wrong temp results in transient thermal-Ansys classic

[Aknil]

Hey all
(i would post this in http:~~qid=210934#post but it's closed)
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I am simulating a micro package, Frame soldered to glass.
cooling down time is below 4ms.
my IC is a hot solder (not liquid tho) at 300°C cooling down to 25°C. no other forces, just a uniform temperature (set prior to IC) of 25 degrees.
when i run the thermal transient solution (Large displc. 100 sub steps, time the end of load stre 0.05) i get funny results, in the first 3-4 steps my frame is -5°C which maked no sence.
I tried:
- increasing load steps
- doing 2 load steps, but IC is lost when running the loadstep 2
- small displacement
nothing worked, pleae advice.

 

[Aknil]

Guys I could really use some help here

 

[kan123]

If you are doing a transient thermal solution, why are you invoking large displacement (NLGEOM)? This is for structural solutions.

If you are doing a steady-state solution in the first load step to set the initial conditions, did you include a change to transient solution for load step 2 (through ANTYPE or TIMINT)?

Maybe it would help to use an input listing from the Verification Manual (VM109 for example) as a template and then substitute your own geometry and loads.

 

[Aknil]

Kan123:
thank you for responding,
- I tried Small displacement option but it gave me the same results, so i took the large displacement maybe it can handle the ''Phase transition''. which obviously didnt.
- YES, i did switch the TIMINT on and off to include the transient in the second load step.
I think im gonna start a new thread and change my questions, right now the problem is that i do get the results but they happen way too fast (solidification happens in micro seconds!) and i think it might be a problem of my unit system.