Modulation of torsional waves in a rod with a crack

Results of experiments concerning nonlinear effects for elastic waves in me tal rods with the crack-type defects are presented. The dependence of the n onlinear effect on the contact type is discussed. The crack has been modele d by cutting a rod and tightly filling the crack with metal plates. Two typ es of contact have been studied: a dry contact and a contact with lubricant . The modulation of high-frequency torsional waves (20 and 22.8 kHz) in the rod under the effect of low-frequency flexural vibrations has been investi gated Flexural vibrations have been excited by a shock and by a vibrator. T he modulation of high-frequency torsional waves under the effect of low-fre quency vibrations has been observed only in the rod with a crack. The level of modulation drastically decreases in the presence of liquid lubricant. ( C) 1999 Acoustical Society of America. [S0001-4966(99)03109-4].