An instrumented fastener for shear force measurements in joints

Abstract

A preliminary investigation has been conducted on instrumented fasteners for use as sensors to measure the shear loads transmitted by individual fasteners installed in double-splice joints. Calibration and load verification tests were conducted for instrumented fasteners installed at three fastener torque levels. Results from calibration tests show that the shear strains obtained from the instrumented fasteners vary linearly with the applied load and that the instrumented fasteners can be effectively used to measure shear loads transmitted by individual fasteners installed in double-splice joints. Tests were also conducted with three instrumented fasteners installed in a typical double-splice joint. The test results showed that the load distribution between individual fasteners is dependent on the location of the fastener in the joint and the fastener torque level. The fastener located near the end of the joint with the single plate carried more load than the fasteners located near the end of the joint with the two plates. Installing the fasteners with a torque greater than finger tight results in a significant amount of the load being carried by friction between the faying surfaces of the plates even if the faying surfaces are polished and lubricated. Increasing the fastener torque increases the load being carried by friction between the faying surfaces of the joint. Increasing friction between the faying surfaces of the joint. Increasing the fastener torque also results in a more uniform distribution of the loads between the individual fasteners for joints in aluminum plates with two fasteners, but does not have a significant effect for joints in steel plates with three fasteners.