modeldamper
Mechanical
I have a question regarding modal analysis after applying thermal load on the structure.
I have built an aluminum structure model. My reference temperature is the room temperature (70F), which I am mentioning in my MAT1 card.
I need to do the modal analysis at 69F and -20F. This is what I have written on NX Nastran
CEND
TITLE = modal analysis
ECHO = NONE
SUBCASE = 1
SPC = 1
TEMP = 100
SUBCASE = 2
STATSUB = 1
DISPLACEMENT(PLOT) = ALL
ESE(PLOT) = ALL
METHOD = 1
SPC = 1
BEGIN BULK
TEMPD 100 -20.
MAT1 1 1.+7 .33 .101 1.2-5 70.
The modal frequencies will naturally increase when the temperature is cold. But, I am seeing the other way around. My analysis predicts frequencies lower for cold temperature (-20F) than at 69F.
Is there anything I am missing?
Thanks
I have built an aluminum structure model. My reference temperature is the room temperature (70F), which I am mentioning in my MAT1 card.
I need to do the modal analysis at 69F and -20F. This is what I have written on NX Nastran
CEND
TITLE = modal analysis
ECHO = NONE
SUBCASE = 1
SPC = 1
TEMP = 100
SUBCASE = 2
STATSUB = 1
DISPLACEMENT(PLOT) = ALL
ESE(PLOT) = ALL
METHOD = 1
SPC = 1
BEGIN BULK
TEMPD 100 -20.
MAT1 1 1.+7 .33 .101 1.2-5 70.
The modal frequencies will naturally increase when the temperature is cold. But, I am seeing the other way around. My analysis predicts frequencies lower for cold temperature (-20F) than at 69F.
Is there anything I am missing?
Thanks
