💥💥💥 How to avoid peak stresses in Structural Analysis in Ansys Workbench

 Peak stresses in structural analysis are often caused by stress singularities, which are artificial stresses computed because of simplification in the FEA model. Some common causes of stress singularities are sharp corners, stiff boundary conditions, point loads, constraint equations, etc.¹

There are several ways to avoid or deal with peak stresses in Ansys Workbench, depending on the nature and purpose of the analysis. Some possible methods are:

- Submodeling: This involves creating a submodel at the high stress locations with enough detail (e.g. fillet radius) along with mesh convergence study. This is the most accurate and reliable method, but also the most time-consuming and complex.¹

- Stress Concentration Calculation: This involves using Roark's formulas for stress and strain or other analytical solutions to determine the appropriate factors relative to the nominal stress. This works well if the load pattern and geometry are close to the textbook cases. It serves as a good way to ballpark a similar type geometry.¹

- Hot Spot Method: This involves creating a path of stress to the singularity and extracting the stress value at a certain distance away from the singularity (e.g. 1 mm), where it is assumed the stresses are adequately far away. Often times a fudge-factor on top of the extracted stress value is applied to build in some conservative margin. This method takes some upfront homework, is quick and dirty and may require good hand waving skills.¹

- ERESX Command: This is a command that controls the extrapolation settings in Ansys. By using ERESX,NO, one can force Ansys to copy the integration point stresses to the nodes. This ensures that stresses will never exceed yield as the stresses at the integration points can never exceed yield.³

- Thermal-Stress Analysis: This is a type of analysis that accounts for the thermal strain due to temperature changes. This can affect the stress distribution and magnitude in the model. One can perform a thermal-stress analysis by sharing model data between thermal and structural using the same or dissimilar mesh.⁴

You can learn more about these methods by following the links in the references. I hope this helps you with your structural analysis. 😊

Source: 

(1) FEA Stress Singularities - Ansys Tips. https://www.ansystips.com/2017/05/fea-stress-singularities.html.

(2) Elastic-Plastic Analysis in ANSYS Gives Stress Above Yield | Nick J .... https://medium.com/@nickjstevens/elastic-plastic-analysis-in-ansys-gives-stress-above-yield-nick-j-stevens-81d990f1a78.

(3) Performing a Thermal-Stress Analysis - ANSYS Innovation Courses. https://courses.ansys.com/index.php/courses/structural-boundary-conditions/lessons/performing-a-thermal-stress-analysis-lesson-6/.

(4) Ansys structural analysis tutorials - Pure bending stress analysis .... https://www.youtube.com/watch?v=8awQ2UYXIBA.

How to perform submodeling in Ansys Workbench?

Submodeling in Ansys Workbench is a technique that allows you to refine the stress analysis of a region of interest without having to mesh the whole model with fine elements. It involves creating a submodel of the area you want to focus on and applying the displacement (and temperature) results from the global model as boundary conditions on the submodel. This way, you can capture the effects of local features, design changes, or non-linearities in the submodel without affecting the overall response of the system.

To perform submodeling in Ansys Workbench, you can follow these general steps:

- Generate the solution on the global model using the Mechanical tool.

- Create the submodel geometry in a separate Mechanical window or in SpaceClaim. You can use a local coordinate system to define the submodel location and orientation.

- Attach the submodel to the engineering data and solution of the full model using the Model cell in the Project Schematic.

- Define a Remote Displacement boundary condition on the submodel and import the Cut Boundary Constraint from the full model solution. This will apply the displacement (and temperature) results from the full model to the submodel.

- Define the mesh size and any other settings for the submodel analysis. You can use Named Selections to control the mesh refinement in the submodel.

- Solve the submodel and review the results. You can compare the results with the full model or with analytical solutions to verify the accuracy of the submodeling technique.

You can find more details and examples of submodeling in Ansys Workbench by following the links in the references¹²³⁴⁵⁶⁷. I hope this helps you with your structural analysis. 😊

Source: 

(1) Performing Submodeling in Ansys Mechanical — Lesson 6. https://www.youtube.com/watch?v=WC9bN2B9w2M.

(2) How to Use Submodeling in Ansys Mechanical | Ansys Tutorials. https://www.youtube.com/watch?v=LEU6LlGUPAI.

(3) Ansys Sub modeling. https://www.youtube.com/watch?v=_7girXRDK2w.

(4) Submodeling in ANSYS Mechanical: Easy, Efficient, and Accurate. https://www.padtinc.com/2013/08/14/submodeling_ansys_mechanical/.

(5) Submodeling using ansys_workbench_v12 | PPT - SlideShare. https://bing.com/search?q=submodeling+in+Ansys+Workbench.

(6) Submodelling in Ansys - Mechead.com. https://www.mechead.com/submodelling-in-ansys/.

(7) Submodeling using ansys_workbench_v12 | PPT - SlideShare. https://www.slideshare.net/sivasankar1977/submodeling-using-ansysworkbenchv12.

(8) https://bit.ly/3Eo8esU.

(9) https://bit.ly/32eEcuR.

(10) https://bit.ly/3qsytK2.

(11) https://bit.ly/3Bbaaow.