Chain and Sprocket Simulation in Inspire Motion

Christopher_Fadanelli
Christopher_Fadanelli
Altair Employee
edited June 20 in Altair Exchange

Overview

INTRODUCTION

Chain and sprockets are commonly used for power transmission in a variety of industries including automotive and agricultural. For many applications, it may be adequate to ignore the chain during the simulation of a system. However, the chain’s behavior during motion can be of interest. The loads on the sprocket or chain from a multibody dynamics analysis can be used in a structural analysis to predict failure. Simulation can also provide insights into chain and sprocket performance under different loading conditions, sprocket diameters, chain sizes, and speeds. Tension and misalignment criteria can be studied and established using a multibody model of the system.

In this model, chain and sprocket geometry is imported into Altair’s Inspire. Inspire is an integrated simulation environment that enables faster decision making by design engineers and CAE analysts. Foregoing the traditional “pre-process - solve - post-process” cycle prevalent in traditional CAE software, it can perform all 3 functions in a single environment. Inspire’s CAD integration, semi-automated MBD model build, and structural solver integration help considerably flatten the learning curve. A design engineer or non-CAE expert may thus take direct advantage of Altair’s high-performance CAE solvers.

In this model, a joint is created between each adjacent link. The sprocket and chain interact using contacts between each link and the sprockets. To drive the motion of the system, one of the sprockets is driven at a constant acceleration.

Pre-Requisite

SOFTWARE REQUIREMENTS

Altair Inspire (2024 or newer)

MODEL FILES

Chain_and_Sprocket_Model.zip (See Attachments)

Usage/Installation Instructions

MODEL SETUP

  1. Import the geometry file Chain_and_Sprocket_Geometry.x_b into Inspire.
  2. Change gravity to the negative y direction.
  3. Create rigid groups for each sprocket.
  4. Add a grounded pin to the small sprocket using the joints tool.
  5. Create a motor with the motors tool by clicking on the large sprocket’s surface and moving the motor to the center of the sprocket.
    1. Restrain the motor’s centerline in the property editor with a revolute joint.
    2. Edit the motion to match the multi-signal motion profile below.

A graph of a speed lineDescription automatically generated

  1. Create joints between all chain links.
    1. Edit the joints in the Property Editor to make all joints locked and flexible.
    2. Change the rotational stiffness about the z-axis to 0 N*mm/rad.
    3. Change the rotational damping about the z-axis to 1 N*mm*s/rad.
  2. Create motion contacts between the sprocket teeth and each chain link.
    1. Enable friction for all contacts in the Property Editor.
  3. Chain_and_Sprocket_Motion_Ready.stmod is an example of a setup model which has completed motion runs available for viewing.

SIMULATION STEPS

  1. Open Run Motion Analysis settings
    1. Run the simulation for 10 seconds at a 100 Hz output rate.
    2. Enable active contact iteration.
    3. Exclude joint deformation under Advanced > Model Checking > Runtime Sensors.
  2. Run the analysis and view the results.

Post-Requisite

RESULTS

The large sprocket accelerates up to 100 rpm in 3 seconds, maintains a constant velocity for 1.5 seconds, and then brakes for 0.5 seconds. Afterwards, the large sprocket repeats this process in the opposite direction.

image

Chain and Sprocket Motion without a Flywheel

After running a baseline run with no load, a shaft with negligible mass and a 10 kg flywheel with a 75 mm radius were added to the system. The motion with the flywheel appears to be similar to the baseline run during the initial acceleration. During the braking period, the chain begins to shake more in the model with the flywheel. The flywheel stores kinetic energy which transfers to the chain during braking, an effect captured by the simulation.

image

Chain and Sprocket Motion with a 10 kg Flywheel

 

The contact forces can be plotted to understand the forces between the chain links and sprockets. Plotting the forces for a specific link shows the forces are at a maximum as the chain link first touches the sprocket. Minimum forces are recorded halfway around the sprocket before increasing to a maximum as the chain leaves the sprocket. Adding the flywheel increases the contact force peaks as the chain link leaves or enters the sprocket.

A screenshot of a graphDescription automatically generated
Contact Forces


In addition to contact forces, joint forces can be plotted which provide insight into the tension in the chain. The force is relatively constant while the chain is off the sprocket, indicating the tension in the chain. While the chain is on the sprocket, the force between links is reduced. Due to no pretension in the chain, the links shake significantly during operation. This behavior is amplified by adding the flywheel. The shaking between the links can be seen as noise in the force data between links.

A graph with red and blue linesDescription automatically generated

Joint Forces Between Links

CONCLUSION

As computing power and simulation improve, it becomes possible to analyze complex assemblies like chain and sprocket systems. Analysis can be used to understand chain and sprocket performance under different loads, chain sizes, sprocket diameters, and sprocket speeds. Loads can be extracted from a multibody dynamics analysis to predict when the chain and sprocket will fail. Overall, simulation allows quick, cheap, and accurate analysis of design changes to expedite the design process.

AUTHORS

John Dagg, Systems Engineering Intern

Christopher Fadanelli, Solution Engineer - Systems Integration

 

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