💥💥💥 How to perform fatique analysis in Ansys Workbench?

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 Fatigue analysis is a process of evaluating the durability and reliability of a structure or a component under cyclic loading conditions. It can help to predict the number of cycles or the time to failure due to fatigue damage. Ansys Workbench is a software that can perform fatigue analysis using various methods and tools.

To perform fatigue analysis in Ansys Workbench, you need to follow these general steps:

  • Create or import a geometry model of the structure or component you want to analyze.
  • Define the material properties and assign them to the model.
  • Apply the boundary conditions, such as fixed supports, loads, pressures, temperatures, etc.
  • Mesh the model using appropriate element types and sizes.
  • Choose a fatigue analysis system from the toolbox, such as Fatigue Tool, Random Vibration Fatigue, or Harmonic Response Fatigue.
  • Define the fatigue parameters, such as loading type, fatigue life method, mean stress correction, S-N curve, etc.
  • Solve the analysis and review the results, such as fatigue life, damage, safety factor, etc.

You can find more detailed instructions and examples on how to perform fatigue analysis in Ansys Workbench in these video tutorials:

You can also refer to these web pages for more information and tips:

What is the difference between static and dynamic fatigue analysis?

Fatigue analysis is a process of evaluating the durability and reliability of a structure or a component under cyclic loading conditions. It can help to predict the number of cycles or the time to failure due to fatigue damage. The difference between static and dynamic fatigue analysis is mainly related to the type and frequency of the loading conditions.

Static fatigue analysis is used to calculate the fatigue life of a structure or a component under constant or slowly varying loads, such as dead weight, pressure, or temperature. Static fatigue analysis assumes that the load is applied so slowly that inertia effects and damping can be neglected. Static fatigue analysis can be performed using stress-life (S-N) or strain-life (ε-N) methods, depending on the material behavior and the stress level.

Dynamic fatigue analysis is used to calculate the fatigue life of a structure or a component under time-varying or cyclic loads, such as impact, vibration, or shock. Dynamic fatigue analysis takes into account the effects of inertia, damping, and frequency on the structural response and the fatigue damage. Dynamic fatigue analysis can be performed using modal superposition, direct integration, or explicit methods, depending on the complexity and nonlinearity of the problem.

You can find more information about static and dynamic fatigue analysis in these web pages:

How do I choose an appropriate S-N curve for my material?

Choosing an appropriate S-N curve for your material depends on several factors, such as the type of material, the loading conditions, the stress ratio, and the available data. Here are some general guidelines to help you select an S-N curve for your material:

  • First, you need to identify the type of material you are using, such as steel, aluminum, titanium, etc. Different materials have different fatigue properties and behavior, and may require different methods to obtain or define their S-N curves.
  • Second, you need to determine the loading conditions that your material will be subjected to, such as constant amplitude, variable amplitude, random vibration, harmonic response, etc. Different loading conditions may affect the fatigue life and damage of your material in different ways, and may require different fatigue analysis systems or tools.
  • Third, you need to specify the stress ratio ® that your material will experience during the loading cycles. The stress ratio is defined as R = S min / S max , where S min is the minimum stress and S max is the maximum stress in the cycle. The stress ratio can range from -1 (fully reversed loading) to 1 (fully compressive loading), and it can affect the shape and slope of the S-N curve.
  • Fourth, you need to find or generate the data points for your S-N curve, either by conducting experimental tests, using existing data from literature or databases, or deriving from material properties or empirical formulas. You can enter or import the data points in a table or a file format, and plot them on a graph to visualize the S-N curve.

Once you have these information and data, you can use Ansys Workbench to assign an S-N curve to your material by following these steps1:

  • In a Fatigue study, add a fatigue event.
  • In the Material dialog, on the Fatigue SN Curves tab, in the Source box do the following:
    • For Interpolate, set the scheme for interpolating alternating stresses against the number of cycles of the S-N curve.
    • Select Define and select a curve from the list. Curves that are already defined have the stress ratio value attached to their names (for example R = -1). Curves that are not defined are tagged as (Not Defined).
    • Select an undefined curve to populate with data. You can define up to 10 S-N curves for different values of stress ratios R to a specific material.
  • In the Table data box, do the following:
    • In the Stress ratio ® box, enter the stress ratio associated with the curve.
    • Set the unit of stress.
    • Populate the curve data by entering Alternating Stress values versus number of cycles to failure due to fatigue, or click File to import data from the Simulation S-N Curve library.
    • Click View to graph the data or Save to save the curve to a data file (*.dat).
  • Type a source of reference for the SN curve data in Source.
  • Click Apply.

You can also use other methods to define an S-N curve for your material, such as deriving from material elastic modulus or using an existing curve from the material database. You can find more information and examples on how to associate S-N curves to a material in these web pages234.

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