scholarly journals Computational investigation of the impact of assumption of affine deformation on constitutive models of soft tissues

2019 ◽  
Vol 13 (2) ◽  
Author(s):  
Burša Jiří ◽  
Martin Slažanský
Keyword(s):  
Soft Tissues ◽  
Constitutive Models ◽  
Computational Investigation ◽  
Affine Deformation ◽  
The Impact

scholarly journals Experimental and Computational Investigation of binary drop collisions under elevated pressure

2017 ◽  
Author(s):  
Jan Breitenbach ◽  
Louis Maximilian Reitter ◽  
Muyuan Liu ◽  
Kuan-Ling Huang ◽  
Dieter Bothe ◽  
...  
Keyword(s):  
Relative Velocity ◽  
Computational Study ◽  
Ambient Pressure ◽  
Experimental System ◽  
Elevated Pressure ◽  
Computational Investigation ◽  
Ambient Conditions ◽  
Influencing Parameters ◽  
Gas Layer ◽  
The Impact

Spray systems often operate under extreme ambient conditions like high pressure, which can have a significant influence on important spray phenomena. One of these phenomena is binary drop collisions. Such collisions, depending on the relative velocity and the impact parameter (eccentricity of the collision), can lead to drop bouncing, coalescence or breakup. This experimental and computational study is focused on the description of the phenomenon of drop bouncing, which is caused by a thin gas layer preventing the drops coalescence. To identify the main influencing parameters of this phenomenon, experiments on binary drop collisions are performed in a pressure chamber. This experimental system allows us to investigate the effect of an ambient pressure (namely the density and viscosity of the surrounding gas) on the bouncing/coalescence threshold.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4758

scholarly journals Computational Modeling of Skull Bone Structures and Simulation of Skull Fractures Using the YEAHM Head Model

Biology ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 267 ◽  
Author(s):  
Alcino Barbosa ◽  
Fábio A. O. Fernandes ◽  
Ricardo J. Alves de Sousa ◽  
Mariusz Ptak ◽  
Johannes Wilhelm
Keyword(s):  
Computational Models ◽  
Soft Tissues ◽  
Constitutive Models ◽  
Human Head ◽  
Head Model ◽  
Head Impacts ◽  
Skull Model ◽  
Linear Behavior ◽  
Local Material ◽  
Direct Head

The human head is a complex multi-layered structure of hard and soft tissues, governed by complex materials laws and interactions. Computational models of the human head have been developed over the years, reaching high levels of detail, complexity, and precision. However, most of the attention has been devoted to the brain and other intracranial structures. The skull, despite playing a major role in direct head impacts, is often overlooked and simplified. In this work, a new skull model is developed for the authors’ head model, the YEAHM, based on the original outer geometry, but segmenting it with sutures, diploë, and cortical bone, having variable thickness across different head sections and based on medical craniometric data. These structures are modeled with constitutive models that consider the non-linear behavior of skull bones and also the nature of their failure. Several validations are performed, comparing the simulation results with experimental results available in the literature at several levels: (i) local material validation; (ii) blunt trauma from direct impact against stationary skull; (iii) three impacts at different velocities simulating falls; (iv) blunt ballistic temporoparietal head impacts. Accelerations, impact forces, and fracture patterns are used to validate the skull model.

A Structural Continuum Constitutive Model for a Two-Phase Soft Tissue

2010 ◽  
Author(s):  
Silvia Wognum ◽  
Michael S. Sacks
Keyword(s):  
Mechanical Behavior ◽  
Soft Tissues ◽  
Bladder Wall ◽  
Constitutive Models ◽  
Tissue Level ◽  
Model Parameters ◽  
Two Phase ◽  
Tissue Properties ◽  
Highly Nonlinear ◽  
Cord Injury

Due to the complexity in determining multi-constituent tissue properties, most structural constitutive models for soft tissues focus on a single constituent. However, many tissues contain multiple load-bearing constituents, such as collagen fibers and smooth muscle (SM) cells. Moreover, to elucidate how observed changes in tissue components are related to altered net mechanical behavior at the tissue level, structural constitutive models require physiological relevant model parameters and formulations for changes in referential configuration when one component is physically removed. As an excellent example application that underscores these issues, we have examined the urinary bladder wall (UBW), which undergoes large deformations and exhibits highly nonlinear and anisotropic mechanical behavior [1,2]. Moreover, it undergoes profound remodeling in response to different pathologies such as spinal cord injury (SCI) [1,2].

