Strain Measurements on Plastic Gear Assembly

Plastic gears are used in many vehicle systems where actuators are required to assist functions such as electric power steering and electro-mechanical braking. Plastic gears are essential components in vehicles due to their lightweight and relatively high-strength mechanical properties. This provides a low-cost solution that contributes to improved fuel efficiency. In this example, a plastic gear was measured during quasi-static loading to better understand strains on the gear teeth. In addition to strain measurements, it was desirable to obtain deflection data in three dimensions.

Strain Measurement

Assembled components typically have complex interactions with one another. Contact points can vary during operational cycles due to part movement. This means that the locations of peak strains can be hard to predict, and they are often not stationary. The movement of parts can also make it impractical to maintain electrical connections with gauges. Even when they are stationary and easy to locate, the highest strains can be concentrated in very small areas or have high gradients. Peak values may be lost to the averaging effect produced by gauges.

Displacement

The VIC-3D system from Correlated Solutions provided a means for making strain measurements across the entire profile of the gear tooth. Because it provides full-field measurements, it was not necessary to choose a particular point at which measurements would be made. This allowed the peak strains to be clearly visualized and accurately measured at various stages of the operational cycle. VIC-3D also measured displacement in three dimensions. This feature allowed our customer to recognize and quantify the twisting of the gear tooth under load.