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Home >> Application >> By Standard >> ISO >> ISO 1 ~ 4999 >> ISO 148-2 Verification Charpy impact testing machines

ISO 148-2 Verification Charpy impact testing machines

ISO 148-2 — Metallic materials — Charpy pendulum impact test — Part 2: Verification of testing machines

ISO 148-2 specifically formulated for the verification, calibration and performance inspection of Charpy pendulum impact testing machines used in Charpy impact tests per ISO 148-1. This standard unifies two core verification approaches (direct and indirect), defines strict dimensional, mechanical and performance tolerances, and standardizes verification procedures, frequency, report rules and measurement uncertainty assessment.

If ISO 148-1 tells you how to test a specimen, ISO 148-2 tells you how to prove your machine is trustworthy before you're allowed to use it for real work. It is the calibration/verification standard for Charpy pendulum impact machines.

Application Scope

Applicable to all pendulum-type Charpy impact machines equipped with 2 mm or 8 mm radius strikers (the two standard striker sizes specified in ISO 148-1), regardless of machine capacity or structural design.

Covers two categories of machines:

Industrial machines: For routine production, general laboratory and commercial testing (the most widely used type).

Reference machines: With stricter tolerance requirements, mainly used for developing and certifying reference specimens (detailed rules in ISO 148-3).

It applies exclusively to metallic material Charpy impact machines and does not cover Izod impact machines or other impact test equipment.

ISO 148-2 Verification Charpy impact testing machines

Core Verification Principles

ISO 148-2 stipulates two complementary verification methods, which must both be completed for full machine validation:

A: Direct Verification

Clause	What's verified
Foundation/Installation	Machine not shaken by external vibrations during impact
Machine Framework	• Pendulum free-hang position • Pendulum vs. support alignment • Bearing play (axial ≤0.25 mm, radial ≤0.08 mm) • Plane of swing = 90.0° ± 0.1° to axis of rotation • Striker contacts full thickness of test piece (carbon-paper proof method described) • Striker centre vs. anvil gap centre: ≤0.5 mm
Pendulum	• Potential energy Kp vs. nominal Kn: ±1% (Formula 1, moment method with force F & distance l₂) • Scale graduation at ~0%, 10%, 20%, 30%, 50%, 80% of Kn — error ≤ ±1% of reading or ±0.5% of Kn (whichever is greater) • Impact velocity: 5.0–5.5 m/s (±0.1 m/s) for machines made after 1998; older machines: 4.3–7 m/s (report actual) • Friction + air resistance loss (p + p′) ≤ 0.5% of Kn • Centre of percussion distance l₁ = 0.995l ± 0.005l, uncertainty <0.5 mm
Anvils & Supports	Geometry: span, anvil radius, taper, parallelism — dimensional compliance per ISO 148-1 requirements
Indicating Equipment	Pointer, dial, digital encoder — resolution, freedom of movement, repeatability of reading

B: Indirect Verification

Item	Requirement
Reference pieces	Certified KV value (KVR) with known expanded uncertainty from an accredited source
Number of pieces	At least 5 at each energy level
Repeatability	scatter of your 5+ results must be within allowed limits
Bias	BV = KVv − KVR … absolute bias must fall within the tolerance band set by the standard / CRM certificate
Limited direct verification	If you only do partial direct checks (e.g. annual vs. full), indirect becomes even more critical

Verification Frequency & Trigger Rules

1 Regular Periodic Verification

Full direct + indirect verification must be conducted at least once every 12 months.

2 Unscheduled Mandatory Re-Verification

Re-verification is required immediately in the following cases:

The machine is moved, re-installed or repaired.

Key components (striker, anvils, pendulum, bearings) are replaced.

Test data is obviously abnormal or disputed between laboratories.

Long-term shutdown (more than 3 months) before re-use.

Test Parameters & Stipulations

Friction Loss Check (the daily/shift ritual embedded in direct verification)

Swing without a specimen → record β₁ or K₁

Second swing without resetting pointer → record β₂ or K₂

Pointer friction p = M(cos β₁ − cos β₂)

10-half-swing decay → bearing/air loss p′ per Formula 8/9

Total p + p′ ≤ 0.5% of KN — if not, fix pointer friction first; then clean/replace bearings.

