scholarly journals Impact of Horse Hoof Wall with Different Solid Surfaces

2020 ◽  
Vol 10 (23) ◽  
pp. 8743
Author(s):  
Jing Zhao ◽  
Dan B. Marghitu ◽  
John Schumacher ◽  
Wenzhong Wang
Keyword(s):  
Contact Force ◽  
Coefficient Of Friction ◽  
Coefficient Of Restitution ◽  
Solid Surfaces ◽  
Effective Coefficient ◽  
In Vitro Investigation ◽  
Equine Hoof ◽  
Impact Angles ◽  
The Impact

This study aimed to investigate the impact of a horse hoof wall on three solid surfaces: steel, concrete and asphalt. Impact experiments were conducted for different impact angles and different initial impact velocities. The effect of impact surfaces, impact angles and initial impact velocities on the coefficient of restitution and the effective coefficient of friction were tested using one-way ANOVA. Analytical and numerical modeling of the impact were developed. The impact interval was divided into two phases: compression and restitution. For compression, a contact force with a damping term was used. The restitution was characterized by an elastic contact force. The stiffness and damping coefficients of the contact force were estimated from the normal impacts. The simulated velocities after the oblique impacts were compared to the velocities in the in vitro investigation. The coefficient of restitution varied significantly on different surfaces. The effective coefficient of friction was lower on steel compared to concrete and asphalt. The model presented in this study can be applied to refine the impact simulation of the equine hoof during locomotion.

Analytical Study of the Oblique Impact of a Rod with a Flat Using an Elasto-Plastic Contact Model

2015 ◽  
Vol 801 ◽  
pp. 25-32
Author(s):  
Ozdes Cermik ◽  
Hamid Ghaednia ◽  
Dan B. Marghitu
Keyword(s):  
Impact Velocity ◽  
Contact Force ◽  
Analytical Study ◽  
Initial Conditions ◽  
Permanent Deformation ◽  
Oblique Impact ◽  
Coefficient Of Restitution ◽  
Contact Model ◽  
Impact Angles ◽  
The Impact

In the current study a flattening contact model, combined with a permanent deformation expression, has been analyzed for the oblique impact case. The model has been simulated for different initial conditions using MATLAB. The initial impact velocity used for the simulations ranges from 0.5 to 3 m/s. The results are compared theoretically for four different impact angles including 20, 45, 70, and 90 degrees. The contact force, the linear and the angular motion, the permanent deformation, and the coefficient of restitution have been analyzed. It is assumed that sliding occurs throughout the impact.

scholarly journals Optimal damping coefficient for a class of continuous contact models

2020 ◽  
Vol 50 (2) ◽  
pp. 169-188
Author(s):  
Mohammad Poursina ◽  
Parviz E. Nikravesh
Keyword(s):  
Contact Force ◽  
Analytical Formula ◽  
Coefficient Of Restitution ◽  
Damping Coefficient ◽  
Optimization Strategy ◽  
Continuous Contact ◽  
Optimal Damping ◽  
Wide Range ◽  
Contact Models ◽  
The Impact

Abstract In this study, we develop an analytical formula to approximate the damping coefficient as a function of the coefficient of restitution for a class of continuous contact models. The contact force is generated by a logical point-to-point force element consisting of a linear damper connected in parallel to a spring with Hertz force–penetration characteristic, while the exponent of deformation of the Hertz spring can vary between one and two. In this nonlinear model, it is assumed that the bodies start to separate when the contact force becomes zero. After separation, either the restitution continues or a permanent penetration is achieved. Therefore, this model is capable of addressing a wide range of impact problems. Herein, we apply an optimization strategy on the solution of the equations governing the dynamics of the penetration, ensuring that the desired restitution is reproduced at the time of separation. Furthermore, based on the results of the optimization process along with analytical investigations, the resulting optimal damping coefficient is analytically expressed at the time of impact in terms of system properties such as the effective mass, penetration velocity just before the impact, coefficient of restitution, and the characteristics of the Hertz spring model.

1322Impact of system impedance in ablation-index guided lesion formation in an in vitro model

EP Europace ◽  
2020 ◽  
Vol 22 (Supplement_1) ◽  
Author(s):  
C Lozano-Granero ◽  
J Moreno Planas ◽  
R Matia Frances ◽  
A Hernandez Madrid ◽  
I Sanchez Perez ◽  
...  
Keyword(s):  
Contact Force ◽  
Lesion Size ◽  
Lesion Volume ◽  
Application Time ◽  
Lesion Formation ◽  
Running Water ◽  
High Impedance ◽  
Ablation Index ◽  
The Impact

