1,667 research outputs found
Control of Tension-Compression Asymmetry in Ogden Hyperelasticity with Application to Soft Tissue Modelling
This paper discusses tension-compression asymmetry properties of Ogden
hyperelastic formulations. It is shown that if all negative or all positive
Ogden coefficients are used, tension-compression asymmetry occurs the degree of
which cannot be separately controlled from the degree of non-linearity. A
simple hybrid form is therefore proposed providing separate control over the
tension-compression asymmetry. It is demonstrated how this form relates to a
newly introduced generalised strain tensor class which encompasses both the
tension-compression asymmetric Seth-Hill strain class and the
tension-compression symmetric Ba\v{z}ant strain class. If the control parameter
is set to q=0.5 a tension-compression symmetric form involving Ba\v{z}ant
strains is obtained with the property
{\Psi}({\lambda}_1,{\lambda}_2,{\lambda}_3 )={\Psi}(1/{\lambda}_1
,1/{\lambda}_2 ,1/{\lambda}_3 ). The symmetric form may be desirable for the
definition of ground matrix contributions in soft tissue modelling allowing all
deviation from the symmetry to stem solely from fibrous reinforcement. Such an
application is also presented demonstrating the use of the proposed formulation
in the modelling of the non-linear elastic and transversely isotropic behaviour
of skeletal muscle tissue in compression (the model implementation and fitting
procedure have been made freely available). The presented hyperelastic
formulations may aid researchers in independently controlling the degree of
tension-compression asymmetry from the degree of non-linearity, and in the case
of anisotropic materials may assist in determining the role played by, either
the ground matrix, or the fibrous reinforcing structures, in generating
asymmetry.Comment: 20 page
Teaching and Learning: Essential Components of the Nurse Executive Role
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98205/1/j.1547-5069.1987.tb00611.x.pd
A continuum model for tension-compression asymmetry in skeletal muscle
[EN] Experiments on passive skeletal muscle on different species show a strong asymmetry in the observed tension-compression mechanical behavior. This asymmetry shows that the tension modulus is two orders of magnitude higher than the compression modulus. Until now, traditional analytical constitutive models have been unable to capture that strong asymmetry in anisotropic solids using the same material parameters. In this work we present a model which is able to accurately capture five experimental tests in chicken pectoralis muscle, including the observed tension-compression asymmetry. However, aspects of the anisotropy of the tissue are not captured by the model.Partial financial support for this work has been given by grant DPI2015-69801-R from the Direccion General de Proyectos de Investigacion of the Ministerio de Economia y Competitividad of Spain. FJM also acknowledges the support of the Department of Mechanical and Aerospace Engineering of University of Florida during the sabbatical period in which this paper was completed and Ministerio de Educacion, Cultura y Deporte of Spain for the financial support for that stay under grant PRX15/00065Latorre, M.; Mohammadkhah, M.; Simms, CK.; Montáns, FJ. (2018). A continuum model for tension-compression asymmetry in skeletal muscle. Journal of the Mechanical Behavior of Biomedical Materials. 77:455-460. https://doi.org/10.1016/j.jmbbm.2017.09.0124554607
Understanding the Impact of INDOT Projects on Automotive Industry Cluster Logistics Costs: A Case Study of the Honda Plant
This study focuses on understanding the impact of INDOT projects on the Honda, Greensburg plant’s supply chain. The goal of the study was th
Demanding stories: television coverage of sustainability, climate change and material demand
This paper explores the past, present and future role of broadcasting, above all via the medium of television, in shaping how societies talk, think about and act on climate change and sustainability issues. The paper explores these broad themes via a focus on the important but relatively neglected issue of material demand and opportunities for its reduction. It takes the outputs and decision-making of one of the world’s most influential broadcasters, the BBC, as its primary focus. The paper considers these themes in terms of stories, touching on some of the broader societal frames of understanding into which they can be grouped. Media decision-makers and producers from a range of genres frequently return to the centrality of ‘story’ in the development, commissioning and production of an idea. With reference to specific examples of programming, and drawing on interviews with media practitioners, the paper considers the challenges of generating broadcast stories that can inspire engagement in issues around climate change, and specifically material demand. The concluding section proposes actions and approaches that might help to establish material demand reduction as a prominent way of thinking about climate change and environmental issues more widely.
This article is part of the themed issue ‘Material demand reduction’
Development of an electrostatic positioner for space material processing
This paper describes an electrostatic positioning instrument which was developed at the Jet Propulsion Laboratory to enable experimenters to conduct containerless material science experiments in space. Samples that are to be studied are electrically charged and controlled by the electrostatic force produced by a set of properly arranged electrodes. Three different types of positioners are described, i.e., the dish type, the ring type, and the tetrahedral type. In all these systems, the positioning and the damping of the sample is accomplished by a feedback control system. The advantage of this electrostatic positioning method, in comparison to the other methods, such as acoustic and electromagnetic, lies in the fact that it can operate in a high vacuum and does not require the material to be electrically conductive as long as the material can carry a certain amount of charge
Concussion in Rugby Union and the Role of Biomechanics
Due to the physical and high-impact nature of rugby, head impacts can occur within the game which can result in concussion injuries as well as other moderate-to-severe head injuries 1. Concussion has been defined as “a complex pathophysiological process affecting the brain, induced by traumatic biomechanical forces”1 and was found to be one of the more common brain injuries throughout the world.2 This is particularly true in sport; it has been estimated that over half of all concussions are sports related.3 A systematic review of the incidence of concussion in contact sports found that rugby union has a higher incidence rate compared with other sports such as American football and soccer.4
Unlike other sports injuries, detecting a concussion is difficult as the neuropathological changes cannot be recognized on standard neuroimaging technology.5,6 \Therefore, if a player is suspected of having a concussion, they are removed from play for a Head Injury Assessment (HIA). The HIA is a standardized tool for the medical assessment of concussion injuries in rugby and aims to improve detection and patient education.7 The HIA assesses a range of degenerative concussive symptoms including memory, cognitive ability, balance and player discomfort. This concussion diagnosis protocol therefore relies heavily on side-line medical staff to identify if a player is exhibiting concussive symptoms. A major disadvantage to this is that concussion has a variable natural history, with transient, fluctuating, delayed and evolving signs or symptoms.8) This means that symptoms can take up to 48 hours to become apparent.8 It has therefore been acknowledged that the content of the HIA will be modified as the research around concussion diagnosis evolves.8
The reliance on side-line medical staff to accurately identify concussive symptoms means that there is a possibility a concussed player may remain on the field; this is one problem that biomechanical research into concussion is trying to overcome. This study will give an overview of concussion in rugby union with a focus on incidence, severity and protection strategies. It will discuss current biomechanical research and further biomechanical research required in the area of concussion injuries in rugby union
THE KINEMATICS OF HEAD IMPACTS IN CONTACT SPORT: AN INITIAL ASSESSMENT OF THE POTENTIAL OF MODEL BASED IMAGE MATCHING
Model Based Image Matching (MBIM) has potential to assess three-dimensional linear and rotational motion patterns from multiple camera views of head impact events in contact sports. The goal of this study is to assess the accuracy of the MBlM method for estimating 6DOF head kinematics in a vehicle-cadaver impact scenario for which Vicon motion analysis data are available as an independent measure. A three camera view MBlM reconstruction yielded RMS errors between 0.14-0.26 mls for change in head linear velocities ranging from 0.56-5.70 m/s, and 0.27-1.38 rad/s for change in head angular velocities ranging from 6.1041 -90 rad/s. The results from this study indicate that the MBlM method is a useful approach for measuring the kinematics of head impacts in sport
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