Thermal expansion with material table

Experimenter
Experimenter

Hi,

I'm having an issue with the thermal expansion, I attach here my 2 nastran files (1 for SOL 101 and 1 for SOL 106) that will help in the explanation. 

I created an axisymmetric problem, there are 4 cylinder (rectangles in the nastran files) and they all expand from 20°C to 180°C.

The first cylinder has for the thermal expansion coefficient a table with values at 20° and 180°:

TABLEM1        2                       1                                +
+           20.0 2.225-5   180.0 2.328-5    ENDT

 

The second cylinder has only the value at 20°:

MAT1           8 72443.0             .33  2.76-9 2.225-5    20.0

 

The third cylinder has only the value at 180°:

MAT1           9 72443.0             .33  2.76-9 2.328-5    20.0

and the fourth cylinder has a table with values at 20° and 179°:

TABLEM1        6                       1                                +
+           20.0 2.225-5   179.0 2.328-5    ENDT

The result is the following (going from left to right):

image.png

What happens is that in the 1,2,and 4 case nastran always uses the value at 20°C, while I would expect this only for the case 2.

Could you please explain to me this strange behaviour?

Many thanks

2 REPLIES 2

Re: Thermal expansion with material table

Siemens Phenom Siemens Phenom
Siemens Phenom

See the rules for what temperatures are used for evaluating properties in remarks 8 and 9 on the TEMPERATURE case control card:

 

TEMPERATURE

 

Note that material properties are only temperature dependent when there is an associated MATTi card pointing to a TABLEMi card to define termperature dependence. Your second and third cases only reference MAT1. Thus, the properties are always constant and TREF is only used in the thermal strain calculations as indicated in Remarks 8 and 9 - it has no bearing on the property values.

Re: Thermal expansion with material table

Experimenter
Experimenter

Hi JimB,

thanks for your answer.

So I followed what the documentation says at Remark 8 for linear analyses and I was able to get the results I wanted for SOL 101.

 

However for what concerns SOL 106, reading Remark 9 for non-linear solution, my nastran file should already be ok because I'm defining: 

TEMP(INIT) = 1
$
SUBCASE 1
TEMP(LOAD) = 2
$
BEGIN BULK
$
$* MATERIAL CARDS
$*
$*  Material: LAH_1
MAT1           7 72443.0             .33  2.76-9 2.225-5    20.0
MATT1          7       1                               2
TABLEM1        2                       1                                +
+           20.0 2.225-5   180.0 2.328-5    ENDT
$*  Material: LAH_2
MAT1           8 72443.0             .33  2.76-9 2.225-5    20.0
$*  Material: LAH_3
MAT1           9 72443.0             .33  2.76-9 2.328-5    20.0
$*  Material: LAH_4
MAT1          10 72443.0             .33  2.76-9 2.225-5    20.0
MATT1         10       5                               6
TABLEM1        6                       1                                +
+           20.0 2.225-5   179.0 2.328-5    ENDT
$
$*  Solver Set: room
TEMPD          1    20.0
$*  Solver Set: oper
TEMPD          2   180.0

I would therefore expect case 1 and 4 to give the same result as case 3 because alfa_load is 2.328-5 in all of them, but this does't happen .

I attach again the complete nastran file for SOL 106.

Thanks again