ISO DIS 20064

Description / Abstract: This document specifies a test method for the determination of brittle crack arrest toughness and is applicable to ferritic steel base metals exhibiting ductile to brittle transition behaviour. Applicable materials are rolled steel plates. It is intended for materials with a tensile strength of 950 MPa or less and a test piece thickness of 200 mm or less. The range of arrest temperatures is between -196 °C and 100 °C. This document can be applied to flat rolled steel plates but not to flattened steel pipes because the flattening can cause changes in arrest toughness. Therefore, this document should not be used for pipes unless the influence of flattening is quantitatively predicted.

The test method may be summarized as follows: after setting a temperature gradient across the width of a test piece, and applying uniform stress to the test piece, strike the test piece to initiate a brittle crack from a mechanical notch in either edge of the test piece and cause crack arrest after propagating in the width direction (temperature gradient type arrest testing). Annex A shows typical devices and method of setting the temperature gradient on the piece. Using the stress intensity factor, calculate the arrest toughness, K_ca, from the applied stress and the arrest crack length. This value is the arrest toughness at the temperature at the point of crack arrest (arrest temperature). To determine K_ca at a specific temperature such as the design temperature of a structure, the method specified in Annex B may be used.

To check the validity of a crack propagation path, Annex C may be used to determine the stress intensity factor for a curved crack.

As a method for initiating a brittle crack, a secondary loading mechanism can be used (see Annex D). The arrest characteristics of the test piece can also be evaluated by welding a crack starter plate to the test plate in the width direction to enable a brittle crack initiated from the mechanical notch at the edge of the test piece to propagate in the crack running plate and observing the propagation behaviour of the crack immediately after entering the test plate (see Annex E)

To determine the dynamic behaviour of crack propagation and measure the dynamic strain of a test piece, the method explained in Annex F may be used.