ASTM E2248, ISO 148-4 Charpy Impact Testing of small specimen

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ASTM E2248 — Standard Test Method for Impact Testing of Miniaturized Charpy V‑Notch (MCVN) Specimens

ISO 148-4 Metallic materials. Charpy pendulum impact test - Testing of miniature Charpy-type V-notch test pieces

ASTM E2248 and ISO 148-4 governs impact tests using fully miniaturized Charpy V-notch (MCVN) specimens, where all linear dimensions (length, cross-section, ligament) are proportionally reduced. It is clearly differentiated from subsize specimens specified in ASTM E23: subsize specimens retain standard length, notch geometry and surface finish while only reducing thickness, whereas MCVN specimens shrink the entire structure to maximize test quantity from limited material.

It is a specialized supplement to the mainstream full-size Charpy standard ASTM E23. This standard comprehensively defines specifications for miniaturized specimens, dedicated test equipment, calibration rules, operational procedures, data evaluation and safety requirements. It is primarily used when standard full-size Charpy V-Notch (CVN) specimens cannot be fabricated due to limited material volume.

Test Principle

An MCVN V‑notch specimen is placed on modified anvils/supports so the notch is centered and the specimen’s centerline aligns with the pendulum center of strike.

A pendulum releases, striker hits the specimen opposite the notch in a single swing.

Absorbed energy is read from the machine indicating device (dial/encoder), optionally refined via instrumentation (ASTM E2298) by recording force vs. time, deriving a force–displacement curve, whose area = instrumented absorbed energy W_t.

Optionally: lateral expansion and shear fracture appearance (SFA) are evaluated.

The “miniature” twist is that anvil span, anvil radii, striker radius are scaled to preserve proportionality (or are defined as an allowed non‑proportional geometry), and temperature control gets stricter because the specimen is tiny.

Specific test methods covered in ASTM E2248

It defines one method family: pendulum impact testing of MCVN V‑notch specimens, with two practical geometry paths:

Path	Geometry (typical reference)	Proportionality
Reference proportional “reduced half‑size” MCVN	~4.83 × 4.83 mm cross‑section, 24.13 mm length, ligament ~3.86 mm, notch root radius ~0.13 mm	Scaled ~½ linearly from CVN 10×10×55 (span ~19.3 mm, anvil radius ~0.48 mm, striker radius ~0.96 mm for “proportional 2 mm” striker)
Non‑proportional 4×3×27 mm MCVN	4 mm × 3 mm × 27 mm (Annex D / ISO 14556 Annex D style)	Not proportional; striker often the standard 2 mm striker, anvil radius 1+0.50 mm, span 22+0.10 mm

Test Specimen Requirements

ASTM E2248 defines two main categories of MCVN specimens: proportional reduced half-size specimens (reference type) and non-proportional specimens (e.g., the 4 mm × 3 mm specimen aligned with ISO 14556).

Reference Proportional MCVN Specimen

(Reduced Half-Size)

Overall dimensions: 24.13 mm (length) × 4.83 mm × 4.83 mm (square cross-section).

V-notch parameters: 45° included angle, standard V-notch design; ligament length 3.86 mm, strict dimensional tolerances for notch centering (±0.12 mm) and angular deviation (±2°).

Surface requirements: Machined surface roughness Ra ≤ 2 μm; high-precision surface to avoid micro-defects affecting test results.

Structural rule: The specimen’s cross-section must be at least five times larger than the material’s maximum microstructural inhomogeneity to ensure representative test data.

Non-Proportional MCVN Specimen

A widely used non-proportional type is 27 mm × 4 mm × 3 mm (aligned with Annex D of ISO 14556).

It is not geometrically scaled from standard CVN specimens but has accumulated abundant industry test data.

Specimen Preparation Rules

Machining methods: Electric Discharge Machining (EDM) or precision grinding is recommended for notches and outer surfaces; the disturbed material layer caused by machining shall not exceed 0.005 mm to prevent microstructure damage.

Special notes for recycled specimens: If MCVN specimens are cut from fractured full CVN specimens, severe plastic deformation areas of the parent material must be excluded.

Optional design: Side-grooved MCVN specimens are permitted to optimize plane strain conditions and reduce deviation in ductile-brittle transition test data.

Unnotched specimens are outside the scope of this standard.

