Re: Shear Modulus Of Ldpe Pellets
Hi,
I thought I'd post a quick answer to your question. You seem to be trying to apply rheology (normally used for characterising liquids and semi-solids) for bulk solids.
Unfortunately this confusion happens a lot (perhaps not helped by the term "powder rheometer" in the marketplace).
If you are looking to measure interactions between bulk solids (in this case pellets) and the silo wall then you need to use a shear cell (either Jenike, Peschl, Schulze or others will be fine) you can then measure the friction properties of the bulk solid against a sample of the silo wall under various stresses and also look at the internal friction (i.e. friction between the bulk solid and itself) under various stresses. ■
Re: Shear Modulus Of Ldpe Pellets
Thank you for your answer. You are right about the shear modulus being a property of semi-solids.
However I also need to do a dynamic calculation in order to find the effect on the shell of the contained bulk solid.
This can be done according "Dynamics of solid-containing Tanks" by Veletsos, Younan and Bandyopadhyay.
They consider the silo to be filled with an equivalent visco-elastic solid, with a certain shear modulus. The question is how to find the equivalent shear modulus.
Please note that the shear wave velocity is also used in the basic physical model for earthquake engineering. In soil these wave travel with very high speeds of several 100 m/sec. However, I guess that this will be considerably smaller for pellets with a density of 600 kg/m stored in the silos of 1000 m.
Please correct me if I am wrong. ■
Sheer Modulus
Excuse my ignorance on this, but it was my understanding that shear modulus applies more to the structural component of the polymer and is determined measuring the deflection of the polymer when presure is applied to it.
Are you trying to determine what the wall thickness should be on a conical storage silo (hopper)? ■
Re: Shear Modulus Of Ldpe Pellets
Excuse my late reply to your question Ed, but I have been rather busy lately.
What I meant is the same shear modulus that is used in the calculation of the speed of shear waves in soil during earthquake.
What I am trying to figure out is the amount of horizontal force during earthquake that is transferred to the soil by intergranular friction rather than by shear in the silo wall.
The higher the shear modulus, the more force can be transferred by the product itself, thus reducing the required wall thickness of the silos. (Earthquake is the governing loadcase for these silos - Earthquake forces are about 8 times the wind load!!!)
For your info : We have to construct 30 x 790 m3 aluminium silos, so any reduction on wall thickness is welcome. ■
Shear Modulus Of Ldpe Pellets
Hello forum members
Can anybody tell me the value of the "Shear modulus" of LDPE Pellets, to be stored in a silo. I need this to determine the product-cylinderwall interaction.
I have a formula saying G = r x v where r is the density of the product in kg/m and v = the velocity of the shear wave through the product in m/sec.
The density is 600 kg/m, however I don't know the velocity of the shear wave.
Greetings
Stef R. ■