Fracture Toughness Testing

KIC and JIC testing per ASTM E399 and E1820, respectively

Evaluation of Fracture Toughness  How well a material stops a crack from spreading under increasing force is measured by the Fracture Toughness Test. The test’s results on fracture toughness can be used to select appropriate materials and assess whether or not a newly discovered weakness in an existing structure poses a threat to the integrity of a critical component.

Infinita Laboratory Testing offers a variety of fracture toughness testing services, including the KIC Test to ASTM E399, the JIC Test to ASTM E1820, and the Master Curve Test to ASTM E1921.

Range of Testing Servces Fracture Toughness

Infinita Lab offers fracture toughness testing from 40 lbf up to 100,000 lbf at temperatures from -323°F to 1800°F. C (T) compact tension and SE (B) single-edge bend test specimens are just two examples of the shapes and sizes that can be accommodated by the available fixture options.

PREPARED TEST SPECIMENS FOR THE ASTM E399, E740, E1820, E1921, AND E2899 TESTING PROCEDURES

For the fracture toughness test, a specimen that has been machined to exacting standards is necessary. The notch required for EDM machined fracture toughness testing can be prepared at the Machine Shop at Infinita Lab

The following are some of the most typical specimen shapes used when evaluating fracture toughness:

• Example specimens of fracture toughness  A rectangular specimen with a slot cut on the long side is loaded in three point bending to create a single edge bend, also known as SE(B) or SENB.
• The most popular geometry is known as Compact Tension (C(T)).
• When a C-R fracture toughness result is needed for a round bar, the DC(T) test is performed.
• Infinita Lab has machined specimens ranging in size from Charpy-sized SE(B) bars to 4.5″ W C(T) specimens.

To discuss your needs for fracture toughness testing (also known as fracture mechanics testing), please get in touch with us.

HOW TO DO A FRACTURE TEST

Since defects are inevitable, the ability of a material to withstand damage before it fails is a crucial attribute for many design applications. Cracks, voids, inclusions, weld faults, and design discontinuities are all possible manifestations of defects.

Tests for fracture toughness characterize a material’s resistance to crack extension when a sharp crack is present and are used to quantify the conditions under which a crack in the material would propagate. Specimens with preexisting, purposefully created cracks or notches are tested under increasing tensile loading conditions to determine their characteristics. The material’s ability to resist further crack extension is calculated by analyzing the relationship between load and displacement as the crack grows in length.

KIC ASTM E399 TESTING

As the load on the specimen is increased, the critical stress intensity, KIc, is calculated in accordance with ASTM E399. The KIC test, KIC, or K1C fracture toughness test describes this technique. Standardization in the aircraft industry uses this test frequently.

MORE THAN JUST ASTM E1820 AND JIC TESTING

Crack length is monitored throughout an ASTM E1820 test by applying a growing force and then periodically relieving some of that strain. It is typically possible to acquire valid results where a KIc test would be impossible or impractical since this method takes measurements throughout the test, providing a lot of data on the behavior of the material as the fracture opens.

KJIc, JIc, and CTOD are all available from ASTM E1820. The analysis also provides the Crack-Tip Opening Displacement (CTOD). Ductile materials, which can deform and resist crack formation under load, have a fracture toughness described by the “J” integral. Each of the three modes of fracture is denoted by adding a Roman number subscript to the “K” or “J” in the test’s name. Mode I fracture occurs when a tensile stress is applied perpendicular to the crack plane and is the most frequent type of fracture. The critical value, KIc or JIc, at which a crack in a material starts to form under Mode I plane-strain circumstances

The experimental values of KIc and JIc can be used in structural design to prevent brittle and ductile component failure, respectively. From the JIc result, we may calculate KJIc.

The ASTM E1921 Master Curve Test

Fracture testing according to ASTM E1921 is commonly used for determining the Reference Temperature (To) for cold-climate steels. The goal is to statistically describe cleavage fracture toughness in ferritic steels throughout a wide temperature range.

This method employs the ASTM E1820 testing procedure with certain modifications. To do a Weibull statistical analysis to find To, you need a minimum of six valid results, taken at different temperatures.

SUPPLEMENTING ACCURATE TESTING WITH DATA AND SAMPLES

We need to know the exact material requirements for your test in order to prepare properly. Please provide a copy if it is confidential. If you don’t know what the data will be used for (e.g., material conformity, comparison, study, or failure analysis), give as much context as feasible.

The yield and tensile strengths, Young’s Modulus, and predicted fracture toughness of the material at the chosen test temperature would also be helpful. It is impossible to do an ASTM E1820 test without measuring the tensile strength, yield strength, and Young’s modulus at the test temperature.

Samples should be sent with the orientation relative to the parent material clearly noted, and specimens should be able to be effectively detached from the parent material.

TALENTS FOR INFINITA LAB

• Loads up to 100,000 lbf are permitted in the following tests: ASTM E399 KIc, ASTM E1820 JIc, KJIc, ASTM E1921, and ASTM E2899.
• Temperature: minus 323 degrees to plus 1800 degrees
• Multiple-sized SE (B) single-edge bend and C (T) compact tension specimen fixtures
• EDM notch capability; test specimens made in Infinita Lab’s Machine Shop per established practices

Video 01: KIC FRACTURE TOUGHNESS