ASTM E2248, ISO 148-4 Charpy Impact Testing of small specimen

Test Equipment of ASTM E2248 Metal impact test methods

Pendulum Impact Testing Machine	Rigid frame structure; the output resolution of the energy indicator shall be ≥ 0.1 J. The absorbed energy of the specimen shall not exceed 80% of the pendulum’s initial potential energy to guarantee valid data. Impact velocity: General range 1 m/s ~ 6 m/s. For instrumented MCVN tests, velocity above 4 m/s is not recommended (excessive signal oscillation will interfere with force-displacement curve analysis). Pendulum swing: Lateral play ≤ 0.75 mm; bearing radial play ≤ 0.075 mm to ensure stable operation. Friction & windage loss: Total energy loss shall not exceed 0.4% of the machine’s full scale; total loss of the whole machine shall not exceed 0.75% of full scale, and pointer friction loss ≤ 0.25% of full scale.
Striker & Anvils	For half-size MCVN: Proportional 2 mm striker (0.96 mm radius) and 8 mm striker (3.86 mm radius); anvil radius 0.48 mm ± 0.025 mm, anvil span 19.3 mm ± 0.025 mm. For 4 mm × 3 mm non-proportional specimens: Standard 2 mm striker, anvil span 22 mm, anvil radius 0.50 mm. Surface finish of strikers and anvils: Ra ≤ 0.1 μm.
Supports	Specimen centering tolerance ≤ 0.25 mm; shims or modified supports are allowed on ASTM E23 machines to adjust support height.
Temperature Conditioning Devices	Liquid bath, gas chamber and matched insulated transfer tongs for heating/cooling specimens.

Key Test Parameters:

Parameter	Requirement / stipulation
Temperature tolerance	±2°C from nominal test temperature
Temperature verification	Use dummy specimens with thermocouples, or surface TC on test specimens, to demonstrate ±2°C is met (especially if not using true in‑situheating/cooling)
Transfer time	If bath transfer used: strike in ~1 s or less class problem (tiny mass → flash cooling)
Notch centering on supports	Within 0.25 mm (use tongs/centering aid)
Energy use	Absorbed energy ≤ 80% of machine initial potential energy
Velocity	1–6 m/s overall; >4 m/s not recommended for instrumented
Free‑swing zero check	Before a batch: free swing shall read 0.0 within 0.1 J (on compensated machines)

Main Test Stipulations

MCVN ≠ sub‑size CVN (different scaling philosophy).

Do not directly substitute MCVN energy/temperature into a standard CVN DBTT spec without correlations.

If extracting MCVN from broken halves of highly ductile CVN, verify that prior plastic deformation hasn’t biased the miniature specimen’s behavior.

For instrumented MCVN, keep velocity/oscillation under control or your F–s curve will be noisy at the exact point you’re trying to read (general yield / initiation).

Operational Procedures of ASTM E2248 Impact Test

Use dedicated tongs to place the specimen accurately on the anvils, ensuring centering compliance.

Lift and lock the pendulum at the initial position, then release it smoothly to strike the specimen.

Record the absorbed energy reading from the indicator; for instrumented tests, collect and store complete force-time/force-displacement curves.

After impact, observe the specimen fracture status; perform lateral expansion and SFA measurement if required.

Post-Test Processing: Sort test data, mark abnormal phenomena (incomplete fracture, specimen deviation), and classify curves for instrumented tests.

Industry / application fields where ASTM E2248 is used

Nuclear & RPV surveillance / life-extension: limited archival material, broken CVN halves recycled into MCVN to stretch data per volume

Plant maintenance & forensic sampling: thin-walled components, in‑service extraction where you can’t cut a full 10×10×55

Advanced materials R&D: additive manufacturing, thin plates, claddings, HAZ-only slices, irradiated or heritage material where mass budget is tiny

Small-scale specimen technology (SSPT) programs: building validated scaling/correlation models back to full-size CVN / fracture toughness.

Related Test Standard:

ISO 148-1	Metallic materials - Charpy pendulum impact test - Part 1: Test method
ASTM E23	Standard Test Methods for Notched Bar Impact Testing of Metallic Materials
AASHTO T 266	Standard Method of Test for Notched Bar Impact Testing of Metallic Materials (CVN)
BS 131-1	Methods for Notched bar tests — Part 1 : The izod impact test on metals
IRAM-IAS U 500 17	Acero. Izod flexural impact test method on notched V specimen.
IS 1598	Metal cantilever beam impact test method
SANS 6223	The Izod impact test for metallic materials
JIS Z 2242	Method for Charpy pendulum impact test of metallic materials
KS B 0810	Method of impact test for metallic materials
GB/T 229	Metallic materials—Charpy pendulum impact test method
ISO 14556	Metallic materials — Charpy V-notch pendulum impact test — Instrumented test method
EN 10045-1	Charpy Impact Test for Metallic Materials - Test Method
ASTM E2298	Instrumented impact test standard, matching E23 to collect force-displacement curves.
ISO 148-2	Metallic materials - Charpy pendulum impact test - Part 2: Verification of testing machines
ISO 148-3	Metallic materials. Charpy pendulum impact test. Preparation and characterization of Charpy V-notch test pieces for indirect verification of pendulum impact machines
ISO 148-4	Metallic materials. Charpy pendulum impact test - Testing of miniature Charpy-type V-notch test pieces

Impact Tester is mainly used to determine the anti-impact capability of ferrous metal materials with high toughness, especially for steel and iron and their alloy, under dynamic load. This series tester is operated semi-automatically.

