Measurement of material hardness (Vickers, Rockwell, Brinell, Knoop, Shore)

Material hardness testing is a fundamental mechanical test used to quantify a material's resistance to penetration or local deformation under the action of a hard object. It is a key indicator of mechanical properties, wear resistance, scratch resistance, and, more broadly, the functional performance of a material under conditions of use. This test is widely used in the packaging, materials, and polymer industries, both for quality control and research and development. Hardness is often correlated with other mechanical properties such as tensile strength, yield strength, and abrasion resistance.

General principle of the hardness test

The principle of hardness measurement is based on applying a controlled load to the material's surface using a penetrator of defined geometry. The size, depth, or shape of the indentation left after load application allows for the calculation of a hardness index specific to the method used. The choice of technique depends on the nature of the material, its thickness, its homogeneity, and the desired scale of analysis. Tests are performed according to international ISO or ASTM standards, guaranteeing the reproducibility and comparability of results. Samples generally need to have a flat, clean, and properly prepared surface to ensure reliable measurements.

Presentation of the main hardness methods

Vickers hardness testing uses a diamond pyramidal indenter and is suitable for a wide range of materials, from metals to rigid polymers. It allows for precise measurements, even on thin materials or localized areas, and is frequently used in R&D or for comparative analyses.
Rockwell hardness testing is based on measuring the depth of penetration under load. It is quick to perform and particularly well-suited for industrial quality control of metals and alloys.
Brinell hardness testing uses a metal or carbide ball and is applicable to relatively homogeneous and thick materials. It is commonly used for metals, cast irons, or alloys with a coarse structure.
Knoop hardness testing , similar to the Vickers method, is specifically designed for brittle materials, thin films, or microstructures. It allows for highly localized measurements with minimal surface damage.
Shore hardness testing , widely used for polymers, elastomers, and rubbers, measures the resistance to indentation by a standardized indenter. Shore A, D or other scales are chosen according to the flexibility of the material.

Industrial interest and applications

Hardness measurement is an essential tool for characterizing a material before its implementation or commercialization. In polymer and plastic materials, it allows for the evaluation of rigidity, resistance to mechanical stress, and the material's suitability for a given application. In the packaging sector, hardness contributes to validating the mechanical strength of materials, particularly for injection-molded parts, rigid films, or components subjected to handling stresses.
For metals and alloys, hardness is a direct indicator of the metallurgical state, the effectiveness of a heat treatment, or the quality of a production batch. In R&D, it allows for the comparison of different formulations, the optimization of manufacturing processes, or the assessment of the impact of aging, wear, or exposure to harsh conditions.

Hardness testing and failure analysis

In the context of defect or non-conformity analysis, hardness measurement helps identify local heterogeneities, weakened areas, or conversely, overhardened areas. An abnormal variation in hardness can reveal a problem with the formulation, process, heat treatment, or material compatibility. The test can be combined with microscopic observations, particularly scanning electron microscopy (SEM), to correlate mechanical properties with the material's microstructure.

Analyzed matrices

Hardness tests can be performed on a wide variety of materials: metals and alloys, thermoplastic or thermosetting polymers, elastomers, rubbers, composite materials, coatings, injected or extruded parts, rigid films, and samples from production or field use. Tests can be carried out on flat surfaces or on samples that have been specifically prepared (polished, cut).

Added value YesWeLab

YesWeLab collaborates with a network of specialized mechanical testing laboratories capable of performing all standardized hardness testing methods according to ISO or ASTM. Our partners, most of whom are ISO 17025 and COFRAC certified or accredited, have the appropriate equipment for macro- and microhardness testing. Our scientific team assists you in selecting the most relevant method based on your material, your industry, and your objective (quality control, R&D, failure analysis). Since 2020, manufacturers, engineers, and design offices have trusted YesWeLab for the centralized management of their analyses via a reliable and responsive digital platform.

Related analyses in the YesWeLab catalog

To complement the hardness measurement, the following analyses are often combined:

• Mechanical tests of tension, bending or compression
• SEM analysis for microstructural study
• Measurement of wear and abrasion
• DSC and TGA analysis for thermal characterization