Traditional stress-based pipeline design methods primarily aim to ensure that pipeline stresses—or equivalent stresses—resulting from external loads do not exceed the material's allowable stress. However, for pipelines subjected to displacement-controlled loads (such as those caused by earthquakes, ground subsidence, landslides, or subsea pipeline laying operations), stresses often exceed the yield limit; consequently, stress-based design methods are no longer applicable, and strain-based design approaches are more appropriate.
A technical research institute plans to utilize the XTDIC 3D full-field strain measurement and analysis system (from XTOP3D) to investigate the strain deformation of large-scale oil pipes under compressive loads through compression tests, thereby analyzing the mechanical properties of the engineering materials used in the pipes.
In this experiment, a large-scale oil pipe section is first placed inside the testing machine, and a pressing head applies load to observe the deformation of the inner surface under stress. The inner surface is then ground and sandblasted, and the probe and light source are secured within the pipe's interior, as shown in the figure.
Suspend the pipe section—complete with the measuring probe—beneath the loading head to enable continuous monitoring of strain and deformation on the inner surface throughout the combined large-deformation test conducted on the pipe.
When the testing machine begins operation, the XTDIC system performs synchronous data acquisition until the loading process concludes and image capture is complete. Calculations are then performed using the XTDIC system's analysis software, enabling the analysis of displacement and strain field data for the oil pipeline based on the results.
This experiment simulated the loading conditions experienced by oil transmission pipes during service. XTOP3D’s XTDIC system and analysis software were employed to capture images and calculate full-field displacement and strain data in real time, with results output in the form of charts and curves.
The experiment successfully achieved full-field strain measurement of the pipe specimens. The experimental data aligned closely with finite element analysis results, providing critical technical parameters for strain-based design in oil pipelines and helping to further enhance the safety of pipe design as well as the operational safety and reliability of the pipeline.
