Detection of surface strain by three-dimensional digital holography

Area of Science:

• Optical Engineering
• Materials Science
• Metrology

Background:

• Surface strain analysis is crucial for understanding metallic object integrity.
• Traditional methods may lack the precision to measure microstrains.
• Digital holography offers advanced optical measurement capabilities.

Purpose of the Study:

• To demonstrate the application of three-dimensional digital holography for surface strain detection in metallic objects.
• To validate the calculation of all three surface displacement components (x, y, z).
• To convert the displacement field into a comprehensive surface strain field.

Main Methods:

• Utilizing a three-dimensional digital holography setup with three object-illuminating beams.
• Irradiating metallic objects from three distinct directions.
• Independently calculating the x, y, and z object surface displacement components.
• Analyzing strain gradients from the displacement data.

Main Results:

• Successfully detected surface strain in metallic objects.
• Demonstrated the conversion of the complete surface displacement field into a surface strain field.
• Achieved measurement of microstrains for out-of-plane surface displacements below 10 micrometers.

Conclusions:

• Three-dimensional digital holography is an effective method for precise surface strain measurement in metals.
• The optical setup allows for independent calculation of all displacement components, enabling detailed strain gradient analysis.
• The technique is highly sensitive, capable of detecting minute surface displacements and microstrains.