The Five-Box Trick in an ANSYS nCode DesignLife Fatigue Simulation

In my last blog, I discussed the difference between HBM nCode DesignLife and ANSYS nCode DesignLife. I explained how ANSYS nCode DesignLife is fully featured, but integrated into the Workbench environment to provide state-of-the-art CAE fatigue analysis capabilities along with the ease of use features of Workbench. In this blog I will discuss the basic workflow of an ANSYS nCode DesignLife simulation.

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Early in your exposure to ANSYS nCode DesignLife, you will probably hear the term “the 5-box trick” and wonder, what does it mean? Essentially, the term 5-box trick is used to succinctly describe the basic steps of an ANSYS nCode DesignLife workflow. The multiple actions required in most ANSYS nCode DesignLife simulations can be summarized into five general categories (i.e., 5-boxes).

The 5-box trick is visually represented as 3 vertically aligned boxes on the left-side of a schematic, connected to one box in the center, which is then connected to one box on the right-side. The simulation process flows from left to right across the schematic. This configuration is analogous with the normal workflow of a typical finite element (FE) based simulation (pre-processing, followed by solving, followed by post-processing). For the 5-box trick, the three boxes on the left (FE Input, Material Mapping, and Load Mapping) entail pre-processing activities, the center box (CAE Fatigue Analysis) entails solving actions, and the box on the right (Fatigue Results Display) entails post-processing activities.

The pre-defined ANSYS nCode DesignLife workflows that are accessible under Analysis Systems in the Workbench Toolbox (described in a previous blog) contain glyphs to perform actions for all five boxes. Some actions are performed by one glyph. Some actions require multiple glyphs.

The actions within “FE Input” obtain the FE mesh and results from the source FE program.  DesignLife can access FE data from most leading commercial FE programs.  As explained in an earlier blog, when ANSYS nCode DesignLife is launched from Workbench, DesignLife automatically accesses the appropriate Mechanical ds.dat and file.rst files from the WB subdirectories. From those files, DesignLife automatically imports all of the necessary FE model information and results without any additional user actions.

The actions within “Material Mapping” define the fatigue material properties. Basic mechanical material properties (Modulus of Elasticity, Poisson’s ratio, density, etc.) are defined in the FE analysis and automatically imported with the FE Input. However, additional material data (e.g., S-N curve) are required for a fatigue evaluation. Again, when ANSYS nCode DesignLife is launched from Workbench, DesignLife automatically imports much of this data from Engineering Data without any additional user actions. Additional material/component details that affect fatigue life (surface finish, surface treatment, etc.) can be defined as needed within DesignLife.

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The actions within “Load Mapping” convert the FE stress/strain results into stress/strain histories. The FE analysis provides stress/strain results at distinct solution times or frequencies, but fatigue damage is caused by fluctuating stress/strain.  ANSYS nCode DesignLife provides several load mapping tools that convert distinct stresses/strains into stress/strain histories. The pre-defined ANSYS nCode DesignLife workflows in the Workbench Toolbox contain a pre-defined load mapping method; Constant Amplitude, Time Series, Time Step, or Vibration. However, you are not limited to those pre-defined load mappings. You have access to the full set of DesignLife load mapping tools, including the capability to create powerful duty cycles. Upcoming blogs will focus on DesignLife load mapping capabilities in more detail.

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The actions within “CAE Fatigue Analysis” read the pre-processing information into the appropriate fatigue analysis engine and calculate the fatigue damage. ANSYS nCode DesignLife has several fatigue solver engines (SN Analysis Engine, EN Analysis Engine, Seam Weld Analysis Engine, Vibration Analysis Engine, etc.). Previous blogs have discussed the Standard SN and EN Analysis Engines. Forthcoming blogs will discuss some of the other DesignLife fatigue engines.

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The actions within “Fatigue Results Display” read the calculated fatigue damage from the solver and present it in format suitable for making engineering decisions. ANSYS nCode DesignLife offers many tools for post-processing fatigue results (contour plots, tables, graphs, etc.).

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I will discuss many of the features in each of the boxes in more detail in forthcoming blogs. In the meantime, if you’d like more information about ANSYS nCode DesignLife, you can visit the ANSYS website.

Below are links to some of my previous blogs on this topic.

5 thoughts on “The Five-Box Trick in an ANSYS nCode DesignLife Fatigue Simulation

  1. Pingback: The Five-Box Trick in an ANSYS nCode DesignLife...

  2. Dear sir,
    I am working in Helical compression spring and want to calculate Fatigue life of Helical compression spring using strain life theory.
    I request you to suggest procedure and ideas for the same.
    Thank you.

  3. And also provide related videos by which i can accomplish my work easily.
    Thank you sir.

  4. Pingback: Simplifying Fatigue AnalysisANSYS Blog

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