Shore-Durometer

2006-09-06T09:01:21Z

Devanshi.shah: /* Durometer of various common materials */

'''Durometer''' is one of several ways to indicate the [[hardness]] of a material, defined as the material's resistance to permanent indentation. The term '''durometer''' can refer to both the measurement, and the instrument used to generate the measurement. Durometer is typically used as a measure of hardness in [[polymer]]s, [[elastomer]]s and [[rubber]]s.<ref name="matweb">{{cite web
|url=http://www.matweb.com/reference/shore-hardness.asp
|title=Shore (Durometer) Hardness Testing of Plastics
|accessdate=2006-07-22 }}</ref>

== Durometer Scales ==

There are several scales of durometer, used for materials with different properties. The two most common scales, using slightly different measurement systems, are the A and D scales. The A scale is for softer plastics, 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.<ref name="uofm">{{cite web
|url=http://www.calce.umd.edu/general/Facilities/Hardness_ad_.htm#3.5
|title=Material Hardness
|publisher=CALCE and the [[University of Maryland, College Park|University of Maryland]]
|year=2001
|accessdate=2006-07-22 }}</ref>

==Method of measurement==

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 [[viscoelasticity|viscoelastic]] properties, the shape of the presser foot, and the duration of the test. Short durometer allows for a measurement of the initial indentation, or the indentation after a given period of time. The basic test requires applying the force in a consistent manner, without shock, for 15 seconds, and measuring the depth of the indentation. If instantaneous depth is desired, force is applied for only 1 second. The material under test should be approximately 6.4 mm (.25 inch) thick.<ref name="npl">{{cite web
|url=http://www.npl.co.uk/force/guidance/hardness/rubber.html
|title=Rubber Hardness
|publisher=[[National Physical Laboratory, UK]]
|year=2006
|accessdate=2006-07-22 }}</ref>

{| class="wikitable" style="text-align:center"
|+ '''Testing equipment - Shore Durometer Type A and D<ref name="npl" />'''
! Durometer || Indenting foot || Applied force (g)
|-
| Type A || Hardened steel rod 1.1 mm - 1.4 mm dia, with a truncated 35º cone, 0.79 mm dia. || 822 grams
|-
| Type D || Hardened steel rod 1.1 mm - 1.4 mm dia, with a 30º conical point, 0.1 mm radius tip || 4550 grams
|}

The final value of the hardness depends on the depth of the indenter's penetration. If the indenter penetrates 2.5mm or more into the material, the durometer is 0 for that scale. If it does not penetrate at all, then the durometer is 100 for that scale. It is for this reason that multiple scales exist. Durometer is a dimensionless quantity, and there is no simple relationship between a material's durometer in one scale, and its durometer in any other scale, or by any other hardness test.<ref name="matweb"/>

==Durometer of various common materials==

[[Image:Tire_tread.jpg|thumb|right|300px|An automotive [[tire]] tread, one of the many rubber or polymer objects categorized by its '''durometer''' hardness. Tires typically range from 50A to 70A, depending on their application.]]
{| class="wikitable" style="text-align:center"
! Material || Durometer || Scale
|-
| Hard Hat || 75 || D
|-
| Ebonite Rubber || 100 || A
|-
| Hard skateboard wheel || 100 || A
|-
| Solid truck tires || 50 || D
|-
| Soft skateboard wheel || 70 || A
|-
| Automotive tire tread || 70 || A
|-
| Door seal || 55 || A
|-
| Rubber band || 25 || A
|-
| Sorbothane || 40 || OO
|-
| Sorbothane || 0 || A
|-
| Chewing Gum || 20 || OO
|}

==References==
<div class="references-small"><references/></div>

==See also==
* [[Hardness]]
* [[Rockwell hardness test]]
* [[Vickers hardness test]]
* [[Brinell hardness test]]
* [[Knoop hardness test]]

[[Category:Dimensionless numbers]]
[[Category:Materials science]]

Wikipedia - Benutzerbeiträge [de]

Shore-Durometer