You can view and download this file on Github: netgenSTLtest.py
#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
# This is an EXUDYN example
#
# Details: Example to import .stl mesh, mesh with Netgen, create FEM model,
# reduced order CMS and simulate under gravity
#
# Author: Johannes Gerstmayr
# Date: 2023-04-21
#
# 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.
#
#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
import exudyn as exu
from exudyn.itemInterface import *
from exudyn.utilities import * #includes itemInterface and rigidBodyUtilities
import exudyn.graphics as graphics #only import if it does not conflict
from exudyn.FEM import *
from exudyn.graphicsDataUtilities import *
SC = exu.SystemContainer()
mbs = SC.AddSystem()
import numpy as np
import time
#%%+++++++++++++++++++++++++++++++++++++++++++++++++++++
#netgen/meshing part:
fem = FEMinterface()
nModes = 16
#steel:
rho = 7850
nu=0.3
Emodulus=1e8#use some very soft material to visualize deformations
#%%+++++++++++++++++++++++++++++++++++++++++++++++++++++
if True: #needs netgen/ngsolve to be installed to compute mesh, see e.g.: https://github.com/NGSolve/ngsolve/releases
import sys
import ngsolve as ngs
import netgen
from netgen.meshing import *
print('load stl file...')
import netgen.stl as nstl
#load STL file; needs to be closed (no holes) and consistent!
# and may not have defects (may require some processing of STL files!)
geom = nstl.STLGeometry('testData/gyro.stl') #Peter's gyro
maxh=0.01
mesh = ngs.Mesh( geom.GenerateMesh(maxh=maxh))
# mesh.Curve(1) #don't do that!
#set True to see mesh in netgen tool:
if False: #set this to true, if you want to visualize the mesh inside netgen/ngsolve
# import netgen
import netgen.gui
ngs.Draw(mesh)
for i in range(10000000):
netgen.Redraw() #this makes the netgen window interactive
time.sleep(0.05)
# sys.exit()
#%%+++++++++++++++++++++++++++++++++++++++++++++++++++++
#Use fem to import FEM model and create FFRFreducedOrder object
[bfM, bfK, fes] = fem.ImportMeshFromNGsolve(mesh, density=rho, youngsModulus=Emodulus,
poissonsRatio=nu, meshOrder=1)
#%%+++++++++++++++++++++++++++++++++++++++++++++++++++++
#compute Hurty-Craig-Bampton modes
if True: #now import mesh as mechanical model to EXUDYN
print("nNodes=",fem.NumberOfNodes())
cyl=np.array([0,0,0])
rCyl = 0.011/2
nodesOnCyl = fem.GetNodesOnCylinder(cyl-[0,0.01,0], cyl+[0,0.01,0], radius=rCyl, tolerance=0.001)
# #print("boundary nodes bolt=", nodesOnBolt)
nodesOnCylWeights = fem.GetNodeWeightsFromSurfaceAreas(nodesOnCyl)
pMid = fem.GetNodePositionsMean(nodesOnCyl)
print('cyl midpoint=', pMid)
#boundaryList = [nodesOnBolt, nodesOnBolt, nodesOnBushing] #for visualization, use first interface twice
boundaryList = [nodesOnCyl]
print("compute HCB modes... (may take some seconds)")
fem.ComputeHurtyCraigBamptonModes(boundaryNodesList=boundaryList,
nEigenModes=nModes,
useSparseSolver=True,
computationMode = HCBstaticModeSelection.RBE2)
print("eigen freq.=", fem.GetEigenFrequenciesHz())
#draw cylinder to see geometry of hole
# gGround = [graphics.Cylinder([0,0,0],[0,0.02,0], radius=0.011/2, color=graphics.color.dodgerblue, nTiles=128)]
# oGround = mbs.AddObject(ObjectGround(referencePosition= [0,0,0], visualization=VObjectGround(graphicsData=gGround)))
#%%+++++++++++++++++++++++++++++++++++++++++++++++++++++
#compute stress modes for postprocessing (inaccurate for coarse meshes, just for visualization):
if True:
mat = KirchhoffMaterial(Emodulus, nu, rho)
varType = exu.OutputVariableType.StressLocal
print("ComputePostProcessingModes ... (may take a while)")
start_time = time.time()
fem.ComputePostProcessingModesNGsolve(fes, material=mat,
outputVariableType=varType)
SC.visualizationSettings.contour.reduceRange=False
SC.visualizationSettings.contour.outputVariable = varType
SC.visualizationSettings.contour.outputVariableComponent = -1 #norm
else:
varType = exu.OutputVariableType.DisplacementLocal
SC.visualizationSettings.contour.outputVariable = exu.OutputVariableType.DisplacementLocal
SC.visualizationSettings.contour.outputVariableComponent = 0
#%%+++++++++++++++++++++++++++++++++++++++++++++++++++++
print("create CMS element ...")
