Damping Based Solution Applications of Powertrain Components for Radiated Noise 2007-01-2284
The continuous improvement of powertrain structure and airborne NVH characteristics has brought both higher expectation of customer acceptability and an increasing challenge to solution innovation. Emergence of “unique” vibro-acoustic power train signatures has been driven by three basic factors; 1) material and manufacturing technologies of power train subsystems and components with new material and structural properties 2) expanded diversity in base power train system concepts (e.g. hybrids, CVT's, Alternative /PEM/SI/common rail fuel delivery, diesel proliferation, “power on demand” combustion strategies etc.) and 3) Acoustic “unmasking” effects with respect to detectable sources of noise as overall sound pressure levels decrease.
This paper presents four distinct damping solution OEM application programs that required vibro-acoustic control of dominant component noise sources through damping approaches optimally engineered to meet/exceed customer defined NVH targets as well as maintaining the bound of design constraints. A brief overview of material and manufacturing history associated with stamped, formed and cast power train component applications as well as the evolution of damping methods is first discussed. Basic principles of damping in vibration control are then addressed with emphasis on elastic vs visco-elastic material characteristics. The challenges in controlling the power train vibro-acoustic signature are presented with respect to multiple source/multiple path characteristics. Acoustic properties and human sensory considerations are presented as a basis of understanding measured vs perceived noise. The power train structural dynamic complexity relative to thin plate, thick plate and shell theory is briefly described. Damping design considerations and method of selection/tuning are introduced as premise for the four applications (front cast timing covers, cast oil pan and powertrain acoustic heat shield system).
Each of the four applications is described in detail relative to the primary customer requirements, technical approach, baseline performance results, iterative development process and the optimal damping solution achieved.