After some soul searching I realized that I was getting the wrong answer for some very simple model set ups. So here is one:

A rod with a 10mm^2 area and 50cm length is pulled by a force of 4000N

Start with some python code here to declare my inputs and expected answer:

E = 220000000000 #Pa the Yong’s modulus

l= 0.5 #meters the length of this cylindrical rod

r= ((3.57 /2)/1000) #meters the radius of the rod

A = 3.1416*(r**2) #the section area of the rod

F=4000 #N #the force applied in newtons

S= F/A #Pa The expected stress

e= (S/E) #the expected strain

dl=l*e #the expected elongation

print (“a load of %2d Newtons is applied” %F )

print (“The strain is %2.2f percent” %(100*e) )
print (“The stress is %2d MPa” %(S/1000000) )
print (“The elongation is %2.2f mm” %(dl*1000) )

Answer:

a load of 4000 Newtons is applied

The strain is 0.18 percent

The stress is 399 MPa !yippy correct answer here!!!

The elongation is 0.91 mm

Calculix is coming up with an elongation of like 60mm and a stress of about 28000MPa or up to 60000MPa as you refine the mesh. But I go to comsol with the same exact STEP file and I get the correct 400MPa all along the length. what gives??

The mesh doesn’t look that bad at all… its like 22Mb so I don’t want to attach it

Material:

*Material, Name=18CrMo4

*Density

7.8E-09

*Elastic

210000, 0.28

*Expansion, Zero=20

1.1E-05

*Conductivity

14

*Specific heat

440000000

**