Effective area for compression versus tension of a link?

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Discussion Overview

The discussion revolves around the effective area used for calculating normal stress in links under tension and compression. It explores the differences in stress calculations for links BD and CE, focusing on the implications of pin diameters and loading conditions.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant notes that the normal stress calculations for links BD and CE should use different effective areas, suggesting that link BD should account for the total area minus the pin diameter, while link CE should use the total area.
  • Another participant explains that for link A & D, the loading pulls toward the outer ends, with tensile strength resisting the load, while for link C & E, the pins push toward the center, compressing the area between them.
  • A participant states that the maximum average normal stress does not occur at the pin for the link in compression, contrasting it with the link in tension.
  • One participant requests clarification on what is meant by the "total area" in this context.

Areas of Agreement / Disagreement

Participants express differing views on the effective areas for stress calculations, indicating that multiple competing perspectives exist regarding the definitions and implications of these areas.

Contextual Notes

There are unresolved questions about the definitions of total area and how it applies to different loading conditions, as well as the assumptions underlying the stress calculations.

joahe
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Thread moved to HH from the technical forums, so no HH Template is shown
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I solved the equilibrium equations and found that link BD is in tension while link CE is in compression, but my resulting answers for normal stress were wrong.

The solutions show that the cross area to be used for normal stress at links BD and CE should be different. Link BD should incorporate the (Total Area - Pin Diameter) while link CE incorporates the Total Area.

Why is this true?
 
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For the A & D link the loading of both pins are pulling toward the outer ends of the link with only the tensile strength of the two areas on each side of each pin resisting the load.

For the C & E link both pins are pushing toward the center of the link, so they are actually trying to compress the area between the C & E pins.
 
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The maximum value of the average normal stress doesn't occur in the pin for the link in compression like it does for the link in tension.
 
Would you mind explaining that what is the total area here being referred to?
 

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