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Shore Hardness Number

 

Shore Hardness Test Formula

\( H  \;=\;  100 - \dfrac{ d  }{  d_{max}  }  \cdot 100   \)     (Shore Hardness Test)

\( d  \;=\;  \dfrac{ (100 - H) \cdot d_{max}  }{ 100  }   \) 

\( d_{max}  \;=\;   \dfrac{ 100 \cdot d  }{  100 - H  }  \)
Symbol English Metric
\( HK \) = Shore Hardness Test \( dimensionless \) \( dimensionless \)
\( d \) = Depth of Identification \(in\) \( mm \)
\( d_{max} \) = Maximum Possible Identification Depth \(in\) \( mm \)
Shore hardness test is a standardized method used to measure the resistance of materials, primarily polymers like rubbers, elastomers, and plastics, to indentation.  It provides a numerical value that indicates the material's hardness, with higher numbers signifying greater resistance to indentation and thus a harder material, while lower numbers indicate a softer, more easily indented material.

The test is performed using a device called a durometer.  This instrument features a spring-loaded indenter (a standardized presser foot) that is pressed into the surface of the material.  The depth of the resulting indentation is measured, and this depth correlates to a specific reading on a Shore hardness scale.   There are several Shore hardness scales, such as Shore A, Shore D, and Shore 00, each designed for different ranges of material hardness.  

For instance, Shore 00 is used for very soft gels and foams,  Shore A for softer rubbers and semi-rigid plastics, and Shore D for hard rubbers and rigid plastics.  The choice of scale depends on the material's expected hardness to ensure accurate and meaningful results.  The test is used for material selection in various industries, helping engineers and manufacturers ensure that components have the appropriate flexibility, durability, and resistance to wear for their intended applications.

Nusselt Number Interpretation 

  • The ASTM D2240 standard, which governs Shore hardness testing, actually defines twelve different durometer types (A, B, C, D, DO, E, M, O, OO, OOO, OOO-S, and R), each designed for specific ranges of material hardness and types.
  • Low/High Shore Hardness Number  -  The value (0–100) indicates how resistant the material is to indentation.  Higher values mean harder materials; lower values mean softer materials.

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