# Understanding Boundary Conditions

Good day please assist in explaining the boundary conditions listed below.

*BOUNDARY
nall,3,3,0.0 i,e explain this condition_______________
1,1,3,0.0 i,e explain this condition_______________
2,1,3,0.0 i,e explain this condition_______________

*BOUNDARY
1,1,6,0.0 i,e explain this condition_______________
2,3,3,0.0 i,e explain this condition_______________
3,3,3,0.0 i,e explain this condition_______________
4,3,3,0.0 i,e explain this condition_______________
5,3,3,0.0 i,e explain this condition_______________

I have read the CalculiX manual, the difference between homogeneous and inhomogeneous boundary conditions

In my understanding

homogeneous boundary conditions can be defined as follows.

*BOUNDARY
1,1,2,3 (This means node 1, is fixed in x(1), y(2) & z(3) direction

inhomogeneous boundary conditions can be defined as follows.

that’s where i get confused how to prescribe a displacement, temperature etc.

I,e i see
*BOUNDARY
LINE3,1,1,0.0 (On line3 what does 1,1,0.0 mean? same as below)
LINE1,2,2,0.0

It’s rather simple because it’s always just:

`node/nset, first DOF, last DOF, magnitude`

Of course, magnitude applies only to BCs within steps since you can prescribe their non-zero values.

DOF numbers are 1,2,3 for x,y,z displacement and 4,5,6 for x,y,z rotation. Then there are non-mechanical DOFs like 11 for temperature.

@Calc_em, Thank You for clarifying this part … node/nset, first DOF, last DOF, magnitude.