ASTM-E1304 Standard Test Method for Plane-Strain (Chevron-Notch) Fracture Toughness of Metallic Materials

ASTM-E1304 - 1997 R14 EDITION - CURRENT -- See the following: ARP-1704
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Standard Test Method for Plane-Strain (Chevron-Notch) Fracture Toughness of Metallic Materials
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Scope

1.1 This test method covers the determination of plane-strain (chevron-notch) fracture toughnesses, KIv or KIvM, of metallic materials. Fracture toughness by this method is relative to a slowly advancing steady state crack initiated at a chevron-shaped notch, and propagating in a chevron-shaped ligament (Fig. 1). Some metallic materials, when tested by this method, exhibit a sporadic crack growth in which the crack front remains nearly stationary until a critical load is reached. The crack then becomes unstable and suddenly advances at high speed to the next arrest point. For these materials, this test method covers the determination of the plane-strain fracture toughness, KIvj or KIvM, relative to the crack at the points of instability.

(A) See Fig. 6.
(A) See Fig. 6.
(B) See Note 1.
(A) Compiled from Refs (1), (2), (3), and (4), and using the polynomials in Table 5.
(B) Minimum value of Y*.
(A) Compiled from Refs (1), (2), (3), and (4).
(B) Y* = exp[C0  + C1 r + C2 r2  + C3 r3  + C4 r4 ], accuracy ±0.5 %.
(C) Estimated from finite element analysis (3), and extrapolated equation from Ref (4). Accuracy for 0.3 r 0.85 is ±0.5 %.
(D) Extrapolated from equations in Ref (4). Accuracy estimated to be ±0.5 % for 0.2 r 0.85.
(E) Equation from Ref (4). Accuracy estimated to be± 0.5 % for 0.15 r 0.6.

Significance and Use

5.1 The fracture toughness determined by this test method characterizes the resistance of a material to fracture by a slowly advancing steady-state crack (see 3.2.5) in a neutral environment under severe tensile constraint. The state of stress near the crack front approaches plane strain, and the crack-tip plastic region is small compared with the crack size and specimen dimensions in the constraint direction. A KIv or KIvj value may be used to estimate the relation between failure stress and defect size when the conditions described above would be expected, although the relationship may differ from that obtained from a KIc value (see Note 1). Background information concerning the basis for development of this test method in terms of linear elastic fracture mechanics may be found in Refs (6-15).

5.1.1 The KIv, KIvj, or KIvM value of a given material can be a function of testing speed (strain rate) and temperature. Furthermore, cyclic forces can cause crack extension at KI values less than KIv, and crack extension can be increased by the presence of an aggressive environment. Therefore, application of KIv in the design of service components should be made with an awareness of differences that may exist between the laboratory tests and field conditions.

5.1.2 Plane-strain fracture toughness testing is unusual in that there can be no advance assurance that a valid KIv, KIvj, or KIvM will be determined in a particular test. Therefore, it is essential that all the criteria concerning the validity of results be carefully considered as described herein.

5.2 This test method can serve the following purposes:

5.2.1 To establish the effects of metallurgical variables such as composition or heat treatment, or of fabricating operations such as welding or forming, on the fracture toughness of new or existing materials.

5.2.2 For specifications of acceptance and manufacturing quality control, but only when there is a sound basis for specification of minimum KIv, KIvj, or KIvM values, and then only if the dimensions of the product are sufficient to provide specimens of the size required for valid KIv determination (9). The specification of KIv values in relation to a particular application should signify that a fracture control study has been conducted on the component in relation to the expected history of loading and environment, and in relation to the sensitivity and reliability of the crack detection procedures that are to be applied prior to service and subsequently during the anticipated life.

5.2.3 To provide high spatial resolution in measuring plane strain fracture toughness variations in parent pieces of material (14).

Note 2: The high spatial resolution is possible because of the small allowable specimen size criterion, B 1.25 (KIv YS)2 (9), and because the toughness is measured at approximately the midline of the specimen, and only in the material covered by the crack's lateral extent, which is about one third of the specimen's lateral dimension, B.

Keywords

ICS Number Code 77.040.10 (Mechanical testing of metals)

To find similar documents by ASTM Volume:

03.01 (Metals -- Mechanical Testing; Elevated and Low-Temperature Tests; Metallography)

To find similar documents by classification:

77.040.10 (Mechanical testing of metals Mechanical testing in general, see 19.060 Mechanical testing of welded joints, see 25.160.40)

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Document Number

ASTM-E1304-97(2014)

Revision Level

1997 R14 EDITION

Status

Current

Modification Type

Reapproval

Publication Date

Oct. 1, 2014

Document Type

Test Method

Page Count

12 pages

Committee Number

E08.02