Unsure about angle inside Mohr's circle?

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Discussion Overview

The discussion revolves around the interpretation of angles within Mohr's circle, specifically addressing why the angle inside the triangle is labeled as θP2 instead of θP1. Participants are seeking clarification on the definitions and relationships between these angles and the corresponding principal stresses.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about why the angle inside the triangle is θP2 rather than θP1, despite understanding other aspects of Mohr's circle.
  • Another participant notes that θP1 is not defined in the context but assumes θP2 corresponds to σ2, indicating a potential link between subscripts and principal stresses.
  • A further contribution reiterates the confusion regarding the designation of θP2 and questions the basis for identifying it over θP1.
  • One participant clarifies that point D corresponds with σ2 and point B with σ1, suggesting that if σ2 is the minimum principal stress, then 2θP2 represents the angle with the x-axis, while 2θP1 would relate to point E, which is positioned 180° from point A.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the definitions and implications of θP1 and θP2, indicating that multiple interpretations and uncertainties remain in the discussion.

Contextual Notes

The discussion highlights the lack of clear definitions for θP1 and the assumptions made regarding the angles and their corresponding principal stresses, which may affect the understanding of the relationships within Mohr's circle.

influx
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Can someone explain why the angle inside the triangle inside Mohr's circle is θP2 rather than θP1 ? I understand everything else but just this small point is frustrating me.

Thanks

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I don't see θP1 defined anywhere but I assume that the subscript 2 is used with θP2 to correspond with σ2.
 
paisiello2 said:
I don't see θP1 defined anywhere but I assume that the subscript 2 is used with θP2 to correspond with σ2.
θP2 is the angle that corresponds to σ2 and θP1 is the angle that corresponds to σ1 but what I am confused about is why the angle inside the triangle is θP2 rather than θP1? How did they know which one it is?
 
Point D corresponds with σ2 and point B corresponds with σ1. If σ2 is the minimum principle stress then by definition 2θP2 would be the angle that point A makes with the x-axis. And 2θP1 would make the angle with point E which would be 180° from point A in Figure 22.9.
 
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