What is Fatigue Analysis?

1. What is Fatigue Analysis?

Fatigue analysis is one of the types of CAE analysis. It helps determine if a structure is durable enough during the design stage.

Fatigue analysis will also allow you to provide a “safety margin” against fatigue failure*1.
*1 Fatigue failure: Failure phenomenon in which a structure is loaded under a repeated or otherwise varying load which never reaches a level sufficient to cause failure in a single application.

2. How to Conduct Fatigue Analysis

First, create design data (CAD model) through CAD software, and import it into CAE software.

Next, define material properties, and such boundary conditions as Young’s modulus (how hard to deform), constraint (how to fix the structure) applied in the structure.

*2 S-N curve: A diagram showing inverse relationship between S (= stress: repeated load) and N (=number of cycles to failure).

Then, create a model of the structure.

Apply the expected service loading in the model, and quantify fatigue life^*3.
*3 Fatigue life: The number of loading cycles that a material or structure endures before failing.

The life estimate or “cycles of usage until the structure fails” are visualized on the model using contour lines. Areas with denser contour lines indicate higher stress concentrations, potentially leading to earlier fatigue failure.

Fatigue analysis involves “endurance limit^*4” instead of ultimate strength^*5.
*4 Endurance limit: The maximum level of a repeated loading or stress below which an infinite number of loading cycles can be applied to a structure without causing fatigue failure. The maximum value is shown on S-N curve.
*5 Ultimate strength: The maximum load (per cross-sectional area) at which a structure or material will fail.

Reason 1: Fatigue failure occurs even below ultimate strength.
Reason 2: Ultimate strength is the basis for Static analysis.

In addition to fatigue life, fatigue analysis can also visualize the maximum deformation the structure will experience under applied loads.

3. Design Using Fatigue Analysis

Fatigue analysis enables the verification of whether the durability of a designed structure is adequate and allows for the establishment of a safety margin. Statistics indicate that fatigue failure of parts accounts for 80% of equipment failures, highlighting the critical importance of integrating Fatigue analysis into product design and development process.

It’s a unique advantage of computer simulation that can replicate physical evaluation tests in which a structure is put under repeated or cyclic service loadings. In addition to these benefits, the numbers of prototypes and testing can be reduced, which saves time and costs. This would lead to the optimization of the entire design process, making CAE analysis highly recommended.

LINE SEIKI offers a series of CAE analysis services. Get in touch with us by calling +81-50-1741-6630, or by sending your valued inquiry through webform.