added comments

Author: RaulDurand

src/mech/mat/willam-warnke.jl

@@ -40,8 +40,8 @@ mutable struct WillamWarnke<:Material
         e  = (fc*fb - fc*ft + 3*fb*ft)/(2*fc*fb + ft*fc)
         @assert 0<e<=1
 
-        ξ0 = √3*fb*ft/(fb-ft)
-        ρ0 = √2*fc*ξ0/(fc + √3*ξ0)
+        ξ0 = √3*fb*ft/(fb-ft) # ok
+        ρ0 = √2*fc*ξ0/(fc + √3*ξ0) # ok
         α = ρ0/ξ0
 
         ψ = args.psi
@@ -100,6 +100,7 @@ end
     end
 end
 
+
 @inline function calc_deriv_ξmax_εpa(mat::WillamWarnke, εpa::Float64)
     if mat.ξfun !== nothing
         dξdεpa = derive(mat.ξfun, εpa)
@@ -271,6 +272,7 @@ function calc_σ_εpa_Δλ(mat::WillamWarnke, state::WillamWarnkeState, σtr::Ve
 
 end
 
+
 function calc_σ_εpa_Δλ_bis(mat::WillamWarnke, state::WillamWarnkeState, σtr::Vec6)
     α  = mat.α
     ᾱ  = mat.ᾱ