[00:00:05] Speaker: ISO 844 defines the procedure for determining the compressive properties
of rigid cellular plastics.
[00:00:11] Speaker: This standard is essential for evaluating how foam materials perform under compressive loads.
[00:00:17] Speaker: Test specimens may have either a square or circular base, but must conform to strict dimensional requirements.
[00:00:24] Speaker: The preferred configuration is a right prism with 100 mm sides, which simplifies alignment and ensures consistency across tests.
[00:00:32] Speaker: Before testing, measure the width and thickness of each specimen three times.
[00:00:38] Speaker: Use the average of these measurements to ensure dimensional accuracy.
[00:00:42] Speaker: This directly impacts the reliability of stress and strain calculations.
[00:00:46] Speaker: An accurate thickness measurement is important because it is used to control both the test speed and the end of test criteria.
[00:00:53] Speaker: The specimen is placed between two rigid platens, each with a minimum diameter of 100 mm.
[00:01:00] Speaker: Proper alignment is critical to avoid applying non-uniform stresses.
[00:01:05] Speaker: To ensure proper centering of the specimen, use the etched center lines on the lower platen as a visual guide.
[00:01:11] Speaker: Strain measurement can be recorded using either the crosshead or an extensometer.
[00:01:16] Speaker: If an extensometer is used, suitable devices include LVDT compression deflectometers or optical devices such as the AVE3, advanced video extensometer.
[00:01:27] Speaker: LVDT devices mount directly to each compression platen and measure strain through linear displacement.
[00:01:34] Speaker: When using a video extensometer, marks are applied to the specimen which the camera tracks to capture strain measurements.
[00:01:42] Speaker: A data acquisition rate of 100 Hz is recommended to capture force and displacement data throughout the test.
[00:01:48] Speaker: The test speed is defined as a percentage of the original specimen thickness per minute.
[00:01:54] Speaker: The material is compressed until 10% relative deformation is reached, or the compressive strength is determined.
[00:02:01] Speaker: The ISO 844 standard specifies the following key outputs: Compressive strength, Relative deformation at compressive strength, Compressive stress at 10% deformation, and the compressive modulus of elasticity.
[00:02:15] Speaker: These values help engineers assess material performance for structural, cushioning, or energy absorbing applications.
[00:02:22] Speaker: This overview highlights the core elements of ISO 844. Be sure to review the full standard before performing any testing to ensure full compliance.
[00:02:32] Speaker: For application specific recommendations, contact your local Sales Engineer or visit instron.com for more information.
