Fastener Failures: PART TWO

摘要

Many times, we run into the usual types of failure modes; they are just on different applications. Some applications become creative in how they perpetrate the failure. Then there are a few that are unusual because of a failure mechanism you rarely see, coupled with multiple causes for the failure. The failure presented here is of a wheel stud made for racing. The shape is unlike standard wheel studs: Instead of a straight shank between the threaded portions, this area is barrel-shaped like a brass compression sleeve. The purpose is for better seating and absorbing load stress. The end of the wheel stud has an internal hex for tightening it into the wheel hub. The nut is a conical hex. The vehicle is a sedan manufactured in Europe. Normally, these vehicles would have stud bolts that thread directly into the wheel hub. However, these were changed out for ease of tire removals. The wheel studs are hardened and tempered steel, Property Class 10.9, 1040 MPa (150 ksi), M12×1.5 with a black zinc plating. Stated maximum torque (to induce yield) is 180 Nm (133 lb-ft); recommended torque is 108 Nm (80 lb-ft); OEM recommendation is 119 Nm (88 lb-ft).