Light Bulb Filament Distortion Thresholds by Voltage and Delta-V 2013-01-0752

Light bulb filaments of a vehicle involved in a collision can provide valuable information about the state of the vehicle's lights at the time of the impact. Through examination of bulb filaments for hot or cold shock, accident reconstruction professionals can gain information about which bulbs were and were not illuminated prior to the collision. A number of papers have been published on the general topic of hot and cold shock, however there is little published research about light bulb voltage and how it relates to filament distortion. Although a normally functioning electrical system of a passenger vehicle will operate at around 12-14 Volts, vehicles that have failing electrical systems or that have experienced damage to their electrical system may deliver less than full voltage to the bulbs. In order to help answer questions about vehicles with sub-optimal electrical systems, this paper focuses on the relationship between hot shock deformation and bulb voltage. Collisions were simulated through use of a pendulum impacting apparatus. Both the striking velocity of the pendulum and the light bulb voltage were varied in the experiment. A hot shock threshold as it relates to bulb voltage and impact acceleration magnitude has been created by plotting acceleration magnitude relative to voltage and identifying those impacts that produce hot shock.