Micro-tensile testing machine

This paper describes a tensile testing machine for microscopic specimens. It can apply loads in the range from 1 mgf to 400 gf to specimens having cross-sectional areas down to 10 -7 mm 2 . Specimen extensions from a few angström units to 15 mm can be measured and, at constant temperature, random errors in the extension measurement system are less than 5 Å (5 × 10 -7 mm). The machine employs a torsion balance to apply the loads and a mirror-autocollimating telescope system to detect the extensions. Since it depends wholly on mechanical and optical principles it is practically drift-free at constant temperature. It is adaptable for tests in special atmospheres, for autographic recording and for tensile testing of thin films.