Digital Image Correlation in Materials Testing

This is an introduction to the seminar program and a presentation of the speakers:

• The introduction and program overview provide an outline of the training's content and structure. A round of introductions helps everyone get to know each other and encourages interaction throughout the event. It also gives participants the opportunity to express their goals and expectations at the beginning of the training.
• The DGM places great importance on promoting communication between participants and speakers, as well as among participants. Valuable contacts are often made during this time and can be beneficial in a professional context later on.

The training begins with an introduction to the theory of Digital Image Correlation (DIC), covering its underlying physical principles and common methods. Participants will learn how DIC works, including the fundamentals of digital image processing and the use of grey level images for accurate displacement and strain measurements. The session will also introduce both 2D and stereo DIC techniques, highlighting their differences and use cases. Additionally, the importance of calibration procedures will be discussed to ensure measurement accuracy and reliable data interpretation in practical setups.

This part of the seminar provides participants insights into how to work with DIC systems effectively. This includes setting up and operating the equipment, selecting appropriate lenses and cameras, and understanding their influence on image quality and measurement accuracy. The session explores a broad range of applications in experimental mechanics and materials testing, demonstrating how DIC can be applied to analyze deformation, strain distribution, and crack propagation under various conditions. Participants will learn how to adapt DIC techniques to suit each experimental setup.

Effective use of DIC begins with proper preparation of the setup and test specimens. This includes careful alignment of cameras, lighting considerations, and the selection of suitable lenses to optimize image capture. A critical aspect is the application of appropriate patterning techniques, such as speckle patterns, which directly influence the accuracy and resolution of the measurements. Participants will learn how to evaluate and quantify pattern quality to ensure reliable data. The session also covers uncertainty measurement, helping users understand the limitations of their setup and how to minimize errors. Finally, guidance will be provided on the choice of DIC settings, such as subset size, step size, and filtering parameters, all of which play a crucial role in the precision and robustness of the results.

The application of DIC in tensile testing provides a full-field analysis of strain distribution and local deformations. This session covers the complete testing setup using stereo-DIC, including camera positioning, lighting, and calibration procedures. Emphasis is placed on specimen preparation and high-quality patterning, which are essential for accurate strain measurements. Participants will learn how to conduct testing analysis and apply data reduction schemes to extract key mechanical properties such as modulus, and strain at failure directly from DIC data. The course also addresses sensitivity and uncertainty studies, providing insights into how variations in DIC settings and experimental conditions can impact the reliability of the results. Special focus is given to strain concentration phenomena, such as those occurring during necking, and how these are influenced by DIC parameters like subset, step, and window size, ensuring a deeper, engineering-based understanding of material behavior and measurement accuracy.

The use of DIC in bending tests enables detailed visualization of deformations and accurate determination of bending properties in materials. Special attention is given to patterning across small thicknesses, which is critical for capturing precise strain measurements in thin specimens. The session also highlights common mistakes during flexural testing, such as improper specimen alignment or inadequate support conditions, and discusses how these can affect DIC results and overall test accuracy.

Notched specimen testing with DIC allows detailed analysis of strain concentrations near notches, providing critical information about local deformation behavior. The accuracy of these measurements is influenced by DIC settings such as subset step and window size, which affect the resolution and reliability of strain data in highly localized regions.

Fracture testing using DIC enables detailed investigation of deformation and strain fields around cracks in precracked specimens. This approach provides valuable insights into crack propagation and local material behavior, with measurement accuracy depending on factors such as DIC settings and specimen preparation. This session covers the complete testing setup using 2D-DIC, including camera positioning, lighting, and calibration procedures.