Engineering Analysis of Side Release Seat Belt Buckles

Abstract

Abstract The automotive seat belt buckle has only one purpose: as a safety device it must properly restrain individuals in a collision. In the engineering and design of a seat belt buckle the dynamic conditions that prevail during collisions must be considered during the design process. In the conventional side release buckle’s thirty year life it has been established it is susceptible to release due to inertial, shock, and impact loading. An engineering analysis of the acceleration levels that induce inertial unlatching of a type 6 seat belt buckle was explored. A test apparatus was designed and fabricated to subject the buckle to inertial accelerations which would simulate the transmission of g-forces through the vehicle’s structure when subjected to impact conditions. Accelerometers were used to measure the g-forces that were induced in to the drop fixture and seat belt buckle housing during testing procedures. The g-forces experienced by the drop test fixture and belt buckle determined that when convergent conditions occur during collisions the seat belt buckle will unlatch. The basic engineering of the side release buckle incorporates a guard that will prevent unlatching in some frontal collisions. But when the loading conditions of real world collisions converge toward a low belt load and high buckle accelerations inertial unlatching can occur. The conditions of the convergence interval in the course of a collision requires engineering analysis.