Absorption of the impact energy in the palmar soft tissues

1975 ◽  
Vol 148 (2) ◽  
pp. 215-221 ◽  
Author(s):  
Vasilije Nikolié ◽  
Janko Hančevié ◽  
Mladen Hudec ◽  
Bóžidar Banović
Keyword(s):  
Impact Energy ◽  
Soft Tissues ◽  
The Impact

scholarly journals The Effect of the Contact Model on the Design of Mechanical Systems

2012 ◽  
Author(s):  
M. R. Brake ◽  
D. S. Aragon ◽  
D. J. VanGoethem ◽  
H. Sumali
Keyword(s):  
Constant Coefficient ◽  
Degrees Of Freedom ◽  
Mechanical Systems ◽  
Constitutive Models ◽  
Coefficient Of Restitution ◽  
Rigid Body Dynamics ◽  
Contact Model ◽  
Elastic Plastic ◽  
Contact Models ◽  
The Impact

Impact is a wide-spread phenomenon in mechanical systems that can have a significant effect on the system’s dynamics, stability, wear, and damage. The simulation of impact in complex, mechanical systems, however, is often too computationally intensive for high fidelity finite element analyses to be useful as design tools. As a result, rigid body dynamics and reduced order model simulations are often used, with the impact events modeled by ad hoc methods such as a constant coefficient of restitution or a penalty stiffness. The consequences of the choice of contact model are studied in this paper for a representative multiple-degrees of freedom mechanical system. Four contact models are considered in the analysis: a constant coefficient of restitution model, two similar elastic-plastic constitutive models, and one dissimilar elastic-plastic constitutive model. The predictions of wear, mechanical failure, and stability are assessed for each of the contact models, and the subsequent effect on the system design is investigated. These results emphasize the importance of choosing a realistic contact model when simulations are being used to drive the design of a system.

How multi-scale approaches can benefit the design of cellular rockfall protection structures

2011 ◽  
Vol 48 (12) ◽  
pp. 1803-1816 ◽  
Author(s):  
F. Bourrier ◽  
S. Lambert ◽  
A. Heymann ◽  
P. Gotteland ◽  
F. Nicot
Keyword(s):  
Constitutive Models ◽  
Structure Model ◽  
Structure Information ◽  
Multi Scale ◽  
Physical Mechanisms ◽  
Macroscopic Structure ◽  
Rockfall Protection Structures ◽  
The Impact ◽  
Impact Experiments ◽  
Rockfall Protection

Cellular structures are efficient technological solutions for rockfall protection. A multi-scale approach is used to develop a cellular rockfall protection structure model for engineering purposes. The macroscopic structure is composed of mesoscale individual layers made up of rocky particles contained in wire netting cages, fine granular material, and a reinforced embankment. Simple constitutive models were developed for the different mesoscale layers of the structure. Information is gathered from experiments at the layer scale to calibrate the parameters of the constitutive models. The capacities of the model are evaluated by comparisons between simulations and impact experiments on small structures. Despite quantitative differences, the comparative analysis highlights that the structure model can account for the main physical mechanisms occurring during the impact on sandwich structures. This analysis also emphasizes the model’s applicability for engineering purposes.

Energy-Shunting Hip Padding System Attenuates Femoral Impact Force in a Simulated Fall

1995 ◽  
Vol 117 (4) ◽  
pp. 409-413 ◽  
Author(s):  
S. N. Robinovitch ◽  
W. C. Hayes ◽  
T. A. McMahon
Keyword(s):  
Soft Tissue ◽  
Soft Tissues ◽  
Impact Force ◽  
The Elderly ◽  
Impact Behavior ◽  
Human Female ◽  
Female Pelvis ◽  
The Mean ◽  
The Impact

