In industrial sectors such as aerospace, energy, and chemical engineering, many components—such as engines and boiler equipment—operate under high-temperature conditions for extended periods, placing stringent demands on the high-temperature mechanical properties of the materials used. High-temperature mechanical properties refer to a material's ability to resist deformation and stress resulting from external forces at elevated temperatures. Accurately evaluating materials, utilizing them effectively, and researching new high-temperature resistant materials are key tasks in the development of these industries and in materials science research.
Digital Image Correlation (DIC) Measurement Solution
Digital Image Correlation (DIC) is a non-contact deformation measurement technique. It employs cameras to capture grayscale data from the surface of a test specimen before and after deformation; the captured images are then processed via software to derive the required strain fields.
The DIC method offers advantages such as simple experimental setups and procedures, full-field measurement capabilities, and minimal requirements regarding the testing environment and vibration isolation; it is particularly well-suited for mechanical testing in complex or extreme environments.
By utilizing the XTOP3D XTDIC 3D full-field strain measurement system to simultaneously monitor material morphology, deformation, and strain at high temperatures, one can capture surface shape changes induced by heat, reveal material failure processes, and quantitatively determine the critical temperatures and strain ranges associated with failure.
Impact of Errors and Mitigation Measures
As with any measurement process, errors can affect the data obtained via Digital Image Correlation (DIC). Consequently, the corresponding uncertainty must be estimated for each new test; sources of error related to both testing and post-processing must be managed and minimized to ensure the reliability of displacement measurements.
In high-temperature mechanical testing of materials, factors such as equipment, the environment, and operational procedures can introduce measurement errors. Potential influencing factors include:
1. The quality of the high-temperature speckle pattern, which directly affects the DIC software's computational results;
2. Thermal expansion of the specimen due to rising temperatures, leading to deformation measurement errors;
3. Red light emitted by the heated specimen, which interferes with image acquisition;
4. Air within the test chamber causing surface oxidation of the material at high temperatures, thereby affecting image acquisition.
To mitigate these factors and reduce measurement errors, XTOP3D technical engineers typically implement the following measures based on the specific testing environment:
1. Creating high-quality speckle patterns with high contrast and uniform distribution to enhance feature recognition;
2. Maintaining the high-temperature state for a period to allow thermal expansion deformation to stabilize before applying the load, thereby eliminating errors caused by thermal expansion;
3. Installing narrow-band optical filters and interference filters, combined with blue LED supplementary lighting, to eliminate infrared interference caused by high temperatures and ensure high-quality speckle image acquisition;
4. Partially evacuating air from the chamber to lower the pressure and reduce the impact of oxidation.
While DIC can be applied to both high- and low-temperature experiments, it is generally limited to measurements below 800°C; performing measurements at ultra-high temperatures (up to 3000°C) remains a significant challenge.
The XTOP3D XTDIC non-contact 3D optical strain measurement system utilizes a proprietary, specialized speckle preparation technique. By combining this with various narrow-band optical filters and interference filters, the system clearly captures high-temperature speckle patterns, enabling full-field strain measurement at temperatures up to 3000°C.
As high-temperature and ablation-resistant materials, composites are frequently used in critical thermal protection components—such as engine nozzle throat inserts, expansion sections, combustion chambers, gas valves, and air intakes—where operating temperatures range from 1,500°C to 3,500°C or even higher.
Thermal expansion of the extensometer itself can cause slippage between the specimen and the extensometer, leading to increased measurement errors; furthermore, the specimen requires electrical heating during testing. Consequently, employing non-contact DIC (Digital Image Correlation) measurement technology resolves issues related to thermal and electrical insulation, enabling a comprehensive and accurate assessment of the high-temperature mechanical properties of composite materials.
High-Temperature Welding of Thin Plates
High-strength, thin-walled components are widely used in sectors such as shipbuilding, automotive manufacturing, and aerospace. Due to their low rigidity, these components are prone to bending, angular distortion, and buckling during welding. Traditional contact-based measurement methods typically capture data at single points and in single directions, making it impossible to intuitively analyze overall deformation trends.
Given the complexity of the deformation, it is difficult for theoretical numerical simulation techniques to accurately predict actual deformation behavior. Digital Image Correlation (DIC) technology is employed to acquire full-field deformation data during the welding process, enabling the analysis of deformation patterns and the optimization of welding procedures, while also providing data to support numerical simulations.
High-Temperature Welding of Cylindrical Structures
High-strength pipeline steels are widely used for transporting oil and gas (particularly natural gas). As pipelines are essentially welded structures, various welding defects—such as cracks, porosity, slag inclusions, incomplete penetration, and lack of fusion—inevitably occur in the weld seam, the adjacent base metal, and the heat-affected zone.
By employing non-contact measurement techniques based on digital speckle correlation to capture the full-field deformation distribution around the weld seam, this research investigates the deformation mechanisms and mechanical behavior of pipelines during welding. The aim is to maximize the pipeline's deformation capacity, thereby ensuring safe and stable operation in complex service environments characterized by seismic zones, fault displacements, landslides, and permafrost regions.
Laser-Induced Thermal Deformation
When a laser acts as an energy source on a target material, it induces a series of deformations. Non-contact measurement techniques allow for the acquisition of full-field deformation data, providing a clear visualization of deformation patterns. This yields extensive experimental data for theoretical research, reveals the underlying mechanisms of laser-target interactions, advances the study of deformation physics, and expands the scope of laser applications.
Experiments involving the laser heating of aluminum and titanium alloy sheets capture deformation data spanning the entire process—from initial heating through to full-thickness melting (burn-through). These data provide a foundation for theoretical research and numerical simulations, supporting fundamental scientific studies and driving the advancement of laser technology in key sectors such as national defense and industrial manufacturing.
