UNSTEADY PLANE SMOOTH WAVE-FRONTS OF COMBINED GROWING-ATTENUATING TYPE

Unsteady plane smooth wave fronts of a combined growing-attenuating ty pe, where the peak of each strain wave is growing, are derived by a qu alitative analysis. There are three different modes in this combined t ype: In mode I, the peak of a particle velocity wave is growing, but t hat of a stress wave is attenuating; in mode II, the former is attenua ting, but the latter is growing; in mode III, both are attenuating. Th ree possible wave fronts belong to made I, five to mode II, and three to mode III. Five new elementary waves are found in these eleven wave fronts. The wave fronts clear the impacted surface of sandstone detect ed by the previous quantitative analysis [Sano, J. Appl. Phys. 73, 118 (1993)] are identified with some of the eleven possible wave fronts. As a result, the theoretical existence of several new wave fronts and a new elementary wave is verified. The equation for the stress at the impacted surface indicates that strain acceleration is responsible fur the formation of the wave fronts of the combined type, which cause an anomalous response, and hence it should be included in the constituti ve relations which describe the response. (C) 1997 American Institute of Physics.