Abstract Funding Acknowledgements Beca de la Sección de Electrofisiología y Arritmias para formación en investigación post-residencia en centros españoles INTRODUCTION Ablation Index and Lesion Size Index are novel markers of ablation lesion quality that incorporate power (W), contact force (CF), and time (T) in a weighted formula to accurately estimate lesion size. While LSI includes system impedance (I) in the formula, this parameter is not considered for AI calculation. PURPOSE The aim of our study was to analyse the impact of I in lesion formation. METHODS Radiofrequency (RF) lesions were created on porcine myocardial slabs by using an open-tip irrigated catheter with real-time monitoring of CF (a TactiCath™ Quartz Contact Force Ablation Catheter for LSI-guided lesions and a ThermoCool® SmartTouch® Catheter for AI-guided lesions). Catheters were mounted in an articulated arm and manually maneuvered over a platform placed within a tank filled with either a low impedance medium (saline solution) or a high impedance medium (running water) with a heating pump to produce non-pulsatile flow directed perpendicularly to the myocardium surface at a rate of 5 l/min and a temperature of 37ºC. For each catheter and medium, ten lesions were performed with a CF of 20 grams and a W of 25, 30, 35 and 40 watts aiming at a LSI of 5 or a AI of 400 (recommended targets for posterior wall pulmonary vein isolation for each index). After RF delivery, the myocardium was cross-sectioned at the level of each lesion and its blanched zone was measured with a dial calliper with a 0.1 mm resolution (image, panel A). Lesion volume was calculated using width and depth, according to a validated formula (image, panel B). RESULTS No difference in application time was noted in the AI-guided lesions depending on the medium (23.8 ± 1.6s, 17.2 ± 1.4s, 13.7 ± 0.8s and 12.2 ± 0.7s for 25W, 30W, 35W and 40W, respectively) while a significant reduction in application time was noted in the LSI-guided lesions performed in a low I medium (93.8 ± 6.6 ohms; 17.9 ± 1.9s, 11.3 ± 3.7s, 9.1 ± 0.9s and 7.3 ± 0.5s for 25W, 30W, 35W and 40W) compared with those performed in a high impedance medium (132.4 ± 6.6 ohms; 27.3 ± 1.4s, 17.9 ± 2.5s, 15.5 ± 1.4 and 13 ± 1.2 for the same programmed W (p < 0.0001 for all comparisons). Both catheters showed differences in lesion size according to the I, with lower lesion volumes in the low I medium and higher lesion volumes in the high I medium. Although globally smaller in size, higher lesion volumes were noted in the AI-guided lesions compared to LSI-guided lesions in a low I medium (image, panel C). On the contrary, a better performance of the LSI-guided lesions was observed in the high I medium (image, panel D). CONCLUSIONS System impedance affected lesion size both in LSI-guided an AI-guided ablation lesions, with smaller lesions seen in a lower I medium. Further studies are needed to assess the clinical relevance of this findings in an in-vivo scenario. Abstract Figure.

scholarly journals In vitro investigation on the impact of airway mucus on drug dissolution and absorption at the air-epithelium interface in the lungs

2019 ◽  
Vol 141 ◽  
pp. 210-220 ◽  
Author(s):  
Emanuela Cingolani ◽  
Safar Alqahtani ◽  
Robyn C Sadler ◽  
David Prime ◽  
Snjezana Stolnik ◽  
...  
Keyword(s):  
Drug Dissolution ◽  
In Vitro Investigation ◽  
Airway Mucus ◽  
The Impact

In vitro investigation on the impact of the surface-active excipients Cremophor EL, Tween 80 and Solutol HS 15 on the metabolism of midazolam

2004 ◽  
Vol 25 (1) ◽  
pp. 37-49 ◽  
Author(s):  
Roberto C. Bravo González ◽  
Jörg Huwyler ◽  
Franziska Boess ◽  
Isabelle Walter ◽  
Beate Bittner
Keyword(s):  
Tween 80 ◽  
Cremophor El ◽  
In Vitro Investigation ◽  
Surface Active ◽  
Solutol Hs 15 ◽  
The Impact

Impact behaviour of elastoplastic spheres with a rigid wall

2000 ◽  
Vol 214 (8) ◽  
pp. 1107-1114 ◽  
Author(s):  
L-Y Li ◽  
C Thornton ◽  
C-Y Wu
Keyword(s):  
Contact Force ◽  
Numerical Study ◽  
Rigid Wall ◽  
Coefficient Of Restitution ◽  
Two Dimensional ◽  
Material Behaviour ◽  
Normal Impact ◽  
Dimensional Finite Element ◽  
The Impact ◽  
Force Displacement

The paper presents a numerical study of the normal impact of elastoplastic spheres with a rigid wall. The analysis is performed by employing DYNA2D, a non-linear, explicit, two-dimensional finite element (FE) code for impact mechanics. Deformations, time evolution of the contact force and contact force-displacement relationships during the impact are presented. Influences of material behaviour are discussed and their effect on the coefficient of restitution is also demonstrated.

