ANCFcable2DuserFunction.py
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1#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
2# This is an EXUDYN example
3#
4# Details: Test model for ANCFCable2D test user functions
5#
6# Author: Johannes Gerstmayr
7# Date: 2023-12-13
8#
9# Copyright:This file is part of Exudyn. Exudyn is free software. You can redistribute it and/or modify it under the terms of the Exudyn license. See 'LICENSE.txt' for more details.
10#
11#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
12
13
14import exudyn as exu
15from exudyn.utilities import *
16
17import numpy as np
18
19useGraphics = True #without test
20#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
21#you can erase the following lines and all exudynTestGlobals related operations if this is not intended to be used as TestModel:
22try: #only if called from test suite
23 from modelUnitTests import exudynTestGlobals #for globally storing test results
24 useGraphics = exudynTestGlobals.useGraphics
25except:
26 class ExudynTestGlobals:
27 pass
28 exudynTestGlobals = ExudynTestGlobals()
29#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
30
31from exudyn.beams import *
32from math import atan
33
34#create an environment for mini example
35SC = exu.SystemContainer()
36mbs = SC.AddSystem()
37
38oGround=mbs.AddObject(ObjectGround(referencePosition= [0,0,0]))
39nGround = mbs.AddNode(NodePointGround(referenceCoordinates=[0,0,0]))
40
41rhoA = 78.
42EA = 100000.
43EI = 2000
44
45#example of bending moment user function
46#limit bending moment with atan function
47def bendingMomentUserFunction(mbs, t, itemNumber, axialPositionNormalized, curvature, curvature_t, curvatureRef, physicsBendingStiffness, physicsBendingDamping,
48 axialStrain, axialStrain_t, axialStrainRef):
49 #m = physicsBendingStiffness*(curvature-curvatureRef) + physicsBendingDamping*curvature_t #this is the linear, conventional case
50 kappa=(curvature-curvatureRef)
51 kappa = 0.1*atan(10*kappa) #nonlinear behavior, somehow like elasto-plastic
52 return physicsBendingStiffness*(kappa) + physicsBendingDamping*curvature_t
53
54#example of axial force user function
55#reduce stiffness over time
56def axialForceUserFunction(mbs, t, itemNumber, axialPositionNormalized, axialStrain, axialStrain_t, axialStrainRef, physicsAxialStiffness, physicsAxialDamping,
57 curvature, curvature_t, curvatureRef):
58 fact = max(0.02,(2-t**0.5)) #make axial stiffness it softer over time
59 return fact*physicsAxialStiffness*(axialStrain-axialStrainRef) + physicsAxialDamping*axialStrain_t
60
61#create ANCF cable object:
62cable = ObjectANCFCable2D(physicsMassPerLength=rhoA,
63 physicsBendingStiffness=EI,
64 physicsBendingDamping = EI*0.1,
65 physicsAxialStiffness=EA,
66 physicsAxialDamping=EA*0.05,
67 bendingMomentUserFunction=bendingMomentUserFunction,
68 axialForceUserFunction=axialForceUserFunction,
69 )
70
71#create several cable elements
72ancf=GenerateStraightLineANCFCable(mbs=mbs,
73 positionOfNode0=[0,0,0], positionOfNode1=[2,0,0],
74 numberOfElements=16, #converged to 4 digits
75 cableTemplate=cable, #this defines the beam element properties
76 massProportionalLoad = [0,-9.81,0],
77 fixedConstraintsNode0 = [1,1, 0,1],
78 )
79
80#assemble and solve system for default parameters
81mbs.Assemble()
82
83endTime = 0.5
84stepSize = 5e-3
85
86simulationSettings = exu.SimulationSettings()
87
88simulationSettings.solutionSettings.writeSolutionToFile = False
89simulationSettings.timeIntegration.verboseMode = 1 #turn off, because of lots of output
90simulationSettings.linearSolverType = exu.LinearSolverType.EigenSparse
91# simulationSettings.displayComputationTime = True
92# simulationSettings.displayStatistics = True
93
94simulationSettings.timeIntegration.numberOfSteps = int(endTime/stepSize)
95simulationSettings.timeIntegration.endTime = endTime
96simulationSettings.timeIntegration.newton.useModifiedNewton = True
97
98SC.visualizationSettings.window.renderWindowSize=[1200,1024]
99#+++++++++++++++++++++++++++++++++++++++++++++++++++++++
100
101
102if useGraphics:
103 exu.StartRenderer() #start graphics visualization
104 mbs.WaitForUserToContinue() #wait for pressing SPACE bar to continue
105
106mbs.SolveDynamic(simulationSettings)
107
108if useGraphics:
109 SC.WaitForRenderEngineStopFlag()#wait for pressing 'Q' to quit
110 exu.StopRenderer() #safely close rendering window!
111
112#evaluate final (=current) output values
113node = ancf[0][-1]
114p = mbs.GetNodeOutput(node, exu.OutputVariableType.Position)
115exu.Print('ANCFcable2DuserFunction test tip pos=',p)
116
117u=sum(p)
118exu.Print('solution of ANCFcable2DuserFunction test =',u)
119
120exudynTestGlobals.testError = u - (0.6015588367721232)
121exudynTestGlobals.testResult = u