Shore Hardness Scale

[timbrisc]

Issue migrated from trac ticket # 5783

component: support material | priority: critical | keywords: Shore Hardness Scale

2021-01-16 18:03:24: william.hess@fda.hhs.gov created the issue

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The Food and Drug Administrations (FDA) needs three new unit of measurement concepts for its Product Quality/Chemistry Manufacturing and Controls (PQ/CMC) unit of measurement terminology. These are:

Shore A Scale Shore D Scale Shore OO Scale

Please see https://en.wikipedia.org/wiki/Shore_durometer.

There are many other Shore scales in existence, but FDA only seems to use these three for its regulated products at the moment.

This is from https://en.wikipedia.org/wiki/Shore_durometer:

The Shore durometer is a device for measuring the hardness of a material, typically of polymers, elastomers, and rubbers.

Higher numbers on the scale indicate a greater resistance to indentation and thus harder materials. Lower numbers indicate less resistance and softer materials.

The term is also used to describe a material's rating on the scale, as in an object having a "'Shore durometer' of 90."

The scale was defined by Albert Ferdinand Shore, who developed a suitable device to measure hardness in the 1920s. It was neither the first hardness tester nor the first to be called a durometer (ISV duro- and -meter; attested since the 19th century), but today that name usually refers to Shore hardness; other devices use other measures, which return corresponding results, such as for Rockwell hardness.

There are several scales of durometer, used for materials with different properties. The two most common scales, using slightly different measurement systems, are the ASTM D2240 type A and type D scales.

The A scale is for softer ones, while the D scale is for harder ones.

However, the ASTM D2240-00 testing standard calls for a total of 12 scales, depending on the intended use: types A, B, C, D, DO, E, M, O, OO, OOO, OOO-S, and R. Each scale results in a value between 0 and 100, with higher values indicating a harder material.

Durometer, like many other hardness tests, measures the depth of an indentation in the material created by a given force on a standardized presser foot. This depth is dependent on the hardness of the material, its viscoelastic properties, the shape of the presser foot, and the duration of the test. ASTM D2240 durometers allows for a measurement of the initial hardness, or the indentation hardness after a given period of time. The basic test requires applying the force in a consistent manner, without shock, and measuring the hardness (depth of the indentation). If a timed hardness is desired, force is applied for the required time and then read. The material under test should be a minimum of 6 mm (0.25 inches) thick.

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2020-10-05 14:42:03: timbrisc@loinc.org changed status from new to closed

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2020-10-05 14:42:03: timbrisc@loinc.org set resolution to spam

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2022-03-08 17:14:20: mitchbre@regenstrief.org commented

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Additional information provided by Bell Hess.

We recommend the addition of the following UCUM codes to represent measurements on the three different Shore scales:

[Shore_A_scale] [Shore_D_scale] [Shore_OO_scale]

I believe that the UCUM convention for dimensionless units of measure is to enclose the code in square brackets, as in the above. This is Shore process for measuring hardness: Shore hardness is tested with an instrument called Durometer. Durometer utilizes an indenter loaded by a calibrated spring. The measured hardness is determined by the penetration depth of the indenter under the load.

Two different indenter shapes (see the picture below) and two different spring loads are used for two Shore scales (A and D). The loading forces of Shore A: 1.812 lb (822 g), Shore D: 10 lb (4536 g).

Trac does not allow embedded images) Link to graphic referenced above: [http://www.substech.com/dokuwiki/lib/exe/detail.php?id=shore_durometer_hardness_test&cache=cache&media=durometer.png]

Shore hardness value may vary in the range from 0 to 100. Maximum penetration for each scale is 0.097-0.1 inch (2.5-2.54 mm). This value corresponds to minimum Shore hardness: 0. Maximum hardness value 100 corresponds to zero penetration.

What is being measured is the amount of indenter penetration on a scale of 0 to 100 where 0 # no indenter penetration and 1000.1 inch indenter penetration. A Shore measurement of 50 would therefore be 0.05 inch indenter penetration. The size and shape of the indenter is what distinguishes Shore A measurements from Shore D measurements.