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Bronislav Prokhorov
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SMART Crack Growth: A Powerful and Easy-to-Use Tool for Crack Growth Analysis in Ansys Workbench



Crack Growth Analysis Using Ansys Workbench: A Portable and Powerful Tool for Engineers




Crack growth analysis is a vital technique for assessing the structural integrity, reliability, and safety of engineering components and systems. It involves simulating the initiation, propagation, and fracture of cracks under various loading conditions. Crack growth analysis can help engineers design better products, optimize performance, prevent failures, and extend service life.




Crack Growth Ansys Workbench Tutorialsl PORTABLE



In this article, we will show you how to use Ansys Workbench, a simulation integration platform that connects various Ansys products, to perform crack growth analysis. We will also show you how to download and install Ansys Workbench software for free on your device. By the end of this article, you will have a clear understanding of what crack growth analysis is, why it is important, how to use Ansys Workbench for crack growth analysis, and how to get started with Ansys Workbench software.


What is Crack Growth Analysis and Why is it Important?




Definition and Concepts of Crack Growth Analysis




Crack growth analysis is a branch of fracture mechanics that deals with the study of crack initiation and crack propagation in materials subjected to cyclic or static loads. The main goal of crack growth analysis is to predict the size, shape, orientation, and location of cracks in a structure, as well as the number of cycles or load levels required for crack growth or failure.


Crack growth analysis is based on the concept of stress intensity factor (SIF), which is a measure of the stress state at the crack tip. The SIF depends on the geometry of the structure, the crack configuration, and the applied load. The SIF can be calculated using analytical or numerical methods, such as finite element analysis (FEA).


The rate of crack growth per cycle, or da/dN, is a function of the SIF range, or ΔK, which is the difference between the maximum and minimum SIF values in a load cycle. The relationship between da/dN and ΔK can be expressed by various empirical or theoretical equations, such as the Paris-Erdogan equation. The crack growth rate can also be influenced by other factors, such as stress ratio, overloads, load history, material properties, environmental conditions, etc.


Applications and Benefits of Crack Growth Analysis




Crack growth analysis has many applications in various engineering domains, such as aerospace, automotive, civil, mechanical, nuclear, biomedical, etc. It can be used to evaluate the performance and durability of structures that are prone to fatigue or static loading, such as aircraft wings, turbine blades, bridges, pipelines, pressure vessels, implants, etc.


Some of the benefits of crack growth analysis are:


  • It can help engineers design structures that are resistant to crack initiation and propagation.



  • It can help engineers optimize the material selection, geometry, dimensions, load distribution, etc. of structures.



  • It can help engineers estimate the remaining life or service intervals of structures based on crack size and growth rate.



  • It can help engineers detect and monitor cracks in structures using non-destructive testing (NDT) methods.



  • It can help engineers prevent catastrophic failures and reduce maintenance costs and downtime.



How to Use Ansys Workbench for Crack Growth Analysis




An Overview of Ansys Workbench Platform and Features




Ansys Workbench is a simulation integration platform that connects various Ansys products, such as Ansys Mechanical, Ansys Fluent, Ansys CFX, etc. It provides a unified and consistent user interface, data management, and project workflow for performing various types of simulations, such as structural, fluid, thermal, electromagnetic, etc.


Ansys Workbench also offers a powerful and flexible tool for crack growth analysis, called SMART (Separating Morphing and Adaptive Remeshing Technology) Crack Growth. SMART Crack Growth is an automated and robust method that can simulate the initiation and propagation of cracks in 2D or 3D models with complex geometries and loading conditions. SMART Crack Growth can handle multiple cracks, mixed-mode loading, crack branching, crack coalescence, crack closure, etc. It can also calculate the SIFs, da/dN, fatigue life, etc. for each crack.


SMART Crack Growth is integrated with Ansys Mechanical, which is a general-purpose FEA software that can perform static, dynamic, linear, nonlinear, thermal, modal, etc. analyses. Ansys Mechanical can also import geometries and meshes from various CAD and meshing software, such as SolidWorks, CATIA, ICEM CFD, etc.