A New Contact Force Model for Low Coefficient of Restitution Impact

2012 ◽  
Vol 79 (6) ◽  
Author(s):  
Mohamed Gharib ◽  
Yildirim Hurmuzlu
Keyword(s):  
Contact Force ◽  
Contact Stiffness ◽  
Coefficient Of Restitution ◽  
Force Model ◽  
Reference Case ◽  
Practical Applications ◽  
Contact Force Model ◽  
Post Impact ◽  
Impact Problems ◽  
The Impact

Impact problems arise in many practical applications. The need for obtaining an accurate model for the inelastic impact is a challenging problem. In general, two approaches are common in solving the impact problems: the impulse-momentum and the compliance based methods. The former approach included the coefficient of restitution which provides a mechanism to solve the problem explicitly. While the compliance methods are generally tailored to solve elastic problems, researchers in the field have proposed several mechanisms to include inelastic losses. In this paper, we present correlations between the coefficient of restitution in the impulse-momentum based method and the contact stiffness in the compliance methods. We conducted numerical analysis to show that the resulting solutions are indeed identical for a specific range of impact conditions. The impulse-momentum based model is considered as a reference case to compare the post impact velocities. The numerical results showed that, the impulse-momentum and the compliance based methods can produce similar outcomes for specific range of coefficient of restitution if they satisfied a set of end conditions. The correlations lead to introduce a new contact force model with hysteresis damping for low coefficient of restitution impact.

Validation of Nonlinear Viscoelastic Contact Force Models for Low Speed Impact

2009 ◽  
Vol 76 (5) ◽  
Author(s):  
Yuning Zhang ◽  
Inna Sharf
Keyword(s):  
Contact Force ◽  
Nonlinear Damping ◽  
Coefficient Of Restitution ◽  
Contact Dynamics ◽  
Dynamics Simulation ◽  
Damping Coefficient ◽  
Force Model ◽  
Nonlinear Viscoelastic ◽  
The Impact ◽  
Viscoelastic Contact

Compliant contact force modeling has become a popular approach for contact and impact dynamics simulation of multibody systems. In this area, the nonlinear viscoelastic contact force model developed by Hunt and Crossley (1975, “Coefficient of Restitution Interpreted as Damping in Vibroimpact,” ASME J. Appl. Mech., 42, pp. 440–445) over 2 decades ago has become a trademark with applications of the model ranging from intermittent dynamics of mechanisms to engagement dynamics of helicopter rotors and implementations in commercial multibody dynamics simulators. The distinguishing feature of this model is that it employs a nonlinear damping term to model the energy dissipation during contact, where the damping coefficient is related to the coefficient of restitution. Since its conception, the model prompted several investigations on how to evaluate the damping coefficient, in turn resulting in several variations on the original Hunt–Crossley model. In this paper, the authors aim to experimentally validate the Hunt–Crossley type of contact force models and furthermore to compare the experimental results to the model predictions obtained with different values of the damping coefficient. This paper reports our findings from the sphere to flat impact experiments, conducted for a range of initial impacting velocities using a pendulum test rig. The unique features of this investigation are that the impact forces are deduced from the acceleration measurements of the impacting body, and the experiments are conducted with specimens of different yield strengths. The experimental forces are compared with those predicted from the contact dynamics simulation of the experimental scenario. The experiments, in addition to generating novel impact measurements, provide a number of insights into both the study of impact and the impact response.

scholarly journals In vitro investigation of the impact of pulsatile blood flow on the vascular architecture of decellularized porcine kidneys

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Peter R. Corridon
Keyword(s):  
Blood Flow ◽  
Blood Perfusion ◽  
Pulsatile Blood Flow ◽  
Venous Outflow ◽  
Venous Flow ◽  
Vascular Architecture ◽  
Arterial Perfusion ◽  
In Vitro Investigation ◽  
The Impact

AbstractA method was established using a scaffold-bioreactor system to examine the impact pulsatile blood flow has on the decellularized porcine kidney vascular architecture and functionality. These scaffolds were subjected to continuous arterial perfusion of whole blood at normal physiological (650 ml/min and 500 ml/min) and pathophysiological (200 ml/min) rates to examine dynamic changes in venous outflow and micro-/macrovascular structure and patency. Scaffolds subjected to normal arterial perfusion rates observed drops in venous outflow over 24 h. These reductions rose from roughly 40% after 12 h to 60% after 24 h. There were no apparent signs of clotting at the renal artery, renal vein, and ureter. In comparison, venous flow rates decreased by 80% to 100% across the 24 h in acellular scaffolds hypoperfused at a rate of 200 ml/min. These kidneys also appeared intact on the surface after perfusion. However, they presented several arterial, venous, and ureteral clots. Fluoroscopic angiography confirmed substantial alterations to normal arterial branching patterns and patency, as well as parenchymal damage. Scanning electron microscopy revealed that pulsatile blood perfusion significantly disrupted glomerular microarchitecture. This study provides new insight into circumstances that limit scaffold viability and a simplified model to analyze conditions needed to prepare more durable scaffolds for long-term transplantation.

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