Fatigue Analysis: Maximum & Minimum Stress

In summary, the Soderberg and Goodman fatigue analysis methods use a two dimensional Cartesian coordinate system with the x-axis representing mean stress and the y-axis representing stress amplitude. The maximum and minimum stresses used in the analysis are the maximum tensile bending stress and the maximum compressive stress, respectively, encountered during a standard rotating beam machine test. These stresses are not principle stresses and their origin is not typically mentioned in graduate level books.
  • #1
Ravi Singh choudhary
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Whether we are using Soderberg or Goodman line; it is two dimensional Cartesian coordinate system in which x-axis is the mean stress and y-axis is stress amplitude. For them to calculate we have two values one is maximum stress and other is minimum; I found on Quora.com that they are not principle stresses by nature. Even in books that I read in graduate level, they not mentioned about their origin. One more thing is that; to calculate endurance limit every specimen goes through the same testing method i.e. rotating beam machine that means maximum and minimum are always maximum tensile bending stress and maximum compressive stress respectively. Mean will be always zero as specimen is made always symmetric.

Pls help what is maximum and minimum stress in the fatigue analysis.
 
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  • #2
Is it principal stress?No, the maximum and minimum stresses used in Soderberg and Goodman's fatigue analysis are not principal stresses. These stresses are simply the maximum tensile bending stress and the maximum compressive stress, respectively, encountered during a standard rotating beam machine test. The mean stress used in the analysis is always zero, as the specimen is always symmetrically loaded.
 

FAQ: Fatigue Analysis: Maximum & Minimum Stress

1. What is fatigue analysis and why is it important?

Fatigue analysis is a method used to predict the failure of a material or structure due to repeated loading and unloading cycles. It is important because it helps engineers and designers determine the durability and safety of a product or structure, ensuring that it can withstand the expected usage without failure.

2. What is maximum stress and how does it affect fatigue analysis?

Maximum stress is the highest stress level that a material or structure experiences during operation. In fatigue analysis, this stress level is used to determine the number of cycles that the material or structure can withstand before failure. A higher maximum stress means a shorter lifespan, while a lower maximum stress means a longer lifespan.

3. Can fatigue analysis predict the exact lifespan of a material or structure?

No, fatigue analysis can only provide an estimate of the expected lifespan based on the maximum and minimum stress levels. Other factors such as material properties, loading conditions, and environmental factors can also affect the lifespan of a material or structure.

4. What is the difference between maximum and minimum stress in fatigue analysis?

Maximum stress is the highest stress level experienced by a material or structure, while minimum stress is the lowest stress level. In fatigue analysis, both maximum and minimum stress are used to calculate the stress range, which is a crucial factor in determining the fatigue life of a material or structure.

5. How can fatigue analysis be used to improve product design?

Fatigue analysis can be used to identify potential failure points in a product design and help engineers make necessary modifications to improve its durability. By analyzing the maximum and minimum stress levels, engineers can optimize the design and select materials that can withstand the expected loading conditions, resulting in a longer lifespan and better performance of the product.

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