Transient thermal analysis in ANSYS

In summary, 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?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?It is coming
  • #1
happytolearn
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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?
upload_2016-4-19_19-34-18.png
 
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  • #2
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?
 
  • #3
It is coming in a region when I run the animation. I have selected the initial temperature as 22 degree centigrade
 
  • #4
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...
 
  • #5
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?
 
  • #6
upload_2016-4-21_15-9-26.png


Maximum temperature is coming 6042 .8 and minimum -132.52! Though i have selected initial temperature as 22 degree centigrade.
 
  • #7
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?
 
  • #8
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.
 
  • #9
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?
 
  • #10
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?
 

1. What is transient thermal analysis in ANSYS?

Transient thermal analysis is a computational technique used to simulate and analyze the time-dependent thermal behavior of a system or component. It involves solving the heat transfer equations over a period of time to understand how temperature changes over time.

2. What are the advantages of using ANSYS for transient thermal analysis?

ANSYS offers a robust and accurate simulation platform for transient thermal analysis, allowing for detailed and precise predictions of thermal behavior. It also has advanced features such as non-linear material properties, radiation, and convection boundary conditions which make it suitable for a wide range of applications.

3. How does ANSYS handle transient thermal analysis?

ANSYS uses the finite element method to discretize the system into small elements and solves the heat transfer equations for each element over a time interval. The results are then combined to give a complete understanding of the thermal behavior of the system.

4. What are some common applications of transient thermal analysis in ANSYS?

Transient thermal analysis can be used in a variety of industries, such as automotive, aerospace, electronics, and energy, to analyze the thermal performance of components and systems. It is commonly used to study the thermal behavior of engines, electronics cooling, and material behavior under changing temperatures.

5. How accurate is transient thermal analysis in ANSYS?

The accuracy of the analysis depends on various factors such as the complexity of the system, the accuracy of material properties and boundary conditions, and the mesh density. With proper setup and validation, ANSYS can provide highly accurate results for transient thermal analysis.

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