Contour plot of the Fatigue damage in the part located in the inner radius 1

SimSolid Advanced – Fatigue Analysis

In this blog, we outline the process of configuring, operating, and analysing a component experiencing a cantilever load subjected to cycles, necessitating a fatigue assessment.

The stress-life fatigue theory, also known as SN theory, is used when a part is subjected to a large number of cycles with lower levels of stress. The maximum stresses experienced by the part are below the yield strength of the material. 

Fatigue analysis requires the use of SimSolid Advanced.

The Altair SimSolid meshless structural analysis tool works on full-featured parts and assemblies is tolerant of geometric imperfections from the CAD model, and runs in seconds to minutes. In this blog, we will show the following:

  • Create the SN time fatigue load case.
  • Import channels and create events.
  • Solve and review results.

1. Model description

The SimSolid model file and *.csv file contain the input fatigue cycle information, known as “channels,” used in Altair SimSolid.

In the industry, fatigue loading input data is typically measured in a laboratory or the field and then exported from the test and measurement equipment.

This channel information is a factor that multiplies the load versus the timetable. This will become clearer once it is inputted into the program.

Part of a lower suspension arm 1

In this analysis, the lugs of a part are considered to have a fixed boundary condition, and a load is applied to the other end of the suspension arm, simulating the force experienced when a vehicle is in motion. The material used for the analysis is steel.

Boundary and loading conditions applied to the suspension arm

A contour plot of the von mises stresses indicates the areas of higher stress.

SimSolid Fatigue Analysis

2. Adding fatigue material properties

The next step requires the definition of the specific fatigue material properties, within the material set-up.

Material properties

The definition of the fatigue material properties is calculated by the software from the ultimate tensile strength of the material. The resulting SN curve (plotted on a log scale for both the stress amplitude and the number of cycles) is shown below:

SN curve for steel estimated from the ultimate tensile strength of the material

3. Fatigue analysis

The fatigue analysis is selected.

The previously solved linear static analysis results will be used as the input for the fatigue analysis. Non-linear static analysis may also be used as an input to a fatigue analysis. The workflow starts at the top and the user works down to complete the definition of a fatigue analysis.

Firstly, the channels with the fatigue loading cases are imported and applied to the model. Finally, the events are defined where several load cases and load scenarios can be applied, depending on the requirements of the analysis. These can then be changed for different loading scenarios.

Importing and application of the channels and events

The channel information is displayed in the *.csv file. If it has not been sourced from measured data, it must be defined outside the software. Contact Simutron for further assistance.

Sample of the channel information

The channel information can be reviewed within the software:

Reviewing of the imported channel information

The event setup allows the user to apply the load factor vs time from a particular channel to a load case that was previously run. In this case that is the linear static analysis. An overall factor of 5 has been applied to the loading for this simulation.

The channel event allows the user to consider a load history that is either applied at the zero offset location or a positive value, implying, a more tensile load application. The event setup allows various definitions to be defined.

4. Reviewing of fatigue results

The simulation is then run and the “fatigue damage” result quantity is selected. The contour plot is shown below:

Contour plot of the Fatigue damage in the part located in the inner radius