scholarly journals Photobleaching as a tool to measure the local strain field in fibrous membranes of connective tissues

2014 ◽  
Vol 10 (6) ◽  
pp. 2591-2601 ◽  
Author(s):  
C. Jayyosi ◽  
G. Fargier ◽  
M. Coret ◽  
K. Bruyère-Garnier
Keyword(s):  
Strain Field ◽  
Local Strain ◽  
Connective Tissues ◽  
Fibrous Membranes

Strain analysis with nanometer resolution using a conventional transmission electron microsopy technique: electron diffraction contrast imaging revisited

1995 ◽  
Vol 53 ◽  
pp. 168-169
Author(s):  
Koenraad G F Janssens ◽  
Omer Van der Biest ◽  
Jan Vanhellemont ◽  
Herman E Maes ◽  
Robert Hull
Keyword(s):  
Electron Diffraction ◽  
Strain Field ◽  
Elastic Strain ◽  
Strain Analysis ◽  
Local Strain ◽  
Contrast Imaging ◽  
Strain Characterization ◽  
Physical Mechanisms ◽  
Diffraction Contrast ◽  
Transmission Electron

There is a growing need for elastic strain characterization techniques with submicrometer resolution in several engineering technologies. In advanced material science and engineering the quantitative knowledge of elastic strain, e.g. at small particles or fibers in reinforced composite materials, can lead to a better understanding of the underlying physical mechanisms and thus to an optimization of material production processes. In advanced semiconductor processing and technology, the current size of micro-electronic devices requires an increasing effort in the analysis and characterization of localized strain. More than 30 years have passed since electron diffraction contrast imaging (EDCI) was used for the first time to analyse the local strain field in and around small coherent precipitates1. In later stages the same technique was used to identify straight dislocations by simulating the EDCI contrast resulting from the strain field of a dislocation and comparing it with experimental observations. Since then the technique was developed further by a small number of researchers, most of whom programmed their own dedicated algorithms to solve the problem of EDCI image simulation for the particular problem they were studying at the time.

Study on Local Strain Field Intensity Approach for Prediction Fatigue Life of Crankshaft Based on Mechanical Mechanics

2013 ◽  
Vol 644 ◽  
pp. 251-255 ◽  
Author(s):  
Ke Bao ◽  
Qiu Fang Wang ◽  
Shu Lin Liu ◽  
Zhong Liang Wei
Keyword(s):  
Field Intensity ◽  
Strain Field ◽  
Local Strain ◽  
Fatigue Tests ◽  
Bending Moments ◽  
Test Results ◽  
Life Test ◽  
Test Load ◽  
Bending Fatigue ◽  
Crack Initiation Life

The bending fatigue limit moment and crack initiation life of 4105 crankishaft in five groups of bending moments are obtained by resonant bending fatigue tests first. Then, the static finite element calculation using sub-model is performed to get the strain distributions in every test load. The results show that in the region where stress concentrate, the strain field could be seen as plane strain state. So two dimensional strain field intensity model is selected. In order to remove the influences of size and surface conditions, the radius of strain field is determined with the strain distribution under the low-life test load. After that, the local strain field intensities under each test load are calculated with the radius of strain field. Finally, the strain-life curve of material is modified by the fatigue intensity limit of crankshaft, and the predicted life agree with the test results.

Axial Strain Measurements in Skeletal Muscle at Various Strain Rates

1995 ◽  
Vol 117 (3) ◽  
pp. 262-265 ◽  
Author(s):  
T. M. Best ◽  
J. H. McElhaney ◽  
W. E. Garrett ◽  
B. S. Myers
Keyword(s):  
Skeletal Muscle ◽  
Strain Field ◽  
High Speed ◽  
Soft Tissues ◽  
Axial Strain ◽  
Local Strain ◽  
Optical Systems ◽  
Rate Dependent ◽  
Strain Formulation ◽  
Tissue Deformations

A noncontact optical system using high speed image analysis to measure local tissue deformations and axial strains along skeletal muscle is described. The spatial resolution of the system was 20 pixels/cm and the accuracy was ±0.125mm. In order to minimize the error associated with discrete data used to characterize a continuous strain field, the displacement data were fitted with a third order polynomial and the fitted data differentiated to measure surface strains using a Lagrangian finite strain formulation. The distribution of axial strain along the muscle-tendon unit was nonuniform and rate dependent. Despite a variation in local strain distribution with strain rate, the maximum axial strain, Exx = 0.614 ± 0.045 mm/mm, was rate insensitive and occurred at the failure site for all tests. The frequency response of the video system (1000 Hz) and the measurement of a continuous strain field along the entire length of the structure improve upon previous noncontact optical systems for measurement of surface strains in soft tissues.

scholarly journals A strain-cue hypothesis for biological network formation

2010 ◽  
Vol 8 (56) ◽  
pp. 377-394 ◽  
Author(s):  
Brian N. Cox
Keyword(s):  
Strain Field ◽  
Network Formation ◽  
Local Strain ◽  
Break Symmetry ◽  
Host Population ◽  
Host Cells ◽  
Vascular Networks ◽  
Host Medium ◽  
Branch Formation ◽  
Order Of Magnitude

