Fracture Analysis on Bolts of Friction Clutch for Extruder

The connecting bolts between pneumatic friction clutch and reducer for extruder fractured frequently in the process of using. Switch to another material of bolt, but it not showed considerable improvement. By means of chemical composition analysis, mechanical property testing, fracture analysis, metallographic examination and so on, the fracture reason of bolt were analyzed. The results showed that the cracks originated at tool marks, surface scratches and microcrack caused by fretting fatigue, where was the stress concentration position. And the cracks extended under the vibration, which reduced the effective bearing area; at last the fatigue fracture occurred in bolts.