Practical methods to control gear whine in transmission manufacturing process
Gear whine of automotive transmissions should be controlled since it is of a nuisance. While many methods are used to control gear whine at gear design stage, this paper deals with it in transmission manufacturing process including gear manufacturing and transmission assemblies. There are high percentages of effects on transmission error and gear whine in these two processes. Idle gear whine noise can be reduced by the introduction of hard finishing which can optimize the gear shapes and surfaces. Bending of helical gear is found playing an important role in generating high frequency gear whine. It is significant for transmission assemblies to study the correlations of End of Line (EOL) and vehicles. The satisfying correlations can identify and control gear whine of an assembled transmission. All the methods mentioned above have been applied in transmission manufacturing process and good results have been achieved.
Optimum Profile Modifications for the Minimization of Static Transmission Errors of Spur Gears
A procedure for computing static transmission errors and tooth load sharing was developed for low and high contact ratio internal and external spur gears. A suitable optimization algorithm was used to minimize any combination of the harmonics of gear mesh frequency components of the static transmission error. Different combinations of tip and root relief may be used to achieve optimization. These include varying the starting point of relief and varying the magnitude of relief, and selecting the gear and/or the pinion teeth to be tip and/or root-relieved. Also, there exists an option for using either linear or parabolic relief. In addition to the presentation of optimal profile modifications, the effects of off-design loads, nonoptimum modifications, and random spacing errors are presented.
Computational fluid dynamics as a development tool for rotary blood pumps.
Computational fluid dynamics (CFD) is beginning to significantly impact the development of biomedical devices, in particular rotary cardiac assist devices. The University of Pittsburgh's McGowan Center for Artificial Organ Development has extensively used CFD as the primary tool to analyze and design a novel axial flow blood pump having a magnetically suspended rotor. The blood-contacting surfaces of the pump were developed using a design strategy based on CFD that involved closely coupling a Navier-Stokes solver to a parameterized geometry modeler and advanced mesh movement techniques. CFD-based blood damage models for shear-induced hemolysis as well as surrogate functions describing thrombosis potential were employed to help guide design improvements. This CFD-based design approach resulted in the timely development of a pump subjected to multiple geometric refinements without building expensive physical prototypes for each design iteration. A physical prototype of the final improved pump was fabricated and experimentally analyzed using particle imaging flow visualization. The CFD predicted results correlated well with the experimental data including pressure-flow (H-Q) performance and specific flow field features. It is estimated that the present CFD-based design approach shortened the overall design time frame from an order of years to months.