Plastizität und Bruchmechanik - Technische Fakultät

Bruchmechanik
K
P
⎛ a ⎞
⎝W
⎠
Q
Q
= Y⎜ ⎟
BW
If size condition ( ) ( ) 2
W a K σ
depending on specimen configuration
− ≥ 2.5
Q YS
is met, then KIc = KQ
Scope
ASTM E 1820:
Standard Test Method for Measurement of Fracture Toughness
Determination of fracture toughness of metallic materials using the parameters K, J, and
CTOD (δ).
Terminology
δ Ic
δ c
δ u
δ c
*
J c
J u
near the onset of slow stable crack extension, Δa p = 0.2 mm,
at the onset of unstable crack extension, Δa p < 0.2 mm,
at the onset of unstable crack extension, Δa p > 0.2 mm,
fracture toughness at fracture instability prior to the onset of significant stable tearing
crack extension,
fracture toughness at fracture instability prior to the onset of significant stable tearing
crack extension,
fracture instability after the onset of significant stable tearing crack extension,
Significance and Use
Assuming the existence of a preexisting, sharp, fatigue crack, the material fracture
toughness values identified by this test method characterize its resistance to
(1) Fracture of a stationary crack
(2) Fracture after some stable tearing
(3) Stable tearing onset
(4) Sustained stable tearing
This test method is particularly useful when the material response cannot be anticipated
before the test.
‣ Serve as a basis for material comparison, selection and quality assurance; rank
materials within a similar yield strength range;
‣ Serve as a basis for structural flaw tolerance assessment; awareness of differences
that may exist between laboratory test and field conditions is required.
fracture-toughness, Wolfgang Brocks, 23-Nov-11, - 3 -