Measuring Strain Distribution During Mesoscopic Domain Reorientation in a Ferroelectric Material

1998 ◽  
Vol 120 (1) ◽  
pp. 1-6 ◽  
Author(s):  
S. B. Park ◽  
S. S. Park ◽  
G. P. Carman ◽  
H. T. Hahn
Keyword(s):  
Experimental Study ◽  
Strain Distribution ◽  
Large Strain ◽  
Polarization Switching ◽  
Ferroelectric Material ◽  
Nonlinear Phenomena ◽  
Moire Interferometry ◽  
Microcrack Initiation ◽  
Shear Strains ◽  
Domain Reorientation

In this paper, we present the results of an experimental study focused on understanding the strain concentrations arising due to nonlinear phenomena associated with polarization switching. A moire interferometry technique is used to measure the normal and shear strains of a PZT-5H piezoceramic undergoing 180 and 90 deg switching. These results include the strain concentrations measured between polarized regions oriented 180 and 90 deg apart. The results show that very large strain mismatches (e.g., as large as 4500 microstrains) occur along the boundary of dissimilar oriented domains, suggesting a source of microcrack initiation and fatigue degradation.

Nanoelectromechanics of Piezoresponse Force Microscopy: Contact Properties, Fields Below the Surface and Polarization Switching

2003 ◽  
Vol 784 ◽  
Author(s):  
S. V. Kalinin ◽  
Junsoo Shin ◽  
M. Kachanov ◽  
E. Karapetian ◽  
A. P. Baddorf
Keyword(s):  
Strain Distribution ◽  
Point Charge ◽  
Closed Form Solution ◽  
Piezoresponse Force Microscopy ◽  
Polarization Switching ◽  
Ferroelectric Material ◽  
Form Solution ◽  
Force Microscopy ◽  
Force Magnitude ◽  
Resolution Limits

ABSTRACTTo achieve quantitative interpretation of Piezoresponse Force Microscopy (PFM), including resolution limits, tip bias- and strain-induced phenomena and spectroscopy, knowledge of elastic and electrostatic field distributions below the tip is required. The exact closed form solution of the coupled electroelastic problem for piezoelectric indentation is derived and used to obtain the tip-induced electric field and strain distribution in the ferroelectric material. This establishes a complete continuum mechanics description of the PFM imaging mechanism. These solutions are reduced to the point charge/force behavior for large separations from contact, and the applicability limits and charge/force magnitude for these models are established. The implications of these results for ferroelectric polarization switching processes are analyzed.

An Experimental Study of Dropped Ply Region in Composite

2006 ◽  
Vol 326-328 ◽  
pp. 1769-1772
Author(s):  
Chun Wang Zhao ◽  
Yong Ming Xing
Keyword(s):  
Experimental Study ◽  
Stress Concentration ◽  
Failure Mechanisms ◽  
Experimental Results ◽  
Epoxy Composites ◽  
Moire Interferometry ◽  
Concentration Region ◽  
Micro Cracks ◽  
Stress Concentration Region ◽  
Mechanical Study

A micro mechanical study of Carbon/Epoxy composites with internally dropped plies has been made using micro-moiré interferometry. The experimental results show that there is a stress concentration region before the dropped ply. Micro cracks were initiated and propagated in this region. Two failure mechanisms in the dropped ply region were observed.

The effects of muscle fatigue on bone strain.

1994 ◽  
Vol 188 (1) ◽  
pp. 217-233 ◽  
Author(s):  
T Yoshikawa ◽  
S Mori ◽  
A J Santiesteban ◽  
T C Sun ◽  
E Hafstad ◽  
...  
Keyword(s):  
Muscle Fatigue ◽  
Strain Distribution ◽  
Distal Tibia ◽  
Muscular Fatigue ◽  
Bone Strain ◽  
Significant Shift ◽  
Inverse Association ◽  
Peak Strain ◽  
Exercise Period ◽  
Shear Strains

