Palmqvist method explained

Materials testing
Palmqvist method
Determined crack lengths from a Vickers indention.
Technical information
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Searched property	Fracture toughness
Year developed	1962^[1]
Practical use	Determination of the fracture toughness for cemented carbides.
Website ISO-standard	ISO 28079:2009, Palmqvist toughness test

The Palmqvist method, or the Palmqvist toughness test, (after Sven Robert Palmqvist) is a common method to determine the fracture toughness for cemented carbides. In this case, the material's fracture toughness is given by the critical stress intensity factor K_Ic.^[2]

Approach

The Palmqvist-method uses the lengths of the cracks from a number of Vickers indentions to determine the fracture toughness. The Palmqvist fracture toughness is given by^[2]

K _{Ic} = 0 . 0028 \sqrt{ HV }\sqrt in units of MPa\sqrt{ m },

where HV is the Vickers hardness in N/mm² (or MPa) (i.e., 9.81 x numerical HV), P is the indentation load in N (typically 30 kgf is used) and T is the total crack length (mm) after application of the indenter.

Notes

1. S. Palmqvist, Occurrence of crack formation during Vickers indentation as a measure of the toughness of hard materials, Arch Eisenhuettenwes, 33 (1962) 629-333.
2. Web site: Palmqvist Toughness for Hard and Brittle Materials . Bryan . Roebuck . Eric . Bennett . Lewis . Lay . Roger . Morrell . National Physical Laboratory . 2008 . 15 April 2020.