Creating .inp file in matlab - matlab

Question

I'm relatively new to abaqus and currently working on an optimisation project for a beam under concentrated load where I have to run multiple files with different parameters(length,width,load) in matlab to create a .inp file to be run on abaqus. My question is, how would I go about tackling this problem and is there a way to generate the nodes and elements automatically?

Answer 1

You can parametrize your Abaqus project using the Python interface. It requires some getting used to, but it can be quite powerful depending on what you want to do. I assume your optimizer is programmed in Matlab, but that should not be a problem. You can write a wrapper function in Matlab which calls Abaqus with the script you want. The command would be abaqus cae noGUI=<script.py> to run the script that creates your input file.
Alternatively you can create a base input file and create a script that looks for the lines that have to be changed. This can be based on the input file keywords, you can put some own parameters (dummy words) that you substitute using your script or a comment that can easily be recognized.
The best approach depends a bit on what exactly you want to change.
Abaqus also offers some parameterization, I think this link may be handy.

Answer 2

Regarding generating the nodes and elements automatically, it very much possible but it is time consuming and rather complicated process.
Nodes can be created by defining the x,y and z coordinates and Elements can be created by defining the Nodal Connectivity. As the model gets complicated, defining the x,y and z coordinates and Nodal Connectivity also get difficult. However, for simple models you can still create the nodes and elements automatically. If I am guessing correctly, your model is rectangular shaped beam, hence creating mesh may not be complicated.
In Abaqus, Nodal Connectivity for each element type is given in Analysis Help Manuals. Following is the example of Nodal Connectivity for 4-Noded Quad and 8-Noded Hex Element.
To get you started, I am providing here the Python code to create Abaqus INPUT mesh file for 2D and 3D beam (Later you can replicate in MATLAB code):
fnm = 'shell.inp'
w = 100 # x-direction
h = 10 # y-direction
npx = 30; npy = 5
fout = open(fnm, 'w')
# Creating node information
fout.write('*Node, Nset=All_Nodes\n')
nds = []; elms = []
for i in range(npy):
y = (i+1)/npy * h
for j in range(npx):
nid = i*npx + j + 1
x = (j+1)/npx * w
nds.append([nid,x,y,0.0])
fout.write('%10d,%10f,%10f,%10f\n'%(nid,x,y,0.0))
# Creating Nodal connectivity
fout.write('*Element, Type=S4, Elset=All_Elements\n')
for m in range(npy-1):
for n in range(npx-1):
eid = m*(npx-1) + n + 1
e1 = n + 2 + npx + m*npx
e2 = e1 - 1
e3 = n + 1 + m*npx
e4 = e3 + 1
elms.append([eid,e1,e2,e3,e4])
fout.write(('%10d,'*4+'%10d\n')%(eid,e1,e2,e3,e4))
fout.close()
# ====================================================================
fnm = 'rect_beam.inp'
w = 10 # z-direction
h = 10 # y-direction
l = 100 # X-direction
npx = 20;npy = 5;npz = 3
fout = open(fnm, 'w')
# Creating node information
fout.write('*Node, Nset=All_Nodes\n')
nds = [];elms = []
for i in range(npz):
z = (i+1)/npz * w
for j in range(npy):
y = (j+1)/npy * h
for k in range(npx):
nid = i*(npx*npy) + j*npx + k + 1
x = (k+1)/npx * l
nds.append([nid,x,y,z])
fout.write('%10d,%10f,%10f,%10f\n'%(nid,x,y,z))
# Creating Nodal connectivity
fout.write('*Element, Type=C3D8, Elset=All_Elements\n')
for m in range(npz-1):
for n in range(npy-1):
for p in range(npx-1):
eid = m*(npy-1)*(npx-1) + n*(npx-1) + p + 1
e1 = p + 2 + npx + n*npx + m*npx*npy
e2 = e1 - 1
e3 = p + 1 + n*npx + m*npx*npy
e4 = e3 + 1
e5 = e1 + (npx*npy)
e6 = e5 - 1
e7 = e3 + (npx*npy)
e8 = e7 + 1
elms.append([eid,e1,e2,e3,e4,e5,e6,e7,e8])
fout.write(('%6d,'*8+'%6d\n')%(eid,e1,e2,e3,e4,e5,e6,e7,e8))
print(m,n,p,'|',eid,e1,e2,e3,e4,e5,e6,e7,e8)
fout.close()