A Step-by-Step Guide to Perform Crack Growth Analysis with Ansys Workbench




In this section, we will provide a step-by-step guide to perform crack growth analysis with Ansys Workbench using SMART Crack Growth. We will use a simple example of a center-cracked plate subjected to tensile loading. The geometry and dimensions of the plate are shown in the table below.



Parameter


Value


Plate length (L)


100 mm


Plate width (W)


50 mm


Plate thickness (t)


5 mm


Initial crack length (a)


10 mm


Material (steel)


E = 200 GPaν = 0.3σy = 250 MPaParis-Erdogan equation: da/dN = CΔKC = 1.0E-12m = 3.0


Loading condition


Tensile stress (σ) = 100 MPaStress ratio (R) = 0.1Frequency (f) = 10 Hz


The steps to perform crack growth analysis with Ansys Workbench are as follows:


Preparing the Geometry and Mesh




The first step is to create or import the geometry of the model in Ansys Workbench. You can use the built-in geometry editor in Ansys Workbench or any other CAD software that is compatible with Ansys Workbench. For this example, we will use the geometry editor in Ansys Workbench.


To create the geometry of the center-cracked plate in Ansys Workbench:



  • Open Ansys Workbench and create a new project.



  • Drag and drop the Static Structural analysis system from the Toolbox to the Project Schematic.



  • Double-click on the Geometry cell to open the geometry editor.



  • Create a new sketch on the XY plane and draw a rectangle with the dimensions L x W.



  • Create another sketch on the XY plane and draw a line segment with the length a at the center of the rectangle.



  • Select both sketches and extrude them by t/2 in both directions along the Z axis.



  • Select the line segment and assign it as a crack edge using the Edge Split tool.



  • Save and close the geometry editor.



The next step is to generate a mesh for the model in Ansys Workbench. You can use the built-in meshing tool in Ansys Workbench or any other meshing software that is compatible with Ansys Workbench. For this example, we will use the meshing tool in Ansys Workbench.


To generate a mesh for the center-cracked plate in Ansys Workbench:



  • Double-click on the Mesh cell to open the meshing tool.



  • Select the model and Apply a mesh control to the crack edge using the Sizing tool. Set the element size to 0.1 mm and the bias factor to 10.



  • Generate the mesh using the default settings. You should see a fine mesh near the crack tip and a coarse mesh away from the crack tip.



  • Save and close the meshing tool.



Defining the Initial Crack and Boundary Conditions




The next step is to define the initial crack and boundary conditions for the model in Ansys Workbench. You can use Ansys Mechanical, which is a FEA software that is linked to Ansys Workbench, to define the crack and boundary conditions.


To define the initial crack and boundary conditions for the center-cracked plate in Ansys Workbench:



  • Double-click on the Setup cell to open Ansys Mechanical.



  • Select the model and apply a material from the Engineering Data library. For this example, we will use steel as the material.



  • Select the crack edge and insert a SMART Crack Growth feature from the Model menu.



  • Define the initial crack length as a/2 and the crack front shape as straight.



  • Select the two opposite faces of the plate and apply a displacement boundary condition from the Static Structural menu.



  • Set the displacement value as σL/E on one face and -σL/E on the other face, where σ is the tensile stress, L is the plate length, and E is the Young's modulus of steel.



  • Select the other two opposite faces of the plate and apply a frictionless support boundary condition from the Static Structural menu.



  • Save and close Ansys Mechanical.



Setting up the SMART Crack Growth Parameters and Options




The next step is to set up the SMART Crack Growth parameters and options for the model in Ansys Workbench. You can use Ansys Workbench to set up the parameters and options for SMART Crack Growth.


To set up the SMART Crack Growth parameters and options for the center-cracked plate in Ansys Workbench:



  • Double-click on the Solution cell to open Ansys Workbench.



