Optical Measurements,Modeling and Metrology

Scale Independent Fracture Mechanics

ABSTRACT Fracture mechanics is considered from the viewpoint of a field theoretical approach based on the physical principle known as gauge invariance. The advantage of this approach is scale independent and universal. All stages of deformation, from the elastic stage to fracturing stage can be treated on the same theoretical foundation. A quantity identified as […]

Consistent Embedding: A Theoretical Framework for Multiscale Modeling

Abstract A fundamental framework for the undertaking of computational science provides clear distinctions between theory, model, and simulation. Consistent embedding provides a set of principles which when appropriately applied can create multi-scale models that capture the physical behavior of more computationally challenging methods within methods that are more easily computed. The consistent embedding methodology is […]

Analysis of Crystal Rotation by Taylor Theory

ABSTRACT Simple shear along specific slip plane in polycrystalline and rotation of grains was discussed. The Taylor theory was applied to bridge between macroscopic deformation behavior and crystal plasticity and to evaluate the orientation distribution. Its theoretical solution can hardly satisfy all of boundary condition and plastic dynamics so that the condition of dynamics was […]

Numerical Solution of the Walgraef-Aifantis Model for Simulation of Dislocation Dynamics in Materials Subjected to Cyclic Loading

Abstract Strain localization and dislocation pattern formation are typical features of plastic deformation in metals and alloys. Glide and climb dislocation motion along with accompanying production/annihilation processes of dislocations lead to the occurrence of instabilities of initially uniform dislocation distributions. These instabilities result into the development of various types of dislocation micro-structures, such as dislocation […]

Photoelastic Determination of Boundary Condition for Finite Element Analysis Part 1

ABSTRACT An experimental-numerical hybrid method for determining stress components in photoelasticity is proposed in this study. Boundary conditions for a local finite element model, that is, tractions along boundaries are inversely determined from photoelastic fringes. The tractions can be obtained by the method of linear least-squares from both principal stress difference and principal direction. On […]

Photoelastic Determination of Boundary Condition for Finite Element Analysis Part 2

EXPERIMENTAL VERIFICATION OF THE PROPOSED METHOD A simple static problem is analyzed to verify the proposed method. A perforated plate made of epoxy resin, 228 mm in height, 50 mm in width and 3 mm in thickness, having a hole of diameter of 10 mm, is subjected to the tensile load of P = 398 […]

Discussion on hybrid approach to determination of cell elastic properties

ABSTRACT This study discusses the application of a hybrid experimental-numerical approach to analyze nano-indentation curves of a biological membrane acquired with an Atomic Force Microscope. The proposed procedure combines experimental measurements, FEM analysis and numerical optimization and is completely general. Variations of estimated Young modulus of the membrane are determined when attributing different constitutive laws […]

Mesh Refinement for Inverse Problems with Finite Element Models

Abstract Many inverse problems arising in experimental mechanics involve solutions to partial differential equations in the forward problem, typically using finite element methods for those solutions. Given that iterative solutions to the inverse problem then involve repeated evaluations of the finite element model, it is useful to carefully consider the mesh to be used and […]

Assessment of inverse procedures for the identification of hyperelastic material parameters

ABSTRACT This work aimed to implement and compare two competitive procedures for the identification of hyperelastic material parameters. Formerly, experimental tests have been conducted on fluorosilicone rubber specimens in equal-biaxial tension; the cruciform shaped-specimens underwent heterogeneous large strain distributions, which were captured by Digital Image Correlation technique; while load cells grabbed the force signals. The […]

Digital image correlation through a rigid borescope

ABSTRACT There occasionally occur situations in field measurements where direct optical access to the area of interest is not possible. In these cases the borescope is the standard method of imaging. Furthermore, if shape, displacement, or strain are desired in these hidden locations, it would be advantageous to be able to do digital image correlation […]