The Fatigue Life Analysis Of Marine Helical Gear Based On Transient Dynamics

“Made in China 2025” Clear direction and objectives for China's development in the next ten years.Shipbuilding industry as one of the ten key areas of development,also faces enormous opportunities and challenges.Strategic policy clearly put forward the large-scale,intelligent ship and the polar ship is needed break through.Both high power and polar conditions have very high requirements for propulsion systems,while marine gearbox is a key component of the propulsion systems.The dynamic performance of gearbox will affect the dynamic performance of the entire propulsion system.In order to understand the dynamic characteristics and reliability of gear transmission system.Therefore,it is necessary to make a transient dynamics analysis and the fatigue life analysis for the helical gear pair,which holds a key to ship design and ship safety.In this paper,the propulsion shafting of the 10000 DWT Sea-River-Through ships is considered as the research object.GWC-type gearbox is included.The main purpose is to analyses the dynamic characteristics and the fatigue life of the marine helical gear pair based on the actual operation conditions.Also to achieve the design of the total life cycle for the marine gearbox.Establish the equivalent shaft model,then free vibration and forced vibration analysis are calculated.“Dangerous rotational speed” of the propulsion shafting can get from the result.Based on Matlab,the transient response of the propulsion shafting under dangerous rotational speed is analyzed and the dynamic characteristics of the propulsion shafting also can get from the transient result.Based on Ansys Workbench,the transient dynamics of the helical gear pair is analyzed and the fatigue life of the helical gear pair is calculated.The main contents in this paper are as follows:1)Based on the equivalent shaft model.The free vibration and forced vibration of the 10000 DWT Sea-River-Through ships' propulsion shafting can be calculated.Use Matlab to calculated the transient response of the propulsion shafting based on the New-mark method.Then analyze the dynamic response of the shaft.Define the dangerous rotational speed.Make a analysis of the transient response of shaft under the dangerous rotational speed.2)Established the contact model of helical gear pair.Use Workbench to make a modal analysis for gear pair.Select time increment for the transient dynamic analysis by the natural frequency of the gear pair.In order to simulate the dynamic response of the gear pair,use the torque data which is calculated by Matlab.3)Use Fatigue Tool to calculate the fatigue life of the helical gear pair.The workflow and theory of fatigue analysis is elaborated.Provides the stress modification method of asymmetric constant amplitude cycle load.According to the calculating to find the influence of concentrated stress and load type on gear's fatigue life.Finally,the fatigue life of gears is calculated by using the stress data calculated by transient dynamic analysis of helical gear pair.