Week 8 Worm Gear Challenge
Ansys Week 6 Challenge - The Worm Gear
AIM
To perform a transient structural analysis on a worm gear assembly.
OBJECTIVE
The challenge is to simulate the transient structural analysis on a worm gear assembly using the Ansys workbench to perform the analysis on the student version the heart contains with over-limit bodies which need to be cut down and evaluate the results by refining the mesh.
THEORY
The worm gear is a gear arrangement in which a worm (which is the ger in the form of a screw) meshes with a worm gear ( which is similar to appearance to a spur gear). The two elements are also called the worm screw and worm wheel. The terminology is often confused by the imprecise use of the term worm gear to refer to the worm gear or the worm drive as a unit.
There are three different types of gears that can be used in a worm drive.
The first is non - throated worm gears. These don't have a throat or groove machined around the circumference of either the worm or worm wheel. The second is single-throated worm gears, in which the worm wheel is throated. The final type is double-throated worm gears, which have both gears throated. This type of gearing can support the highest loading.
An enveloping (hourglass) worm has one or more teeth and increases in diameter from its middle portion toward both ends.
Double-enveloping worm gearing comprises enveloping worms mated with fully enveloping wormgears. It is also known as globoid worm gearing.
Fig 1: Worm Gear
MATERIAL PROPERTIES
Structural Steel
Fig 2: Structural steel properties
PROCEDURE
Geometry
The geometry is with many faces that exceed the student academic limit, so the bottom part of the gear is cut down and reduces the faces so that geometry could accept the simulation process for the academic version.
Fig 3: Worm Gear
In the mechanical module opening the geometry and then renaming the part to consider by their name based definition for connections. As we are using only the structural steel material.
Connections
The contact renamed based on the definition and adding a few targets of the gear for rotating the worm on the gear. The total number of contacts of the worm - 9 faces and the contact faces - 31 Faces and the types to be used as frictionless.
Fig 4: Frictionless contact
Joints
The two joints are provided as a Revolute (body to the ground) one joint to the gear, selecting the bottom b]face of the gear, and checking the coordinate system as the gear revolutes in the (RZ) Z-direction.
Fig 5: Revolute joint- Ground to gear
Ans second joints are provided to the worm selecting the inner face of the worm and checking the codinate system revolutes in the RZ direction.
Fig 6: Revolute joint - ground to worm
Mesh
The worm gear simulation is refined with a 1.5mm mesh size and then generated then mesh, Obtain mesh has nodes below academic limits Nodes - 17649 and elements - 9080.
Fig 7: Mesh on Worm Gear
Analysis Settings
For setting up the simulation for this setup total of 15 steps are taken for step 1 the time value for initial time setup 0.2s, minimum time 0.2s, and final time step 0.5s. For output, controls switch ON all the parameters except the contact miscellaneous is OFF
And for step 2 to 15, keeping the time step ON and also carry over time step is ON with minimum time step is 0.2s and maximum time step 0.5s.
Fig 8: Analysis settings
To rotate the worm on the gear the joint load is given as a rotation (revolute ground to worm) and rotation at 50 degrees at each step.
Fig 9: Joint Load Rotation
RESULTS AND CONCLUSION
Equivalent von mises stress
Fig 10: Equivalent von mises stress
Equivalent elastic strain
Fig 11: Equivalent elastic strain
Total Deformation
Fig 12: Total deformation
The simulation runs successfully for the worm gear with materials, the equivalent von Mises stress with the minimum value of 3.856 e-08 MPa to maximum 1482.4 MPa, the equivalent elastic strain with the minimum value of 4.922 e-13 mm/mm to the maximum value of 0.0075615 mm/mm and the total deformation with a minimum value 0 mm and to the maximum value 14.819 mm.
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