ASTM D882:18 pdf free download – Standard Test Method for Tensile Properties of Thin Plastic Sheeting.
6.1.4 Drive Mechanism—A drive machanism for imparting to the movable mcmbcr a uniform, controlled velocity with respect to thc stationary. The velocity shall be regulated as specified in Section 10.
6.1.5 Force IndEcalor—A suitable forccindicating mechanism capable of showing the total tensile force carried by the test specimen held by the grips. This mechanism shall be essentially free of inertial lag at the specified rate of testing (see Note 8). Unless a suitable cxtensometcr is used (sec 6.2). the motion of the weighing system shall not exceed 2 % of the specimen extension within the range being measured. The force indicator shall determine the tensile force applied to the specimen with an accuracy of ± I % of the indicated value, or better. The accuracy of the testing machine shall be verified in accordance with Practices E4.
6.1.6 Crosshead Extension Indicator—A suitable cxtcnsionindicating mechanism capabic of showing the amount of change in the separation of the grips, that is, crosshcad movement. This mechanism shall be essentially free of inertial lag at the specified rate of testing (sec Note 8) and shall indicate the crosshcad movement with an accuracy of ± I % of the indicated value, or better.
6.2 Extensometer Optional—A suitable instrument used for determining the distance between two designated points on the test specimen as the specimen is stretched. The use of this type of instrument is optional and is not required in this test method. This apparatus. if employed, shall be so designed as to minimize stress on the specimen at the contact points of the specimen and the instrument (see 9.3). Ii is desirable that this instrument automatically record the distance, or any change in it. as a function of the Ibree on the test specimen or of the elapsed time from the start of the test, or both. If only the latter is obtained, force-time data must also be taken. This instrument must be essentially free of inertial lag at the specified speed of testing (see Note 8).
6.2. 1 Modulus of Elasticiti’ and Low-Extension Measurrmcnrs—Extcnsomctcrs used for modulus of elasticity and low-extension (less than 20 % elongation) measurements shall, at a minimum, be accurate to ± I % and comply with the requirements set forth in Practice E83 for a Class C instrument.
6.2.2 High-Ertcn.sion .1kasurcineiirslnstrumcn tation and measuring techniques used fbi high-extension (20 % elongation or greater) measurements shall be accurate to ± 10 % of the indicated value, or better.
Note 8—A sufficiently high response speed in the indicating and recording system for the force and extension data is essential. The response speed required of the system will depend in part on the material tested (high or los elongation) and the rate of straining.
6.3 Thickness Gauge—A dead-weight dial or digital micrometer as described in Test Methods D5947 or D6988 as appropriate for the material or specimen geometry being tested.