Recent studies suggest that hip padding systems reduce the incidence of hip fractures during falls. However, no data exist on the force attenuating capacity of hip pads under realistic fall impact conditions, and thus it is difficult to compare the protective merit of various pad designs. Our goal is to design a comfortable hip padding system which reduces femoral impact force in a fall below the mean force required to fracture the elderly cadaveric femur. In pursuit of this objective, we designed and constructed a hip pad testing system consisting of an impact pendulum and surrogate human pelvis. We then developed a hip pad containing a shear-thickening material which allows for shunting of the impact energy away from the femur and into the surrounding soft tissue. Finally, we conducted experiments to assess whether the surrogate pelvis accurately represents the impact behavior of the human female pelvis in a fall, and to determine whether our energy-shunting pad attenuates femoral impact force in a fall more effectively than seven available padding systems. We found the surrogate pelvis accurately represented the human female pelvis in regional variation in soft tissue stiffness, total effective stiffness and damping, and impact force attenuation provided by trochanteric soft tissues. We also found that our padding system attenuated femoral impact force by 65 percent, thereby providing two times the force attenuation of the next best system. Moreover, the energy-shunting pad was the only system capable of lowering femoral impact force well below the mean force required to fracture the elderly femur in a fall loading configuration. These results suggest that the force attenuating potential of hip pads which focus on shunting energy away from the femur is superior to those which rely on absorbing energy in the pad material. While these in-vitro results are encouraging, carefully designed prospective clinical trials will be necessary to determine the efficacy of these approaches to hip fracture prevention.

Finite Element Analysis of Electroactive and Magnetoactive Coupled Behaviors in Multi-Field Origami Structures

2017 ◽  
Author(s):  
Wei Zhang ◽  
Anil Erol ◽  
Saad Ahmed ◽  
Sarah Masters ◽  
Paris von Lockette ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Smart Materials ◽  
Electromechanical Coupling ◽  
Material Selection ◽  
Constitutive Relations ◽  
Computational Cost ◽  
Constitutive Models ◽  
Element Analysis ◽  
The Impact

Active origami designs, which incorporate smart materials such as electroactive polymers (EAPs) and magnetoactive elastomers (MAEs) into mechanical structures, have shown good promise in engineering applications. In this study, finite element analysis (FEA) models are developed using COMSOL Multiphysics software for two configurations that incorporate a combination of active and passive material layers, namely: 1) a single-notch unimorph folding configuration actuated using only external electric field and 2) a bimorph configuration which is actuated using both electric and magnetic (i.e. multifield) stimuli. Constitutive relations are developed for both electrostrictive and magnetoactive materials to model the coupled behaviors directly. Shell elements are adopted for their capacity of modeling thin films, reduction of computational cost and ability to model the intrinsic coupled behaviors in the active materials under consideration. A microstructure-based constitutive model for electromechanical coupling is introduced to capture the nonlinearity of the EAP’s relaxor ferroelectric response; the electrostrictive coefficients are then used as input in the constitutive modeling of the coupled behavior. The magnetization of the MAE is measured by experiment and then used to calculate magnetic torque under specified external magnetic field. The objective of the study is to verify the effectiveness of the constitutive models to simulate multi-field coupled behaviors of the active origami configurations. Through quantitative comparisons, simulation results show good agreement with experimental data, which is a good validation of the shell models. By investigating the impact of material selection, location, and geometric parameters, FEA can be used in design, reducing trial-and-error iterations in experiments.

Development of an agroforest on a Micronesian high island: prehistoric Kosraean agriculture

Antiquity ◽  
1996 ◽  
Vol 70 (270) ◽  
pp. 834-846 ◽  
Author(s):  
J. Stephen Athens ◽  
Jerome V. Ward ◽  
Gail M. Murakami
Keyword(s):  
Soft Tissues ◽  
Pacific Island ◽  
Prehistoric Agriculture ◽  
Human Presence ◽  
The Pacific ◽  
The Impact

The impact of the human presence on the fauna of a Pacific island is often immediately archaeologically visible in the slaughter of its land birds seen in the bones. The impact on vegetation is less distinct archaeologically, and many of the Pacific cultigens have soft tissues which rarely preserve. So a study of prehistoric agriculture on one of the high Micronesian islands largely involves pollen and charcoal.

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