Effective Elastic Moduli of Two-Dimensional Brittle Solids With Interacting Microcracks, Part II: Evolutionary Damage Models

1994 ◽  
Vol 61 (2) ◽  
pp. 358-366 ◽  
Author(s):  
J. W. Ju ◽  
Tsung-Muh Chen
Keyword(s):  
Elastic Moduli ◽  
Biaxial Tension ◽  
Interaction Model ◽  
Evolutionary Models ◽  
Two Dimensional ◽  
Damage Models ◽  
Brittle Solids ◽  
Biaxial Tests ◽  
Integration Algorithms ◽  
Microcrack Interaction

In Part I of this series, basic formulations of stationary micromechanical theory and overall responses are presented for two-dimensional brittle solids with randomly dispersed microcracks. The basic formulations hinge on an ensemble average approach which includes pairwise microcrack interactions. In this paper, statistical micromechanical evolutionary models are proposed to account for “cleavage 1” growth of randomly oriented and located microcracks under microcrack interaction effects. Biaxial tension/compression loadings are also considered to take into account mixed microcrack opening and closure effects. Efficient numerical integration algorithms for the proposed ensemble averaged constitutive equations are subsequently given. Further, uniaxial and biaxial tests are presented to illustrate the proposed models and procedures. Finally, a higher-order microcrack interaction model within the proposed micromechanical framework is discussed.

Effective Elastic Moduli of Two-Dimensional Brittle Solids With Interacting Microcracks, Part I: Basic Formulations

1994 ◽  
Vol 61 (2) ◽  
pp. 349-357 ◽  
Author(s):  
J. W. Ju ◽  
Tsung-Muh Chen
Keyword(s):  
Elastic Moduli ◽  
Effective Elastic Moduli ◽  
Two Dimensional ◽  
Damage Models ◽  
Brittle Solids ◽  
Averaged Equations ◽  
Approximate Analytical Solutions ◽  
Special Cases ◽  
Microcrack Growth ◽  
Microcrack Interaction

Statistical micromechanical formulations are presented to investigate effective elastic moduli of two-dimensional brittle solids with interacting slit microcracks. The macroscopic stress-strain relations of elastic solids with interacting microcracks are micromechanically derived by taking the ensemble average over all possible realizations which feature the same material microstructural geometry, characteristics, and loading conditions. Approximate analytical solutions of a two-microcrack interaction problem are introduced to account for microcrack interaction among many randomly oriented and located microcracks. The overall elastic-damage compliances of microcrack-weakened brittle solids under uniaxial and biaxial loads are also derived. Therefore, stationary statistical micromechanical formulation is completed. Moreover, some special cases are investigated by using the proposed framework. At variance with existing phenomenological continuum damage models, the proposed framework does not employ any fitted “material parameters. ” “Cleavage 1” microcrack growth and “evolutionary damage models” within the proposed context will be presented in Part II of this series. It is emphasized that microstructural statistical informations are already embedded in the proposed ensemble-averaged equations and, therefore, no Monte Carlo simulations are needed.

Optimizing the Shape and Size of Cruciform Specimens Used for Biaxial Tensile Test

2014 ◽  
Vol 658 ◽  
pp. 167-172 ◽  
Author(s):  
Liviu Andrusca ◽  
Viorel Goanta ◽  
Paul Doru Barsanescu
Keyword(s):  
Mechanical Properties ◽  
Tensile Test ◽  
Continuous Monitoring ◽  
Biaxial Tension ◽  
Cruciform Specimen ◽  
Testing Method ◽  
Biaxial Tests ◽  
Properties Of Materials ◽  
Failure Theories ◽  
Shape And Size

Testing cruciform specimens subjected to biaxial tension is one of the most widely used experimental techniques and more accurate at this time to determine the mechanical properties of materials and to verify the failure theories. This type of experiment allows the continuous monitoring of behavior of materials from the beginning of deformation until fracture under different ratios of forces and directions of the deformation, which transforms it into a very versatile testing method. We have varied the number of parameters and their values in order to achieve a uniform distribution of biaxial state of stresses and strains in the area tested. In theory, any material can be tested by stretching a biaxial cruciform specimen, but must be investigated in what way the shape of the specimen influence the data obtained. In this paper are presented the requirements that must be fulfilled by the samples used for tensile / compression biaxial tests and the design of cruciform specimens through FEA that meet these demands.

