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Coupled Field Simulation in Ansys Mechanical

Written By: 
Wynand Prinsloo

Many mechanical designs are greatly affected by structural and thermal aspects. It is important to account for both these aspects when performing Finite Element Analysis on such designs, since both can lead to the success of failure of the design. 

Along with their respective individual importance from a design point of view, the thermal and structural aspects of a system also affect each other in significant ways. The change in temperature of the material causes thermal expansion/contraction and can change the material properties. Both of these aspects have to be taken into account when considering the structural response of the system. 

Traditionally, in cases where there is a significant thermal load on a system, a thermal-only FEA simulation will be completed on the system initially. The temperature distribution from the thermal simulation would then be used as an input to the structural simulation in order to account for the effect of the temperature on the structural response. 

This is a straight forward method and it works well for most cases. However, since the thermal simulation is completed in isolation, this way of simulation cannot reflect the effect that the structural response has on the thermal response in return. In many cases, this effect is negligible, but there are certain cases where the structural and thermal response are more closely coupled. 

In the past, setting up a simulation where the thermal and structural response of the system where coupled in both directions was relatively complex and required the use of ANSYS APDL coding. As of the final release from 2019, however, this functionality has been made available natively in ANSYS Mechanical. With this functionality, setting up simulations in which the structural and thermal degrees of freedom are solved simultaneously is extremely easy. 

By using the new “Coupled Field” Analysis Systems in Workbench, shown in Figure 1, a static or transient coupled thermal-structural simulation can be initiated. Through the use of Physics Region definitions, the bodies in the simulation can be designated for thermal-structural coupled degrees of freedom; or thermal or structural degrees of freedom only, as shown in Figure 2. Structural and thermal boundary conditions will be available on the Environment ribbon of Mechanical, as shown in Figure 3. 


Figure 1

Figure 2
Figure 2


Figure 3

Solving the thermal and structural degrees of freedom in a coupled sense allow for the accurate simulation of more complex thermal-structural interactions. Take for instance, the case where the thermal expansion of the components closes a contact that was open initially. The fact that the contact closes can significantly change the flow of thermal energy through the component, and hence lead to a complete different final state. An example of this can be seen in VIDEO 1 and VIDEO 2. 

Running a coupled filed simulation also allows us to take into account the energy that is released while material undergoes certain types of non-linear deformation, which can lead to an increase in temperature of the components. This functionality is exposed through the Plastic- and Viscoelastic Heating boundary conditions, as can be seen in Figure 4. An example of plastic heating can be seen in the tensile test sample in VIDEO 3 and VIDEO 4. 

 

 


Figure 4

With functionalities such as this, ANSYS are still improving the functionality and usability on a release to release basis, allowing us to simulate more accurately in a shorter amount of time. I don’t know about you, but I am excited to see what the next year of releases will hold. 

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