  • Select Analysis Settings from the Solution menu.



  • Set the analysis type as Transient and the number of steps as 1000.



  • Set the time step size as 0.1/f, where f is the loading frequency. This will ensure that each load cycle is captured by 10 time steps.



  • Select SMART Crack Growth from the Solution menu.



  • Set the crack growth criterion as da/dN and the crack growth equation as Paris-Erdogan.



  • Enter the values of C and m for the Paris-Erdogan equation, which are the material constants for crack growth rate. For this example, we will use C = 1.0E-12 and m = 3.0.



  • Set the stress ratio as R, which is the ratio of the minimum to maximum stress in a load cycle. For this example, we will use R = 0.1.



  • Set the maximum crack length as L/2, which is the half of the plate length. This will stop the simulation when the crack reaches the plate edge.



  • Save and close Ansys Workbench.



Running the Simulation and Analyzing the Results




The final step is to run the simulation and analyze the results for the model in Ansys Workbench. You can use Ansys Workbench to run the simulation and view the results for SMART Crack Growth.


To run the simulation and analyze the results for the center-cracked plate in Ansys Workbench:



  • Click on the Update Project button to update the project with the latest settings and options.



  • Click on the Run Calculation button to start the simulation. The simulation may take some time depending on the complexity of the model and the number of steps.



  • Click on the Solution Information cell to view the status and progress of the simulation. You can also view the output messages and error messages if any.



  • Click on the Results cell to open Ansys Mechanical and view the results.



  • Select SMART Crack Growth from the Results menu. You can view various results, such as SIFs, da/dN, crack length, fatigue life, etc. for each crack and each time step.



  • Select Total Deformation from the Results menu. You can view the deformation of the model due to the applied load and the crack growth.



  • Select Equivalent Stress from the Results menu. You can view the stress distribution in the model and the stress concentration at the crack tip.



  • Select Crack Front from the Results menu. You can view the crack front shape and location at each time step.



  • Select Crack Surface from the Results menu. You can view the crack surface shape and area at each time step.



  • Save and close Ansys Mechanical.



How to Download and Install Ansys Workbench Software for Free




Ansys Student Versions: Free Simulation Software for Students and Educators




If you are a student or an educator who wants to learn and practice crack growth analysis using Ansys Workbench, you can download and install Ansys Student versions for free on your device. Ansys Student versions are free simulation software that can be used for academic purposes only. They have some limitations in terms of model size, features, and functionality, but they are still powerful enough to perform various types of simulations, including crack growth analysis.


Ansys Student versions include Ansys Mechanical, Ansys CFD, Ansys Electronics, Ansys Discovery, etc. You can choose the version that suits your needs and interests. For crack growth analysis, you will need Ansys Mechanical Student version, which includes SMART Crack Growth feature.


How to Download and Install Ansys Student Versions on Your Device




To download and install Ansys Student versions on your device, you need to follow these steps:



  • Go to the Ansys Student portal and register with your academic email address.



  • Select the Ansys Student version that you want to download from the list of available products. For this example, we will select Ansys Mechanical Student version.



  • Read and accept the terms and conditions of the license agreement.



  • Download the installation package for your operating system (Windows or Linux).



  • Extract the installation package to a folder on your device.



  • Run the setup.exe file as an administrator and follow the instructions on the screen.



  • Enter the license key that you received in your email after registration.



  • Complete the installation process and restart your device if required.



  • Launch Ansys Workbench from your desktop or start menu and enjoy your free simulation software.



Conclusion and FAQs




Summary of the Main Points and Takeaways




In this article, we have learned about crack growth analysis using Ansys Workbench. We have covered the following topics:



  • What is crack growth analysis and why is it important?



  • How to use Ansys Workbench for crack growth analysis?



  • How to download and install Ansys Workbench software for free?



