Life Prediction Model for High-Cycle and Very-High-Cycle Fatigue of Ti-6Al-4V Titanium Alloy Under Symmetrical...

Area of Science:

• Materials Science
• Mechanical Engineering
• Aerospace Engineering

Background:

• Ti-6Al-4V titanium alloy is crucial for aero-engine components like fans and discs.
• Modern aero-engines require component lifespans exceeding 10^8 cycles, rendering traditional infinite life design insufficient.
• High-cycle and very-high-cycle fatigue behavior is critical for ensuring the reliability of these components.

Purpose of the Study:

• To establish a nonlinear cumulative damage life prediction model for Ti-6Al-4V alloy under high-cycle fatigue.
• To develop a prediction model for very-high-cycle fatigue life by incorporating plastic strain energy and internal stress parameters.
• To enhance the accuracy of fatigue life predictions for titanium alloys in critical engineering applications.

Main Methods:

• Conducted symmetrical loading high-cycle fatigue tests on Ti-6Al-4V titanium alloy.
• Performed very-high-cycle fatigue tests to analyze material damage evolution.
• Introduced an internal stress parameter to describe plastic strain energy variation.
• Developed and validated fatigue life prediction models for both high-cycle and very-high-cycle regimes.
• Performed sensitivity analysis on the model parameters.

Main Results:

• Established nonlinear cumulative damage models for high-cycle and very-high-cycle fatigue.
• The models demonstrated good agreement with experimental test data.
• Sensitivity analysis and parameter optimization reduced the average prediction error from 59% to 38%.
• Quantified the role of plastic strain energy in very-high-cycle fatigue damage.

Conclusions:

• The developed fatigue models accurately predict the life of Ti-6Al-4V titanium alloy in the high-cycle and very-high-cycle ranges.
• Optimized model parameters significantly improve prediction accuracy, crucial for engineering applications.
• This research provides a valuable tool for predicting the operational lifespan of titanium alloy components in demanding environments like aero-engines.