A Contactless Laser Doppler Strain Sensor for Fatigue Testing with Resonance-Testing Machine

Area of Science:

• Mechanical Engineering
• Optical Metrology
• Materials Science

Background:

• Fatigue testing requires precise strain measurement for material durability assessment.
• Conventional strain gauges can be intrusive and may affect test dynamics.
• Non-contact methods offer potential advantages in certain testing scenarios.

Purpose of the Study:

• To present a novel non-contact laser Doppler strain sensor for resonance-based fatigue testing.
• To detail the sensor's optical design and mathematical framework.
• To validate the sensor's performance against conventional methods.

Main Methods:

• Utilized in-plane laser-Doppler vibrometry to measure displacements at two adjacent points.
• Computed strain from relative displacements and the distance between measurement points.
• Developed a mathematical model to estimate noise-limited resolution.

Main Results:

• The laser-Doppler strain sensor achieved high accuracy in measuring strain.
• Maximum strain deviation compared to conventional strain gauges was below 4×10-5.
• The sensor demonstrated suitability for fatigue testing applications.

Conclusions:

• The developed non-contact laser Doppler strain sensor meets the stringent requirements for fatigue testing.
• This technology offers a precise and non-intrusive alternative to traditional strain measurement techniques.
• The sensor's performance validates its potential for advanced materials testing and analysis.