We have also provided a step-by-step guide to perform crack growth analysis with Ansys Workbench using SMART Crack Growth feature. We have used a simple example of a center-cracked plate subjected to tensile loading. We have shown how to create or import the geometry and mesh, define the initial crack and boundary conditions, set up the SMART Crack Growth parameters and options, run the simulation and analyze the results.


We hope that this article has helped you understand what crack growth analysis is, why it is important, how to use Ansys Workbench for crack growth analysis, and how to get started with Ansys Workbench software. If you have any questions or feedback, please feel free to contact us or leave a comment below.


Frequently Asked Questions about Crack Growth Analysis and Ansys Workbench




Here are some frequently asked questions about crack growth analysis and Ansys Workbench:



  • What are some of the challenges or limitations of crack growth analysis?



Some of the challenges or limitations of crack growth analysis are:


  • The accuracy of crack growth analysis depends on the quality of the geometry, mesh, material properties, loading conditions, crack growth equation, etc. Any errors or uncertainties in these inputs can affect the crack growth predictions.



  • The crack growth analysis can be computationally expensive and time-consuming, especially for 3D models with complex geometries and loading conditions. The crack growth analysis may require multiple iterations and remeshing to capture the crack evolution.



  • The crack growth analysis may not account for some of the physical phenomena that can affect the crack behavior, such as plasticity, creep, corrosion, fatigue-creep interaction, etc. These phenomena may require additional models or methods to be incorporated in the crack growth analysis.



  • What are some of the alternatives or complements to crack growth analysis?



Some of the alternatives or complements to crack growth analysis are:


  • Experimental testing: This involves creating physical specimens with cracks and subjecting them to controlled loading conditions. The crack growth can be measured using various techniques, such as optical microscopy, digital image correlation, acoustic emission, etc. Experimental testing can provide reliable data and validation for crack growth analysis, but it can also be costly, time-consuming, and limited by the availability of materials and equipment.



  • Probabilistic methods: This involves using statistical models and methods to account for the uncertainties and variability in the inputs and outputs of crack growth analysis. Probabilistic methods can provide a range of possible outcomes and probabilities for crack growth and failure, rather than a single deterministic value. Probabilistic methods can enhance the confidence and robustness of crack growth analysis, but they can also increase the complexity and computational effort of the analysis.



  • Damage tolerance methods: This involves using empirical or analytical criteria to determine the maximum allowable crack size or load level for a structure based on its fracture toughness or residual strength. Damage tolerance methods can provide a simple and conservative approach for ensuring the structural integrity and safety of structures with cracks, but they can also be overly conservative and neglect the effects of crack growth rate and load history on the structure.



  • What are some of the best practices or tips for performing crack growth analysis with Ansys Workbench?



Some of the best practices or tips for performing crack growth analysis with Ansys Workbench are:


  • Use a high-quality geometry and mesh that can capture the shape and size of the structure and the crack accurately. Use mesh controls or refinements to ensure a fine mesh near the crack tip and a smooth transition to a coarse mesh away from the crack tip.



  • Use appropriate material properties and loading conditions that reflect the actual behavior and environment of the structure. Use material data from reliable sources or experimental tests. Use realistic load cycles or spectra that represent the service conditions of the structure.



  • Use suitable crack growth equation and parameters that match the material and loading characteristics. Use empirical or theoretical equations that have been validated by experimental data or other sources. Use material constants that have been calibrated or fitted by experimental data or other sources.



  • Use reasonable SMART Crack Growth options and settings that can balance the accuracy and efficiency of the simulation. Use adaptive remeshing to update the mesh as the crack grows. Use automatic time stepping to adjust the time step size according to the crack growth rate. Use convergence criteria to check if the simulation has reached a steady state or a maximum limit.



  • Use various result items and plots to visualize and analyze the simulation results. Use SIFs, da/dN, crack length, fatigue life, etc. to evaluate the crack growth behavior and performance of the structure. Use total deformation, equivalent stress, crack front, crack surface, etc. to visualize the deformation, stress, and crack evolution of the structure.



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