Effects of Foot Strike and Step Frequency on Achilles Tendon Stress During Running

Achilles tendon (AT) injuries are common in runners. The AT withstands high magnitudes of stress during running which may contribute to injury. Our purpose was to examine the effects of foot strike pattern and step frequency on AT stress and strain during running utilizing muscle forces based on a musculoskeletal model and subject-specific ultrasound-derived AT crosssectional area. Nineteen female runners performed running trials under 6 conditions, including rearfoot strike and forefoot strike patterns at their preferred cadence, +5%, and –5% preferred cadence. Rearfoot strike patterns had less peak AT stress (P < .001), strain (P < .001), and strain rate (P < .001) compared with the forefoot strike pattern. A reduction in peak AT stress and strain were exhibited with a +5% preferred step frequency relative to the preferred condition using a rearfoot (P < .001) and forefoot (P=.005) strike pattern. Strain rate was not different (P > .05) between step frequencies within each foot strike condition. Our results suggest that a rearfoot pattern may reduce AT stress, strain, and strain rate. Increases in step frequency of 5% above preferred frequency, regardless of foot strike pattern, may also lower peak AT stress and strain.

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Evolution of specimen strain rate in split Hopkinson bar test

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406218813386 ◽

2019 ◽

Vol 233 (13) ◽

pp. 4667-4687 ◽

Cited By ~ 5

Author(s):

Hyunho Shin ◽

Jong-Bong Kim

Keyword(s):

Strain Rate ◽

Rate Equation ◽

Constant Strain Rate ◽

Strain Curve ◽

Hopkinson Bar ◽

Stress Strain ◽

Split Hopkinson Bar ◽

Specimen Diameter ◽

Strain And Strain Rate ◽

Split Hopkinson

The specimen strain rate in the split Hopkinson bar (SHB) test has been formulated based on a one-dimensional assumption. The strain rate is found to be controlled by the stress and strain of the deforming specimen, geometry (the length and diameter) of specimen, impedance of bar, and impact velocity. The specimen strain rate evolves as a result of the competition between the rate-increasing and rate-decreasing factors. Unless the two factors are balanced, the specimen strain rate generally varies (decreases or increases) with strain (specimen deformation), which is the physical origin of the varying nature of the specimen strain rate in the SHB test. According to the formulated strain rate equation, the curves of stress–strain and strain rate–strain are mutually correlated. Based on the correlation of these curves, the strain rate equation is verified through a numerical simulation and experiment. The formulated equation can be used as a tool for verifying the measured strain rate–strain curve simultaneously with the measured stress–strain curve. A practical method for predicting the specimen strain rate before carrying out the SHB test has also been presented. The method simultaneously solves the formulated strain rate equation and a reasonably estimated constitutive equation of specimen to generate the anticipated curves of strain rate–strain and stress–strain in the SHB test. An Excel® program to solve the two equations is provided. The strain rate equation also indicates that the increase in specimen stress during deformation (e.g., work hardening) plays a role in decreasing the slope of the strain rate–strain curve in the plastic regime. However, according to the strain rate equation, the slope of the strain rate–strain curve in the plastic deformation regime can be tailored by controlling the specimen diameter. Two practical methods for determining the specimen diameter to achieve a nearly constant strain rate are presented.

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Estimation of Stress-Strain behavior of polyethylene terephthalate (PET) at different strain rates by Artificial Neural Network under simultaneous stretch scenario

10.25518/esaform21.1995 ◽

2021 ◽

Author(s):

Fei Teng ◽

Gary Menary ◽

Savko Malinov ◽

Shiyong Yan

Keyword(s):

Neural Network ◽

Artificial Neural Network ◽

Strain Rate ◽

Strain Rates ◽

Stress Strain ◽

Strain Behavior ◽

Strain And Strain Rate ◽

Artificial Neural ◽

Artificial Neural Network Ann ◽

High Degree

In this paper, an Artificial Neural Network (ANN) is used to predict the stress-strain behavior of PET at conditions relevant to Stretch Blow Moulding i.e. Large equibiaxial deformation at elevated temperature and high strain rate. The input vectors considered are temperature, strain, and strain rate with a corresponding output parameter of stress. In the present work, a feed-forward back backpropagation algorithm was used to train the ANN. The ANN is able to approximate the relationship between stress and strain at various strain rates & temperatures to a high degree of accuracy for all conditions tested.

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Stress, strain and strain-rate cemented carbide properties determined with a fem-supported evaluation of impact test imprints

International Journal of Refractory Metals and Hard Materials ◽

10.1016/j.ijrmhm.2020.105384 ◽

2021 ◽

Vol 94 ◽

pp. 105384

Author(s):

Antonios Bouzakis ◽

Georgios Skordaris ◽

Konstantinos-Dionysios Bouzakis ◽

Mehmet-Gökhan Gökcen ◽

Apostolos Boumpakis ◽

...

Keyword(s):

Strain Rate ◽

Impact Test ◽

Cemented Carbide ◽

Stress Strain ◽

Strain And Strain Rate

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An Empirical Creep Law From a Single Test

Journal of Basic Engineering ◽

10.1115/1.3657292 ◽

1962 ◽

Vol 84 (2) ◽

pp. 236-238

Author(s):

Iain Finnie

Keyword(s):

Strain Rate ◽

Creep Test ◽

Constant Load ◽

Constant Stress ◽

Single Test ◽

Creep Tests ◽

Stress Strain ◽

Strain And Strain Rate ◽

Single Constant

A method is described by which an empirical creep law, relating stress, strain, and strain rate, may be obtained from a single constant-load creep test. An example to illustrate the method is given, and the empirical creep law is compared with the results of several constant stress creep tests.

