time_domain_analysis does not seem to work with point_masses

[RibeiroAndre]

Hi, Taylor. I'm trying to do my time domain analyses using point masses now instead of the inertia matrix, as the point masses improved my modal analyses (as per https://discourse.julialang.org/t/ann-gxbeam-jl-v0-3-0-geometrically-exact-beam-theory/71337/11). However, time time_domain_analysis doesn't seem to converge with point masses. Here's an example of a case that runs just fine without point masses, and does not converge with them:

using GXBeam, StaticArrays, LinearAlgebra
stiff = [1000000 0 0 -.5 -1 -50000; 0 3000000 0 0 0 0; 0 0 3000000 0 0 0; 0 0 0 7 .1 -.02; 0 0 0 0 5 .1; 0 0 0 0 0 3000]
stiff = Symmetric(stiff)
mass = [.02 0 0 0 -5e-7 -1e-7; 0 .02 0 5e-7 0 1e-4; 0 0 .02 1e-7 -1e-4 0; 0 0 0 1e-5 1e-8 2e-10; 0 0 0 0 6e-7 9e-9; 0 0 0 0 0 1e-5]
mass = Symmetric(mass)

nodes = [SA_F64[0,i,0] for i in 0:.1:1]

nElements = length(nodes)-1
start = 1:nElements
stop =  2:(nElements+1)
transformation = [[0 -1 0; 1 0 0; 0 0 1] for _ in 1:nElements];

stiffness = [stiff for i in 1:nElements]
massmatrix = [mass./0.1 for i in 1:nElements] # here I divide by the element length, which I don't do for the lumped mass

assembly = GXBeam.Assembly(nodes, start, stop, stiffness=stiffness, frames=transformation, mass=massmatrix);
prescribed_conditions = Dict(1 => GXBeam.PrescribedConditions(ux=0, uy=0, uz=0, theta_x=0, theta_y=0, theta_z=0),
                             length(nodes) => GXBeam.PrescribedConditions(Fz=30, My=-0.2));
t=0:.05:.05
system,history,converged = time_domain_analysis(assembly, t;
                                                prescribed_conditions = prescribed_conditions);

Here converged==true.

nodes = sort(vcat(nodes,nodes[2:end]))

nElements = length(nodes)-1
start = 1:nElements
stop =  2:(nElements+1)
transformation = [[0 -1 0; 1 0 0; 0 0 1] for _ in 1:nElements];

stiffness = [i%2==0 ? 0*stiff : stiff for i in 1:nElements]

pointmass = Dict(2 => PointMass(GXBeam.transform_properties(mass, transformation[2]')))
for i in 4:2:nElements
    pointmass[i] = PointMass(GXBeam.transform_properties(mass, transformation[i]'))
end
pointmass[nElements] = PointMass(GXBeam.transform_properties(mass, transformation[nElements]')./2) # last lumped mass is half of the others, as it represents the last half of an element

assembly = GXBeam.Assembly(nodes, start, stop, stiffness=stiffness, frames=transformation);
prescribed_conditions = Dict(1 => GXBeam.PrescribedConditions(ux=0, uy=0, uz=0, theta_x=0, theta_y=0, theta_z=0),
                             length(nodes) => GXBeam.PrescribedConditions(Fz=30, My=-0.2));
t=0:.05:.05
system,history,converged = time_domain_analysis(assembly, t;
                                                prescribed_conditions = prescribed_conditions,
                                                point_masses = pointmass);

Here converged==false.

Any help would be much appreciated!

[taylormcd]

It looks like the initial condition analysis doesn't converge. I'll have to look into that at some point. For now, you can just set initialize=false to skip the initialization.

[RibeiroAndre]

Thanks! As I'm doing FSI I'll need to wait for your next update, then, as I need to use initial conditions. Thanks again!