Effect of the In Vitro Boundary Conditions on the Surface Strain Experienced by the Vertebral Body in the Elastic Regime

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Valentina Danesi ◽  
Paolo Erani ◽  
Nicola Brandolini ◽  
Mateusz M. Juszczyk ◽  
Luca Cristofolini
Keyword(s):  
Boundary Conditions ◽  
Axial Loading ◽  
Surface Strain ◽  
Strain Gauges ◽  
Nondestructive Tests ◽  
Elastic Regime ◽  
Vertebral Strength ◽  
Strain Magnitude ◽  
Principal Strains

The vertebral strength and strain can be assessed in vitro by both using isolated vertebrae and sets of three adjacent vertebrae (the central one is loaded through the disks). Our goal was to elucidate if testing single-vertebra-specimens in the elastic regime provides different surface strains to three-vertebrae-segments. Twelve three-vertebrae sets were extracted from thoracolumbar human spines. To measure the principal strains, the central vertebra of each segment was prepared with eight strain-gauges. The sets were tested mechanically, allowing comparison of the surface strains between the two boundary conditions: first when the same vertebra was loaded through the disks (three-vertebrae-segment) and then with the endplates embedded in cement (single-vertebra). They were all subjected to four nondestructive tests (compression, traction, torsion clockwise, and counterclockwise). The magnitude of principal strains differed significantly between the two boundary conditions. For axial loading, the largest principal strains (along vertebral axis) were significantly higher when the same vertebra was tested isolated compared to the three-vertebrae-segment. Conversely, circumferential strains decreased significantly in the single vertebrae compared to the three-vertebrae-segment, with some variations exceeding 100% of the strain magnitude, including changes from tension to compression. For torsion, the differences between boundary conditions were smaller. This study shows that, in the elastic regime, when the vertebra is loaded through a cement pot, the surface strains differ from when it is loaded through the disks. Therefore, when single vertebrae are tested, surface strain should be taken with caution.

Surface Strain on the Equine Hoof Wall In Vivo: Implications for the Material Design and Functional Morphology of the Wall

1992 ◽  
Vol 166 (1) ◽  
pp. 145-168
Author(s):  
J. J. THOMASON ◽  
A. A. BIEWENER ◽  
J. E. BERTRAM
Keyword(s):  
Weight Bearing ◽  
Material Design ◽  
Anterior Wall ◽  
Surface Strain ◽  
Biaxial Compression ◽  
Peak Strain ◽  
The Third ◽  
Principal Strains

Surface strains were recorded from four rosette gauges at different sites on the right forehooves of three ponies running on a treadmill at seven constant speeds and using three gaits. Principal strains determined from the rosette signals indicate that the hoof material is loaded predominantly in compression and that the wall is distorted in a regular, repeatable manner at all speeds and gaits. Peak principal strains reach −5000 με, compared with −2800 με reported for the equine radius under similar locomotory conditions. Orientations of peak compressive strains do not correlate strongly with microstructural axes in the material. Comparison of our in vivo strain records with previous in vitro studies of the material properties of the wall shows that hoof keratin behaves as a multidirectional composite, capable of tolerating its usual operating strains in any direction. This mechanical behaviour also allows the material to withstand many unpredictable loading situations when the hoof contacts irregular substrata. An important property of the hoof wall is its ability to resist or redirect cracks. We found that the anterior aspect of the wall is loaded in biaxial compression, which assists in preventing the formation or propagation of cracks and reduces peak strain magnitudes. The strain patterns correlate well with current models of hoof distortion during weightbearing. In these models, transmission of force between the ground and the skeleton is seen as the primary cause of compression in the material. The third phalanx, which transmits the weight, is effectively suspended from the inner surface of the hoof wall. Spreading of the posterior borders (heels) of the hoof also occurs. The combination of weight-bearing, suspension of the third phalanx and heel spreading is probably responsible for the uncommon loading condition of biaxial compression on the anterior wall.

