Standard Test Method for Conducting Drop-Weight Test to Determine Nil-Ductility Transition Temperature of Ferritic Steels

Importancia y uso:

5.1 The fracture-strength transitions of ferritic steels used in the notched condition are markedly affected by temperature. For a given “low” temperature, the size and acuity of the flaw (notch) determines the stress level required for initiation of brittle fracture. The significance of this test method is related to establishing that temperature, defined herein as the NDT temperature, at which the “small flaw” initiation curve, Fig. 1, falls to nominal yield strength stress levels with decreasing temperature, that is, the point marked NDT in Fig. 1.

FIG. 1 Generalized Fracture Analysis Diagram Indicating the Approximate Range of Flaw Sizes Required for Fracture Initiation at Various Levels of Nominal Stress, as Referenced by the NDT Temperature3 ^, 4

CAT (crack arrest temperature)–the temperature of arrest of a propagating brittle fracture. CAT curve is thus a stress versus temperature curve as related to crack arrest.

FTE (fracture transition elastic) temperature–the crack arrest temperature for a stress level equal to the yield strength thus marks the highest temperature of fracture propagation for purely elastic loads.

FTP (fracture transition plastic) temperature–the temperature above which fractures are entirely shear, that is, show no center regions of cleavage fracture, and the stress required for fracture approximates the tensile strength of the steel.

5.2 Interpretations to other conditions required for fracture initiation may be made by the use of the generalized flaw-size, stress-temperature diagram shown in Fig. 1. The diagram was derived from a wide variety of tests, both fracture-initiation and fracture-arrest tests, as correlated with the NDT temperature established by the drop-weight test. Validation of the NDT temperature has been documented by correlations with numerous service failures encountered in ship, pressure vessel, machinery component, forged, and cast steel applications.

5.3 Lists of Selected References Relating to Development of Drop-Weight Test. Selected References Relating to Correlation of NDT temperature to Service Failures, and Selected References Relating to Neutron Irradiation Embrittlement are presented following Section 17 on Precision and Bias.

Subcomité:

E28.07

Referida por:

A0945_A0945M-16R21, E0185-21, E0436-03R21, A0541_A0541M-05R20, A0426_A0426M-18, A0859_A0859M-23, A0508_A0508M-23A, E2215-24, A0020_A0020M-20, A0006_A0006M-24B, E1221-23, A0985_A0985M-21, A0703_A0703M-20A, A0703_A0703M-20A, E1921-24

Volúmen:

03.01

Número ICS:

77.040.10 (Mechanical testing of metals)