There is anecdotal evidence that bone strains may increase to the point that bone becomes susceptible to rapid failure when muscles become fatigued. To determine whether neuromuscular response could be a factor in accelerating bone failure, we tested the hypothesis that muscle fatigue causes a significant increase in peak principal and shear strains in bone. Ten adult foxhounds were subjected to rigorous exercise that caused muscular fatigue while myoelectrical activity of the quadriceps and hamstrings and strain on the distal tibia were monitored simultaneously. Ground reaction forces on the dog hindlimbs were measured before and after strain gauges had been applied to the tibia. The data show a significant shift to lower median myoelectrical frequencies in the quadriceps, indicating muscular fatigue, following the 20 min exercise period. In conjunction with this shift, peak principal and shear strains increased on both compressive and tensile cortices of the tibia and shear strain on the tensile cortex increased significantly (P = 0.02). The largest changes were along the anterior and anterolateral surfaces of the tibia, where peak principal strain increased by an average of 26-35% following muscular fatigue. The cross-sectional strain distribution was calculated at the gauge site at peak strain at the beginning of the exercise period and at peak strain after 20 min of exercise. These data show a change in strain distribution when muscle becomes fatigued. Strains on the posterior cortex of the bone showed the greatest change. Correlation analysis demonstrated a significant inverse association between median myoelectrical frequency and bone strain after 20 min of exercise (Spearman r2 = 1.00; P = 0.05). These data show that muscle fatigue may be associated with increased bone strain.

Experimental Study on Bending Behavior of Timber Beams Reinforced with CFRP/AFRP Hybrid FRP Sheets

2011 ◽  
Vol 255-260 ◽  
pp. 728-732
Author(s):  
Qing Chun ◽  
Jian Wu Pan
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Bearing Capacity ◽  
Strain Distribution ◽  
Failure Modes ◽  
Bending Behavior ◽  
Timber Beams

Based on the experiment of timber rectangle beams made of pine and fir reinforced with CFRP/AFRP hybrid FRP (HFRP) sheets. The failure modes and bending bearing capacity and load-deflection curves and strain distribution at mid-span section were analyzed. The results showed that: Comparing with the specimens without being reinforced by HFRP, there is certain improvement in bending bearing capacity and stiffness of the specimens reinforced with HFRP respectively. Bending bearing capacity of the pine specimens improve 18.1%~62.0% and bending bearing capacity of the fir specimens improve 7.7%~29.7%. Stiffness of the pine specimens improve 13%~21%, and stiffness of the fir specimens improve 6%~10%. Based on the experimental data, the computing formulas of bending bearing capacity of timber rectangle beams made of pine and fir reinforced with HFRP were presented.

scholarly journals A Comprehensive Method for Accurate Strain Distribution Measurement of Cell Substrate Subjected to Large Deformation

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Hong He ◽  
Rong Zhou ◽  
Yuanwen Zou ◽  
Xuejin Huang ◽  
Jinchuan Li
Keyword(s):  
Digital Image Correlation ◽  
Large Deformation ◽  
Digital Image ◽  
Strain Distribution ◽  
Large Strain ◽  
Image Correlation ◽  
Cell Substrate ◽  
Substrate Stretching ◽  
Different Strains

Cell mechanical stretching in vitro is a fundamental technique commonly used in cardiovascular mechanobiology research. Accordingly, it is crucial to measure the accurate strain field of cell substrate under different strains. Digital image correlation (DIC) is a widely used measurement technique, which is able to obtain the accurate displacement and strain distribution. However, the traditional DIC algorithm used in digital image correlation engine (DICe) cannot obtain accurate result when utilized in large strain measurement. In this paper, an improved method aiming to acquire accurate strain distribution of substrate in large deformation was proposed, to evaluate the effect and accuracy, based on numerical experiments. The results showed that this method was effective and highly accurate. Then, we carried out uniaxial substrate stretching experiments and applied our method to measure strain distribution of the substrate. The proposed method could obtain accurate strain distribution of substrate film during large stretching, which would allow researchers to adequately describe the response of cells to different strains of substrate.

Experimental study of nonlinear phenomena in an upright piano.

2011 ◽  
Vol 129 (4) ◽  
pp. 2542-2542
Author(s):  
Antoine Chaigne ◽  
Juliette Chabassier
Keyword(s):  
Experimental Study ◽  
Nonlinear Phenomena
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