Chapter 9 Fracture Testing

1
Chapter 9Fracture Testing
2
Impact Testing
Impact Testing
Charpy Impact Testing
(a) Charpy impact testing machine. (b) Charpy
impact test specimen. (c) Izod impact test
specimen.
3
Energy Absorbed vs. Temperature
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.)?
4
Temperature Effect on Fracture Appearance
Effect of temperature on the morphology of
fracture surface of Charpy steel specimen. Test
temperatures Ta lt Tb lt Tc lt Td. (a) Fully brittle
fracture. (b, c)? Mixed-mode fractures. (d) Fully
ductile (fibrous) fracture.
5
Charpy Testing of Steel DBTT
Energy absorbed, cleavage area ,and lateral
expansion as a function of temperature of testing
for AISI 1018 steel (cold drawn).
6
Drop-Weight Test Specimen
7
Charpy V-notch Curve for a Pressure Vessel Steel
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.)?
8
Instrumented Charpy Test
(a) Typical oscilloscope record of an
instrumented Charpy impact test. (b) Schematic
representation of (a).
9
Fracture Toughness Test Specimens
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.)?
10
Load Displacement Curves vs. Fracture Toughness
Test
Schematic of typical loaddisplacement curves in
a KIc test.
11
Plastic Zone at Crack Tip
Plastic zone at the x1 crack tip in a plate of
finite thickness.
12
Clip Gage for Displacement Measurement
Assembly for measuring displacement in a notched
specimen.
13
Procedure for Measuring Conditional KQ
14
Checklist for the KIc Test
15
Variation of Kc with Specimen Dimensions
Variation in Kc with flaw size, specimen
thickness, and specimen width.
16
Load vs. Crack Opening Displacement
17
Plastic Hinge Mechanism
18
J-Integral Testing
Method for determining JIc. (a) Load identical
specimens to different displacements. (b)
Measure the average crack extension by heat
tinting. (c) Calculate J for each specimen. (d)
Plot J versus ?a to find JIc.
19
Flexure Test
Normal stresses along a section of beam for a
linearly elastic material.
20
Three-Point and Four-Point Bend (Flexure) Tests
TThree-Point
Application of load and bending moment diagrams
for (a) three-point bending and (b)? four-point
bending tests.
21
Miniaturized SpecimenFour-Point Bending
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.)?
22
Fracture Testing Methods for Ceramics
Fracture-testing methods for brittle materials.
(a)? Double-cantilever beam (DCB). (b)? Double
torsion. (c) Notch flexure. (d) Chevron notch
23
Chevron Notch Test
(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.
24
Hardness Indentation in Brittle Materials
Fractures produced by hardness indentations in
(a) AsS3 glass (courtesy of B. R. Lawn and B. J.
Hockey) and (b) Al2O3.
25
Plastic Deformation and Crack in Indentation of
Brittle Material
Schematic representation of indentation
generating a plastic deformation region and a
semicircular crack.
26
Fracture Toughness for Ceramics and Glasses
Comparison of Results
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.)?
27
Adhesion of Thin Film to Substrate Testing
Indentation tests for the determination of
toughness of bond between substrate and thin
film (a) Method used for ductile coating on
brittle substrate (typical of electronic
components) (b)? Method used for brittle
coatings on 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.)?