In industrial frames subjected to dynamic loads, the problem is not usually an immediate failure. The problem appears over time, when small repeated stresses end up causing cracks and unexpected stoppages. That is where fatigue calculation comes in.
Fatigue calculation in frames subjected to dynamic loads
Frames that support machinery, actuators or moving assemblies work under variable loading. Vibration, accelerations and repetitive cycles create a scenario in which static calculation is not enough.
Why fatigue is critical in dynamic frames
Under dynamic loads, stresses change over time. Even if they are below the strength limit, their repetition can cause accumulated damage.
This type of failure usually appears in welds, bolted joints and areas with abrupt changes of section.
Identifying cycles and load levels
The first step is to understand how the frame works in service. Real cycles, load amplitude and the number of repetitions over the expected service life are analysed.
Without this information, any fatigue calculation loses its practical value.
FEM model of the frame
An FEM model is built that represents geometry, materials and joints. The mesh is refined especially in areas sensitive to stress concentrations.
This work is part of the finite element calculation FEM services applied to industrial structures.
Dynamic analysis prior to the fatigue calculation
Before evaluating fatigue, a dynamic analysis is carried out to obtain time-varying stresses. It may be a modal, harmonic or transient analysis, depending on the type of excitation.
From this analysis the stress histories needed for the damage study are extracted.
Fatigue damage assessment
With the dynamic stresses, fatigue criteria based on the material’s S–N curves are applied. Accumulated damage and the estimated service life of the frame are evaluated.
- Detection of critical zones.
- Life estimation under real conditions.
- Comparison between different design solutions.
Design adjustments from the calculation
Fatigue calculation does not stop at diagnosis. It allows localised changes to be introduced: reinforcements, weld improvements or geometry modifications.
These adjustments reduce stress concentrations and extend service life without oversizing the entire frame.
Final validation of the frame
After the changes, the analysis is repeated to confirm the improvement in behaviour. The frame is validated to work under dynamic loads for the intended period.
This approach is integrated into innovative mechanical engineering projects, where calculation accompanies the design from the early stages.
Application to industrial lines and structures
Fatigue calculation is applied both to isolated frames and to complete lines. In installations integrated into buildings, it is coordinated with civil engineering and industrial BIM to ensure structural consistency.
General information is available at kernova.es.
Frequently asked questions
Can a frame fail from fatigue even if it holds up statically?
Yes. Repeated loads can cause accumulated damage even if the stresses are moderate.
Is it necessary to calculate fatigue in all frames?
In frames subjected to vibration or repetitive cycles, yes.
Can it be applied to existing structures?
Yes. FEM makes it possible to evaluate remaining life and propose reinforcements.
