PSI - Issue 17

Available online at www.sciencedirect.com Structural Integrity Procedia 00 (2019) 000 – 000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2019) 000 – 000 Available online at www.sciencedirect.com ScienceDirect

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Procedia Structural Integrity 17 (2019) 986–991

ICSI 2019 The 3rd International Conference on Structural Integrity Digital image correlation with a moving camera using structure from motion calibration Francisco Barros a, *, Pedro J. Sousa a,b , Paulo J. Tavares a , Pedro M. G. P. Moreira a a INEGI, Universidade do Porto, Rua Dr. Roberto Frias, 400, Porto 4200-465, Portugal b Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, s/n, Porto 4200-465, Portugal The application of digital image correlation (DIC) in structural monitoring can benefit from the use of remote controlled image acquisition systems such as unmanned aerial vehicles (UAVs) in cases where the structure to be assessed is of difficult accessibility. However, this configuration does not always allow normal camera calibration procedures to be followed. In this work, a camera is manually moved around an object prepared with a speckle pattern, in a reference state and later in a loaded state, in an attempt to emulate the behaviour of a UAV. A structure from motion (SfM) algorithm is applied to the captured images in order to obtain camera calibration parameters for each image, using the features found in the object’s surroundings. An image pair from each state is chosen and 3D DIC is performed on the object using the previously obtained calibration. ICSI 2019 The 3rd International Conference on Structural Integrity Digital image correlation with a moving camera using structure from motion calibration Francisco Barros a, *, Pedro J. Sousa a,b , Paulo J. Tavares a , Pedro M. G. P. Moreira a a INEGI, Universi de do Porto, Rua Dr. Roberto Frias, 400, Porto 4200-465, Portugal b Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, s/n, Porto 4200-465, Portugal Abstract The application of digital image correlation (DIC) in structural monitoring can b nefit from the use of remote controlle image quisition systems suc as unmanned aerial vehicles (UAVs) in cases where the structure to be assessed is of difficult accessibility. However, this configuration oes not always allow normal camera calibration procedures to be followed. In this work, a c mera is manually moved around an object prepared with a speckle pattern, in a reference state and later in a loaded state, in an attempt to emulate the behaviour of a UAV. A structure from motion (SfM) algorithm is applied to the capture images in order to obtain camera calibratio parameters for each image, using the features found in the object’s surroundi gs. An image pair from each state is chosen and 3D DIC is performed on the object using the previously obtained calibration. Abstract

© 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers.

Keywords: digital image correlation; structure from motion; camera calibration; structural monitoring; unmanned aerial vehicle Keywords: digital image correlation; structure from motion; camera calibration; structural monitoring; unmanned aerial vehicle

1. Introduction 1. Introduction

A growing suitability of digital image correlation (DIC) for field applications such as structural monitoring requires development of the technique in terms of versatility and robustness, due to the fact that the measuring conditions are typically not as easily controllable as in laboratory tests. A growing suitability of digital image correlation (DIC) for field applications such as structural monitoring requires development of the technique in terms of versatility and robustness, due to the fact that the measuring conditions are typically not as easily controllable as in laboratory tests.

* Corresponding author. Tel.: +351-22-9578710. E-mail address: fbarros@inegi.up.pt * Correspon ing author. Tel.: +351-22-9578710. E-mail address: fbarros@inegi.up.pt

2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers. 2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers.

2452-3216  2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers. 10.1016/j.prostr.2019.08.131