Ultrasonic Fatigue Testing in the Tension-Compression Mode.

Area of Science:

• Materials Science
• Mechanical Engineering
• Solid Mechanics

Background:

• Conventional fatigue testing is time-consuming, especially for ultra-high cycle fatigue analysis.
• Simulating high-speed operational conditions, like those in jet engines, requires specialized testing methods.
• Investigating material behavior under extreme loading rates is crucial for component reliability.

Purpose of the Study:

• To describe a protocol for evaluating material fatigue properties using high-frequency ultrasonic fatigue testing.
• To detail the necessary steps for accurate fatigue testing at approximately 20 kHz resonance frequency.
• To enable faster assessment of material endurance in the ultra-high cycle fatigue regime.

Main Methods:

• Utilizing longitudinal vibrations at a resonance frequency near 20 kHz for specimen excitation.
• Carefully designing and calculating specimen dimensions to meet ultrasonic system resonance conditions.
• Harmonizing specimens with the ultrasonic system frequency to account for manufacturing deviations.
• Automated test termination upon crack initiation and propagation to a specific length.

Main Results:

• Ultrasonic fatigue testing significantly reduces the time required for ultra-high cycle fatigue analysis.
• The method allows for the simulation of material loading experienced in high-speed applications.
• Specimen design and frequency harmonization are critical for successful resonance testing.
• Tests are terminated automatically based on crack propagation, not complete fracture.

Conclusions:

• High-frequency ultrasonic fatigue testing provides an efficient method for determining material properties in the ultra-high cycle region.
• The protocol ensures accurate and repeatable fatigue evaluations by addressing specimen design and system resonance.
• This technique is valuable for assessing the durability of materials used in demanding, high-speed operational environments.