The Elastic Moduli of Silver Thin Films Measured with a New Microtensile Tester

1991 ◽  
Vol 239 ◽  
Author(s):  
J. Ruud ◽  
D. Josell ◽  
A. L. Greer ◽  
F. Spaepen
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Diffraction Grating ◽  
Strain Measurement ◽  
Elastic Moduli ◽  
Two Dimensional ◽  
Bulk Crystals ◽  
Free Standing ◽  
Tensile Direction ◽  
Silver Thin Films

ABSTRACTA new design for a thin film microtensile tester is presented. The strain is measured directly on the free-standing thin film from the displacement of laser spots diffracted from a thin grating applied to its surface by photolithography. The diffraction grating is two-dimensional, allowing strain measurement both along and transverse to the tensile direction. In principle, both Young's modulus and Poisson's ratio of a thin film can be determined. Ag thin films with strong <111> texture were tested. The measured Young moduli agreed with those measured on bulk crystals, but the measured Poisson ratios were low, most likely due to slight transverse folding of the film that developed during the test.

scholarly journals Elastic Moduli of Collagen Gels Can Be Predicted from Two-Dimensional Confocal Microscopy

2009 ◽  
Vol 97 (7) ◽  
pp. 2051-2060 ◽  
Author(s):  
Ya-li Yang ◽  
Lindsay M. Leone ◽  
Laura J. Kaufman
Keyword(s):  
Confocal Microscopy ◽  
Elastic Moduli ◽  
Two Dimensional ◽  
Collagen Gels

A Novel Technique to Determine Elastic Constants of Thin Films

2008 ◽  
Vol 1139 ◽  
Author(s):  
Klaus Martinschitz ◽  
Rostislav Daniel ◽  
Christian Mitterer ◽  
Keckes Jozef
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Elastic Moduli ◽  
Elastic Anisotropy ◽  
Interaction Model ◽  
X Ray Diffraction ◽  
X Ray ◽  
Anisotropic Factor ◽  
Polycrystalline Thin Films ◽  
Cu Thin Film

AbstractA new X-ray diffraction technique to determine elastic moduli of polycrystalline thin films deposited on monocrystalline substrates is demonstrated. The technique is based on the combination of sin2ψ and X-ray diffraction wafer curvature techniques which are used to characterize X-ray elastic strains and macroscopic stress in thin film. The strain measurements must be performed for various hkl reflections. The stresses are determined from the substrate curvature applying the Stoney's equation. The stress and strain values are used to calculate hkl reflection dependent X-ray elastic moduli. The mechanical elastic moduli can be then extrapolated from X-ray elastic moduli considering film macroscopic elastic anisotropy. The derived approach shows for which reflection and corresponding value of the X-ray anisotropic factor Γ the X-ray elastic moduli are equal to their mechanical counterparts in the case of fibre textured cubic polycrystalline aggregates. The approach is independent of the crystal elastic anisotropy and depends on the fibre texture type, the texture sharpness, the amount of randomly oriented crystallites and on the supposed grain interaction model. The new method is demonstrated on a fiber textured Cu thin film deposited on monocrystalline Si(100) substrate. The advantage of the new technique remains in the fact that moduli are determined non-destructively, using a static diffraction experiment and represent volume averaged quantities.

Strength nature of two-dimensional woven nanofabrics under biaxial tension

2018 ◽  
Vol 28 (3) ◽  
pp. 367-379
Author(s):  
Yinfeng Li ◽  
Simanta Lahkar ◽  
Qingyuan Wei ◽  
Pizhong Qiao ◽  
Han Ye
Keyword(s):  
Lattice Structure ◽  
Biaxial Tension ◽  
Failure Process ◽  
High Strength ◽  
Two Dimensional ◽  
Strength Performance ◽  
Fabric Strength ◽  
Dynamics Simulations ◽  
Gap Spacing ◽  
Space Interval

Woven nanostructures have been acknowledged as a platform for solar cells, supercapacitors, and sensors, making them especially of interest in the fields of materials sciences, nanotechnology, and renewable energy. By employing molecular dynamics simulations, the mechanical properties of two-dimensional woven nanofabrics under biaxial tension are evaluated. Two-dimensional woven nanostructures composed of graphene and graphyne nanoribbons are examined. Dynamic failure process of both graphene woven nanofabric and graphyne woven nanofabric with the same woven unit cell initiates at the edge of interlaced ribbons accompanied by the formation of cracks near the crossover location of yarns. Further stress analysis reveals that such failure mode is attributed to the compression between two overlaced ribbons and consequently their deformation under biaxial tension, which is sensitive to the lattice structure of nanoribbon as well as the density of yarns in fabric. Systemic comparisons between nanofabrics with different yarn width and interval show that the strength of nanofabric can be effectively controlled by tuning the space interval between nanoribbons. For nanofabrics with fixed large gap spacing, the strength of fabric does not change with the ribbon width, while the strength of nanofabric with small gap spacing decreases anomalously with the increase in yarn density. Such fabric strength dependency on gap spacing is the result of the stress concentration caused by the interlace compression. The outcomes of simulation suggest that the compacted arrangement of yarns in carbon woven nanofabric structures should be avoided to achieve high strength performance.

Sign in / Sign up

Export Citation Format

Share Document