Views: 68 Author: Site Editor Publish Time: 2026-03-31 Origin: Site
Fatigue Problem of Wind Turbine Pitching Disc Spring: Engineering Practice from Failure Analysis to System Optimization
As the core component for wind turbine attitude control, the pitch system's braking and damping mechanisms impose stringent reliability requirements on disc springs. Under frequent start-stop cycles, these springs are prone to elastic deformation and crack initiation, directly impacting both operational safety and maintenance costs. Based on a real-world case study from a 5MW wind farm, this paper systematically analyzes the fatigue failure mechanisms of disc springs and proposes a comprehensive end-to-end solution.
The disc spring in the pitch system primarily performs two critical functions: the safety brake provides continuous preload force to ensure reliable locking of the pitch bearing; the buffer compensation mechanism absorbs impact loads and compensates for thermal expansion/contraction as well as installation errors.
However, the pitch control system undergoes over 50 start-stop cycles daily, accumulating more than 15,000 cycles annually, subjecting the disc springs to prolonged exposure of alternating and impact loads. Key failure mechanisms include: insufficient preload force due to elastic fatigue; micro-crack formation at stress concentration zones; plastic deformation caused by overload impacts; with replacement costs exceeding 50,000 yuan per wind turbine's disc spring, resulting in 15%-20% annual operational maintenance expenses increase.
Project Overview: A 10-unit 5MW wind farm in Northwest China, where disc springs are applied to pitch brake systems with 12 sets of disc spring assemblies per unit. After two years of operation, faults such as insufficient brake pressure and failure to achieve rapid blade locking were observed.
Failure cause analysis:
Material level: The original 60Si2MnA alloy exhibited insufficient anti-fatigue performance, with reduced toughness at 25°C low temperatures.
Design level: Incorrect stacking method resulted in a stress concentration factor of 1.8, exceeding the allowable value.
Process level: Shot peening reinforcement was not applied, and surface tool marks became fatigue crack initiation sites.
Operation and maintenance level: No stateless monitoring mechanism, passive replacement occurs after failure
Under alternating loads, the average stress in disc springs approaches 80% of the yield strength, with stress amplitudes reaching 1.5 times the rated value during emergency start-stop operations. Stress concentration coefficients at geometric discontinuities such as end faces and inner holes reach 1.5 to 2.0. Microscopically, dislocation slip forms microplastic zones, element segregation at grain boundaries promotes microcrack growth along grain boundaries, and nanoscale carbide precipitation further reduces fatigue resistance. Environmental factors including low temperatures, vibration coupling, and inadequate lubrication accelerate the damage progression.
55CrSi spring steel was selected, and a two-phase zone pre-cooling + graded quenching process was adopted. The martensite lath width was refined to 0.3 μm, with a nanoscale carbide volume fraction reaching 8.2%. Under an alternating temperature field of 25°C to 40°C for 20,000 hours, the stiffness decay rate remained below 3.5%, significantly better than the original material's 9.2%.
In accordance with the GB/T 1972.12023 standard, the h/t ratio was optimized from 1.2 to 1.3, the internal hole chamfer radius was increased from 0.1mm to 0.3mm, and the stacking method was uniformly standardized as opposing stacking. Finite element analysis demonstrated a 30% reduction in maximum stress, with the optimal preload force of 25kN determined through pitch shaft load simulation.
Shot peening reinforcement: Automated robotic shot peening forms a residual compressive stress layer of 0.10.2 mm, resulting in a threefold increase in fatigue life.
End face treatment: Planarity control within 0.005 mm to avoid eccentric loading deformation
Surface protection: Molybdenum disulfide + polytetrafluoroethylene (PTFE) lubricating coating, with friction coefficient reduced from 0.35 to 0.08
Micro-pressure and temperature sensors are installed, with a first-level warning triggered when the preload force falls below 22 kN and a second-level warning (planned shutdown) activated when it drops below 20 kN. By integrating LSTM deep learning algorithms, precise fatigue life prediction is achieved.
Implement a monthly inspection and annual disassembly system using batch management with lifespan tracking, recording installation times and operational parameters for each disc spring to ensure precise replacement.
After six months of operational validation, all disc spring-related failures were eliminated, with stiffness decay rate controlled within 3%. Maintenance costs decreased by 40%, and the expected service life of single-disc springs increased from 2 years to 8 years.
Jiangsu Sunzo Spring has long been dedicated to the R&D of high-performance disc springs, offering material solutions including 60Si2MnA, 50CrVA, 55CrSi, and Inconel. The company conducts parameter optimization and finite element analysis in compliance with national disc spring standards, equipped with advanced processes such as automated shot peening, precision grinding, and lubrication coating. It provides end-to-end technical support ranging from selection calculations to on-site installation.
For wind turbine pitch system disc spring selection or customized solutions, please contact our sales team for details.
SUNZO has it’s own researching and development team and test center, has participate in rule-making of the latest national industry standards and the international ISO standards for disc springs.
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