Fracture Toughness Testing

ASTM E399 KIC Test & ASTM E1820 JIC Testing

fatigue test labThe Fracture Toughness Test determines how well a material can resist the growth of a crack under increasing load. It is valuable in determining whether there is a danger of component failure when a flaw is discovered in an existing structure.

The experienced staff at Laboratory Testing Inc. in Pennsylvania (USA) performs the following methods of Fracture Toughness Testing: KIC Test to ASTM E399, JIC Testing to ASTM E1820 and ASTM E1921.

Scope of Testing

LTI’s 29 servo-hydraulic load frames can generate loads up to 110,000 lbf. and cyclic loading up to 40 hertz. Temperatures range from -323°F and 2250° F. We have both compression and tension loading capabilities and have load cells for precision loading down to a 40 lbf. mean load.

Fixturing is available to test specimens in a range of sizes, including SE(B) (single edged bend) and C(T) (compact tension) specimens.

Test Methods/Specifications

  • Fracture toughness specimensASTM E399
  • ASTM E1820
  • ASTM E1921

Test Specimens Prepared by LTI

The fracture toughness test requires a precisely machined specimen prepared to specification. The Machine Shop at LTI can prepare specimens for all types of fracture toughness testing and provides an EDM machined notch. Specimen sizes ranging from Charpy-sized SE(B) bars up to 4.5” W C(T) specimens have been machined.

Contact us to discuss your requirements for fracture toughness testing services.

The Fracture Toughness Test Process

Fracture toughness is an important material property in design applications since the occurrence of flaws is not completely avoidable. Flaws may appear as cracks, voids, inclusions, weld defects or design discontinuities.

A fracture toughness test measures the conditions under which an existing crack in a material will extend by characterizing the resistance of the material to crack extension when a sharp crack is present. The properties are obtained by testing specimens containing preexisting deliberately introduced cracks or notches that are subjected to increasing tensile loading conditions. By measuring the combination of load and displacement as the crack lengthens, the material’s resistance to further crack extension is determined.

ASTM E399 / KIC Test

Fracture toughness testing according to ASTM E399 applies a continuously increasing load to the specimen and determines the critical stress intensity KIc. This method is known as the KIC test, KIC or K1C fracture toughness test.

ASTM E1820 / JIC Testing

During testing to ASTM E1820, a rising load with periodic partial unloading is applied to measure the crack length as the test progresses. ASTM E1820 provides KJIc and JIc. Crack-Tip Opening Displacement (CTOD, δ) is also available from the data analysis.

The “J” integral describes elastic-plastic fracture toughness in more ductile materials which are better able to deform and resist crack growth under load. A Roman numeral subscript added to “K” and “J” indicates which of the three modes of fracture is used in the test. Mode I fracture is most common and is the condition in which a tensile load is applied normal to the direction of the crack plane. When a cracked material under Mode I plane-strain conditions reaches a critical value, denoted as KIc or JIc, the crack will begin to grow. Experimental values of KIc and JIc can be applied to the design of structures to ensure that a component does not fail by brittle or ductile fracture. KJIc is derived from the JIc result.

ASTM E1921

ASTM E1921 is a fracture test method used for determination of a reference temperature, To, which statistically characterizes fracture toughness as a function of temperature of ferritic steels that experience cleavage fracture mechanisms.

LTI Capabilities

  • Test Methods – ASTM E399 per KIc; ASTM E1820 JIc, KJIc; ASTM E1921
  • Loads – to 110,000 lbf.
  • Temperature – range from -323° F to +2250° F
  • Fixturing – SE(B) single edge bend and C(T) compact tension specimen geometries in a range of sizes
  • Test Specimens – prepared in LTI’s Machine Shop according to standard procedures; EDM notch capabilities

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