A Novel Test Method for Measuring Mechanical Properties at the Small-Scale: The Theta Specimen

Abstract

A test method has been developed for measuring mechanical properties of material structures at the small-scale. Round or hexagonal rings are compressed vertically on their ends thereby creating a uniform tension stress in a horizontal crossbar that serves as the gauge section. The compression loading scheme is simple and eliminates the need for special grips. A conventional nanoindentation hardness machine serves as a small-scale universal testing machine that applies load and monitors displacement. Prototype miniature silicon specimens were fabricated by deep reactive ion etching (DRIE) of a single crystal wafer and were tested to fracture. Finite element analysis confirmed that the stress distribution was very uniform in the web portion of the specimen. The theta specimen is a versatile configuration and has great potential for use with a variety of materials and for testing extremely small structures.