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A CTOD test is usually done on materials that undergo plastic deformation prior to failure. The testing material more or less resembles the original one, although dimensions can be reduced proportionally. Loading is done to resemble the expected load. More than 3 tests are done to minimize any experimental deviations. The dimensions of the testing material must maintain proportionality. The specimen is placed on the work table and a notch is created exactly at the centre. The crack should be generated such that the defect length is about half the depth. The load applied on the specimen is generally a three-point bending load. A type of [[strain gauge]] called a crack-mouth clip gage is used to measure the crack opening.<ref name=":0" /> The crack tip plastically deforms until a critical point after which a cleavage crack is initiated that may lead to either partial or complete failure. The critical load and strain gauge measurements at the load are noted and a graph is plotted. The crack tip opening can be calculated from the length of the crack and opening at the mouth of the notch. According to the material used, the fracture can be brittle or ductile which can be concluded from the graph.
Standards for CTOD testing can be found in the ASTM E1820 - 20a code.<ref>{{Cite journal|last=E08 Committee|title=Test Method for Measurement of Fracture Toughness|url=http://www.astm.org/cgi-bin/resolver.cgi?E1820-20A|language=en|doi=10.1520/e1820-20a|url-access=subscription}}</ref>
=== Laboratory measurement ===
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