πŸ’₯πŸ’₯πŸ’₯ How to avoid peak stresses in Structural Analysis in Ansys Workbench

on

 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.

Comments

Post a Comment

Popular POSTS

Image

Quick Tip: How to fix Error: GENERAL-CAR-CDR in Ansys (Fluent)

 The error message Error: GENERAL-CAR-CDR: invalid argument [1]: improper list means that there is a problem with the scheme code or the UDF (user-defined function) in your case or data file . Some possible solutions are: Save the case and data file and try to reopen it. Reset the Fluent Setup tab and try opening the mesh. Remesh the geometry and reopen in Fluent. Change the material definition from “Solid” to “Fluid” in Design Modeler. Change the transient to steady if you are using evaporation-condensation as the phase interaction mechanism. Check the syntax of your UDF and make sure it follows the new rules in Fluent 6.2.16 or later. I hope this helps you resolve the error. If you need more assistance, please visit the Ansys Learning Forum or contact Ansys Support . Have a nice day! 😊 Sources: 1. smartadm.ru 2. cfd-online.com 3. forum.ansys.com 4. forum.ansys.com In Polish  BΕ‚Δ…d: GENERAL-CAR-CDR oznacza, ΕΌe wystΔ…piΕ‚ problem z kodem Scheme w programie Ansys Fluent. Scheme to jΔ™zyk
Image

Types of supports and examples - Ansys Static Structural

Supports are used to represent parts that are not present in the model but are interacting with it. Supports help truncate the domain, which helps in efficiently obtaining numerically accurate results without modeling parts of the geometry that are not of primary interest. There are different types of support available, among which you need to choose the appropriate one for your analysis. Here are some of the common types of supports and their explanations: - **Fixed Support**: This type of support constrains all the degrees of freedom of the selected entity (body, face, or edge). It means that the entity cannot move or rotate in any direction. Fixed support is equivalent to applying zero displacement to all directions. Fixed support is useful for modeling rigid connections or supports that do not allow any movement. For example, you can use fixed support to model a bolted joint or a clamped beam. - **Displacement Support**: This type of support specifies a zero or non-zero displacemen
Image

How to define porosity (porous medium) in Ansys CFD (Fluent, CFX)

 To model porosity in ANSYS Fluent , you need to define the porous zone and the porous media properties in the setup. You can follow these steps: In the Fluent interface, go to the Cell Zone Conditions panel and select the zone that you want to make porous. Check the Porous Zone option and click Edit. In the Porous Zone panel, you can choose between two methods to specify the porous media resistance: the Superficial Velocity method or the Physical Velocity method. The Superficial Velocity method uses the superficial velocity (the velocity of the fluid if there were no porosity) to calculate the pressure drop across the porous zone. The Physical Velocity method uses the physical velocity (the velocity of the fluid inside the pores) to calculate the pressure drop across the porous zone. You can also choose between isotropic or anisotropic porosity, depending on whether the porosity is uniform or varies in different directions. Depending on the method and the type of porosity you choose,
Image

How to... fix "gui-domain-label: no domain selected" in Ansys Fluent and MEMERR in CFX

In today's post, we will deal with another error that may occur during the analysis. The error that is described below concerns Fluent and the wrong definition of user monitors that are displayed during simulation. These can be monitors concerning the average velocity in the domain volume, the values of the maximum temperatures of the solid domains, the average values of the heat transfer coefficient from the defined planes of the model, etc. Generally speaking, today's entry is about how to correctly define monitors and how to transfer them between subsequent analyzes. Example of "gui-domain-label" error in Fluent