Fatique analysis in Ansys Mechanical (with models description)

 ANSYS Mechanical is a software that can help you perform fatigue analysis on your models and predict the fatigue life and damage of your materials. ANSYS Mechanical offers various tools and features to help you set up, run, and post-process your fatigue analysis. For example:

• You can use the Fatigue tool in ANSYS Mechanical to perform stress-based or strain-based fatigue analysis in both the time and frequency domains. You can also choose between different fatigue models, such as SN curve, EN curve, or Morrow model.
• You can use the Fatigue Sensitivity tool in ANSYS Mechanical to perform a parametric study on your fatigue analysis and evaluate how different design variables affect the fatigue life and damage of your materials.
• You can use the Fatigue Crack Growth tool in ANSYS Mechanical to simulate the crack initiation and propagation in your materials due to fatigue loading. You can also use different fracture mechanics models, such as Paris law, NASGRO equation, or Forman equation.

I searched the web  and found some results that might be helpful. The first result is a course overview of ANSYS Mechanical Fatigue that covers the use of the Fatigue tool to perform stress-based and strain-based fatigue analysis in both the time and frequency domains. The second result is a video tutorial that explains how to perform fatigue analysis in ANSYS Workbench. The third result is another video tutorial that shows how to use the Fatigue tool in ANSYS Mechanical. The fourth result is a PDF document that provides an introduction to ANSYS fatigue analysis.

Below You can see the models of SN curve, EN curve and Morrow models. These are some of the models that are used to predict the fatigue life of a material based on the stress or strain cycles.

• SN curve: This is a stress-life (S-N) curve that plots the stress amplitude versus the number of cycles to failure for a material. The SN curve is usually obtained from experimental tests under constant amplitude loading and fully reversed loading (R=-1), where R is the ratio of minimum to maximum stress. The SN curve can have different slopes depending on the stress level and the material behavior. For example, some materials may exhibit a fatigue limit, which is a stress level below which the material can endure an infinite number of cycles without failure. Other materials may not have a fatigue limit and show a continuous decrease in fatigue life with increasing stress. The SN curve can be used to estimate the fatigue life of a material when the stress is mostly elastic and the mean stress is low.
• EN curve: This is a strain-life (E-N) curve that plots the strain amplitude versus the number of cycles to failure for a material. The EN curve is also obtained from experimental tests under constant amplitude loading and fully reversed loading (R=-1), but it considers both the elastic and plastic components of strain. The EN curve can be divided into three regions: low-cycle fatigue (LCF), high-cycle fatigue (HCF), and transition fatigue. In the LCF region, the plastic strain dominates and the material fails after a relatively small number of cycles. In the HCF region, the elastic strain dominates and the material fails after a relatively large number of cycles. In the transition region, both elastic and plastic strains are significant and the material exhibits an intermediate fatigue life. The EN curve can be used to estimate the fatigue life of a material when the strain is partly plastic and the mean stress is high.
• Morrow model: This is a mean stress correction model that modifies the EN curve to account for the effect of mean stress on fatigue life. The mean stress is the average of the maximum and minimum stress in a cycle. The mean stress can influence the fatigue life of a material by changing the effective strain amplitude and causing either damage accumulation or damage recovery. The Morrow model assumes that only the plastic strain amplitude is affected by the mean stress, while the elastic strain amplitude remains constant. The Morrow model uses a modified endurance limit to calculate the corrected plastic strain amplitude based on the mean stress. The Morrow model can be used to improve the accuracy of fatigue life prediction when the mean stress is not zero.

I hope this description helps you understand more about these models. 😊

How to improve (reduce) skewness factor in Ansys Mechanical and CFD

Cooling process of the gear on Transient Thermal (Ansys Workbench)

What is Ansys Speos and how to use

What is Young Modulus in Ansys Mechanical (impact of this factor for structural analysis)

How to define porosity (porous medium) in Ansys CFD (Fluent, CFX)