Tensile Test Methods for Plastics: ASTM D638

ASTM D638 requires a test force accuracy that meets ASTM E4 Class 1, accuracy within ±1% of the indicated test force. Shimadzu’s AG-X plus series, AGS-X series, and EZ-X series test frames and load cells all meet the test force accuracy requirements for ASTM D638.

Specimens for ASTM D638 are dumbbell-shaped with either a 25 mm or 50 mm gauge length; a 50 mm gauge length is recommended. Gauge length changes with ASTM E83 Class B-2 accuracy; an absolute accuracy of 10 μm for a 50 mm gauge length and relative accuracy within ±0.5% are required by ASTM D638 for measuring the tensile modulus of elasticity. Also, for elongation beyond the yield point but less than 20%, Class C accuracy is specified; an absolute accuracy of 50 μm for a 50 mm gauge length and relative accuracy within 1%, and ±10% relative accuracy are required for the rest of the test. For ASTM D638 compliant elongation testing, Shimadzu offers SIE-560SA automatic extensometers, TRViewX non-contact digital video extensometers, and SSG-H one-touch, strain gauge extensometers. In particular, the SIE-560SA automatic extensometer can be programmed to attach and detach automatically from the specimen and can be used for either 25 mm or 50 mm gauge length, improving test efficiency and repeatability.