A Convex Tactile Sensor for Isotropic Tissue Elastic Modulus Estimation Based on the Plane Contact Model

2019 ◽  
Vol 19 (15) ◽  
pp. 6251-6259 ◽  
Author(s):  
Chenggang Li ◽  
Dengdeng Yan ◽  
Jingjin Shen
Keyword(s):  
Elastic Modulus ◽  
Tactile Sensor ◽  
Contact Model ◽  
Plane Contact

On the indentation contact area of a creeping solid during constant-strain-rate loading by a sharp indenter

2007 ◽  
Vol 22 (4) ◽  
pp. 893-899 ◽  
Author(s):  
Naoki Fujisawa ◽  
Michael V. Swain
Keyword(s):  
Elastic Modulus ◽  
Strain Rate ◽  
Contact Model ◽  
Indentation Hardness ◽  
Strain Rates ◽  
Analysis Method ◽  
Constant Loading ◽  
Perfectly Plastic ◽  
Rate Dependent ◽  
Elastic Perfectly Plastic

Poly(methyl methacrylate) was contacted by a Berkovich indenter at a range of constant loading strain rates. This particular loading scheme was used to maintain the strain-rate-dependent elastic modulus and indentation hardness of the creeping solid constant throughout loading. A loading curve analysis method identical to that of Malzbender and de With but based on the elastic-perfectly plastic contact model of Hochstetter et al. [Tribol. Int.36, 973–985, 2003] was used to process the load-displacement curves. Using the analysis method together with the strain-rate-dependent elastic modulus of the creeping solid known a priori, the strain-rate-dependent hardness could then be predicted. The predicted hardness versus strain-rate relationship was compared with that evaluated from the observed topographic images of the residual impressions due to heavier indentations at three constant loading strain rates. Based on this comparison, the elastic-perfectly plastic contact model was shown to be applicable to the creeping solid only when deformation takes place at a quasi-static strain rate.

Are elastic moduli of biological cells depth dependent or not? Another explanation using a contact mechanics model with surface tension

Soft Matter ◽  
2018 ◽  
Vol 14 (36) ◽  
pp. 7534-7541 ◽  
Author(s):  
Yue Ding ◽  
Jian Wang ◽  
Guang-Kui Xu ◽  
Gang-Feng Wang
Keyword(s):  
Surface Tension ◽  
Elastic Modulus ◽  
Contact Mechanics ◽  
Elastic Moduli ◽  
Contact Model ◽  
Biological Cells ◽  
Mechanics Model ◽  
Afm Indentation ◽  
A Cell ◽  
Indent Depth

Contrary to the existing reports that the apparent elastic modulus of a cell depends strongly on the indent depth in many AFM indentation experiments, we present a contact model with surface effects, and show that the actual elastic modulus of cell materials could be independent of the indent depth if surface tension is taken into account.

Monitoring the Cardiovascular Changes of a Rabbit Caused by Phenylephrine via a Microfluidic-Based Tactile Sensor

2019 ◽  
Author(s):  
Dan Wang ◽  
Frank A. Lattanzio ◽  
Mario C. Rodriguez ◽  
Zhili Hao
Keyword(s):  
Blood Pressure ◽  
Elastic Modulus ◽  
Pulse Signal ◽  
High Sensitivity ◽  
Tactile Sensor ◽  
Arterial Pulse ◽  
Record Blood Pressure ◽  
Baseline Values ◽  
Low Sensitivity ◽  
Model Based Analysis

Abstract In this work, a microfluidic-based tactile sensor was investigated for monitoring changes in the cardiovascular (CV) system of a rabbit caused by phenylephrine. The sensor was fixed on the front right leg of an anesthetized rabbit to measure the arterial pulse signal. Phenylephrine, as a vasoconstrictor, was used to introduce CV changes of the rabbit. Two sensors, one with high sensitivity and the other with low sensitivity, were tested on their suitability for measuring the pulse signals of the rabbit. The sensor with low sensitivity generated clear pulse signals and was further used to monitor the CV changes of the rabbit caused by phenylephrine. An automated sphygmomanometer and an ECG were used to record blood pressure and heart rate for comparison. Three low-dose injections of phenylephrine were sequentially performed on the rabbit. Through model-based analysis of the measured pulse signals, arterial elastic modulus, arterial radius and pulse wave velocity (PWV) were obtained. As compared with the baseline values measured before injection, injections of phenylephrine caused an increase in mean blood pressure (MAP) recorded by the medical instruments, and a decrease in arterial radius (increase in peripheral vascular resistance (PVR)) and an increase in arterial elastic modulus and PWV captured by the tactile sensor. Thus, the tactile sensor was proven to be feasible for monitoring the changes in the CV system caused by phenylephrine.

scholarly journals Rock physics model of glauconitic greensand from the North Sea

Geophysics ◽  
2011 ◽  
Vol 76 (6) ◽  
pp. E199-E209 ◽  
Author(s):  
Zakir Hossain ◽  
Tapan Mukerji ◽  
Jack Dvorkin ◽  
Ida L. Fabricius
Keyword(s):  
Elastic Modulus ◽  
Elastic Properties ◽  
North Sea ◽  
Rock Physics ◽  
Growth Patterns ◽  
Contact Model ◽  
Single Type ◽  
Initial Modulus ◽  
Physics Model ◽  
Rock Physics Model

