Box profile¶
A box profile for studying buckling of thin shells.
Recording of the process with furhter explanations in the video Box profile.
In [ ]:
from abaqus import *
from abaqusConstants import *
def boxpro(modelname, L, b, h, t, esize, loadcase, value):
'''
loadcase=1: Cantilever beam subjected to tip load, flapwise
laodcase=2: Flapwise rotation imposed at x=L
loadcase=3: Cantilever beam subjected to tip load edgewise
loadcase=4: Edgewise rotation imposed at x=L
loadcase=5: Freely supported beam subjected to a center load, flapwise
'''
mod = mdb.Model(name=modelname, modelType=STANDARD_EXPLICIT)
# Part
ske = mod.ConstrainedSketch(name='__profile__', sheetSize=200.0)
ske.rectangle(point1=(-b/2.0, -h/2.0), point2=(b/2.0, h/2.0))
prt = mod.Part(name='Box', dimensionality=THREE_D, type=DEFORMABLE_BODY)
prt.BaseShellExtrude(sketch=ske, depth=L)
del mod.sketches['__profile__']
# Partition
id = prt.DatumPlaneByPrincipalPlane(principalPlane=XYPLANE, offset=L/2.0).id
prt.PartitionFaceByDatumPlane(datumPlane=prt.datums[id], faces=prt.faces)
# Material and section
mat = mod.Material(name='Alu')
mat.Elastic(table=((70000.0, 0.33), ))
mod.HomogeneousShellSection(name='Section-shell',
preIntegrate=OFF, material='Alu', thicknessType=UNIFORM, thickness=t,
thicknessField='', nodalThicknessField='',
idealization=NO_IDEALIZATION, poissonDefinition=DEFAULT,
thicknessModulus=None, temperature=GRADIENT, useDensity=OFF,
integrationRule=SIMPSON, numIntPts=5)
region = prt.Set(faces=prt.faces, name='faces-all')
prt.SectionAssignment(region=region, sectionName='Section-shell', offset=0.0,
offsetType=MIDDLE_SURFACE, offsetField='', thicknessAssignment=FROM_SECTION)
# Mesh
prt.setMeshControls(regions=prt.faces, elemShape=QUAD, technique=STRUCTURED)
prt.seedPart(size=esize, deviationFactor=0.1, minSizeFactor=0.1)
prt.generateMesh()
# Assembly and constraints
ass = mod.rootAssembly
ass.DatumCsysByDefault(CARTESIAN)
ins = ass.Instance(name='Box', part=prt, dependent=ON)
ass.rotate(instanceList=('Box', ), axisPoint=(0.0, 0.0, 0.0), axisDirection=(0.0, 1.0, 0.0), angle=90.0)
ass.rotate(instanceList=('Box', ), axisPoint=(0.0, 0.0, 0.0), axisDirection=(1.0, 0.0, 0.0), angle=90.0)
rf1id = ass.ReferencePoint(point=(0.0, 0.0, 0.0)).id
rf2id = ass.ReferencePoint(point=(L, 0.0, 0.0)).id
regionRF1=ass.Set(referencePoints=(ass.referencePoints[rf1id],), name='RF1')
regionRF2=ass.Set(referencePoints=(ass.referencePoints[rf2id],), name='RF2')
edges1=ins.edges.getByBoundingBox(xMax=0.0)
region1 = ass.Set(edges=edges1, name = 'EDGES1')
edges2=ins.edges.getByBoundingBox(xMin=L)
region2 = ass.Set(edges=edges2, name = 'EDGES2')
mod.MultipointConstraint(name='Constraint-1',
controlPoint=regionRF1, surface=region1, mpcType=BEAM_MPC,
userMode=DOF_MODE_MPC, userType=0, csys=None)
mod.MultipointConstraint(name='Constraint-2',
controlPoint=regionRF2, surface=region2, mpcType=BEAM_MPC,
