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

 

VIOTTI, Matias Roberto; LOTHAMMER, Livia Rodrigues

PUBLICADO NA EXPERIMENTAL MECHANICS (Online), v. 57, p. 341-352, 2017. https://doi.org/10.1007/s11340-016-0214-6

​

Resumo

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.

​