Background
Electrification has continued to permeate the automotive market. Future projections show an exponential growth in market share for both light and heavy-duty applications. Existing test machines for the automotive industry were originally developed to model internal combustion engine-propelled operation and are now less representative. One such machine, the Universal Mechanical Tester (UMT), is used to evaluate friction and wear on modeled surfaces simulating in-vehicle operation. However, there are no provisions to evaluate friction and wear performance in the presence of an applied voltage, which is a more representative approach for electric vehicles (EV). This project was undertaken to help establish EV specific tribological test methods.
Approach
One of SwRI’s UMTs was modified to isolate a voltage input into a tribological contact. New parts were designed and initially created through 3D printing to check fit and performance before final manufacture out of polyether ether ketone (PEEK) to improve thermal and durability performance. With all necessary parts in hand, a test matrix was completed analyzing different temperatures, load conditions, speed conditions, voltage input type, frequency of AC signal, and shape of AC signal. These parameters were tested on three test lubricants – two typical automatic transmission fluids (ATF) formulations and a gear oil used in differential applications. Following completion of the test matrix, a detailed statistical analysis was performed to understand the impact of electrification on wear.
Accomplishments
After statistical analysis of the test results, it appeared that the AC tests did show a significantly different result from the DC and no voltage conditions for one of the ATF formulations especially. Outside of the test results, the primary goal of the project – establishing a tool for EV fluid development – has been achieved. Several customer projects have been performed on the electrified test rig since completion of the project.