3D Strain Mapping of Opaque Materials Using an Improved Digital Volumetric Speckle Photography Technique with X-Ray Microtomography

Lingtao Mao,Haizhou Liu,Rui Guo,Ying Zhu,Fu-Pen Chiang,Ziyan Zhu

doi:10.3390/app9071418

Abstract

Digital volumetric speckle photography (DVSP) method has been used to strain investigation in opaque materials. In this paper, an improved DVSP algorithm is introduced, in which a multi-scale coarse–fine subset calculation process and a subvoxel shifting technique are applied to increase accuracy. We refer to the new algorithm as Multi-scale and Subvoxel shifting Digital Volumetric Speckle Photography (MS-DVSP). The displacement and strain fields of a red sandstone cylinder exposed to uniaxial compression and a woven composite beam under three-point bending are mapped in detail. The characteristics of the interior deformation of the specimens are clearly depicted, thus elucidating the failure mechanism of the materials.

Highlights

Speckle photography, a technique that uses a random speckle pattern to quantitatively measure displacement and strain, is a major milestone in the archive of experimental mechanics
Its ease of use and versatility were greatly enhanced by the development of the digital speckle photography (DSP)
As an extension of the 2D DSP (Digital Speckle Photography) method [5,6], we have developed a 3D interior full field deformation measurement technique called digital volumetric speckle photography (DVSP) with the help of X-ray microtomography [32]

Summary

Introduction

A technique that uses a random speckle pattern to quantitatively measure displacement and strain, is a major milestone in the archive of experimental mechanics. The basic principle of the white light speckle technique was first proposed in a 1968 paper by J. After the advent of laser, the laser speckle photography technique [2] was developed, followed by a major expansion of the white light speckle photography approaches [3]. The method’s spatial resolution was significantly increased with the development of the electron speckle photography technique by Chiang et al, in 1997 [4], which employs submicron and nano-sized speckles. Its ease of use and versatility were greatly enhanced by the development of the digital speckle photography (DSP)

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