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Case Study - RecurDyn Simulations Guide Engineers to Improved CV Joint Boot Designs

 
A manufacturer of Constant Velocity (CV) joints had a client request a half-shaft that could operate at an increased angle of bend, but the existing boot for the CV joint was already at its operating limit, exhibiting structural failure at higher bend angles. Traditional Finite Element Analysis (FEA) was not sufficient for modeling the flexible CV boot because it undergoes complex nonlinear deformation during the combined rotation and bending of the CV joint, and it also makes contact with itself and potentially other components throughout this motion. Because of this, the manufacturer contacted MotionPort to apply the best available technology to understand boot behavior and to provide a solution.

MotionPort used RecurDyn (with the FFlex module) to model the existing flexible boot as well as multiple new designs, performing the following steps:

  • Imported Finite Element Analysis (FEA) meshes of the boots into Multi-Body Dynamics (MBD) models of the CV joint.
  • Configured the boots into their installation positions with respect to the bell and driveshaft.
  • Defined flexible body contacts between the folds of the boots and other locations.
  • Ran the simulations through bend angles and rotational speeds of interest.

Customer benefits realized:

  • RecurDyn correctly validated the behavior of the existing design (see images/animations below).
  • Further analysis helped guide the engineers to a new boot design which undergoes less material stress throughout the operating range of the CV joint.
  • The new boot avoids contact with the rotating components inside the boot, which could cause boot failure due to rubbing.
  • The new design does not exhibit the problematic dimpling effect found in the existing design (see images/animations below).
  • Intended performance improvement was achieved.
The images and videos below demonstrate the high fidelity of the simulations (shown is the previously existing boot design).
 
Images showing matching number of collapsed folds seen on actual and simulated CV boots. Images showing matching dimpling effects seen on actual and simulated CV boots.

Figure 1: RecurDyn correctly validated the number of collapsed folds.

 

Figure 2: RecurDyn correctly validated the formation of dimples. Animations of the boot gave the engineers insight into the dynamic formation of these dimples.

 

Video 1: RecurDyn correctly captures the overall shape of the flexible boot as the CV joint bends and rotates.

 

Video 2: RecurDyn captures with high fidelity the problematic dimpling effect seen on several folds.

 

Video 3: RecurDyn displays stress contour plots within the boot to help identify areas of high stress.

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Case Study - RecurDyn in Automotive (Gears)

An automotive supplier needed to simulate the meshing of two gears. It is a challenging contact modeling problem because of the detailed geometry of the gear teeth. The supplier want to consider two values of the fillet radius for the gear teeth, two backlash spacing values, two magnitudes for the actuator force, and two sets of initial velocities.

Even with an incomplete set of model data, the RecurDyn results for the various design configurations showed trends that agreed with observed trends for the product that had been learned over many years. The supplier was confident that RecurDyn could model their product with the proper level of fidelity.

The engineers were surprised at the RecurDyn results because they had experience with another Multi-Body Dynamics (MBD) software. That background caused them to think that it was not possible to model complex gear contact. They are very happy with RecurDyn and are looking forward to using in on their next design program.

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