stress conditions. For long time, extensive efforts are
conducted to reduce its weight and consequently affecting inertia force
and cost. The purpose of this work is to study the factors which control
the stresses affecting external and internal surfaces of connecting rod
small end.These stresses result from inertia force of piston group mass
and part of connecting rod. The transient section between small end and
shank is considered as the most critical sectionat angle φz. The value of
internal stress is found to be zero at certain value of this angle.In this
study, a comprehensive investigation has been conducted to study the
effect of changing small end design parameters on the value of angle
(φzο) at which internal stress equals zero. The results showed that there is
no effect of inertia force and small end width, while small end thickness,
mean radius, and load distribution factor have dominant effect on this
angle value. By using regression, a new correlation between (φzο) and
dominant design parameters has been introduced with maximum error
0.7%. Verification of analytical study has been conducted using ANSYS
numerical analysis software.Such a relation could be a useful tool for
engine designers to predict the value of (φzο) to be a guide to change
small end dimensions and its material which participate in reduction of
connecting rod weight and price.