Limb mechanics as a function of speed and gait: a study of functional strains in the radius and tibia of horse and dog

1982 ◽  
Vol 101 (1) ◽  
pp. 187-211 ◽  
Author(s):  
C. T. Rubin ◽  
L. E. Lanyon
Keyword(s):  
Stance Phase ◽  
Strain Gauges ◽  
Peak Strain ◽  
Force Transducers ◽  
Safety Margins ◽  
Wide Range ◽  
Speed Range ◽  
Ultimate Failure ◽  
Strain Magnitude ◽  
Principal Strains

Rosette strain gauges were attached to the midshaft of the radius and tibia of two horses and two dogs, which ran on a treadmill through their entire range of speed and gait. The relative magnitudes of the principal strains on the opposite cortices of each bone remained constant through the stance phase of the stride, and their orientation varied by a maximum of only 14 degrees through the entire speed range. The maximum strain rate increased linearly with speed, but the peak strain magnitude was also dependent upon the gait used, increasing incrementally by up to 59% at the transition from walk to trot, and dropping by 42% from a trot to a canter. Force transducers attached to the shoes of one horse indicated similar changes in ground load. The peak strains induced during vigorous activity are remarkably uniform in a wide range of animals. This suggests that the skeleton is scaled to provide constant safety margins between peak functional strains and those at which yield and ultimate failure occur.

scholarly journals Influence of angulation and vertical misfit in the evaluation of micro-deformations around implants

2017 ◽  
Vol 20 (1) ◽  
pp. 32 ◽  
Author(s):  
Vinícius Anéas Rodrigues ◽  
João Paulo Mendes Tribst ◽  
Leandro Ruivo de Santis ◽  
Dimas Renó de Lima ◽  
Renato Sussumu Nishioka
Keyword(s):  
Strain Gauge ◽  
Axial Load ◽  
Axial Loading ◽  
Load Application ◽  
Strain Gauges ◽  
Correlation Test ◽  
Wax Pattern ◽  
Stereo Microscope ◽  
Pearson's Correlation

<div><p class="Body1"><strong>Objective</strong>: This <em>in vitro</em> study was to evaluate micro-strains around of implant, under the influence of angulations and vertical misfit in three-element implant-supported fixed partial dentures during axial loading by using strain gauge analysis. <strong>Materials and Methods</strong>: Three external hexagon implants with straight configuration and three external hexagon implants with angled (17°) configuration were inserted into two polyurethane blocks. To measure micro-strain, four strain gauges were bonded onto the surface of each block. Plastic copings were adapted to a standard wax pattern and cast. An axial load of 30 kgf was applied on the center of each implant for 10 seconds, using a load application device. The vertical misfit was measured at six different points by using a stereo microscope with 100-X magnification. <strong>Results:</strong> The results showed that the values for different implant angulations were significant (<em>P</em>= 0.0086). The Pearson’s correlation test between micro-strain and vertical misfit revealed no correlation between angled configuration (<em>P</em>= 0.891) and straight configuration (<em>P</em>= 0.568). <strong>Conclusion</strong>: The micro strain was higher for angled implants; no correlation was found between the vertical misfit and the micro strain values.</p></div>

scholarly journals The effect of frog pressure and downward vertical load on hoof wall weight-bearing and third phalanx displacement in the horse - an in vitro study : research communication

2001 ◽  
Vol 72 (4) ◽  
Author(s):  
A. Olivier ◽  
J. Wannenburg ◽  
R.D. Gottschalk ◽  
M.J. Van der Linde ◽  
H.T. Groeneveld
Keyword(s):  
Solar Surface ◽  
Weight Bearing ◽  
Testing Machine ◽  
Vertical Component ◽  
In Vitro Study ◽  
Vitro Study ◽  
Total Weight ◽  
Strain Gauges ◽  
Tensile Testing Machine

