Thin Wall Exhaust Systems 2006-01-1371

Steel prices soared in the past years due to the increased demand on the Asian market. Due to difficult economic conditions of the automotive industry it is not possible to transfer expenses to the final customer. Reduction of steel is therefore required to compensate for higher steel prices.

Whereas the underbody design space decreases in European vehicles, requirements are getting higher in terms of tailpipe noise and backpressure reduction. This leads to flat structures for mufflers which are integrated into the underbody to achieve as much inner volume for tailpipe noise damping as possible. That requires larger surfaces and results in a rise in costs, weight and radiated noise over surfaces.

Additionally, original equipment manufacturers (OEM) require lightweight designs to meet carbon dioxide and consumption targets. Especially for Diesel applications the weight of exhaust systems is penalized by heavy Diesel particle filters. This forces exhaust system suppliers to concentrate their light weight efforts on all components of an exhaust system.

These boundary conditions are regularly fixed by technical reasons. Wall thickness reduction is therefore necessary to decrease costs and weight. The main technical issues rather concern acoustics than durability. Radiated noise over surfaces increases without additional measures by 6 dB per wall thickness bisection. New technologies are required to ensure that the customer is not disturbed by noises. Therefore Computational Aided Engineering (CAE) [1] and measurement tools [2] are established in a development which result in innovative designs of muffler surfaces. Regular formed bead pattern is placed irregular onto a structure as a favorable solution in view of cost reduction and acoustical comfort. The development process and also design applications are outlined in this paper.