Structure Optimization And Research On Impulse Resistant Performance Of Marine Gearbox

The marine gearbox is one of the decelerate devices and propulsion systems necessary for all ships. The overall performances of the ships greatly depend on the quality of gearboxes. The marine gearbox must have long working duration and high reliability. At the same time, the gearbox should have light weight and good impact resistance. The project in this thesis is from one of the major special projects founded by Science and Technology Department of Zhejiang Province——"Research and Application of the Major Techniques of Higher Power Marine Gearboxes". We investigated a certain type of high power marine gearbox. By theoretical analysis, computation of mathematical models and computation simulation, we studied the strength, rigidity and vibration characteristics of the gearboxes under different working conditions. Besides, the structure of the gearbox and the shape of the gears'teeth were optimized. The strength, rigidity and resistance of impact of the optimized gearboxes were also analyzed. The main contents of this thesis are as follows:First, the entity model of the gearbox was constructed. The static analysis was applied to the structure of the gearbox. Thus, we investigated the tension and strain of the gearbox under different working conditions, and assessed the strength and rigidity of the gearbox. Based on the method of Block Lanczos, Nastran solver was used to do the restrained modal analysis for the gearbox model. Then we derived the natural frequencies of the gearbox and the relationships between the different orders of the modes of vibration corresponding to different natural frequencies.Secondly, the gearbox and the shape of the gears were optimized. We applied the structural optimization to the gearbox and compared the static analysis results of the gearbox before and after optimization. Then we used the software MASTA to optimize the shapes of the gears'teeth. We also compared the contact stress of the tooth surfaces, the total bending stress at the root of the gear teeth, errors and amplitudes of transmission between the teeth of two gears, the load distribution of the contact line of the gears, the damage ratios and the safety factors before and after optimization.Finally, the optimized gearbox was assembled again. Numerical experiments of impact resistance in the frequency domain were done to the optimized gearbox with DDAM. The impact resistances of the optimized gearbox were accessed according to the standard criteria of impact resistance.