Chapter 9Fracture Testing

(a) Charpy impact testing machine. (b) Charpy impact test specimen. (c) Izod impact test specimen.

Impact TestingImpact TestingCharpy Impact Testing

Energy absorbed versus temperature for a steel in annealed and in quenched and tempered states. (Adapted with permission from J. C. Miguez Suarez and K. K. Chawla, Metalurgia-ABM, 34 (1978) 825 .)

Energy Absorbed vs. Temperature

Effect of temperature on the morphology of fracture surface of Charpy steel specimen. Test temperatures Ta < Tb < Tc < Td. (a) Fully brittle fracture. (b, c) Mixed-mode fractures. (d) Fully ductile (fibrous) fracture.

Temperature Effect on Fracture Appearance

Energy absorbed, cleavage area ,and lateral expansion as a function of temperature of testing for AISI 1018 steel (cold drawn).

Charpy Testing of Steel: DBTT

Drop-Weight Test Specimen

Charpy V-notch curve for a pressure-vessel steel. Note that the NDT temperature determined by the drop-weight test corresponds to the high-toughness region of the Charpy curve. Pneumatic pressurization; material: 21/4 Cr-1 Mo steel, yield stress 590 MPa. (After W. J. Langford, Can. Met. Quart., 19 (1980) 13.)

Charpy V-notch Curve for a Pressure Vessel Steel

(a) Typical oscilloscope record of an instrumented Charpy impact test. (b) Schematic representation of (a).

Instrumented Charpy Test

Typical ASTM standard plane-strain fracture toughness test specimens. (a) Compact tension. (b) Bending. (c) Photograph of specimens of various sizes. Charpy and tensile specimens are also shown, for comparison purposes. (Courtesy of MPA, Stuttgart.)

Fracture Toughness Test Specimens

Schematic of typical load–displacement curves in a KIc test.

Load Displacement Curves vs. Fracture Toughness Test

Plastic zone at the x1 crack tip in a plate of finite thickness.

Plastic Zone at Crack Tip

Assembly for measuring displacement in a notched specimen.

Clip Gage for Displacement Measurement

Procedure for Measuring Conditional KQ

Checklist for the KIc Test

Variation in Kc with flaw size, specimen thickness, and specimen width.

Variation of Kc with Specimen Dimensions

Load vs. Crack Opening Displacement

Plastic Hinge Mechanism

Method for determining JIc. (a) Load identical specimens to differentdisplacements. (b) Measure the average crack extension by heat tinting. (c) Calculate J for each specimen. (d) Plot J versus a to find JIc.

J-Integral Testing

Normal stresses along a section of beam for a linearly elastic material.

Flexure Test

Application of load and bending moment diagrams for(a) three-point bending and (b) four-point bending tests.

Three-Point and Four-Point Bend (Flexure) Tests

TThree-Point

Shematic drawing of the miniaturized disk-bend test. (Adapted from H. Li, F. C. Chen, and A. J. Ardell, Met. Trans A, 22 (1991) 2061.)

Miniaturized Specimen:Four-Point Bending

Fracture-testing methods for brittle materials. (a) Double-cantilever beam (DCB). (b) Double torsion. (c) Notch flexure.(d) Chevron notch

Fracture Testing Methods for Ceramics

(a) Schematic of the test arrangement and the details of the notch plane. (b) The chevron tip length, a0, can be measured from optical micrographs of broken specimens. (c) Chevron short-rod specimen.

Chevron Notch Test

Fractures produced by hardness indentations in (a) AsS3 glass (courtesy of B. R. Lawn and B. J. Hockey) and (b) Al2O3.

Hardness Indentation in Brittle Materials

Schematic representation of indentation generating a plastic deformation region and a semicircular crack.

Plastic Deformation and Crack in Indentation of Brittle Material

Comparison between conventional and indentation fracture toughness determinations for glasses and ceramics. (From G. R. Anstis, P. Chankitul, B. R. Lawn, and D. B. Marshall, J. Am. Cer. Soc., 64 (1981) 533.)

Fracture Toughness for Ceramics and Glasses Comparison of Results

Indentation tests for the determination of toughness of bond between substrate and thin film; (a) Method used for ductilecoating on brittle substrate (typicalof electronic components); (b) Method used for brittle coatingson ductile substrate; (c) Calculated normalized energy release rate as a function of normalized crack diameter.

(Adapted from J. J. Vlassak, M. D. Drory, and W. D. Nix, J. Mater. Res., 12 (1997) 100.)

Adhesion of Thin Film to Substrate: Testing