A shoe was designed to combine the advantages of a reverse shoe and an adjustable heart bar shoe in the treatment of chronic laminitis. This reverse even frog pressure (REFP) shoe applies pressure uniformly over a large area of the frog solar surface. Pressure is applied vertically upward parallel to the solar surface of the frog and can be increased or decreased as required. Five clinically healthy horses were humanely euthanased and their dismem-bered forelimbs used in an in vitro study. Frog pressure was measured by strain gauges applied to the ground surface of the carrying tab portion of the shoe. A linear variable distance transducer (LVDT) was inserted into a hole drilled in the dorsal hoof wall. The LVDT measured movement of the third phalanx (P3) in a dorsopalmar plane relative to the dorsal hoof wall. The vertical component of hoof wall compression was measured by means of unidirectional strain gauges attached to the toe, quarter and heel of the medial hoof wall of each specimen. The entire limb was mounted vertically in a tensile testing machine and submitted to vertical downward compressive forces of 0 to 2500 Nat a rate of 5 cm/minute. The effects of increasing frog pressure on hoof wall weight-bearing and third phalanx movement within the hoof were determined. Each specimen was tested with the shoe under the following conditions: zero frog pressure; frog pressure used to treat clinical cases of chronic laminitis (7 N-cm); frog pressure clinically painful to the horse as determined prior to euthanasia; frog pressure just alleviating this pain. The specimens were also tested after shoe removal. Total weight-bearing on the hoof wall at zero frog pressure was used as the basis for comparison. Pain-causing and pain-alleviating frog pressures decreased total weight-bearing on the hoof wall (P < 0.05). Frog pressure of 7 N-cm had no statistically significant effect on hoof wall weight-bearing although there was a trend for it to decrease as load increased. Before loading, the pain-causing and pain-alleviating frog pressures resulted in a palmar movement of P3 relative to the dorsal hoof wall compared to the position of P3 at zero frog pressure (P < 0.05). This difference remained statistically significant up to 1300 Nload. At higher loads, the position of P3 did not differ significantly for the different frog pressures applied. It is concluded that increased frog pressure using the REFP shoe decreases total hoof wall weight-bearing and causes palmar movement of P3 at low weight-bearing loads. Without a shoe the toe and quarter hoof wall compression remained more constant and less in magnitude, than with a shoe.

scholarly journals Performance of composite reinforced short column under axial loading

2018 ◽  
Vol 7 (3) ◽  
pp. 1376
Author(s):  
N Chaitanya ◽  
V Ranga Rao ◽  
M Achyutha Kumar Reddy
Keyword(s):  
Axial Loading ◽  
Element Model ◽  
Strain Gauges ◽  
Load Carrying Capacity ◽  
Short Column ◽  
Equal Angle ◽  
Short Columns ◽  
Load Carrying ◽  
Strain Stress ◽  
Loaded Column

The purpose of this paper is to compare the behaviour of composite reinforced concrete square short columns and conventional square short column. Experiments are conducted on four axially loaded column specimens till failure. Among four specimens, two are conventional and remaining two columns are having equal angles as main reinforcement. Short columns are designed using IS 456 2000. The obtained details of main reinforcement are replaced in area wise by equal angle (ISA 2525). The tie reinforcement used to withhold the main reinforcement in position are retained with the same deformed bars. Performance of columns are measured in terms of load carrying capacity, longitudinal strain, stress, crushing modes, strains in each face using strain gauges. Outcome of the experiments are compared and plotted in the form of stress vs strain of the column. A finite element model was developed using Abaqus to simulate the results.  

1998 William J. Stickel Gold Award. The effects of extrinsic muscle forces on the forefoot-to-rearfoot loading relationship in vitro. Tibia and Achilles tendon

1998 ◽  
Vol 88 (10) ◽  
pp. 471-482 ◽  
Author(s):  
ED Ward ◽  
RD Phillips ◽  
PE Patterson ◽  
GJ Werkhoven
Keyword(s):  
Achilles Tendon ◽  
Gait Cycle ◽  
Axial Loading ◽  
Muscular Activity ◽  
Linear Increase ◽  
Muscle Forces ◽  
Limited Data ◽  
Loading System ◽  
Inclination Angles

The effects of muscular activity on the distribution of forces under the foot, as well as within the foot, are of great importance for determining the mechanisms of foot pathologies. Limited data exist concerning muscle forces during the gait cycle and the effects of muscle forces conveyed to the ground-reactive forces of the foot. The authors developed a cadaveric loading system to determine the effects of force applied to the Achilles tendon on the forefoot-to-rearfoot loading relationship in eight cadaveric specimens. The study indicated that, during axial loading of the tibia, force was inherently transferred from the rearfoot to the forefoot. However, the observed forefoot-to-rearfoot loading relationship did not match the predicted loading relationship from a rigid-body diagram, as would be observed in a class I lever. The results indicated that, as the force was increased on the Achilles tendon, the change in loads on the forefoot and rearfoot was not linear. Specimens with calcaneal inclination angles greater than 20 degrees demonstrated a more linear increase as compared with those with inclination angles less than 20 degrees.

