Thermal and Thermal Stress Analysis

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nTop Platform features built-in steady-state thermal analysis using a range of boundary conditions. The temperature result can be used to assess the thermal performance of a part, and can also be converted into a field so that a part’s geometry can be driven by local temperature. In addition to thermal analysis, nTop’s static analysis can include a thermal expansion load, either from an imported temperature field or from a thermal analysis performed in nTop. This article and its associated file will demonstrate how to set up a thermal analysis with all available boundary conditions, and how to use the resulting temperature field to set up a thermal stress analysis in the same nTop Notebook. 

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1. Defining Material Properties

To set up a material for thermal analysis, a Thermal Property block must be added to the Properties list of a Material. These include conductivity and specific heat. For static analysis without thermal stress, the Young’s Modulus and Poisson’s ratio are needed. If the static analysis includes thermal stress, a third property, the Coefficient of Thermal Expansion Property, must be added, which includes the coefficient of thermal expansion (CTE). (An isotropic material is used in this example, but nTop supports orthographic materials as well.)

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2. Thermal Analysis 

The Thermal Analysis block consists of an FE Model input and a Boundary Condition List. The available boundary conditions for thermal analysis are listed below. For more information on each boundary condition block and their inputs, click on the Info Panel (the gray question mark on the right side of the block). All thermal boundary conditions are included in the example file for demonstration, but not all are necessarily needed to set up a proper thermal analysis. 

Available Boundary Conditions

  • Heat Generation 
  • Volumetric Heat Generation
  • Surface Heat Flux 
  • Radiation Boundary Load
  • Convection Boundary Load 
  • Temperature Restraint

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3. Obtaining a Temperature Field from Thermal Analysis

Once the thermal analysis is complete, the resulting temperature is viewable through the HUD, but the following steps can be taken to convert the temperature to a field: Create a Temperature Point Map block, and drag the thermal analysis into the input. Then use a Field from Point Map to interpolate the point map data into a field. The Barycentric interpolation works best, and no extrapolation is needed.

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4. Thermal Stress Analysis

With the temperature field defined, an applied thermal load can be applied to a static analysis just like any other structural boundary condition (such as forces, pressure, and displacement restraints). The applied temperature load will cause expansion and contraction of the material based on its CTE. An initial temperature load can be applied as a reference point for the initial expansion before the temperature load is applied, and should usually be set to the ambient temperature of the part before thermal loading. 

Available Boundary Conditions

  • *Any structural boundary condition*
  • Applied Temperature Load
  • Initial Temperature

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Looking for more information on Simulation? Check out this article.

Labels: analysis surface field boundary stress heat performance restraint condition material thermal temperature radiation expansion istropic generation volumetric flux convection 
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