# stressMask meaning in class PeriTriaxController

I want to know how stressMask in in class PeriTriaxController control stress or strain along three axis.

I guess I should convert the value of stressMask to the value of binary system first, then I can decide which axis direction is controlled by stress via 1 or strain via 0.

Take doc/sphinx/

I am not sure wherther I understand the stressMask's meaning right?

Could you give me a detail explanation and whether there is a possible range (0~7) for the choice of the value of stressMask in class PeriTriaxContro

Thank you very much!

## Question information

- Language:
- English Edit question

- Status:
- Answered

- For:
- Yade Edit question

- Assignee:
- No assignee Edit question

- Last query:
- 2019-08-27

- Last reply:
- 2019-08-27

Jérôme Duriez (jduriez) said : | #1 |

Hi,

Everything you said is correct, so I guess you almost understood stress masks, congratulations !

In order to nail it down once for all (hopefully) and understand more complex cases than the isotropic 111 = 7, let say that

stressMask = a*2^0 + b*2^1 + c*2^2 = a + 2b + 4c, with a,b,c = 0 or 1.

Then a corresponds to x direction (direction "0"),

b corresponds to y direction (direction "1"),

and c corresponds to z direction (direction "2")

and the 0/1 values tell you whether each direction is strain (0) or stress (1)-controlled.

And, as you said, the range of possible values for a + 2b + 4c, with a,b,c = 0 or 1, indeed goes from 0 to 7.

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