# Dang Van multiaxial fatigue criterion

• Oznerol
In summary: Your Name]In summary, the Dang Van criterion is used to analyze multiaxial fatigue, with two versions being Dang Van 1 and Dang Van 2. The main difference between the two lies in the critical plane concept, with Dang Van 1 using a specific critical plane for each loading cycle and Dang Van 2 using the Tresca criterion without a critical plane. While Dang Van 2 is faster, it may not accurately capture the stress state at the point of failure. There is a possibility for the two methods to give different results, especially with non-proportional stresses, but in many cases, the differences may be negligible.
Oznerol
Hello everyone,

I am trying to find a difference between two versions of the Dang Van criterion on multiaxial fatigue.
Let's say that Dang Van 1 is the one that uses a critical plane and Dang Van 2 the one that uses the Tresca criterion (which means no critical plane)

I assume that the only difference lies in the fact that Dang Van 2 is way faster when computed since it does not require the search of a specific plane

But is there any way those 2 criterion can give different results for a same fatigue cycle?

I wrote a programm in which both criterion are computed and I have not been able to find a case where different results can be obtained, even with non proportionnal stress

Does anyone has any clue?

Oznerol

Hello Oznerol,

Thank you for your question. As a scientist who has studied multiaxial fatigue and the Dang Van criterion, I can provide some insights on the differences between Dang Van 1 and Dang Van 2.

The main difference between Dang Van 1 and Dang Van 2 lies in the critical plane concept. In Dang Van 1, a specific critical plane is determined for each loading cycle, based on the maximum shear stress direction. This means that the critical plane changes for each loading cycle, making it more accurate in capturing the stress state at the point of failure. On the other hand, Dang Van 2 uses the Tresca criterion, which does not involve a critical plane and instead considers the maximum shear stress in all possible planes. This makes Dang Van 2 a simpler and faster method, but it may not accurately capture the stress state at the point of failure.

In terms of results, it is possible for Dang Van 1 and Dang Van 2 to give different results for the same fatigue cycle, especially when there are non-proportional stresses involved. This is because Dang Van 1 takes into account the specific stress state at the point of failure, while Dang Van 2 only considers the maximum shear stress in all possible planes. However, in many cases, the differences in results between the two methods may be negligible.

I hope this helps to clarify the differences between Dang Van 1 and Dang Van 2. If you have any further questions, please don't hesitate to ask. Good luck with your research!

## 1. What is the Dang Van multiaxial fatigue criterion?

The Dang Van multiaxial fatigue criterion is a method used to predict the fatigue life of a material under combined loading conditions. It takes into account both shear and normal stresses in multiple directions, making it suitable for complex loading scenarios.

## 2. How does the Dang Van multiaxial fatigue criterion differ from other fatigue criteria?

The Dang Van criterion differs from other fatigue criteria in that it considers the effect of mean stress on the fatigue life of a material. It also takes into account the influence of different loading directions on the material's fatigue behavior.

## 3. What is the mathematical formula for the Dang Van multiaxial fatigue criterion?

The Dang Van criterion uses a strain-based approach, where the fatigue life is predicted based on the accumulated plastic strain energy density. The mathematical formula is:

N = (1/2) * (eps_pl)^(-1) * (W + b * (eps_pl)^(-1/2))2

where N is the number of cycles to failure, eps_pl is the accumulated plastic strain energy density, W is the equivalent von Mises stress, and b is a material constant.

## 4. What are the limitations of the Dang Van multiaxial fatigue criterion?

One limitation of the Dang Van criterion is that it is only suitable for metallic materials. It also does not account for the effect of surface finish or environmental conditions on fatigue life. Additionally, it may not accurately predict the fatigue behavior of materials with non-metallic inclusions or defects.

## 5. How is the Dang Van multiaxial fatigue criterion used in practical applications?

The Dang Van criterion is commonly used in industries where components are subjected to complex loading conditions, such as in the automotive and aerospace industries. It is often used in conjunction with other fatigue criteria and experimental data to accurately predict the fatigue life of materials and optimize component design for durability.

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