Speckle photography combined with speckle interferometry

Molin, Nils-Erik; Sjödahl, Mikael; Gren, Per; Svanbro, Angelica

doi:10.1016/s0143-8166(02)00175-6

Cited by 11 publications

(5 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In situ observations of inelastic strain produced during loading at atmospheric pressure may be made using image processing to analyze the deformation of material at local scales. Among these techniques, which are well established, are measurements of distortions of a regular grid of marks on the sample surface [ Allais et al , ; Biery et al , ; Ghadbeigi et al , ; Karimi , ; Moulart et al , ; Wu et al , ] and determinations of local displacements using speckle patterns [ Barrientos et al , ; Dudderar et al , ; Larsson et al , ; Molin et al , ; Synnergren and Sjödahl , ] or image correlations [ Amiot et al , ; Bornert et al , ; Bruck et al , ; McNeill et al , ; McNeill et al , ; Sutton , ]. The literature is extensive, and many other papers could be cited.…”

Section: Introductionmentioning

confidence: 99%

Direct observations of damage during unconfined brittle failure of Carrara marble

2016

View full text Add to dashboard Cite

To observe and quantify the production of microfracturing from initial yield to failure, we deformed Carrara marble samples in uniaxial compression at 20, 105, and 180°C and continuously observed a region of about 1 mm2 on an exposed face with a long‐working distance microscope. Using image processing and microscale strain‐mapping techniques, we measured local strains over a length scale of tens of micrometers. By treating the images with various filters, we identified linear damage features, as well as the magnitude of localized strain and the mode of deformation, i.e., shear versus normal deformation. In general, shear deformation is more prevalent after initial yielding, while tensile deformation dominates closer to peak stress. Independent measurements of both stress and microcrack density at different stages of each experiment provide a unique opportunity to explicitly compare the data with damage models. The model of Ashby and Sammis (1990) significantly underestimated the damage that the rock could sustain before peak stress, perhaps owing to the influence of weak grain boundaries on the damage production. In these samples, microcracks tended to form near boundaries before yield stress. During strain hardening, the damage parameters increased rapidly as longer microcracks grew along the boundaries and finally transected grains as loading neared peak stress. The microcrack density can be empirically related to the reduction of Young's modulus; stiffness ratios decay exponentially with increasing microcrack density for T ≤ 105°C.

show abstract

Section: Introductionmentioning

confidence: 99%

Direct observations of damage during unconfined brittle failure of Carrara marble

2016

View full text Add to dashboard Cite

show abstract

“…DSP has been applied for full-field displacement measurement in many applications, e.g. Wattrisse et al (2001), Jernkvist and Thuvander (2003), and Molin et al (2004). However, the combination of a high-speed camera and DSP in high-strain rate experiments has been used, to the authors' knowledge, only in Grantham et al (2003) and Kajberg and Sjö dahl (2003).…”

Section: Introductionmentioning

confidence: 99%

Viscoplastic parameter estimation by high strain-rate experiments and inverse modelling – Speckle measurements and high-speed photography

Kajberg

Wikman

2007

International Journal of Solids and Structures

View full text Add to dashboard Cite

A methodology based on inverse modelling for estimating viscoplastic material parameters at high strain-rate conditions is presented. The methodology is demonstrated for a mild steel exposed for compression loading in a split Hopkinson pressure bar arrangement. By using dog-bone shaped specimens nonhomogeneous states of deformation are obtained throughout the entire deformation process. The resulting nonhomogeneous deformation of the specimens is evaluated using digital speckle photography (DSP) to give in-plane point-wise displacement and strain fields. The photographs are captured with a high-speed camera of image converter type, which acquire time resolved images during the impact loading. The experiments are simulated using finite element analysis (FEA), where the material model suggested by Johnson-Cook for high-strain rate conditions are utilised. Experimental and FE-calculated field information are compared in order to estimate the viscoplastic parameter in the Johnson-Cook material model. The estimation is performed by minimising least-square functions that contain the differences in displacements and strains, respectively. The quality of the estimated parameters is studied from statistical point of view.

show abstract

“…There are several methodologies to measure displacement fields, including, for example, the analysis of speckle patterns [Barrientos et al, 2004;Dudderar et al, 1983;Larsson et al, 2004;Molin et al, 2004;Pan et al, 2009;Sutton et al, 2009;Synnergren and Sjödahl, 1999] or digital image correlation [Amiot et al, 2013;Bornert et al, 2009;Bruck et al, 1989;McNeill et al, 1987McNeill et al, , 1997Sharpe, 2008]. For our microscale strain maps (MSSM), we used a grid technique [Allais et al, 1994;Ghadbeigi et al, 2012;Karimi, 1984;Moulart et al, 2007;Sharpe, 2008;Wu et al, 2006] to analyze the relative displacement of regularly spaced markers before and after deformation.…”

Section: The Mssm Techniquementioning

confidence: 99%

Heterogeneity of inelastic strain during creep of Carrara marble: Microscale strain measurement technique

Quintanilla-Terminel

Evans

2016

JGR Solid Earth

View full text Add to dashboard Cite

We combined the split cylinder technique with microfabrication technology to observe strain heterogeneities that were produced during high‐pressure transient creep of Carrara marble. Samples were patterned with a custom‐designed grid of markers spaced 10 µm apart and containing an embedded coordinate system. The microscale strain measurement (MSSM) technique described here allowed us to analyze the local strain distribution with unprecedented detail over large regions. The description of the strain field is a function of the area over which strain is being computed. The scale at which the strain field can be considered homogeneous can provide insight into the deformation processes taking place. At 400–500°C, when twinning production is prolific, we observe highly strained bands that span several grains. One possible cause for the multigrain bands is the need to relieve strain incompatibilities that result when twins impinge on neighboring grains. At 600–700°C, the strain fields are still quite heterogeneous, and local strain varies substantially within grains and near grain boundaries, but the multigrain slip bands are not present. Deformation is concentrated in much smaller areas within grains and along some grain boundaries. The disappearance of the multigrain slip bands occurs when the deformation conditions allow additional slip systems to be activated. At 600°C, when the total strain is varied from 0.11 to 0.36, the spatial scale of the heterogeneity does not vary, but there are increases in the standard deviation of the distribution of local strains normalized by the total strain; thus, we conclude that the microstructure does not achieve a steady state in this strain interval.

show abstract

Speckle photography combined with speckle interferometry

Cited by 11 publications

References 12 publications

Direct observations of damage during unconfined brittle failure of Carrara marble

Direct observations of damage during unconfined brittle failure of Carrara marble

Viscoplastic parameter estimation by high strain-rate experiments and inverse modelling – Speckle measurements and high-speed photography

Heterogeneity of inelastic strain during creep of Carrara marble: Microscale strain measurement technique

Contact Info

Product

Resources

About