Multi-physics analysis of valve train systems: from system level to microscale interactions

The paper highlights a holistic, integrated, and multi-disciplinary approach to design analysis of valve train systems, referred to as multi-physics. The analysis comprises various forms of physical phenomena and their interactions, including large displacement inertial dynamics, small amplitude oscillations due to system compliances, tribology, contact mechanics, and durability at the cam-tappet contact. Therefore, it also represents a multi-scale investigation, where the phenomena can be investigated at system level and referred back to underlying causes at subsystem or component level, in other words, implications of an event at microcosm can be ascertained on the overall system performance. This approach is often referred to in industry as down-cascading and up-cascading. The particular case reported here to outline the merits of this approach concerns a four-stroke single-cylinder engine. This promotes a system approach to engineering analysis for integrated noise, vibration, and harshness, durability and frictional assessment (efficiency). Experimental validation is provided with a motored test rig, using laser doppler vibrometry.