Chapter 9Fracture Testing

(a) Charpy impacttesting machine. (b) Charpy impacttest specimen. (c) Izod impact testspecimen.

Impact TestingImpact TestingCharpy Impact Testing

Energy absorbed versustemperature for a steel in annealedand in quenched and temperedstates. (Adapted with permissionfrom J. C. Miguez Suarez and K. K.Chawla, Metalurgia-ABM, 34 (1978)825.)

Energy Absorbed vs. Temperature

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

Temperature Effect on Fracture Surface

Results of Charpy testsfor AISI 1018 steel (cold drawn).

Charpy Testing of Steel: DBTT

Drop-weight testspecimen.

Drop-Weight Test Specimen

Charpy V-notch curvefor a pressure-vessel steel. Notethat the NDT temperaturedetermined by the drop-weighttest corresponds to the high-toughregion of the Charpy curve.Pneumatic pressurization; material:21/4 Cr-1 Mo steel, yield stress590 MPa. (After W. J. Langford,Can. Met. Quart., 19 (1980) 13.)

Charpy V-notch Curve

(a) Typical oscilloscoperecord of an instrumented Charpyimpact test. (b) Schematicrepresentation of (a).

Oscilloscope Record

Typical ASTM standardplane-strain fracture toughnesstest specimens. (a) Compacttension. (b) Bending. (c)Photograph of specimens ofvarious sizes. Charpy and tensilespecimens are also shown, forcomparison purposes. (Courtesyof MPA, Stuttgart.)

Fracture Toughness Test Specimens

Schematic of typicalload–displacement curves in a KIctest.

Load Displacement Curves vs. Fracture Toughness Test

Plastic zone at the x1crack tip in a plate of finitethickness.

Plastic Zone at Crack Tip

Assembly formeasuring displacement in anotched specimen.

Displacement Measurement

Measuring Conditioned Value KQ

Variation in Kc withflaw size, specimen thickness, andspecimen width.

Variation of Kc with Specimen Thicckness

Load P vs. Crack Opening Displacement: Different Responses

“Plastic hinge” mechanism of deformation.

Plastic Hinge Mechanism

Method fordetermining JIc. (a) Load identicalspecimens to differentdisplacements. (b) Measure theaverage crack extension by heattinting. (c) Calculate J for eachspecimen. (d) Plot J versus a tofind JIc.

J-Integral Testing

Normal stresses alonga section of beam for linearlyelastic material.

Flexure Test

Application of loadsand 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 ofthe 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-testingmethods for brittle materials. (a)Double-cantilever beam (DCB). (b)Double torsion. (c) Notch flexure.

Fracture Testing Methods for Ceramics

Chevron notch test.(a) Schematic of the testarrangement and the details of thenotch plane. (b) The chevron tiplength, a0, can be measured fromoptical micrographs of brokenspecimens. (c) Chevron short-rodspecimen.

Chevron Notch Test

Fractures produced byhardness indentations in (a) AsS3glass (courtesy of B. R. Lawn andB. J. Hockey) and (b) Al203.

Hardness Indentation in Brittle Materials

Schematicrepresentation of indentationgenerating a plastic deformationregion and a semicircular crack.

Plastic Deformation and Crack in Indentation of Brittle Material

Comparison betweenconventional and indentationfracture toughness determinationsfor 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: Comparison by Different test Methods

Indentation tests forthe determination of toughness ofbond between substrate and thinfilm; (a) method used for ductilecoating on brittle substrate (typicalof electronic components); (b)method used for brittle coatingson ductile substrate; (c) calculatednormalized energy release rate asa function of normalized crackdiameter. (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