(material science) Fatigue life prediction using integral

In summary, the conversation discusses the calculation of delta sigma for a question involving tensile and compressive stresses. The speaker initially thought that delta sigma was equal to the maximum stress, but their professor clarified that it is only equal to the tensile stress in the case of tensile and compression. In the case of tensile and tensile, the delta sigma is equal to the maximum tensile stress minus the minimum tensile stress. To find the critical crack length, the speaker would use the largest tensile stress. They are seeking confirmation on their understanding of this concept.
  • #1
Pipsqueakalchemist
130
18
Homework Statement
I have question and solutions pictures below
Relevant Equations
Pictures of equations posted below
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So for this question, I understand the math but just wanted to be clear on a few things. So I had this question on my midterm but instead of tensile and compressive stresses, it was tensile and tensile stress. I initially thought that the delta sigma in the integral was the maximum stress so in the example 100 MPa. But I believe my professor said that if it's tensile and compression then delta sigma is just equal to the tensile stress, but if it's tensile and tensile then the delta sigma would be max tensile - min tensile. And of course to find critical crack length I would use the largest tensile stress. I just wanted to make sure that this was correct because I ask my professor awhile ago and can't be 100% sure if this was correct, so please can someone confirm if I'm correct.
 
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  • #2
In your example, in my judgment, ##\Delta \sigma## should be 150 MPa.
 

1. What is fatigue life prediction using integral?

Fatigue life prediction using integral is a method used in material science to estimate the lifespan of a material under repeated loading and unloading cycles. It involves using mathematical equations and experimental data to determine the point at which a material will fail due to fatigue.

2. How does fatigue life prediction using integral work?

This method uses an integral equation, which takes into account the material properties, loading conditions, and stress levels to predict the number of cycles a material can withstand before failure. It also considers the effects of stress concentration, surface roughness, and environmental factors on the fatigue life of a material.

3. What are the advantages of using fatigue life prediction using integral?

One of the main advantages is that it can provide a more accurate and efficient way to estimate the fatigue life of a material compared to traditional experimental methods. It also allows for the prediction of fatigue life under different loading conditions, which can help in optimizing the design and use of materials.

4. What are the limitations of fatigue life prediction using integral?

Some of the limitations include the need for accurate and reliable material data, as well as the complexity of the equations used. It may also not be suitable for all materials and loading conditions, and further research is needed to improve its accuracy and applicability.

5. How is fatigue life prediction using integral used in real-world applications?

This method is commonly used in industries such as aerospace, automotive, and manufacturing, where the durability and reliability of materials are crucial. It can help in the design and selection of materials for various components, as well as in predicting the maintenance and replacement schedules for existing structures.

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