Mohr-Coulomb Stress Tool In ANSYS® Mechanical(Illustrated Expression)

This is another stress tool in ANSYS® Mechanical that you can solve your static problems. There are other theories such as the Maximum Equivalent Stress Tool and Maximum Shear Stress Tool in ANSYS® Mechanical. Here, we explain the Mohr-Coulomb Stress theory and how to solve a problem according to this theory.

What Is Mohr-Coulomb Stress?

In the most basic explanation, Mohr-Coulombs stress theory is used for brittle materials. For brittle materials, compression stress is also a very important parameter for failure as tensile stress. Unlike other theories for ductile materials, compression strength is also considered.

Calculation of Mohr-Coulomb stress for brittle materials is very basic. Here is the general formula for Mohr-Coulomb stress.

In this formula, Sigma1 refers to maximum tensile stress that occurs on specific stress elements on a brittle part or material. Sigma1 is the biggest tensile principal stress value. Sigma2 refers to minimum compressive stress that occurs on the same stress element on that brittle part. Stensile-limit and Scompressive-limit values are the material’s maximum stress values. As you see above calculation, this equation must be ensured for the safety of that part.

Brittle materials can be calculated such as concrete, glass, ceramics, etc.

How To Calculate Mohr-Coulomb Stress In ANSYS® Mechanical?

Mohr-Coulomb stress in ANSYS® Mechanical.

For example, you defined all of your boundary conditions for your problem in ANSYS® Mechanical like above. To see ‘Mohr-Coulomb Stress’, right-click on ‘Solution’ then hover your mouse on the ‘Insert’ option, then do the same thing for ‘Stress Tool’ as shown by red arrows above. Then select ‘Mohr-Coulomb Stress’ as shown in the red box above in ANSYS® Mechanical.

Select a calculation method for Mohr-Coulomb Stress.

As you see above, you can select one of three options that we stated below. You just need to right-click on ‘Stress Tool’ after adding ‘Mohr-Coulomb Stress’. Then hover your mouse on the ‘Stress Tool’ option. Then select a method.

The above formulae define the calculation methods for Mohr-Coulomb stresses. You can view your part’s situation by selecting one of these values.


Do not forget to leave your comments and questions below about Mohr-Coulomb Stress Tool in ANSYS® Mechanical below. Your precious feedbacks are very important to us.

NOTE: All the screenshots and images are used in education and informative purposes. Images used courtesy of ANSYS, Inc.


3 responses to “Mohr-Coulomb Stress Tool In ANSYS® Mechanical(Illustrated Expression)”

  1. Rodrigo Evangelista Aguiar de Souza Rodrigo Evangelista Avatar
    Rodrigo Evangelista Aguiar de Souza Rodrigo Evangelista

    this YouTube video says FS must be greater than 1 to ensure structure safety, and this left me wondering which equation I should consider. Could you guide me?

    1. MB-Editor Avatar

      If you take a look at the Safety Margin and Safety Factor formulas above, you can see the requirement of a value which must be bigger than 1 to obtain safe structure.

  2. Abhishek Yadav Avatar
    Abhishek Yadav

    While evaluating the stress tool with safety factor. I get the following error. I’m doing the analysis for PMMA(Acryllic) and it’s Yield strength is defined in materials property.

    An error occurred while evaluating Stress Tool results: Yield strength is required but not defined.

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