S-cam brake is a drum-type foundation brake used in heavy commercial vehicles. It
is a safety-critical device; hence, thorough validation of its performance by
lab test rigs and field tests is essential. During prototype testing, an unusual
impact was observed during dynamic braking at high pressure application,
specifically when the brake drum is rotating, after a period of operation of
about 10,000 cycles. This phenomenon was then observed even at static braking
when the brake drum was at rest. From initial inspection, it is due to the cam
roller, which rides on the web-slot provided at the shoe assembly, while the
S-cam is rotating and falls back instantly. This phenomenon occurs repeatedly
and creates an audible noise, which needs to be eliminated. The study aims to
correlate the phenomenon using finite element analysis (FEA) as in a prototype
test and to identify the root cause and optimize the design variables. Since the
friction coefficient at the cam roller–web interface is unknown after a period
of operation, different values of friction coefficient, ranging from 0.1 to 0.8,
are iterated and simulated by rotating the S-cam until the braking effort is
reached. The dynamic implicit analysis procedure in Abaqus standard is used to
simulate this condition. Based on the results, design variables were improved to
mitigate the issue. A quick solution, achieved by modifying a minor feature,
successfully prevented the fallback behavior and was validated through physical
testing. Furthermore, a permanent solution was developed to eliminate both the
“ride-on” and “fallback” phenomena by optimizing component dimensions. This FEA
methodology helps to validate the design in an initial concept phase itself for
future variants. Using this method, even the structural and fatigue performance
of braking parts can be validated at a system-level simulation with better
accuracy.