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THE SIMULATION OF MECHANICAL STIMULATION EFFECT ON BONE ELASTICITY LIMIT BASED ON FINITE ELEMENT METHOD (FEM)

Jurnal Teknologi ◽

10.11113/jurnalteknologi.v83.14479 ◽

2021 ◽

Vol 83 (3) ◽

pp. 21-27

Author(s):

Khusnul Yakin ◽

Ita Setyaningsih ◽

Nurani Indha Rusmana ◽

Mohammad Tirono ◽

Rofiqul Umam

Keyword(s):

Bone Density ◽

Strain Rate ◽

Mechanical Stimulation ◽

Stress And Strain ◽

Mechanical Stimuli ◽

Elasticity Limit ◽

Bone Properties ◽

Strain And Strain Rate ◽

Reversal Phase ◽

The Difference

Osteoporosis is a disease affecting bones which is characterized by decreased bone density; bones become porous and susceptible to fractures. Osteoporosis occurs because of an imbalance during bone remodeling phase between resorption and formation processes. This study aims to simulate the effects of mechanical stimulations on the femoral bone elasticity limit. It is hoped that these mechanical stimuli can provide information on bone elasticity limits. Initially, we constructed the femur in two layers using triangular elements. Then we entered the bone properties (Young’s modulus and Poisson’s ratio) based on the age of the femur. After that we calculated the value of the stress, strain, and strain rate in the reversal phase. Next, we calculated the bone density using the thermodynamic equation and calculation of the bone elasticity limit using particle swarm optimization (PSO) methods. The value of stress and strain caused by walking is higher than the value of stress and strain when standing still. In this case, the difference in activity results an increase in stress by 33.82% and an increase in strain and strain rate by 34.57%. Based on these simulation results, it can be concluded that mechanical stimulation can increase the limit of bone elasticity to 2.99% in cortical bone and 0.975% in trabecular bone. Bone elasticity limit can be used to determine the level of osteoporosis that occurs. The higher value of the bone elasticity, the smaller the possibility of osteoporosis.

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The Biomechanical Determinants of Concussion: Finite Element Simulations to Investigate Tissue-Level Predictors of Injury During Sporting Impacts to the Unprotected Head

Journal of Applied Biomechanics ◽

10.1123/jab.2014-0223 ◽

2015 ◽

Vol 31 (4) ◽

pp. 264-268 ◽

Cited By ~ 32

Author(s):

Declan A. Patton ◽

Andrew S. McIntosh ◽

Svein Kleiven

Keyword(s):

Finite Element ◽

Corpus Callosum ◽

Strain Rate ◽

Tissue Level ◽

Von Mises Stress ◽

Tolerance Limits ◽

Stress Strain ◽

Head Impacts ◽

Strain And Strain Rate ◽

Von Mises

Biomechanical studies of concussions have progressed from qualitative observations of head impacts to physical and numerical reconstructions, direct impact measurements, and finite element analyses. Supplementary to a previous study, which investigated maximum principal strain, the current study used a detailed finite element head model to simulate unhelmeted concussion and no-injury head impacts and evaluate the effectiveness of various tissue-level brain injury predictors: strain rate, product of strain and strain rate, cumulative strain damage measure, von Mises stress, and intracranial pressure. Von Mises stress was found to be the most effective predictor of concussion. It was also found that the thalamus and corpus callosum were brain regions with strong associations with concussion. Tentative tolerance limits for tissue-level predictors were proposed in an attempt to broaden the understanding of unhelmeted concussions. For the thalamus, tolerance limits were proposed for a 50% likelihood of concussion: 2.24 kPa, 24.0 s−1, and 2.49 s−1 for von Mises stress, strain rate, and the product of strain and strain rate, respectively. For the corpus callosum, tolerance limits were proposed for a 50% likelihood of concussion: 3.51 kPa, 25.1 s−1, and 2.76 s−1 for von Mises stress, strain rate, and the product of strain and strain rate, respectively.

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Stress, strain and strain-rate in the shock-induced processes

2015 International Conference on Mechanics - Seventh Polyakhov's Reading ◽

10.1109/polyakhov.2015.7106709 ◽

2015 ◽

Author(s):

K. R. Abdullaev ◽

T. A. Khantuleva

Keyword(s):

Strain Rate ◽

Stress Strain ◽

Strain And Strain Rate

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Analytical Formulation of a Rate and Temperature Dependent Stress-Strain Relation

Journal of Engineering Materials and Technology ◽

10.1115/1.3443685 ◽

1979 ◽

Vol 101 (3) ◽

pp. 254-257 ◽

Cited By ~ 23

Author(s):

A. Merzer ◽

S. R. Bodner

Keyword(s):

Plastic Strain ◽

Strain Rate ◽

Uniaxial Stress ◽

Plastic Strain Rate ◽

Isotropic Hardening ◽

Stress Strain ◽

Rate Dependent ◽

Strain Relation ◽

Strain And Strain Rate ◽

Stress Strain Relation

The equation for plastic strain rate in the Bodner-Partom viscoplastic formulation is integrated under conditions of uniaxial stress, constant plastic strain rate, and isotropic hardening to give an analytical expression for the stress as a function of plastic strain and strain rate. Temperature dependence is introduced which leads to a general relationship between stress, strain, strain rate, and temperature. The resulting equation indicates an asymptotic saturation stress whose dependence on strain rate and temperature appears to agree with experimental results. Strain hardening given by the analytical equation also seems to be consistent with experiments. A possible new definition of yield stress is a consequence of the rate dependent stress-strain relation.

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