Questions tagged [granulated-materials]
26 questions
12
votes
5 answers
Is there a definite boundary between a powder and a fluid?
Given a powder of solid substance what will happen if we make the granules smaller and smaller mechanically? Will this eventually make a liquid or gas from the powder?
Can there be gaseous substanse made not from single molecules but from…
Anixx
- 11,524
11
votes
1 answer
Why do random slabs stay dry in the rain?
The image below shows the slabbed area I can see from my work window
Whenever it rains some of the slabs stay dry however, it is never consistent which ones. Can anyone explain why this happens to satisfy my curiosity?
Kingsley-James
- 111
8
votes
3 answers
Why do good materials operate in non-equilibirium conditions?
If we look at the majority of useful or industrial materials surrounding us, like metallic alloys, glasses, ceramics, or plastics, it is often the case that these materials went through really hard times or difficult stages of their life during…
YoussefMabrouk
- 937
2
votes
2 answers
Computational modelling of sand pile
I'm currently working on a computational model of the way sand acts when being pushed around, say, by a bulldozer. Specifically, I'm trying to determine the dynamic equations which govern the way that sand will move under gravity from an arbitrary…
Tom
- 123
2
votes
1 answer
How does the structure factor reflect the characteristics of particle distribution?
The structure factor is defined as follows:
$$S(\mathbf k)=\frac{1}{N}\sum_i\sum_je^{-\mathbf k\cdot\mathbf r_{ij}\sqrt{-1}}$$
It is related to the radial distribution function by Fourier transform:
$$S(\mathbf k)=1+\rho\int[g(\mathbf…
fan duan
- 21
2
votes
1 answer
Is there a name for this phenomenon?
Imagine I have a cylindrical pipe closed on both ends with lids. I fill it with sand and compress the sand tightly. Now I hold the cylinder vertically and remove the bottom lid. The sand will counter intuitively not fall off apart from a few loose…
yathish
- 427
2
votes
2 answers
Definition of granular material
I am doing a project on some properties of granular materials. I might have to face people who ask the definition of granular material. How can we define granular materials? One answer is "it is sand-like materials," which is true but not enough.…
fahd
- 438
2
votes
2 answers
Are there materials that strongly (macroscopically) vibrate under light of certain frequencies? If so why?
Picture an imperfect plane of loose particulate matter like sand or silt. Are there materials where if I shine light (not isotropically) on the plane I could get the particles to vibrate with large enough magnitudes that you could move (at least in…
Skyler
- 1,989
2
votes
1 answer
Suffocation in a granular medium
I read of a recent accident in Alberta in which three girls fell into an open bed truck carrying canola seeds and suffocated.
In that situation would it have been possible to keep breathing by using a shirt as a filter to breath through, keeping the…
Ambrose Swasey
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2
votes
1 answer
formula for the angle of repose
If we make piles of sand or of sugar, they form cones; the maximum slope of the cones depends on the material. Is there a formula which gives this slope (or the angle of the cone), given some quantities such as density, dimensions of the grains,…
Michele O.
- 141
1
vote
0 answers
Calculating Pore Size from Permeability
I am building an experiment where one has a bed of sand on top of a porous plate. The pores allow air to be blown through the plate from the bottom but the pores must be sufficiently fine to not allow sand to fall back through.
The sand grains will…
Tom
- 1,447
1
vote
1 answer
What determines if a transgranular or intergranular fracture is more likely to occur?
As an example, why does glass tend to break by means of intergranular fracture?
My analysis so far led me to believe that the tendency can be related to the intermolecular bond strength in a given crystal grain and the intergranular bond strength. A…
hendlim
- 856
1
vote
1 answer
How do sand balls retain their integrity for so long?
A friend showed me how to make sand balls at the beach, like shown here on this YouTube video.
We were both wondering how they managed to keep their shape way longer than any other sandcastle bits. I’m thinking this has to do with water tension…
U0001
- 111
1
vote
1 answer
Using abrasive lapping, is it possible to make a perfectly round cylinder starting with imperfect cylinder(s)?
Centerless cylindrical lapping is a technique used to create a smooth and round cylinder through the use of microscopic abrasive compounds.
My question is a chicken and egg problem, because it seems to me that one would require perfectly round and…
user391339
- 609
1
vote
1 answer
When pressing coffee, why does boiling water and coffee mixture appear to decrease after grounds are pressed to bottom?
When pressing coffee, why does total volume of boiling water and coffee appear to decrease after grounds are pressed to bottom?
Cecil Cole
- 11
- 1