Some Tensile Properties of Amalgam

¹ Dental Research Section, National Bureau of Standards, Washington, D.C.

A method of preparing miniature specimens of amalgam for testing tensile strength and other tensile properties was developed. Varying the head speed over a range of 0.003-0.050 in/min produced no significant differences in tensile strength of 7-day-old amalgam specimens. One-hour-old amalgam specimens attained only about 10-15 per cent of the tensile strength (7,000-8,000 psi) attained in 1 week. The tensile-strength values of specification-type alloys were approximately one-fifth to one-fourth of their compressive strength. Amalgam had a low percentage elongation, approximately 0.3-0.5, indicating its brittleness or lack of ductility. The chord modulus of elasticity of amalgam from stresses of 1,000-3,000 psi ranged from 3.3 x 10⁶ to 4.1 x 10⁶ psi, whereas the chord modulus of elasticity from stresses of 1,000-5,000 psi ranged from 2.2 x 10⁶ to 2.8 x 10⁶ psi.