The Effects of Geometry and Static Boundary Conditions on Microvessel Outgrowth in a 3D Model of Angiogenesis

2010 ◽  
Author(s):  
Clayton J. Underwood ◽  
Laxminarayanan Krishnan ◽  
Lowell T. Edgar ◽  
Steve Maas ◽  
James B. Hoying ◽  
...  
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Direct Relationship ◽  
3D Model ◽  
Mechanical Strain ◽  
Matrix Stiffness ◽  
Collagen Gels ◽  
3D Collagen ◽  
In Vitro Angiogenesis

We reported previously that, in addition to mechanical strain, a constrained boundary condition alone can alter the organization of microvessel outgrowth during in vitro angiogenesis [1]. After 6 days of culture in vitro, microvessels aligned parallel to the long axis of rectangular 3D collagen gels that had constrained edges on the ends. However, unconstrained cultures did not show any alignment of microvessels. The ability to direct microvessel outgrowth during angiogenesis has significant implications for engineering prevascularized grafts and tissues in vitro, therefore an understanding of this process is important. Since there is direct relationship between the ability of endothelial cells to contract 3D gels and matrix stiffness [2], we hypothesize that some constrained boundary conditions will increase the apparent matrix stiffness and in turn will limit gel contraction, prevent microvessel alignment, and reduce microvessel outgrowth. The objective of this study was to compare microvessel growth and alignment under several different static boundary conditions.

High-resolution 3D surface strain magnitude using 2D camera and low-resolution depth sensor

2014 ◽  
Vol 50 ◽  
pp. 34-42
Author(s):  
Matthew Shreve ◽  
Mauricio Pamplona ◽  
Timur Luguev ◽  
Dmitry Goldgof ◽  
Sudeep Sarkar
Keyword(s):  
High Resolution ◽  
Surface Strain ◽  
Low Resolution ◽  
Depth Sensor ◽  
3D Surface ◽  
Strain Magnitude

EXOSKELETAL STRAIN: EVIDENCE FOR A TROT-GALLOP TRANSITION IN RAPIDLY RUNNING GHOST CRABS

1993 ◽  
Vol 179 (1) ◽  
pp. 301-321
Author(s):  
R. Blickhan ◽  
R. J. Full ◽  
L. Ting
Keyword(s):  
Axial Loading ◽  
Maximum Load ◽  
Strain Gauges ◽  
Bone Strain ◽  
Muscular Tension ◽  
Ocypode Quadrata ◽  
Ghost Crabs ◽  
Leg Design ◽  
Treadmill Locomotion

Equivalent gaits may be present in pedestrians that differ greatly in leg number, leg design and skeletal type. Previous studies on ghost crabs found that the transition from a slow to a fast run may resemble the change from a trot to a gallop in quadrupedal mammals. One indication of the trot-gallop gait change in quadrupedal mammals is a distinct alteration in bone strain. To test the hypothesis that ghost crabs (Ocypode quadrata) change from a trot to a gallop, we measured in vivo strains of the meropodite of the second trailing leg with miniature strain gauges. Exoskeletal strains changed significantly (increased fivefold) during treadmill locomotion at the proposed trot-gallop transition. Maximum strains attained during galloping and jumping (1000×10-6-3000×10-6) were similar to the values reported for mammals. Comparison of the maximum load possible on the leg segment (caused by muscular tension) with the strength of the segment under axial loading revealed a safety factor of 2.7, which is similar to values measured for jumping and running mammals. Equivalent gaits may result from similarities in the operation of pedestrian locomotory systems.

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