What is a fracture test?

The methodology of fracture toughness tests revolves around the application of incremental loads to the material until failure occurs. Prior to testing, meticulous preparation is imperative, involving the creation of a fatigue notch to facilitate crack initiation, commonly achieved through Electric Discharge Machining (EDM).

To conduct a fracture toughness test, the initial step entails the preparation of a testing sample featuring a pre-existing crack. This crack facilites intended crack propagation during the test. Utilizing a universal testing machine (UTM) is imperative for conducting fracture toughness tests, given its versatility in accommodating various testing methodologies, including tensile testing. Moreover, adherence to reference standards is paramount, as prescribed by renowned organizations such as ASTM and ISO. These standards delineate specific requirements concerning machine calibration and test setup, ensuring procedural uniformity across diverse testing scenarios.

One common method employed in fracture toughness testing is the Crack Tip Opening Displacement (CTOD) test. This method entails subjecting a pre-cracked material specimen to a 3-point bend test setup. The procedural steps for conducting a CTOD test are as follows:

• Sample Preparation: Machining a notch at the midpoint of the material specimen, followed by inducing a fatigue crack at the machined notch.
• Loading Procedure: Placing the specimen within a 3-point bending setup machine to apply the requisite load.
• Strain Measurement: Attaching strain gauges to either side of the crack to meticulously measure strain variations throughout the testing process.
• Failure Analysis: Applying a progressive load until failure occurs, meticulously documenting the ensuing results for comprehensive analysis and evaluation.