Shore durometer
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2008-05-18T17:52:44Z
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Reverted edits by [[Special:Contributions/69.138.166.126|69.138.166.126]] ([[User talk:69.138.166.126|talk]]) to last version by Peforsythe
<!-- Unsourced image removed: [[Image:Durometer.jpg|An analog durometer {{speedy-image-c|2006-06-08}}|right|thumb]] -->
'''Durometer''' is one of several ways to indicate the [[hardness]] of a material, defined as the material's resistance to permanent indentation. It is named for instrument maker Albert F. Shore, who developed a measurement device called a '''durometer''' in the 1920s. The term '''durometer''' is often used to refer to the measurement, as well as the instrument itself. 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 ASTM D2240 type A and type 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. 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 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 6.4 mm (.25 inch) thick.<ref name="npl">{{cite web
|url=http://www.npl.co.uk/server.php?show=ConWebDoc.379
|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 mass [kg] || Resulting force [N]
|-
| Type A || Hardened steel rod 1.1 mm - 1.4 mm dia, with a truncated 35º cone, 0.79 mm dia. || 0.822 || 8.064
|-
| Type D || Hardened steel rod 1.1 mm - 1.4 mm dia, with a 30º conical point, 0.1 mm radius tip || 4.550 || 44.64
|}
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
|-
| Bicycle gel seat || 15-30 || OO
|-
| [[Chewing Gum]] || 20 || OO
|-
| [[Sorbothane]] || 40 || OO
|-
| [[Sorbothane]] || 0 || A
|-
| [[Rubber band]] || 25 || A
|-
| Door seal || 55 || A
|-
| [[Automotive tire]] tread || 70 || A
|-
| Soft [[skateboard wheel]] || 75 || A
|-
| Hydraulic O-Rings || 70-90 || A
|-
| Hard skateboard wheel || 98 || A
|-
| [[Ebonite|Ebonite Rubber]] || 100 || A
|-
| Solid truck tires || 50 || D
|-
| [[Hard Hat]] || 75 || D
|-
| [[Urethane Bandsaw Tires]] || ? || D
|}
==Patents==
* {{US patent reference
| number = 1770045
| title = Apparatus for Measuring the Hardness of Materials
| inventor = A.F. Shore
| y = 1930 | m = 07 | d = 08
}}
* {{US patent reference
| number = 2421449
| title = Hardness Measuring Instrument
| inventor = J.G. Zuber
| y = 1947 | m = 06 | d = 03
}}
==References==
<div class="references-small"><references/></div>
==External links==
[http://checkline.com/docs/d2240.pdf ASTM Standard D2240 - Standard Test Method for Rubber Property - Durometer Hardness]
==See also==
* [[Hardness]]
* [[Rockwell hardness test]]
* [[Vickers hardness test]]
* [[Brinell hardness test]]
* [[Knoop hardness test]]
[[Category:Dimensionless numbers]]
[[Category:Hardness tests]]
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