The direction of migration of a cell invading a host population is assumed to be controlled by the magnitude of the strains in the host medium (cells plus extracellular matrix) that arise as the host medium deforms to accommodate the invader. The single assumption that invaders are cued by strains external to themselves is sufficient to generate network structures. The strain induced by a line of invaders is greatest at the extremity of the line and thus the strain field breaks symmetry, stabilizing branch formation. The strain cue also triggers sprouting from existing branches, with no further model assumption. Network characteristics depend primarily on the ratio of the rate of advance of the invaders to the rate of relaxation of the host cells after their initial deformation. Intra-cell mechanisms that govern these two rates control network morphology. The strain field that cues an individual invader is a collective response of the combined cell populations, involving the nearest 100 cells, to order of magnitude, to any invader. The mechanism does not rely on the pre-existence of the entire host medium prior to invasion; the host cells need only maintain a layer several cells thick around each invader. Consistent with recent experiments, networks result only from a strain cue that is based on strain magnitudes. Spatial strain gradients do not break symmetry and therefore cannot stabilize branch formation. The theory recreates most of the geometrical features of the nervous network in the mouse gut when the most influential adjustable parameter takes a value consistent with one inferred from human and mouse amelogenesis. Because of similarity in the guiding local strain fields, strain cues could also be a participating factor in the formation of vascular networks.

scholarly journals Time dependence of cellular responses to dynamic and complex strain fields

2019 ◽  
Vol 11 (1) ◽  
pp. 4-15 ◽  
Author(s):  
Sophie Chagnon-Lessard ◽  
Michel Godin ◽  
Andrew E Pelling
Keyword(s):  
Strain Gradient ◽  
Strain Field ◽  
Local Strain ◽  
Cellular Responses ◽  
Strain Fields ◽  
Strain Gradients ◽  
Biologically Relevant ◽  
Physical Cues ◽  
History Of ◽  
Strain Direction

Abstract Exposing cells to an unconventional sequence of physical cues can reveal subtleties of cellular sensing and response mechanisms. We investigated the mechanoresponse of cyclically stretched fibroblasts under a spatially non-uniform strain field which was subjected to repeated changes in stretching directions over 55 h. A polydimethylsiloxane microfluidic stretcher array optimized for complex staining procedures and imaging was developed to generate biologically relevant strain and strain gradient amplitudes. We demonstrated that cells can successfully reorient themselves repeatedly, as the main cyclical stretching direction is consecutively switched between two perpendicular directions every 11 h. Importantly, from one reorientation to the next, the extent to which cells reorient themselves perpendicularly to the local strain direction progressively decreases, while their tendency to align perpendicularly to the strain gradient direction increases. We demonstrate that these results are consistent with our finding that cellular responses to strains and strain gradients occur on two distinct time scales, the latter being slower. Overall, our results reveal the absence of major irreversible cellular changes that compromise the ability to sense and reorient to changing strain directions under the conditions of this experiment. On the other hand, we show how the history of strain field dynamics can influence the cellular realignment behavior, due to the interplay of complex time-dependent responses.

scholarly journals Microscopic characterization of local strain field in healing tissue in the central third defect of mouse patellar tendon at early-phase of healing

2021 ◽  
Author(s):  
Eijiro Maeda ◽  
Kaname Kuroyanagi ◽  
Takeo Matsumoto
Keyword(s):  
Patellar Tendon ◽  
Strain Field ◽  
Collagen Fibre ◽  
Local Strain ◽  
Mechanical Stimuli ◽  
Tendon Tissue ◽  
Collagen Fibres ◽  
Normal Tendon ◽  
Healing Tissue ◽  
Healing Tendon

Tendons exhibit a hierarchical collagen structure, wherein higher-level components, such as collagen fibres and fascicles, are elongated, slid, and rotated during macroscopic stretching. These mechanical behaviours of collagen fibres play important roles in stimulating tenocytes, imposing stretching, compression, and shear deformation. It was hypothesised that a lack of local fibre behaviours in healing tendon tissue may result in a limited application of mechanical stimuli to cells within the tissue, leading to incomplete recovery of tissue structure and functions in regenerated tendons. Therefore, the present study aimed to measure the microscopic strain field in the healing tendon tissue. A central third defect was created in the patellar tendon of mice, and the regenerated tissue in the defect was examined by tensile testing, collagen fibre analysis, and local strain measurement using confocal microscopy at 3 and 6 weeks after surgery. Healing tissue at 3 weeks exhibited a significantly lower strength and disorganised collagen fibre structure compared with the normal tendon. These characteristics at 6 weeks remained significantly different from those of the normal tendon. Moreover, the magnitude of local shear strain in the healing tissue under 4% tissue strain was significantly smaller than that in the normal tendon. Differences in the local strain field may be reflected in the cell nuclear shape and possibly the amount of mechanical stimuli applied to the cells during tendon deformation. Accordingly, restoration of a normal local mechanical environment in the healing tissue may be key to a better healing outcome of tendon injury.

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