Electric impact specimen U/V notching machine is a specialized specimen preparation device for metal Charpy pendulum impact tests. It is driven by a motor and lead screw, and uses forming cutting tools to cut a V-shaped or U-shaped notch in a single pass, meeting standards such as GB/T 229, ISO 148,

CST-50 projector is a supplemental equipment for impact test, mainly used to check the accuracy of impact specimen U/V notch. Put the notched specimen on projector working table, multiple 50* and compare the projection image with standard plate, then identify the quality of impact specimen notch.

DWC low temperature chamber is a supplemental equipment for impact test under low temperature. Use imported high quality compressor to refrigerate, single-chip micro processor control, auto control temperature, timing, alarm etc.; Refrigeration fast, big volume.

Q1: What is ASTM E2248?

A: ASTM E2248 is the current American standard for impact tests using Miniaturized Charpy V-Notch (MCVN) specimens for metallic materials. It is a dedicated supplement to ASTM E23 (standard full-size Charpy tests), focusing on test rules, apparatus, specimen preparation, calibration and data evaluation for fully scaled-down mini specimens. It supports both conventional and instrumented impact testing.

Q2: What is the key difference between MCVN specimens and subsize Charpy specimens?

A: This is a critical distinction:

MCVN (Miniaturized): All linear dimensions (length, cross-section, notch, ligament) are proportionally reduced. Specimens are shorter, designed to maximize tests from limited material volume.

Subsize (per ASTM E23 Annex A3): Only the thickness is reduced; the full length, notch geometry, notch radius and surface finish remain identical to standard CVN specimens. They belong to the standard Charpy system.

Data from the two types cannot be mixed or directly compared.

Q3: What is the main purpose of the ASTM E2248 test?

A: It provides a valid impact testing solution when standard full-size Charpy V-Notch (CVN) specimens cannot be manufactured due to insufficient material volume. It evaluates the notch toughness, ductility and fracture behavior of metallic materials using mini specimens.

Q4: Why is ASTM E2248 important for metallic materials?

A:It solves the testing dilemma for limited material, such as thin products, small components and samples taken from in-service equipment.

It enables regular safety assessment of operating metal parts without large-scale destructive sampling.

It improves material utilization: fractured full-size CVN specimens can be reprocessed into MCVN samples for further testing.

It supports material R&D: more test groups can be arranged with a small amount of raw material to accelerate performance research.

It complements the ASTM Charpy test system, forming a complete set covering full-size, subsize and mini specimens.

Q5: What materials does ASTM E2248 apply to? Are unnotched specimens allowed?

A: It applies to all ferrous and non-ferrous metallic materials. Standard tests use V-notched MCVN specimens; unnotched specimens are outside the scope of this standard.

Q6: Can MCVN test data be directly used for engineering design or determining service temperature?

A: No. MCVN absorbed energy, ductile-brittle transition temperature (DBTT) and upper shelf energy (USE) cannot be directly converted to standard CVN data. Users must establish material-specific correlation formulas. Also, MCVN results shall not be used alone to define the minimum operating temperature of in-service components; a comprehensive fracture mechanics assessment is required.

Q7: Can we make MCVN specimens from broken full-size CVN samples?

A: Yes. But you must exclude areas with severe plastic deformation generated during the fracture of the original CVN specimen, as deformation will alter material properties.

Q8: Are side-grooved MCVN specimens permitted?

A: Yes. Side grooves help maintain plane strain conditions, reduce the deviation of ductile-brittle transition data caused by miniaturization, though they cannot fully eliminate the need for data correlation.

Q9: Can a standard ASTM E23 Charpy machine be used for MCVN tests?

A: Yes. You only need to replace the matched miniaturized anvils and strikers, or add shims to adjust the support height. Dedicated low-capacity MCVN pendulum machines are also acceptable.

Q10: What is the limit for valid absorbed energy?

A: The energy consumed to fracture the specimen shall not exceed 80% of the pendulum’s initial potential energy to ensure accurate readings.

Q11: What is the difference between ASTM E2248 and ISO 14556 for mini specimens?

A: ASTM E2248 covers multiple proportional and non-proportional MCVN types and complete machine rules; ISO 14556 only specifies one type of mini specimen in its annex and focuses more on instrumented signal processing.

Q12: Does instrumented MCVN testing require extra equipment?

A: Yes. It needs a strain-gage equipped striker and high-speed data acquisition system complying with ASTM E2298. Instrumentation is optional but recommended for in-depth fracture analysis.

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