Computation of Bending Stress in Pipes Using Weighted Hole-Drilling and DSPI Measurements

• Published in: Experimental mechanics Vol. 57; no. 2; pp. 341 - 352
• Main Authors: Viotti, M. R., Lothammer, L. R.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-02-2017; Springer Nature B.V
• Subjects: Axial stress; Bending stresses; Biomedical Engineering and Bioengineering; Characterization and Evaluation of Materials; Control; Cross-sections; Data analysis; Drill pipe; Drilling; Dynamical Systems; Electronic speckle pattern interferometry; Engineering; Lasers; Mechanical properties; Optical Devices; Optics; Outliers (statistics); Photonics; Pipelines; Residual stress; Solid Mechanics; Speckle patterns; Stress concentration; Stress distribution; Vibration; DSPI; Residual stress distribution; Bending computation; Hole-drilling; Pipeline
• ISSN: 0014-4851; 1741-2765
• DOI: 10.1007/s11340-016-0214-6

Pipelines usually operate under bending and axial stresses, caused by external loads, combined with residual stress distributions (manufacturing stresses), which affect the mechanical behavior of the pipe. Despite its semi-destructive nature, the hole drilling technique and digital speckle pattern interferometry (DSPI) can be applied to determine combined stresses along a cross-section. To achieve this, a set of equally-spaced angular points spread along the cross-section perimeter are measured. For non-uniform stress computations the hole drilling technique frequently gives a detailed stress distribution which is related to the external layer (1 mm) of the pipeline. In order to obtain a representative and unique value for the stress acting at each point, a novel approach can be used to evaluate a weighted average stress from each available stress distribution and to identify possible outlier measured points. In accordance with this approach, weighting coefficients are calculated using some particular features found in the residual stress profiles of pipelines. A reference bending test bench was used to evaluate the proposed methodology and it verified good agreement between the reference and computed stresses.