Design optimization of a wind turbine gear transmission based on fatigue reliability sensitivity
Genshen LIU1, Huaiju LIU1(), Caichao ZHU1, Tianyu MAO1, Gang HU2
1. State Key Laboratory of Mechanical Transmissions, Chongqing University, Chongqing 400044, China 2. School of Mechatronic Engineering, Southwest Petroleum University, Chengdu 610500, China
Fatigue failure of gear transmission is one of the key factors that restrict the performance and service life of wind turbines. One of the major concerns in gear transmission under random loading conditions is the disregard of dynamic fatigue reliability in conventional design methods. Various issues, such as overweight structure or insufficient fatigue reliability, require continuous improvements in the reliability-based design optimization (RBDO) methodology. In this work, a novel gear transmission optimization model based on dynamic fatigue reliability sensitivity is developed to predict the optimal structural parameters of a wind turbine gear transmission. In the model, the dynamic fatigue reliability of the gear transmission is evaluated based on stress–strength interference theory. Design variables are determined based on the reliability sensitivity and correlation coefficient of the initial design parameters. The optimal structural parameters with the minimum volume are identified using the genetic algorithm in consideration of the dynamic fatigue reliability constraints. Comparison of the initial and optimized structures shows that the volume decreases by 3.58% while ensuring fatigue reliability. This work provides new insights into the RBDO of transmission systems from the perspective of reliability sensitivity.
Transverse load factor of bending stress calculation
Face load factor of contact stress calculation
Transverse load factor of contact stress calculation
Dynamic factor
Normal module, mm
Gear velocity
Planetary gear in Stage I
Dynamic reliability, %
Initial bending fatigue reliability, %
Initial contact fatigue reliability, %
Initial bending fatigue reliability determined by the safety factor, %
Initial contact fatigue reliability determined by the safety factor, %
Fatigue reliability of the optimized structure
Fatigue reliability of the initial structure
Dynamic fatigue reliability of Stages II and III, %
Dynamic contact fatigue reliability of Stages II and III, %
Dynamic bending fatigue reliability of Stages II and III, %
Dynamic fatigue reliability of Stage I, %
Dynamic bending fatigue reliabilities of the ring gear, %
Dynamic contact fatigue reliabilities of the ring gear, %
Dynamic bending fatigue reliabilities of the sun gear, %
Dynamic contact fatigue reliabilities of the sun gear, %
Dynamic bending fatigue reliabilities of the planetary gear, %
Dynamic contact fatigue reliabilities of the planetary gear, %
Sun gear in Stage I
Residual fatigue strength of the gear under n loading cycle numbers, N/mm2
Initial fatigue strength of the gear without any damage
Equivalent peak load of the gear, N/mm2
Initial bending safety factor
Initial contact safety factor
Ring gear in Stage I
Sample torque for stress calculation
Service time, year
Gear ratio
Volume of the optimized structure, m3
Volume of the initial structure, m3
Circumferential velocity, m/s
Basic factor set
Stress calculation factor set
Fatigue strength calculation factor set
Initial design parameter set
Design variable set
Tooth form factor
Dedendum stress concentration factor
Contact ratio factor of bending stress calculation
Helix angle factor of bending stress calculation
Stress correction factor of bending fatigue strength calculation
Life factor of bending fatigue strength calculation
Size factor of bending fatigue strength calculation
Zone factor
Elasticity factor
Contact ratio factor of contact stress calculation
Helix angle factor of contact stress calculation
Life factor of contact fatigue strength calculation
Lubrication factor
Velocity factor
Roughness factor
Work hardening factor
Size factor of contact fatigue strength calculation
First tooth of the ring gear in Stage I
Second tooth of the ring gear in Stage I
Fifth tooth of the sun gear in Stage I
Calculation factor of the zone factor,
Helix angle, º
Reliability index
Calculation factor of the zone factor,
Mutation probability
Mean value of dynamic fatigue reliability
Correction coefficient between two design parameters
Bending stress of tooth root, N/mm2
Maximum bending static strength, N/mm2
Maximum bending static allowable strength, N/mm2
Allowable bending stress number, N/mm2
Contact stress of tooth face, N/mm2
Maximum contact static strength, N/mm2
Maximum contact static allowable strength, N/mm2
Allowable contact stress number, N/mm2
Variance of dynamic fatigue reliability function
Cumulative distribution function of the standard normal distribution
Probability density function of standard normal distribution
Kronecker product
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