charpy impact toughness Testing Services: Measuring Material Resistance to Brittle Fracture

As an independent third-party testing service provider, we offer comprehensive charpy impact toughness testing for metallic materials, welds, and occasionally polymers. The Charpy V‑notch (CVN) impact test is the most widely used method to measure a material’s ability to absorb energy during high‑rate loading, providing critical insight into its ductile‑to‑brittle transition behaviour. This test is essential for quality control, material qualification, and fracture safety assessment in industries such as construction, oil & gas, pipeline, pressure vessel, shipbuilding, automotive, and aerospace. Our accredited laboratory follows international standards (ASTM E23, ISO 148‑1, EN 10045‑1, GB/T 229) using precision pendulum impact testers equipped with temperature control baths (from -196°C to +300°C). This article outlines our Charpy impact testing capabilities – including scope, key test items, and standard test methods – to help engineers, metallurgists, and quality professionals assess material toughness and transition temperature.

1. Our Testing Scope for charpy impact toughness

We cover a wide range of metallic materials, specimen configurations, and test conditions:

By material type: Carbon steel (low, medium, high); Alloy steel (Cr‑Mo, Ni‑Cr‑Mo); stainless steel (austenitic, martensitic, ferritic); Cast iron; Aluminium alloys; Copper alloys; Titanium alloys; Nickel alloys; Welded joints (weld metal, heat‑affected zone – HAZ, fusion line).

By specimen type: Standard Charpy V‑notch (CVN) – 10 mm × 10 mm cross‑section, 55 mm length, 2 mm deep V‑notch (45° angle, 0.25 mm root radius); Sub‑size specimens (7.5 mm × 10 mm, 5 mm × 10 mm, 5 mm × 5 mm, 2.5 mm × 10 mm – for limited material thickness); Charpy U‑notch (keyhole notch – less common).

By test parameter: Absorbed energy (KV – Joules, ft·lbf); Lateral expansion (LE – mm or inch); Fracture appearance (percent shear / percent cleavage); Transition temperature (ductile‑to‑brittle – FATT, T_27J, T_{50% shear}).

By test condition: Ambient temperature (23°C); Low temperature (as low as -196°C using liquid nitrogen baths); Elevated temperature (up to +300°C using heating chambers).

By industry standard / application: Pressure vessel steels (ASME, ASTM A20, EN 10028); Pipeline steels (API 5L); Structural steels (ASTM A36, A572, EN 10025); Shipbuilding (LR, DNV, ABS, CCS); Weld procedure qualification (AWS D1.1, ISO 15614).

2. Key Test Items & Measurements We Perform

Our Charpy impact testing services provide quantitative toughness data and fracture characterisation. Each test is performed on a calibrated pendulum impact machine (up to 750 J capacity) with certified reference specimens.

2.1 Absorbed Energy (Impact Energy)

KV (Charpy V‑notch absorbed energy – Joules) – energy absorbed by the specimen during fracture, measured directly by the pendulum’s loss of potential energy. Reported as KV, KV₂ (for 2 mm striker), or KV₈ for sub‑size specimens.
Energy at specific temperatures – for transition curve determination (e.g., K_V at -40°C, -20°C, 0°C, +20°C).
Energy ratio (e.g., 20°C / -40°C) – toughness retention indicator.
Minimum specified energy compliance – pass/fail against material standards (e.g., ASTM A333 Grade 6 requires ≥ 18 J at -45°C).

2.2 Lateral Expansion (LE)

Lateral expansion (mm) – increase in specimen width on the compression side opposite the notch, measured after fracture. Particularly important for pipeline and pressure vessel steels (e.g., API 5L, ASME). A more reliable indicator of ductility than energy for some high‑strength steels.
LE at specified temperature – often alongside absorbed energy.

2.3 Fracture Appearance (Shear / Cleavage)

Percent shear fracture (%) – percentage of ductile (shear) fracture surface area. The remainder is brittle (cleavage). Measured visually (with ruler or comparator) or by image analysis.
Percent cleavage – indicator of brittle fracture tendency.
Fracture appearance rating – reported as “100% shear”, “50% shear/50% cleavage”, “100% cleavage”.

2.4 Ductile‑to‑Brittle Transition Temperature (DBTT)

FATT (Fracture Appearance Transition Temperature) – temperature at which fracture surface exhibits 50% shear / 50% cleavage.
T_27J – temperature at which absorbed energy equals 27 J (common for structural steels).
T_40J, T_68J – for specific energy thresholds.
Transition curve – plot of KV energy vs. temperature, with fitted sigmoidal curve and defined transition temperatures.

2.5 Sub‑Size Specimen Testing

When material thickness is insufficient for standard 10×10 mm specimens, we machine and test sub‑size specimens (e.g., 5×10, 5×5, 2.5×10). Absorbed energy values are reported as KV₅, KV_2.5, etc., and may be scaled using industry‑recognised correlation methods (e.g., proportional or non‑proportional scaling).