Abstract
Photoelasticity is applied to measure the residual stress of the pincher portion of light bulbs for automobiles. The difference of principal stresses is measured in the pincher portion on the assumption of plane stress condition. The difference of principal stresses is also measured in the vicinity of lead wires both on the assumption of plane stress and by a three-dimensional method. The measurement results say that the average value of the difference of principal stresses is 3.5MPa, which is smaller than the strength of glass of 60-170MPa. However there exists the region of high residual stress in the vicinity of lead wires where the difference of principal stresses is close to the fracture strength of glass.
