The Test for Withstanding Fracture Capacity of Worm Gear Made of Antifriction Composite Material of Polymer Matrix Under Static Loads

Abstract: Worm gear is usually made of bronze, which is a precious and nonferrous metal. In order to substitute for the bronze, a new kind of antifriction composite material of polymer-matrix, ZW-1 material has been successfully developed. Compared with worm gear made of bronze, worm gear made of ZW-1 material has made worm gear transmission possess many advantageous properties. In order to bring the excellent properties of worm gear transmission of ZW-1 material into play and substitute for bronze, the test for anti-fracture capacity of worm gear made of ZW-1 material under static load has been made. A simple test-bed is designed. The test has been carried out under static load. The test of worm gear with ZW-1 and nylon materials, different teeth numbers、tooth width and tooth forms is made. The test findings show that in the test conditions the invalidation of ZW-1 worm gear is radial fracture in gear rim. Applying stress transmission theory and micrographic analysis, fracture mechanism of ZW-1 material is found out, namely degumming on the interface between fiber and polymer. Anti-fracture capacity of worm gear of ZW-1 material is twenty three times as much as that of bronze worm gear(Q/ZB125-73).Archimedes worm gear has the same anti-fracture capacity as arc tooth worm gear of ZW-1 material. Macrographic analysis shows that load concentration and contact stress concentration of bolt hole caused by bending bolt are significant factors which affect invalidation of worm gear. The test result shows an important fact that overlapping coefficient of worm gear transmission of ZW-1 material worm gear is much higher than that of calculating in theory, for small modulo of elasticity has a good effect upon the worm gear transmission of ZW-1 worm gear