Determination of Interior NVH Levels from Tire/Wheel Variations using a Monte Carlo Process 2011-01-1580

Variability in design (e.g. tolerance), material, manufacturing, or other sources of variation causes significant variation in vehicle noise, vibration and harshness (NVH) response. This leads to a higher percentage of produced vehicles with higher levels of NVH leading to higher number of warranty claims and loss of customer satisfaction, which are proven costly to the original equipment manufacturers (OEM). Measures must be taken to insure less warranty claims and higher levels of customer satisfaction. As a result, original equipment manufacturers have implemented design for variation in the design process to secure an acceptable (or within specification) response. We will focus on some aspects of design variations in a tire/wheel assembly that should be considered in the design process. In particular, certain materials (e.g. rubber) are known to have variation in stiffness that is either unavoidable or proven costly if tighter control is desired. Rubber materials are used as engine mounts, sub frame mounts, exhaust hangers, tires, as well as other components. In other examples, variations due to imbalance in rotating components can also be unavoidable or costly to control. Some of the major components in the vehicle that are known to have imbalance and traditionally cause NVH issues and concerns include the crankshaft, the drivetrain components, and wheels. In the tire/wheel assembly, both material and imbalance variations will be encountered. The purpose of this paper is to develop a framework for determining interior NVH levels resulting from these sources of variation in a wheel assembly and to discuss the methods used in vehicle design to secure a more robust system to such variations.