userMode=DOF_MODE_MPC, userType=0, csys=None)
# Steps, BC and loading
bc1 = mod.DisplacementBC(name='BC1', createStepName='Initial',
region=regionRF1, u1=SET, u2=SET, u3=SET, ur1=SET, ur2=SET, ur3=SET)
bc2 = mod.DisplacementBC(name='BC2', createStepName='Initial',
region=regionRF2, u1=SET, u2=SET, u3=SET, ur1=SET, ur2=SET, ur3=SET)
mod.BuckleStep(name='Step-Buck', previous='Initial', numEigen=2, vectors=4, maxIterations=500)
mod.StaticStep(name='Step-Stat', previous='Step-Buck')
if loadcase == 1: # Canteliver beam, tip load flapwise
bc2.setValuesInStep(stepName='Step-Buck',
u1=FREED, u2=FREED, u3=value, ur1=FREED, ur2=FREED, ur3=FREED, buckleCase=PERTURBATION_AND_BUCKLING)
bc2.setValuesInStep(stepName='Step-Stat',
u1=FREED, u2=FREED, u3=value, ur1=FREED, ur2=FREED, ur3=FREED)
if loadcase == 2: # flapwise rotation
bc2.setValuesInStep(stepName='Step-Buck',
u1=FREED, u2=FREED, u3=FREED, ur1=FREED, ur2=value, ur3=FREED, buckleCase=PERTURBATION_AND_BUCKLING)
bc2.setValuesInStep(stepName='Step-Stat',
u1=FREED, u2=FREED, u3=FREED, ur1=FREED, ur2=value, ur3=FREED)
if loadcase == 3: # Canteliver beam, tip load edgewise
bc2.setValuesInStep(stepName='Step-Buck',
u1=FREED, u2=value, u3=FREED, ur1=FREED, ur2=FREED, ur3=FREED, buckleCase=PERTURBATION_AND_BUCKLING)
bc2.setValuesInStep(stepName='Step-Stat',
u1=FREED, u2=value, u3=FREED, ur1=FREED, ur2=FREED, ur3=FREED)
if loadcase == 4: # flapwise rotation
bc2.setValuesInStep(stepName='Step-Buck',
u1=FREED, u2=FREED, u3=FREED, ur1=FREED, ur2=FREED, ur3=value, buckleCase=PERTURBATION_AND_BUCKLING)
bc2.setValuesInStep(stepName='Step-Stat',
u1=FREED, u2=FREED, u3=FREED, ur1=FREED, ur2=FREED, ur3=value)
if loadcase == 5: # freely supported beam, center load, flapwise
bc1.setValuesInStep(stepName='Step-Buck',
ur2=FREED, buckleCase=PERTURBATION_AND_BUCKLING)
bc1.setValuesInStep(stepName='Step-Stat',
ur2=FREED)
bc2.setValuesInStep(stepName='Step-Buck',
u1=FREED, ur2=FREED, buckleCase=PERTURBATION_AND_BUCKLING)
bc2.setValuesInStep(stepName='Step-Stat',
u1=FREED, ur2=FREED)
edges = ins.edges.getByBoundingBox(xMin=L/2.0, xMax=L/2.0, zMin=h/2.0)
region3 = ass.Set(name='CENTERLINE', edges=edges)
bc3 = mod.DisplacementBC(name='BC3', createStepName='Initial', region=region3,
u1=UNSET, u2=UNSET, u3=UNSET, ur1=UNSET, ur2=UNSET, ur3=UNSET)
bc3.setValuesInStep(stepName='Step-Buck', u3=-value, buckleCase=PERTURBATION_AND_BUCKLING)
bc3.setValuesInStep(stepName='Step-Stat', u3=-value)
# Job:
mdb.Job(name=modelname, model=modelname)
boxpro(modelname='BP-1', L=300, b=60, h=30, t=1, esize=5, loadcase=1, value=1)
boxpro(modelname='BP-2', L=300, b=60, h=30, t=1, esize=5, loadcase=2, value=1)
boxpro(modelname='BP-3', L=300, b=60, h=30, t=1, esize=5, loadcase=3, value=1)
boxpro(modelname='BP-4', L=300, b=60, h=30, t=1, esize=5, loadcase=4, value=1)
boxpro(modelname='BP-5', L=300, b=60, h=30, t=1, esize=5, loadcase=5, value=1)
