Fractographic Analysis of Very Small Theta Specimens
The theta test specimen is a versatile tool for evaluating the strength of extremely small structures. Round and hexagonal rings are compressed vertically on their ends creating a uniform tension stress in the middle gauge section. The simple compression loading scheme eliminates the need for special grips. A conventional nanoindentation hardness machine with a flat indenter applied load, monitored displacement, and recorded fracture loads. Prototype miniature specimens with web sections as thin as 7.5 m were fabricated by deep reactive ion etching (DRIE) of single crystal silicon wafers. The strength limiting flaws were 200 nm to 500 nm deep surface etch pits.
J. Dusza, R. Danzer, R. Morrell and G.D. Quinn
G. D. Quinn "Fractographic Analysis of Very Small Theta Specimens", Key Engineering Materials, Vol. 409, pp. 201-208, 2009