The objective of this study was to establish a rock physics model of North Sea Paleogene greensand. The Hertz-Mindlin contact model is widely used to calculate elastic velocities of sandstone as well as to calculate the initial sand-pack modulus of the soft-sand, stiff-sand, and intermediate-stiff-sand models. When mixed minerals in rock are quite different, e.g., mixtures of quartz and glauconite in greensand, the Hertz-Mindlin contact model of single type of grain may not be enough to predict elastic velocity. Our approach is first to develop a Hertz-Mindlin contact model for a mixture of quartz and glauconite. Next, we use this Hertz-Mindlin contact model of two types of grains as the initial modulus for a soft-sand model and a stiff-sand model. By using these rock physics models, we examine the relationship between elastic modulus and porosity in laboratory and logging data and link rock-physics properties to greensand diagenesis. Calculated velocity for mixtures of quartz and glauconite from the Hertz-Mindlin contact model for two types of grains are higher than velocity calculated from the Hertz-Mindlin single mineral model using the effective mineral moduli predicted from the Hill’s average. Results of rock-physics modeling and thin-section observations indicate that variations in the elastic properties of greensand can be explained by two main diagenetic phases: silica cementation and berthierine cementation. These diagenetic phases dominate the elastic properties of greensand reservoir. Initially, greensand is a mixture of mainly quartz and glauconite; when weakly cemented, it has relatively low elastic modulus and can be modeled by a Hertz-Mindlin contact model of two types of grains. Silica-cemented greensand has a relatively high elastic modulus and can be modeled by an intermediate-stiff-sand or a stiff-sand model. Berthierine cement has different growth patterns in different parts of the greensand, resulting in a soft-sand model and an intermediate-stiff-sand model.

Microstructure simulation of early paper forming using immersed boundary methods

TAPPI Journal ◽  
2011 ◽  
Vol 11 (11) ◽  
pp. 23-30 ◽  
Author(s):  
ANDREAS MARK ◽  
ERIK SVENNING ◽  
ROBERT RUNDQVIST ◽  
FREDRIK EDELVIK ◽  
ERIK GLATT ◽  
...  
Keyword(s):  
Early Paper ◽  
Contact Model ◽  
Fiber Suspension ◽  
Beam Equation ◽  
Immersed Boundary ◽  
Paper Machine ◽  
Immersed Boundary Methods ◽  
Element Discretization ◽  
Microstructure Simulation ◽  
Boundary Methods

Paper forming is the first step in the paper machine where a fiber suspension leaves the headbox and flows through a forming fabric. Complex physical phenomena occur as the paper forms, during which fibers, fillers, fines, and chemicals added to the suspension interact. Understanding this process is important for the development of improved paper products because the configuration of the fibers during this step greatly influences the final paper quality. Because the effective paper properties depend on the microstructure of the fiber web, a continuum model is inadequate to explain the process and the properties of each fiber need to be accounted for in simulations. This study describes a new framework for microstructure simulation of early paper forming. The simulation framework includes a Navier-Stokes solver and immersed boundary methods to resolve the flow around the fibers. The fibers were modeled with a finite element discretization of the Euler-Bernoulli beam equation in a co-rotational formulation. The contact model is based on a penalty method and includes friction and elastic and inelastic collisions. We validated the fiber model and the contact model against demanding test cases from the literature, with excellent results. The fluid-structure interaction in the model was examined by simulating an elastic beam oscillating in a cross flow. We also simulated early paper formation to demonstrate the potential of the proposed framework.

Effect Of Elevated Temperatures On Complete Concrete Deformation Diagrams

2019 ◽  
pp. 9-14
Keyword(s):  
Experimental Data ◽  
Elastic Modulus ◽  
Elevated Temperatures ◽  
Peak Load ◽  
Relative Deformation ◽  
Deformation Characteristics ◽  
Compression Tests ◽  
Strain Behavior ◽  
Different Temperatures ◽  
Deformation Diagrams

The analysis of the previous results of the study on concrete stress-strain behavior at elevated temperatures has been carried out. Based on the analysis, the main reasons for strength retrogression and elastic modulus reduction of concrete have been identified. Despite a significant amount of research in this area, there is a large spread in experimental data received, both as a result of compression and tension. In addition, the deformation characteristics of concrete are insufficiently studied: the coefficient of transverse deformation, the limiting relative compression deformation corresponding to the peak load and the almost complete absence of studies of complete deformation diagrams at elevated temperatures. The two testing chambers provided creating the necessary temperature conditions for conducting studies under bending compression and tension have been developed. On the basis of the obtained experimental data of physical and mechanical characteristics of concrete at different temperatures under conditions of axial compression and tensile bending, conclusions about the nature of changes in strength and deformation characteristics have been drawn. Compression tests conducted following the method of concrete deformation complete curves provided obtaining diagrams not only at normal temperature, but also at elevated temperature. Based on the experimental results, dependences of changes in prism strength and elastic modulus as well as an equation for determining the relative deformation and stresses at elevated temperatures at all stages of concrete deterioration have been suggested.

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