Week 1 Spur Gear Challenge
Week 1 Challenge: Spur Gear Challenge
Course: Introduction to Structural Analysis using ANSYS Workbench
Submitted by: Amanpreet Singh Whan
Supervisor: Vineet G
February 25, 2022
List of Figures
Figure 2- Static Structural Analysis workflow and material defined for case 1.
Figure 3-Static Structural Analysis workflow and material defined for case 2.
Figure 4-Static Structural Analysis workflow and material defined for case 3.
Figure 5- Imported given Spur Gear CAD Model.
Figure 6- Mesh generated for the given Spur Gear CAD Model.
Figure 7- Revolute joint created for the Left Spur Gear.
Figure 8-Moment joint created for the Left Spur Gear.
Figure 9- Frictional Contact defined between surfaces of Spur Gear Models.
Figure 10- Modified Structural Analysis Settings.
Figure 11- Procedure to be followed to calculate results.
Table of Contents
3.1 Importing and Meshing of CAD Models.
1 Introduction
ANSYS is a general-purpose, finite-element modeling package for numerically solving a wide variety of mechanical problems. These problems include static/dynamic, structural analysis, heat transfer, and fluid problems, as well as acoustic and electromagnetic problems. There are two methods to use ANSYS. One method is to use the graphical user interface (GUI). This method follows the conventions of popular Windows and X-Windows-based programs. Another method is to use command files. The command-file approach has a steeper learning curve for many, but it has the advantage that the entire analysis can be described in a small text file, typically in less than 50 lines of commands. This approach enables easy model modifications and minimal file-space requirements. The ANSYS environment contains two windows: the main window and an output window. A large number of files are created when ANSYS simulation is run.
Theory
Spur gears are a type of cylindrical gear, with shafts that are parallel and coplanar, and teeth that are straight and oriented parallel to the shafts. They’re arguably the simplest and most common type of gear – easy to manufacture and suitable for a wide range of applications. The teeth of a spur gear have an involute profile and mesh one tooth at a time. The involute form means that spur gears only produce radial forces (no axial forces), but the method of tooth meshing causes high stress on the gear teeth and high noise production. Because of this, spur gears are typically used for lower-speed applications, although they can be used at almost any speed.
Spur gears can be made from metals such as steel or brass, or plastics such as nylon or polycarbonate. Gears made of plastic produce less noise, but at the expense of strength and loading capability. Unlike other gear types, spur gears don’t experience high losses due to slippage, so they generally have high transmission efficiency. Multiple spur gears can be used in series to achieve large reduction ratios.
There are two primary types of spur gears: external and internal. External gears have teeth that are cut on the outside surface of the cylinder. Two external gears mesh together and rotate in opposite directions. Internal gears, in contrast, have teeth that are cut on the inside surface of the cylinder. An external gear sits inside the internal gear, and the gears rotate in the same direction. Because the shafts are positioned closer together, internal gear assemblies are more compact than external gear assemblies. Internal gears are primarily used for planetary gear drives. Spur gears are generally seen as best for applications that require speed reduction and torque multiplication, such as ball mills and crushing equipment.
2 Aims
- Run rotational simulations for the given Spur Gear CAD model.
- Apply appropriate Boundary Conditions and simulate for three different materials.
- Determine Total Deformation and Maximum Stress results for the performed simulations and compare the results for the same.
3 Methodology and Results
The section describes the different stages that were performed using an engineering tool Ansys Workbench 2022 for the completion of the Week 1 Challenge. These stages can be further broadly sub-categorized into three key steps, importing the CAD model to apply the boundary conditions and finally performing the simulation to obtain the desired results.
3.1 Importing and Meshing of CAD Models
After opening the Ansys Workbench, the first step is to select the Analysis type and then define appropriate material from the Engineering Data options for the given CAD model. Considering the challenge requirements, Static Structural was selected for the System Analysis type. In addition, three different material cards were created to perform the simulations for the given Spur Gear CAD Model and are presented in the following figures.
After updating the CAD model in the Ansys Workbench, the next step is to generate a good quality mesh. Meshing is a phase where the CAD geometry is discretized to represent the computational domain in which the solver will discover a solution. A refined mesh helps to achieve better results. The tetrahedral mesh with an element size of 0.5 mm was generated for the Spur Gear model.
3.2 Joints
A joint is a type of connection or junction at which usually two bodies are joined together in a way that restricts some degrees of freedom (DOFS) while leaving others free. For a joint, one reference is considered the stationary reference, while the other is considered the mobile or moving reference. The mobile and stationary references of the joint must be on two different bodies. Joints can also be defined as “grounded”. In this case, the joint connects the mobile reference to a fixed location in space. The stationary references are fixed in space, that is they have all DOFs fixed. Properties of a joint are defined as a joint behavior and can be applied to more than one joint. Joint behavior is characterized by the rotational and translational degrees of freedom of the mobile reference of the joint, as fixed or free concerning the stationary one.
The following figures represent the two revolute joints created; one was given a clockwise rotational motion while the other was provided an anticlockwise moment as per the challenge requirements.
3.3 Contact
In structural analysis software, the contact is generated by pair. Three different contact behaviors are available. They are named node to node (point to point), node to the surface (point to the surface), and surface to surface. As default in Ansys software, point to surface and surface to surface contact types are used. For the point to surface contact, the “point” is contact, and the “surface” is the target. Several contact types are used. These names might be called with different names according to software. In Ansys software, contact names are titled frictional, frictionless, rough, bonded, and have no separation. The Frictional Contact was defined for the challenge purposes and is represented in the following figure.
3.4 Analysis Settings
The given spur gear model was assumed to be simulated for a rotation of 180 degrees in order to determine appropriate total deformation and other stress-strain results. Therefore, the problem was divided into 6 steps and the Large Deflection option was turned on to prevent Penetration and Intersection errors. The following figure represents the modifications performed in the analysis settings.
Simulation Results
To visualize the simulation or results, the desired output cards have to be created. Total Deformation, Equivalent Elastic Strain, and Equivalent Stress (Von Mises Stress) cards were created using the procedure illustrated in the following picture. It must be noted that the results have to be generated by running the solve command.
Case 1: Simulation Results of Spur Gear having Cast Iron Material
Case 2: Simulation Results of Spur Gear having Cast Steel Material
Case 3: Simulation Results of Spur Gear having Cast Bronze Material
Summarization of Results
4 Conclusion
In conclusion, the main aim of the Week 1 challenge was to assign appropriate Materials Cards, apply Boundary Constraints and run the simulation and compare the obtained results for the same. It was found that the total deformation in all cases is identical. However, the stresses and strains generated in case 1 and case 2 are higher in comparison to case 3. Considering the above aspects, the Spur Gear having Cast Bronze material should be selected for both designing and manufacturing purposes.