ANALYZING MICRO-MACRO TRANSITIONAL LENGTH SCALE IN UNIDIRECTIONAL COMPOSITES

2021 ◽  
Author(s):  
NAND KISHORE SINGH ◽  
KAZI ZAHIR UDDIN ◽  
RATNESHWAR JHA ◽  
BEHRAD KOOHBOR
Keyword(s):  
Volume Fraction ◽  
Local Stress ◽  
Local Strain ◽  
Fiber Composites ◽  
Analytical Models ◽  
Experimental Measurements ◽  
Length Scales ◽  
Full Field ◽  
Material Stiffness

Understanding the hierarchy in the mechanical behavior of heterogeneous materials requires a systematic characterization of the material response at different length scales, as well as the nature and characteristics of the transitional scales. Characterization of such transitional length scales has been carried out in the past by analytical models that calculate and compare stiffness values at micro and macro scales. The convergence of the material stiffness at the two scales has been used as the criterion for quantification of the so-called transitional length scales. These stiffness calculation approaches are based on the idea of local strain and stress distributions obtained from complex finite element models. Recent advancements in full-field experimental strain measurements have made it possible to identify the transitional length scales in fiber composites based on pure experimental measurements without the requirement of local stress analysis. In this work, we study the validity of such ‘strain-based’ approaches that are used to identify the RVE size in unidirectional fiber composites. Our modeling platform replicates the realistic conditions present in experimental measurements through the randomization of fiber locations and volume fraction within an epoxy matrix.

Fabrication and Characterization of MEMS Deformable Mirrors for Adaptive Optics

2006 ◽  
Author(s):  
Hyunkyu Park ◽  
David Horsley
Keyword(s):  
Adaptive Optics ◽  
Laser Doppler Vibrometer ◽  
Surface Shape ◽  
Analytical Models ◽  
Deformable Mirror ◽  
Experimental Measurements ◽  
Vision Science ◽  
Step Voltage ◽  
Fabrication And Characterization

A bimorph deformable mirror (DM) for use in ophthalmologic adaptive optics is presented. The fabrication process and the results of characterization of the DM are described. Interferometric measurements of the DM surface shape and voltage-to-displacement characteristics are shown. The response of the DM to a step voltage input is measured using a commercial laser Doppler vibrometer (LDV). Experimental measurements of the DM are compared with both finite-element and analytical models. Analysis of the experimental measurements compared to the theoretical model will be used to design and fabricate an optimized DM for vision science.

Characterization of Strain Fields Around Weld Defects

1987 ◽  
Vol 109 (3) ◽  
pp. 226-229
Author(s):  
S. A. Chavez ◽  
V. A. Deason
Keyword(s):  
Surface Defect ◽  
Local Strain ◽  
Moiré Interferometry ◽  
Moire Interferometry ◽  
Strain Gages ◽  
Strain Fields ◽  
Full Field ◽  
Strain Data ◽  
Set Up

Moire interferometry is used as an alternate technique to resistance strain gages in finding full-field, local strain response of weldments to applied loads. The principles of moire interferometry and the experimental set-up are explained. Data from the two techniques are compared, with no major discrepancies. The strain field around a surface defect is analyzed using moire data. It is concluded that the moire technique is useful for obtaining full-field strain data in welds.

Permeability models of 0°/45° alternating multilayer fabrics considering the effect of layer shift

2016 ◽  
Vol 36 (3) ◽  
pp. 163-175 ◽  
Author(s):  
Shuo Feng
Keyword(s):  
Mathematical Models ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Unit Cell ◽  
Analytical Models ◽  
Experimental Measurements ◽  
Fiber Volume ◽  
Local Permeability ◽  
Out Of Plane

In this paper, the effect of layer shifting on out-of-permeability of 0°/45° alternating multilayer fabrics was studied. Three mathematical models with three extreme structures were developed to predict the out-of-plane permeability, respectively. By segmenting the unit cell into several different zones according to characteristic yarn arrangement, the global permeability was modeled by using a rule of mixture of local permeability. The influences of local permeability of each zone on the global value of unit cell were carefully researched. In addition, experimental measurements of the permeability were carried out to validate the analytical models. And the differences of the results of three extreme structures with respect to fiber volume fraction were also investigated.

