Submicron deformation field measurements: Part 1. Developing a digital scanning tunneling microscope

Vendroux, G.; Knauss, W. G.

doi:10.1007/bf02321262

Cited by 49 publications

(25 citation statements)

References 10 publications

(2 reference statements)

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“…It is possible, however, to circumvent the involvement of eq (12) in an excellent approximation, l o To this end, consider the components ofeq (12) as derived from eqs (8) and (9) and given by…”

Section: Vvc(p) = \mentioning

confidence: 99%

Submicron deformation field measurements: Part 2. Improved digital image correlation

Vendroux

Knauss

1998

Experimental Mechanics

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ABSTRACT--This is the second paper in a series of three devoted to the application of scanning tunneling microscopy (STM) to mechanics problems. In this paper, improvements to the digital image correlation method are outlined, a technique that compares digital images of a specimen surface before and after deformation to deduce its two-dimensional surface displacement field and strains. The necessity of using the framework of large deformation theory for accurately addressing rigid body rotations to reduce associated errors in the strain components is pointed out. In addition, the algorithm is extended to compute the three-dimensional surface displacement field from STM data; also, significant improvements are achieved in the rate as well as the robustness of the convergence. For (STM) topographs, the resolution yields 4.8 nm for the in-plane and 1.5 nm for the out-of-plane displacement components spanning an area of 10 Ixm x 10 Ixm.

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Section: Vvc(p) = \mentioning

confidence: 99%

Submicron deformation field measurements: Part 2. Improved digital image correlation

Vendroux

Knauss

1998

Experimental Mechanics

Self Cite

481

271

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“…The Newton-Raphson 11 method is used to solve for the roots of eq (6). This method uses an approximate value for the root of a function, then iterates until it converges to the actual roots.…”

Section: Spesmentioning

confidence: 99%

Deformation measurements by digital image correlation: Implementation of a second-order displacement gradient

Cary²

2000

Experimental Mechanics

357

171

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ABSTRACT--This paper outlines the procedure for refining the digital image correlation (DIC) method by implementing a second-order approximation of the displacement gradients. The second-order approximation allows the DIC method to directly measure both the first-and second-order displacement gradients resulting from nonlinear deformation. Thirteen unknown parameters, consisting of the components of displacement, the first-and second-order displacement gradients and the gray-scale value offset, are determined through optimization of a correlation coefficient. The previous DIC method assumes that the local deformation in a subset of pixels is represented by a first-order Taylor series approximation for the displacement gradient terms, so actual deformations consisting of higher order displacement gradients tend to distort the infinitesimal strain measurements. By refining the method to measure both the first-and second-order displacement gradients, more accurate strain measurements can be achieved in large-deformation situations where second-order deformations are also present. In most cases, the new refinements allow the DIC method to maintain an accuracy of 4-0.0002 for the first-order displacement gradients and to reach 4-0.0002 per pixel for the second-order displacement gradients.

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“…Because the basic principles of DIC algorithm have been fully described in literature, the algorithm is described here only briefly for clarity. [37][38][39] DIC generally employs a zeromean normalized sum-of-square difference (ZNSSD) criterion to compute the similarity in pixel intensity between reference and deformed image subsets. [40] In this manner, displacements with pixel accuracy are obtained.…”

Section: Digital Image Correlation Of Shpb Resultsmentioning

confidence: 99%

Impact Testing of Polymer‐filled Auxetics Using Split Hopkinson Pressure Bar

et al. 2017

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In this paper, impact testing of auxetic structures filled with strain rate sensitive material is presented. Two dimensional missing rib, 2D re-entrant honeycomb, and 3D re-entrant honeycomb lattices are investigated. Structures are divided into three groups according to type of filling: no filling, low expansion polyurethane foam, and ordnance gelatine. Samples from each group are tested under quasistatic loading and dynamic compression using Split Hopkinson Pressure Bar. Digital image correlation is used for assessment of in-plane displacement and strain fields. Ratios between quasistatic and dynamic results for plateau stresses and specific energy absorption in the plateau are calculated. It is found out that not only the manufactured structures, but also the wrought material exhibit strain rate dependent properties. Evaluation of influence of filling on mechanical properties shows that polyurethane increases specific absorbed energy by a factor of 1.05-1.4, whereas the effect of gelatine leads to increase of only 5-10%. Analysis of the Poisson's function reveals influence of filling on achievable (negative) values of Poisson's ratio, when compared to unfilled specimens. The results for the Poisson's function yielded apparently different values as the assessed minima of quasi-static Poisson's ratio in small deformations are constrained by a factor of 15.

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Submicron deformation field measurements: Part 1. Developing a digital scanning tunneling microscope

Cited by 49 publications

References 10 publications

Submicron deformation field measurements: Part 2. Improved digital image correlation

Submicron deformation field measurements: Part 2. Improved digital image correlation

Deformation measurements by digital image correlation: Implementation of a second-order displacement gradient

Impact Testing of Polymer‐filled Auxetics Using Split Hopkinson Pressure Bar

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