Strength of Materials | How to draw Mohr's circle? | Determination of Principal stresses and Plane

Michael Thomas Rex F12 minutes read

The Mohr circle method helps determine principle stresses in an element, with maximum and minimum normal stresses and maximum shear stress identified. Principal stresses of 13.66 MPa and 9.66 MPa are found at orientations rotated 15.48 degrees counter-clockwise from the horizontal axis, with the maximum shear stress being 11.66 MPa.

Insights

  • Mohr circle is a graphical method used to analyze stress states in materials, providing insight into maximum and minimum normal stresses as well as the maximum shear stress present.
  • Understanding the sign convention for stresses is crucial: tensile normal stresses are considered positive, compressive normal stresses are negative, and a clockwise rotation of shear stress is positive, guiding the interpretation of Mohr circle results.

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Recent questions

  • How is Mohr circle used in stress analysis?

    Mohr circle determines principle stresses and maximum shear stress.

  • What is the significance of the sign convention in Mohr circle analysis?

    Sign convention aids in interpreting normal and shear stresses.

  • How are principal stresses determined using Mohr circle?

    Principal stresses are found at Mohr circle intersections.

  • What is the role of Mohr circle in material design optimization?

    Mohr circle aids in optimizing material designs for structural integrity.

  • How does Mohr circle analysis enhance understanding of stress states?

    Mohr circle analysis provides insights into stress distributions and orientations.

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Summary

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Determining Principle Stresses with Mohr Circle

  • Mohr circle is used to determine principle stresses in a given element, including maximum and minimum normal stresses and maximum shear stress.
  • In the given element, normal stresses are 8 MPa along x-face (compressive) and 12 MPa along y-face (tensile), with a shear stress of 6 MPa.
  • Sign convention: Tensile normal stresses are positive, compressive normal stresses are negative, and clockwise shear stress rotation is positive.
  • To construct Mohr circle, find points A and B on x and y faces respectively, and the center at (2,0) by averaging normal stresses.
  • Draw Mohr circle using points A, B, and center C, with the radius representing maximum shear stress (11.66 MPa).
  • Principal stresses are found at the intersection of Mohr circle with the horizontal axis, with minimum stress at 9.66 MPa and maximum stress at 13.66 MPa.
  • The orientation of the principal plane is determined by rotating the element 15.48 degrees counter-clockwise from the horizontal axis.
  • Exercise problem provided for practice, with directions of normal and shear stresses reversed, encouraging further understanding of Mohr circle concepts.
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