This standard specifies the test method for evaluating the friction performance of wet automatic transmission friction elements under different working conditions and its relationship with changes in pressure, speed, and temperature. The core of this method involves the use of a specialized device called the SZBL-type friction testing machine. On this testing machine, by precisely controlling and varying the pressure applied to the friction elements, the relative speed between the friction pairs, and the temperature of the oil, key performance data such as the friction coefficient are systematically tested and collected. The purpose is to obtain a quantitative relationship of how friction performance varies with these three core parameters, thereby enabling a scientific assessment of the material performance and reliability of the friction elements.