横衝突を受けるアクリル梁に作用する荷重とそれに伴う応力

抄録

An acrylate beam of 10×10×55mm with a notch was subjected to lateral impact at supports 40mm apart in distance by using a steel hammer of 0.615kg in weight sliding on an air bearing runway. The impact velocity ranged from 0.9 to 1.4mm/ms. The notch sizes were 1, 2, and 5mm in depth with each 1mm bottom radius. The displacement of the hammer was measured as a function of time by the optical interferometry. From the result, the time dependence of load on the specimen was estimated. The theory of contact was successfully utilized to calculate the magnitude of the load. Also the stress in the specimen was obtained by means of the photoelastic method using a multi-giant-pulse laser as a light source.
The time to the initiation of crack in the specimen, measured from the instance of the first contact of the hammer, ranged from 500 to 900μs depending upon the notch sizes. On the other hand, the duration from crack initiation to fracture was almost constant and was estimated about 50μs irrespectively of the notch dimensions. As was known before, the impact value calculated on the basis of the kinematic energy of the hammer varied as the notch size changed. However, nearly the same number of isochromatic fringes was observed at the notch bottom for all specimens at the moment of crack appearance. By using a photoelastic sensitivity-0.0527mm/kg, the stress was calculated to be in the range of 8 to 9kg/mm².