Mechanistic Model of Fatigue in Ultrasonic Assisted Machining

Area of Science:

• Materials Science
• Mechanical Engineering
• Manufacturing Processes

Background:

• Optimizing fatigue life in aviation materials requires advanced machining to improve surface integrity.
• Current processes need holistic models to maximize fatigue life.

Purpose of the Study:

• To investigate the effect of axial ultrasonic assisted milling on Inconel 718 fatigue life.
• To develop a hybrid model correlating machining factors to fatigue life via surface integrity aspects.

Main Methods:

• Axial ultrasonic assisted milling of Inconel 718.
• Hybrid model combining regression analysis and analytical modeling.
• Mapping process inputs to surface integrity aspects (roughness, hardness, residual stress).
• Mapping surface integrity aspects to fatigue life using a stress-based approach.

Main Results:

• Close agreement between measured and predicted fatigue life (error < 2x dispersion).
• Ultrasonic vibration, high amplitude, feed rate, and cutting velocity significantly improve fatigue life (3x improvement).
• Enhanced compressive residual stress and work hardening contribute to improved fatigue life.

Conclusions:

• Axial ultrasonic assisted milling is effective for enhancing Inconel 718 fatigue life.
• The developed hybrid model accurately predicts fatigue life.
• Optimized process parameters, particularly with ultrasonic vibration, are crucial for maximizing fatigue performance.