Essential Experimental Setup
Core components
Vickers hardness tester – applies controlled load using a diamond pyramidal indenter
Load control and dwell system – ensures reproducible loading/unloading conditions
Polished specimen stage – provides a smooth, flat surface for symmetric crack formation
Optical/SEM microscope – measures indentation diagonals and crack lengths accurately
Data analysis software/calculator – computes hardness and K_IC
Experimental Procedure for Measuring Fracture Toughness (Vickers Indentation Method)

Specimen Preparation
Prepare a flat ceramic sample and polish the surface sequentially using finer abrasives, followed by diamond paste polishing, to obtain a mirror-like finish. Ensure the surface is free from scratches, pores, and residual stresses, as these can influence crack formation.

Indentation Loading
Mount the specimen securely on the Vickers hardness tester stage. Apply a controlled indentation load (e.g., 1 kgf ≈ 10 N) using the diamond pyramidal indenter (Figure 1). Maintain a constant dwell time of approximately 10 seconds to allow stable crack development, then unload gradually to minimize dynamic effects.

Indent Selection
Produce multiple indents at well-spaced locations (at least 3–4 times the indentation diagonal apart) to avoid crack interaction. Select only those impressions showing clear and symmetric radial–median cracks at all four corners.

Crack Measurement
Observe the indentation under an optical or scanning electron microscope (Figure 1d).

Measure:
the average indentation diagonal (for hardness, if needed),
the crack length c, defined as the distance from the center of the indent to each crack tip.
Take the average of the four crack lengths for accuracy.

Property Inputs
Obtain the elastic modulus Eand hardness Hof the material from nano/microindentation measurements or literature values.

Fracture Toughness Calculation
Substitute the measured values into the Anstis equation.

Repeatability Check
Perform at least 5–10 indentations and report the average fracture toughness with standard deviation to ensure reliability.

Figure 1: (a) Pyramidal diamond tip Vickers indenter. (b), (c), and (d) shows a schematic representation of the indentation process and cracks developed. The measurement of cracks is done using the optical/electron microscope.