Membrane Analogy for Torsion — Lesson 3

This lesson covers the concept of torsion in different cross sections such as rectangular, triangular, and elliptical. It explains how to calculate the constant m, the stress at the end of the x-axis, and the maximum stress in a square cross section. The lesson also introduces Prandtl’s membrane analogy to understand the torsion problem and provides examples of how to apply this analogy to various cross sections. It further explains the concept of shear stress and how it varies across different points in a cross section. The lesson concludes with a discussion on the uniqueness of stress and how it can be used to determine the stress at the corners of a cross section.

Video Highlights

00:42 - Introduction to the example on rectangular section and the function phi
05:36 - Calculation of the stress at the end of the x axis
12:40 - Explanation of the Prandtl’s membrane analogy
39:28 - Analysis of different cross sections like triangular and elliptical
49:59 - Discussion on the stress at the corner of a rectangular section
52:16 - Analysis of stress in a T cross section

Key Takeaways

- The constant m in a rectangular cross section can be calculated using the function phi and the boundaries of the cross section.
- The stress at the end of the x-axis and the maximum stress in a square cross section can be calculated using the constant m.
- Prandtl’s membrane analogy can be used to understand the torsion problem and apply it to various cross sections.
- Shear stress varies across different points in a cross section, with the maximum stress occurring at the farthest point in a circular cross section and at a point closer to the center in a rectangular or triangular cross section.
- The uniqueness of stress can be used to determine the stress at the corners of a cross section, which is always zero.