find_densification_limit: find_densification_limit

In tbgitoo/textureAnalyzerGels: Reading and analyzing texture analyzer data

find_densification_limit

Description

For porous (foam-like) materials, estimates the end of the plateau segment where the compression force starts to raise dramatically. In foams, this marks the end of pore space compression in favour of increasing wall material loading (Gibson&Ashby, 1997).

Usage

find_densification_limit(theData,touch_point,elastic_limit,gel_thickness=NULL)

Arguments

theData	Smoothened texture analyzer data, as produced by the smooth_texture_analyzer_data function; should contain only a one-way movement (down or up) for the chuck
touch_point	Point where the chuck touches the gel. This can be found from the Force - Distance diagram. where the force curve in a Force - Distance diagram raises abruptly
elastic_limit	Output of find_elastic_limit, which should be run before this function.
gel_thickness	If an estimation of the overall gel thickness is known, this is used to generate a better initial guess of the densification limit.

Details

The function uses both the slope and the actual stress (force per area, pressure) to find the initial touch point, hence the theData argument must have at least the columns Distance, pressure and pressureSlope. The estimation is based on the idea to find the point where the measured pressure starts to rise substantially above the expected plateau pressure. Quantitatively, this is judged by comparing measured pressure to extrapolated plateau pressure (linear extrapolation based on minimal slope), with the requirement that the excess pressure exceeds the actual plateau pressure value.

Value

Numerical value, indicating the position of the densification limit

Author(s)

Thomas Braschler

References

Gibson, L. J. & Ashby, M. F. Cellular Solids: Structure and properties. (Cambridge University Press, 1997).

See Also

smooth_texture_analyzer_data

Examples

data(sampleGelSmooth)
touch_point=find_initial_touch_point(sampleGelSmooth[sampleGelSmooth$direction=="down",])
elastic_limit = find_elastic_limit(sampleGelSmooth,touch_point)
densification_limit=find_densification_limit(sampleGelSmooth[sampleGelSmooth$direction=="down",],touch_point,elastic_limit)
plot(Force ~ Distance, sampleGelSmooth[sampleGelSmooth$direction=="down",]) 
lines(rep(touch_point,2),c(0,11),col="black")
lines(rep(elastic_limit,2),c(0,11),col="black")
lines(rep(densification_limit,2),c(0,11),col="red")
text(touch_point,11.5,labels="Touch point",adj=0.5)
text(elastic_limit,11.5,labels="Elastic limit",adj=0.5)
text(densification_limit,11.5,labels="Densification limit",adj=0.5,col="red")

tbgitoo/textureAnalyzerGels documentation built on March 30, 2022, 4:53 a.m.