scholarly journals Heterogeneous Strain Distribution in the Subchondral Bone of Human Osteoarthritic Femoral Heads, Measured with Digital Volume Correlation

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4619
Author(s):  
Melissa K. Ryan ◽  
Sara Oliviero ◽  
Maria Cristiana Costa ◽  
J. Mark Wilkinson ◽  
Enrico Dall’Ara
Keyword(s):  
Volume Fraction ◽  
Local Strain ◽  
Digital Volume Correlation ◽  
Yield Strain ◽  
Bone Volume Fraction ◽  
Trabecular Thickness ◽  
Full Field ◽  
Microstructural Parameters ◽  
Novel Approach ◽  
Femoral Heads

Osteoarthritis (OA) is a chronic disease, affecting approximately one third of people over the age of 45. Whilst the etiology and pathogenesis of the disease are still not well understood, mechanics play an important role in both the initiation and progression of osteoarthritis. In this study, we demonstrate the application of stepwise compression, combined with microCT imaging and digital volume correlation (DVC) to measure and evaluate full-field strain distributions within osteoarthritic femoral heads under uniaxial compression. A comprehensive analysis showed that the microstructural features inherent in OA bone did not affect the level of uncertainties associated with the applied methods. The results illustrate the localization of strains at the loading surface as well as in areas of low bone volume fraction and subchondral cysts. Trabecular thickness and connectivity density were identified as the only microstructural parameters with any association to the magnitude of local strain measured at apparent yield strain or the volume of bone exceeding yield strain. This work demonstrates a novel approach to evaluating the mechanical properties of the whole human femoral head in case of severe OA.

Bovine Cortical Bone Stiffness and Local Strain are Affected by Mineralization and Morphology

2011 ◽  
Vol 79 (1) ◽  
Author(s):  
É. Budyn ◽  
J. Jonvaux ◽  
C. Funfschilling ◽  
T. Hoc
Keyword(s):  
Cortical Bone ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Local Stress ◽  
Local Strain ◽  
Monte Carlo Algorithm ◽  
Young’S Moduli ◽  
Frame Work ◽  
Mechanical Factors ◽  
Haversian Canals

A multiscale analysis of the mechanical behavior of bovine Haversian cortical bone is presented in the frame-work of linear elasticity. Cortical bone displays a complex microstructure that includes four phases: Haversian canals, osteons, cement lines, and interstitial bone. Based on close experimental observations, a Monte Carlo algorithm is implemented to build the natural bone composite microstructure. To represent the hierarchical nature of bone, the algorithm incorporates macroscopic morphological components, such as its porosity and osteonal volume fraction, as well as microscopic parameters, such as the characterized distributions of the osteons diameters. Bone local mechanical properties are measured by nanoindentation and microextensometry. The three-dimensional microstructures are discretized by a finite element method in order to evaluate the representative volume element of bovine cortical bone. The numerical model calculates the macroscopic bulk and material Young’s moduli and describes the local stress and strain. How geometrical or mechanical factors affect bone failure is investigated through a comparison of the macroscopic anisotropy and local strain to experimental data.

Local strain and defects in silicon wafers due to nanoindentation revealed by full-field X-ray microdiffraction imaging

2015 ◽  
Vol 22 (4) ◽  
pp. 1083-1090 ◽  
Author(s):  
Z. J. Li ◽  
A. N. Danilewsky ◽  
L. Helfen ◽  
P. Mikulik ◽  
D. Haenschke ◽  
...  
Keyword(s):  
Local Strain ◽  
Strain Engineering ◽  
Silicon Wafers ◽  
Defect Characterization ◽  
Quantitative Characterization ◽  
Strain Fields ◽  
Full Field ◽  
X Ray ◽  
Quantitative Mapping

Quantitative characterization of local strain in silicon wafers is critical in view of issues such as wafer handling during manufacturing and strain engineering. In this work, full-field X-ray microdiffraction imaging using synchrotron radiation is employed to investigate the long-range distribution of strain fields in silicon wafers induced by indents under different conditions in order to simulate wafer fabrication damage. The technique provides a detailed quantitative mapping of strain and defect characterization at the micrometer spatial resolution and holds some advantages over conventional methods.

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