scholarly journals Axisymmetric Contact Problem for a Flattened Cell: Contributions of Substrate Effect and Cell Thickness to the Determination of Viscoelastic Properties by Using AFM Indentation

Scanning ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-11
Author(s):  
Xinyao Zhu ◽  
Lanjiao Liu ◽  
Zuobin Wang ◽  
X. Liu
Keyword(s):  
Mechanical Properties ◽  
Linear Elasticity ◽  
Viscoelastic Properties ◽  
Present Model ◽  
Finite Thickness ◽  
Contact Model ◽  
Substrate Effect ◽  
Biological Cells ◽  
Hertz Contact ◽  
Hertz Contact Model

Nanoindentation technology has proven to be an effective method to investigate the viscoelastic properties of biological cells. The experimental data obtained by nanoindentation are frequently interpreted by Hertz contact model. However, in order to validate Hertz contact model, some studies assume that cells have infinite thickness which does not necessarily represent the real situation. In this study, a rigorous contact model based upon linear elasticity is developed for the interpretation of indentation tests of flattened cells. The cell, normally bonded to the Petri dish, is initially treated as an elastic layer of finite thickness perfectly fixed to a rigid substrate. The theory of linear elasticity is utilized to solve this contact issue and then the solutions are extended to viscoelastic situation which is regarded as a good indicator for mechanical properties of biological cells. To test the present model, AFM-based creep test has been conducted on living human hepatocellular carcinoma cell (SMMC-7721 cell) and its fullerenol-treated counterpart. The results indicate that the present model could not only describe very well the creep behavior of SMMC-7721 cells, but also curb overestimation of the mechanical properties due to substrate effect.

Modified Analytical Expression of Damping Constant in the Hertz Contact Model with Non-Linear Damping for Structural Pounding

2010 ◽  
Vol 29-32 ◽  
pp. 220-225 ◽  
Author(s):  
Kun Ye ◽  
Rong Fu ◽  
Sha Qi Ma
Keyword(s):  
Impact Force ◽  
Analytical Formula ◽  
Nonlinear Damping ◽  
Coefficient Of Restitution ◽  
Contact Model ◽  
Spring Stiffness ◽  
Hertz Contact ◽  
Structural Pounding ◽  
Linear Damping ◽  
Hertz Contact Model

Structural pounding under earthquakes has been recently extensively investigated by using different models of impact force. In this paper, reexamination into the Hertz contact model with nonlinear damping is made. Based upon this reexamination, the formula used to determine the damping constant in terms of the spring stiffness, the coefficient of restitution and relative approaching velocity of two colliding bodies is found to be wrong. In order to correct this error, a more accurate approximating formula for the damping constant is theoretically derived. The correctness of the derived analytical formula has been confirmed through numerical simulations.

Dynamic Interaction of Vehicle and Discontinuous Slab Track Considering Nonlinear Hertz Contact Model

2016 ◽  
Vol 142 (4) ◽  
pp. 04016011 ◽  
Author(s):  
Javad Sadeghi ◽  
Amin Khajehdezfuly ◽  
Morteza Esmaeili ◽  
Davood Poorveis
Keyword(s):  
Dynamic Interaction ◽  
Contact Model ◽  
Hertz Contact ◽  
Slab Track ◽  
Hertz Contact Model

scholarly journals A cell-based mechanical model of coronary artery tunica media

2017 ◽  
Vol 14 (132) ◽  
pp. 20170028 ◽  
Author(s):  
N. B. Melnikova ◽  
A. I. Svitenkov ◽  
D. R. Hose ◽  
A. G. Hoekstra
Keyword(s):  
Coronary Artery ◽  
Mechanical Model ◽  
Adhesive Contact ◽  
Contact Model ◽  
Chain Model ◽  
Hertz Contact ◽  
Wormlike Chain ◽  
Tunica Media ◽  
Hertz Contact Model

A three-dimensional cell-based mechanical model of coronary artery tunica media is proposed. The model is composed of spherical cells forming a hexagonal close-packed lattice. Tissue anisotropy is taken into account by varying interaction forces with the direction of intercellular connection. Several cell-centre interaction potentials for repulsion and attraction are considered, including the Hertz contact model and its neo-Hookean extension, the Johnson–Kendall–Roberts model of adhesive contact, and a wormlike chain model. The model is validated against data from in vitro uni-axial tension tests performed on dissected strips of tunica media. The wormlike chain potential in combination with the neo-Hookean Hertz contact model produces stress–stretch curves which represent the experimental data very well.

ANALYSIS OF HIGH-SPEED RAIL ACCOUNTING FOR JUMPING WHEEL PHENOMENON

2014 ◽  
Vol 11 (03) ◽  
pp. 1343007 ◽  
Author(s):  
KOK KENG ANG ◽  
JIAN DAI ◽  
MINH THI TRAN ◽  
VAN HAI LUONG
Keyword(s):  
High Speed ◽  
Computational Study ◽  
Dynamic Responses ◽  
Contact Model ◽  
High Speed Train ◽  
Train Track ◽  
Hertz Contact ◽  
High Speed Rail ◽  
Track System ◽  
Hertz Contact Model

In this paper, a computational study using the moving element method (MEM) was carried out to investigate the dynamic response of a high-speed train–track system. Results obtained using Hertz contact model and linearized Hertz contact model are compared and discussed. The dynamic responses of a train travelling across a uniform foundation and a transition region are also investigated. Parametric study is performed to understand the effect of various factors on the occurrence and patterns of the jumping wheel phenomenon such as the variation of foundation stiffness, travelling speed of the train and the severity of railhead roughness.

