NLSF Viscous Constitutive Law always returns force of zero
Using MBDyn buit from the git 'devel' branch, the NLSF Viscous Constitutive Law always returns a force of zero. Below is an example demonstrating the issue. This file is makes two spherical bodies of radius 0.1m and mass 1kg, clamps one, and connects the two by a deformable displacement joint, which uses the nlsf viscous constitutive law. I would expect to see a force from this joint when the second mass begins to move, but the force from the joint remains zero.
begin: data;
problem: initial value;
end: data;
# initial value problem
begin: initial value;
initial time: 0.0;
final time: 20.0;
time step: 0.100000000000000006;
tolerance: 0.000000001;
max iterations: 20;
end: initial value;
begin: control data;
structural nodes: 2;
rigid bodies: 2;
joints: 2;
gravity;
default orientation: orientation matrix;
output results: netcdf, no text;
end: control data;
begin: nodes;
# 6 DOF structural node
structural : 1, dynamic, # label, type
position, 0.0, 0.0, 0.0, # absolute position
orientation,
matr,
1.0, 0.0, 0.0,
0.0, 1.0, 0.0,
0.0, 0.0, 1.0, # absolute orientation
velocity, 0.0, 0.0, 0.0, # absolute velocity
angular velocity, 0.0, 0.0, 0.0 # absolute angular velocity
; # end structural node
# 6 DOF structural node
structural : 2, dynamic, # label, type
position, 0.0, 0.0, 0.0, # absolute position
orientation,
matr,
1.0, 0.0, 0.0,
0.0, 1.0, 0.0,
0.0, 0.0, 1.0, # absolute orientation
velocity, 0.0, 0.0, 0.0, # absolute velocity
angular velocity, 0.0, 0.0, 0.0 # absolute angular velocity
; # end structural node
end: nodes;
scalar function : "nlsf damping", const, 4.905000000000000249 ;
begin: elements;
# body
body : 3, 1, # label, node label
1.0, # mass
0.0, 0.0, 0.0, # relative centre of mass
matr,
0.004000000000000001, 0.0, 0.0,
0.0, 0.004000000000000001, 0.0,
0.0, 0.0, 0.004000000000000001 # inertia matrix
; # end one-mass body
# body
body : 4, 2, # label, node label
1.0, # mass
0.0, 0.0, 0.0, # relative centre of mass
matr,
0.004000000000000001, 0.0, 0.0,
0.0, 0.004000000000000001, 0.0,
0.0, 0.0, 0.004000000000000001 # inertia matrix
; # end one-mass body
# clamp
joint : 5, clamp,
1, # node label
position, node, # absolute position
orientation, node # absolute orientation
; # end clamp
# deformable displacement joint with name PTO_Damper
joint : 6, deformable displacement joint,
1, # node label
position, reference, node, null,
2, # node label
position, reference, other node, null,
nlsf viscous, null, null, null, "nlsf damping"
; # end deformable displacement joint
gravity : uniform, single, 0.0, 0.0, -1.0, const, 9.810000000000000497;
end: elements;