Development of a crack gauge by using ion beam mixing

The ion beam mixing technique has been applied to develop a crack gage. The gage consists of an array of insulator/conductor bands on an insulating substrate which is attached to the test piece. The principle of a gage is based on the measurement of resistance change brought by cutting of conductive bands due to crack growth in the test piece. An array of insulator/conductor sets was formed by ion bombardment on a thin conductor layer which had been evaporated onto the insulator substrate. For the insulator substrate, SiO sub 2 was used, and Ru was the conductor. An array pattern was produced with a mask by separating the ion beam. To confirm the idea, a crack gage of 8x8 mm was fabricated on a compact tension test piece of stainless steel. The spacing of the conductive bands of 0.1 mm width was 0.1 mm. To measure the resistivity, thin multilayers of Si(5 nm)/Ru(50 nm)/Si(30 nm)/SiO sub 2 (300 nm) films were mixed by 300 keV Xe exp + ions. The resistivity of the mixing region was found to change drastically at the dose of 7x10 exp 16 Xe exp + /cm exp 2 . When the test piece cracked under tension, the gauge measured the crack length with good accuracy.