Transient thermal analysis in ANSYS

[happytolearn]

I want to do a transient thermal analysis in butt welded joint.The heat flow I have given 3200 watt(Q = efficiency x current x voltage = 0.8 x 160 amp x 25 volt)to the welding zone, given 20 load step(as welding is completed in 20 sec),convection co-efficient = 11.14, emissivity = .4 and applied both boundary condition convection and radiation on every surface except welding zone. But after solving the minimum temperature of the plate is coming in negative.Can anybody tell me what i am missing?

 

[Mech_Engineer]

Where does this minimum temperature occur? Is it at a single node, or over a portion of the part? Also, what did you use for your starting temperature in the analysis?

 

[happytolearn]

It is coming in a region when I run the animation. I have selected the initial temperature as 22 degree centigrade

 

[Mech_Engineer]

For troubleshooting purposes try disabling the convection and radiation boundary conditions one at a time and see if either is the culprit. I'm guessing one of those is causing an unexpected result for some reason...

 

[happytolearn]

I have tried to analyse the result by activating and deactivating one after another.But still it is coming very high temperature.One thing to mention i have applied the boundary conditions to the whole assembly(welding zone and the two plates).What can be the other possibilities for the troubleshooting?

 

[happytolearn]

Maximum temperature is coming 6042 .8 and minimum -132.52! Though i have selected initial temperature as 22 degree centigrade.

 

[Mech_Engineer]

There's something weird going on with the boundary conditions, because there's really shouldn't be a cooling effect on the part based on what I'm seeing. Do you have any other boundary conditions set up other than the heat flows?

 

[happytolearn]

No i have just given heat flow,convection and radiation.should i add any other boundary condition?What is the thing i am missing. Please help.

 

[Mech_Engineer]

Are you using nonlinear material properties? Honestly there isn't much more input we can provide without more context. Have you re-meshed the geometry with a higher density to see if the results change?

 

[happytolearn]

yes I have used nonlinear (temperature dependent)material property. I am now trying to see the effect by remeshing according to your advice. One thing can we cool the assemble by applying cooling cycle?I have linked the transient analysis to a new transient analysis where i have omitted the load and run it for 20 second but the imported temperature has not changed.In journaIs I saw everyone cool the assemble for some time.Is there any way to run the cooling cycle in workbench?