```{index} Strain diagram torsion
```
# ... for torsion

For torsion, the assumed strain diagram depends on the cross-section

```{index} Strain diagram torsion; thin-walled circular tubes
```
```{index} Strain diagram torsion; thin-walled non-circular tubes
```
## ... in thin-walled circular and closed thin-walled non-circular tubes

The strain diagram is parallel to the centre line and are constant over the wall thickness

The thin-walled circular tube is treated in chapter 6.2.1 and the thin-walled non-circular tube in chapter 6.3.1 of the book Engineering Mechanics Volume 2 {cite:p}`Hartsuijker2007`.

```{index} Strain diagram torsion; solid circular bars
```
```{index} Strain diagram torsion; thick-walled circular tubes
```
## ... in solid circular bars and thick-walled circular tubes


The strain diagram is parallel to the surface and is proportional to the distance to the axis of the bar.

The solid circular bar is treated in chapter 6.2.2 and the thick-walled circular tubes in chapter 6.2.3 of the book Engineering Mechanics Volume 2 {cite:p}`Hartsuijker2007`.

```{index} Strain diagram torsion; thin-walled cross-sections
```
## ... in open thin-walled cross-sections

The strain diagram is parallel to the surface, is proportional to the distance to the axis of the bar and flows around near the edges of the strip.

This is treated in chapter 6.3.2 of the book Engineering Mechanics Volume 2 {cite:p}`Hartsuijker2007`.