Search Results

It was demonstrated that a bypass duct similar to a Herschel- Quincke tube could be used to increase the transmission loss of mufflers at selected frequencies. In many cases, the duct can be short and thought of as a leak. It was shown that the optimal length and cross-sectional area could be determined by using a simple optimization technique known as the Vincent Circle. Most importantly, it was demonstrated that the attenuation at low frequencies could be improved by as much as 15 dB. To prove the concept, a muffler was designed and optimized using transfer matrix theory. Then, the optimized muffler was constructed and the transmission loss measured using the two-load method. The measured results compared well with prediction from transfer matrix theory. Boundary element simulation was then used to further study the attenuation mechanism.

A procedure for the computation of fatigue life of shafts subjected to variable amplitude independent bending and torsion loading is described. The elastic superposition technique, followed by a Neuber plasticity correction, also allows for the initial and possibly cyclic plasticity dependent residual stress states caused by induction hardening or other surface altering processing effects. The present study documents the formation and alteration of residual stresses caused by initial induction hardening and followed by a straightening process. Sample calculations are presented for two critical finite elements of a prototype shaft, and lives are predicted using a traditional equivalent axial stress and by a new procedure that searches for and computes lives at critical angles.