Parameter design methodologies for vertical skewed line gears taking lubrication performance into account

2019 ◽  
Vol 233 (10) ◽  
pp. 1496-1507
Author(s):  
Yangzhi Chen ◽  
Anshi Zhu ◽  
Yueling Lyu
Keyword(s):  
Simulation Experiment ◽  
Design Method ◽  
Elastohydrodynamic Lubrication ◽  
Contact Model ◽  
Parameter Design ◽  
Design Parameters ◽  
Hertz Contact ◽  
Design Methodologies ◽  
Lubrication Performance ◽  
Hertz Contact Model

Based on the elastohydrodynamic lubrication (EHL) theory, design methodologies are proposed aiming to improve the EHL state of the vertical skewed line gear (VSLG) in this article. First of all, the parametric equations of the driving and driven VSLG surfaces are established and then converted into equivalent Hertz contact model. Then, the influences of the design parameters of the VSLG on the ellipticity are analyzed by its equivalent Hertz contact model. Finally, the parameter design method for improving the EHL state of VSLG is deduced. The results of optical elastohydrodynamic experiment and simulation experiment indicate that the parameter design method is effective for the formation of EHL film without changing the kinematic characteristics of VSLG. In short, this paper provides reliable and convenient parameter design methods for VSLG in consideration of EHL.

Microindentation Test for Assessing the Mechanical Properties of Silicone Rubber Exposed to a Simulated Polymer Electrolyte Membrane Fuel Cell Environment

2009 ◽  
Vol 6 (4) ◽  
Author(s):  
Jinzhu Tan ◽  
Y. J. Chao ◽  
Xiaodong Li ◽  
J. W. Van Zee
Keyword(s):  
Mechanical Properties ◽  
Fuel Cell ◽  
Polymer Electrolyte Membrane ◽  
Compressive Load ◽  
Pem Fuel Cells ◽  
Mechanical Degradation ◽  
Hertz Contact ◽  
Electrolyte Membrane ◽  
Elastomeric Materials ◽  
Hertz Contact Model

The elastomeric materials used as seals and gaskets in polymer electrolyte membrane (PEM) fuel cells are exposed to acidic environment, humid air, and hydrogen, and subjected to mechanical compressive load. The long-term mechanical and chemical stability of these materials is critical to both sealing and the electrochemical performance of the fuel cell. In this paper, mechanical degradation of two elastomeric materials, Silicone S and Silicone G, which are potential gasket materials for PEM fuel cells, was investigated. Test samples were subjected to various compressive loads to simulate the actual loading in addition to soaking in a simulated PEM fuel cell environment. Two temperatures, 80°C and 60°C, were selected and used in this study. Mechanical properties of the samples before and after exposure to the environment were studied by microindentation. Indentation load, elastic modulus, and hardness were obtained from the loading and unloading curves. Indentation deformation was studied using Hertz contact model. Dynamic mechanical analysis was conducted to verify the elastic modulus obtained by Hertz contact model. It was found that the mechanical properties of the samples changed considerably after exposure to the simulated environment over time. The temperature and the applied compressive load play a significant role in the mechanical degradation. The microindentation method is proved to provide a simple and efficient way to evaluate the mechanical properties of gasket materials.

scholarly journals Age-dependent and radial sectional differences in the dynamic viscoelastic properties of bamboo culms and their possible relationship with the lignin structures

2020 ◽  
Vol 66 (1) ◽  
Author(s):  
Yoko Okahisa ◽  
Keisuke Kojiro ◽  
Hatsuki Ashiya ◽  
Takeru Tomita ◽  
Yuzo Furuta ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Viscoelastic Properties ◽  
Structural Variation ◽  
Thermal Softening ◽  
Peak Temperature ◽  
Outer Side ◽  
Phyllostachys Pubescens ◽  
Age Dependence ◽  
Age Dependent ◽  
S Peak

Abstract Age is an important factor that dictates bamboo’s mechanical properties. In Japan, bamboo plants aged 3–5 years are selected for use as materials because of their robustness and decorative or craft-friendly characteristics. In this study, the age-dependent and radial sectional differences in bamboo’s dynamic viscoelastic properties in relation to lignin structural variation, were evaluated. We used Phyllostachys pubescens samples at the current year and at 1.5, 3.5, 6.5, 9.5, 12.5, and 15.5 years of age. There was a clear age dependence in the peak temperature of tan δ and in the yield of thioacidolysis products derived from β-O-4 lignin structures. The highest peak temperature tan δ value was detected in 3.5-year-old bamboo, which contained the highest amount of the thioacidolysis products. Moreover, tan δ’s peak temperature was always higher on the outer side, and the ratio of S/G thioacidolysis products was always higher on the inner side of bamboo plants of all ages. These results suggest that changes in bamboo’s thermal softening properties from aging are caused by the maturation and degradation of lignin in bamboo.

Sign in / Sign up

Export Citation Format

Share Document