References for values of cohesive energy density

Hi Tapan,

I've used a little the linear cohesion model. For my experience, it is quite hard to find literature that give you an idea of energy density values. It is very dependent of many characteristics of your material and your simulation.
The cohesive force depends on the overlap area, so it is very dependent on the Young modulus you are using in your simulation. For lower Young modulus you have to use lower energy density, since a higher overlap is allowed for the particles. As you increase the Young modulus, in the same way, you have to increase your energy density to keep the same cohesive force, since a smaller overlap (repulsive force increases faster) is allowed for the particles. Particle size will also affect the value of the energy density (bigger particles, higher energy density) but not in the same proportion.
Also it is good to keep in mind the effect you are trying to model. The amount of liquid, for this cohesion model, may not say much about your system. Let's suppose you have a bucket of glass beds and a bucket of some ore. If you add the same amount of liquid in both, they are going to behave different. The glass beds will be cohesive with small amount of liquids, and after they loose their cohesive properties, but the ore will probably increase its cohesive properties with liquid up to a higher limit before loosing the cohesive properties. This makes a correlation between amount of liquid and cohesive properties a hard work.
I would highly recommend that you calibrate your model to correctly simulate the cohesive force. You could use a shear cell, some equipment were you could calculate the mass flow using dry and then wet material, or even do a repose angle test with dry and wet material. This could be a good starting point for you to understand how much this amount of liquid affect the cohesive properties of your material.
Trying to answer your question, unfortunately I don't know any literature to point you, but if you are thinking in calibrating your model, this might help: something like a Young modulus of 5E+06, Poisson's ratio 0.3, particle bed diameter 1mm and density 2500 kg/m3 you could use something like 50000-60000 (J/m^3) as a starting point, and see if your simulation has a behavior similar to your material. If you are using higher Young, let's say 5E+08, you could use something like 1.5-2M as a starting point. With that you can increase/decrease and adjust your model according to your material behavior. Hope that helps.

Best Regards,

Daniel

Great question! I have been meaning to dig into the physical meaning of the cohesive energy density. It took me a while to realise that J/m3 is dimensionally the same as N/m2, or Pa. I have also seen some papers talking about the equivalence of tensile strength and cohesion energy density, under certain circumstances, which makes some sense.

I would love to know if anyone knows if surface energy (i.e. a material property describing the adhesion energy, in J/m2) can be readily converted to cohesive energy density as used in LIGGGHTS?

Cheers, Mark