22 June 2015 Bending stress determination in pipes using a radial in-plane digital speckle pattern interferometer combined with instrumented indentation
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Abstract
This paper presents a modular device based on digital speckle pattern interferometry (DSPI) combined with an instrumented indenter. The system is divided in two modules, the interferometric and the indentation module. The former uses a diffractive optical element (DOE) to obtain radial in-plane sensitivity. This module measures the whole shallow displacement field generated by the indentation print on the surface of the material under testing. The latter module is sized suitably with the interferometric module. The indentation module uses a mechanical/hydraulic scheme to provide the system a high loading capability. A piezoelectric loading cell and an inductive transducer are used to simultaneously measure the load applied on the ball indenter and its penetration on the material. For the experimental tests, a bench capable to apply in a specific pipe a very well-known bending moment was used. This bench is mounted with two 12- meters pipes disposed horizontally. A transverse load is applied in the central cross-section of both pipes. The load application is made by a hydraulic actuator and measured with a load cell. Strain-gages are also used in a half-bridge configuration to measure the strain in the 8 cross-sections distributed along the pipe length. Each cross-section was measured by the proposed instrumented indentation system and compared with the strain-gages and load cell measurements. The results obtained show an uncertainty level around 20-30% of the measured bending stress. Good agreement was found between the computed bending stress using the strain-gages, load cell and the proposed method using the instrumented indentation system.
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Filipe Fontana, Filipe Fontana, Matias R. Viotti, Matias R. Viotti, Armando Albertazzi G. Jr., Armando Albertazzi G. Jr., } "Bending stress determination in pipes using a radial in-plane digital speckle pattern interferometer combined with instrumented indentation", Proc. SPIE 9525, Optical Measurement Systems for Industrial Inspection IX, 95250V (22 June 2015); doi: 10.1117/12.2184732; https://doi.org/10.1117/12.2184732
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