yade-dev team mailing list archive

["Sergei D." <sj2001@xxxxxxxxx>]

>
> Precisely, the effective mass (for a given contact) is not computed in
> SimpleViscoelasticRelationships. So cn can be larger than the critical
> value for this contact. You agree?
>From this equation

> m_eff * dn'' + cn * dn' + kn * dn = 0

we have tc and en:

(*) tc = pi 2 m_eff / sqrt( 4 kn m_eff - cn^2 )   (note your delta in
brackets)
en = exp( -cn tc / 2 / meff )

where we have kn and cn:

kn = m_eff / tc^2 * ( pi^2 + ln^2(en) )
cn = -2 * m_eff / tc * ln(en)

Then, for pair spheres with mass m1 we have
m1_eff = m1/2, en1, tc1 => kn1 and cn1.

For pair spheres with mass m2 we have
m2_eff = m2/2, en2, tc2 => kn2 and cn2.

For pair spheres with mass m1 and m2 we have
1) 1/m12_eff = 1/m1+1/m2, en12, tc12 => kn12, cn12,
OR we have
2) 1/kn12 = 1/kn1 + 1/kn2 and 1/cn12 = 1/cn1 + 1/cn2.

>From (*) cn^2 can't be more  than cn_crit^2 = (4 kn m_eff)...