cms = ObjectFFRFreducedOrderInterface(fem)
objFFRF = cms.AddObjectFFRFreducedOrder(mbs, positionRef=[0,0,0],
initialVelocity=[0,0,0],
initialAngularVelocity=[0,0,0],
color=[0.9,0.9,0.9,1.],
gravity=[0,0,-9.81]
)
#%%+++++++++++++++++++++++++++++++++++++++++++++++++++++
#add markers and joints
nodeDrawSize = 0.0005 #for joint drawing
#add constraint for cylinder
if True:
oGround = mbs.AddObject(ObjectGround(referencePosition= [0,0,0]))
altApproach = True
mCyl = mbs.AddMarker(MarkerSuperElementRigid(bodyNumber=objFFRF['oFFRFreducedOrder'],
meshNodeNumbers=np.array(nodesOnCyl), #these are the meshNodeNumbers
weightingFactors=nodesOnCylWeights))
#due to meshing effects and weighting, the center point is not exactly at [0,1.5,0] as intended ...
pm0 = mbs.GetMarkerOutput(mCyl, exu.OutputVariableType.Position,exu.ConfigurationType.Reference)
print('marker0 ref pos=', pm0)
mGroundCyl = mbs.AddMarker(MarkerBodyRigid(bodyNumber=oGround,
localPosition=pm0,
visualization=VMarkerBodyRigid(show=True)))
mbs.AddObject(GenericJoint(markerNumbers=[mGroundCyl, mCyl],
constrainedAxes = [1]*6,
visualization=VGenericJoint(show=False, axesRadius=0.01, axesLength=0.01)))
if False: #activate to animate modes
from exudyn.interactive import AnimateModes
mbs.Assemble()
SC.visualizationSettings.nodes.show = False
SC.visualizationSettings.openGL.showFaceEdges = True
SC.visualizationSettings.openGL.multiSampling=4
SC.visualizationSettings.openGL.lineWidth=2
SC.visualizationSettings.window.renderWindowSize = [1600,1080]
SC.visualizationSettings.contour.showColorBar = False
SC.visualizationSettings.general.textSize = 16
#%%+++++++++++++++++++++++++++++++++++++++
#animate modes of ObjectFFRFreducedOrder (only needs generic node containing modal coordinates)
SC.visualizationSettings.general.autoFitScene = False #otherwise, model may be difficult to be moved
nodeNumber = objFFRF['nGenericODE2'] #this is the node with the generalized coordinates
AnimateModes(SC, mbs, nodeNumber, period=0.1, showTime=False, renderWindowText='Hurty-Craig-Bampton: 2 x 6 static modes and 8 eigenmodes\n',
runOnStart=True)
# import sys
# sys.exit()
#%%+++++++++++++++++++++++++++++++++++++++++++++++++++++
#animate modes
SC.visualizationSettings.markers.show = True
SC.visualizationSettings.markers.defaultSize=nodeDrawSize
SC.visualizationSettings.markers.drawSimplified = False
SC.visualizationSettings.loads.show = False
SC.visualizationSettings.openGL.multiSampling=4
SC.visualizationSettings.openGL.lineWidth=2
mbs.Assemble()
simulationSettings = exu.SimulationSettings()
SC.visualizationSettings.nodes.defaultSize = nodeDrawSize
SC.visualizationSettings.nodes.drawNodesAsPoint = False
SC.visualizationSettings.connectors.defaultSize = 2*nodeDrawSize
SC.visualizationSettings.nodes.show = False
SC.visualizationSettings.nodes.showBasis = True #of rigid body node of reference frame
SC.visualizationSettings.nodes.basisSize = 0.12
SC.visualizationSettings.bodies.deformationScaleFactor = 100 #use this factor to scale the deformation of modes
SC.visualizationSettings.openGL.showFaceEdges = True
SC.visualizationSettings.openGL.showFaces = True
SC.visualizationSettings.sensors.show = True
SC.visualizationSettings.sensors.drawSimplified = False
SC.visualizationSettings.sensors.defaultSize = 0.01
h=2e-5 #make small to see some oscillations
tEnd = 0.5
simulationSettings.timeIntegration.numberOfSteps = int(tEnd/h)
simulationSettings.timeIntegration.endTime = tEnd
simulationSettings.solutionSettings.writeSolutionToFile = False
simulationSettings.timeIntegration.verboseMode = 1
simulationSettings.timeIntegration.simulateInRealtime = True
simulationSettings.timeIntegration.realtimeFactor = 0.01
simulationSettings.timeIntegration.newton.useModifiedNewton = True
simulationSettings.solutionSettings.sensorsWritePeriod = h
simulationSettings.timeIntegration.generalizedAlpha.spectralRadius = 0.8
#simulationSettings.displayStatistics = True
simulationSettings.displayComputationTime = True
SC.visualizationSettings.window.renderWindowSize=[1920,1080]
SC.visualizationSettings.openGL.multiSampling = 4
SC.visualizationSettings.general.autoFitScene=False
exu.StartRenderer()
if 'renderState' in exu.sys: SC.SetRenderState(exu.sys['renderState']) #load last model view
mbs.WaitForUserToContinue() #press space to continue
mbs.SolveDynamic(simulationSettings=simulationSettings)
if varType == exu.OutputVariableType.StressLocal:
mises = CMSObjectComputeNorm(mbs, 0, exu.OutputVariableType.StressLocal, 'Mises')
print('max von-Mises stress=',mises)
SC.WaitForRenderEngineStopFlag()
exu.StopRenderer() #safely close rendering window!
# mbs.PlotSensor(sensorNumbers=[sensBushingVel], components=[1])