Scale Calibration Check

Set the pointer at each major graduation mark (0%, 10%, 20%, 30%, 50%, 80%), measure the rise angle β, calculate Kcalc = M(cos β − cos α), then check:

At ≥50% KN: |Kcalc − KS| / KS × 100 ≤ 1%

At <50% KN: |Kcalc − KS| / KN × 100 ≤ 0.5%

Measurement Uncertainty Assessment

Annex	Purpose
Annex A	Uncertainty of the indirect verification result — calculates bias BV, its standard uncertainty u(BV), combined uV, effective degrees of freedom, and expanded U — with a worked example
Annex B	Uncertainty of direct verification — propagates uncertainties from striker radius, anvil geometry, centre-of-strike, energy calc, velocity, centre of percussion, and scale reading into a combined budget
Annex C	A jig method for field-verifying geometric properties (striker position, axis horizontality, perpendicularity, alignment) — especially useful on older machines without a factory reference plane

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
ASTM E2298	Standard for instrumented impact testing, matching conventional impact tests in ASTM E23 to collect force-displacement curves.
AASHTO T 266	Standard Method of Test for Notched Bar Impact Testing of Metallic Materials (CVN)
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
GB/T 19748	Metallic materials—Charpy V-notch pendulum impact test—Instrumented 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
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
ASTM E2248	Standard Test Method for Impact Testing of Miniaturized Charpy V-Notch Specimens

Related products and device

ISO 148 Metal Charpy Impact Testing Machine

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.

ISO 148 impact specimen U/V notching machine

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,

ISO 148 Impact Test Sample UV Notch Profile Projector

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.

ISO 14556 Instrumented Impact Testing Machine

Instrumented impact tester is adopts advanced foreign technology and cooperate with China National Engineering & Physical research institute to developed a new products. Instrumented impact tester is measuring the impact value, collect and analysis the impact process data, figure energy curve.

ISO 148 Low Temperature Chamber For Impact Test

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.

Related Standard

ISO 148-1 Metal Charpy pendulum impact test methods –

ISO 148-1 defines the method for the Charpy (V-notch & U-notch) pendulum impact test to determine the absorbed energy when a notched metallic specimen is broken by a single swinging pendulum blow. It does not cover instrumented impact testing (that belongs to ISO 14556).

ASTM E23 Impact Test Methods for Metal Notched Bar –

ASTM E23 covers both Charpy (simple‑beam) and Izod (cantilever‑beam) notched-bar impact tests. It applies to all metallic materials for impact tests using pendulum machines.

EN 10045-1 Charpy Impact Test for Iron and Steel Castings –

EN 10045‑1 regulates the Charpy simple-beam pendulum impact test for metallic materials, covering both V-notch and U-notch specimens. It defines unified rules for specimen preparation, machine requirements, operating conditions and result reporting.

ISO 14556 Instrumented Impact Test Charpy V-notch pendulum impact –

ISO 14556 applies exclusively to instrumented Charpy V-notch pendulum impact tests for all metallic materials. It captures real-time force-displacement curves and a full set of dynamic characteristic parameters.

ASTM E2298 Instrumented Impact Testing of Metallic Materials –

ASTM E2298 dedicated to instrumented Charpy V-notch (CVN) and miniaturized Charpy V-notch (MCVN) impact tests for metallic materials. Instead of only obtaining a single absorbed energy value, this standard extracts force, displacement and segmented energy parameters to analyze the full fracture process.

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

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.

ISO 148-2 Verification Charpy impact testing machines –

ISO 148-2 specifically formulated for the verification, calibration and performance inspection of Charpy pendulum impact testing machines used in Charpy impact tests per ISO 148-1.

ISO 148-3 Charpy V-notch test pieces for indirect verification of pendulum impact machines –

ISO 148-3 core focus is to establish unified rules for manufacturing, qualification, certification and proper use of Charpy V-notch reference test pieces, which are essential for the indirect verification of Charpy impact machines as required by ISO 148-2.

FAQs for ISO 148-2 (Verification of Charpy Pendulum Impact Testing Machines)

Q1: What is ISO 148-2?

A: It is the third edition international standard for the verification and calibration of Charpy pendulum impact testing machines. It is Part 2 of the ISO 148 series, paired with ISO 148-1 (test method) and ISO 148-3 (reference specimens). It defines two main verification methods, dimensional tolerances, performance limits and reporting rules for impact machines.

Q2: What is the core purpose of this standard?

A: To ensure Charpy impact machines work within specified technical limits, eliminate errors caused by machine installation, component wear or mechanical deviation, and make test results from different machines and laboratories comparable worldwide.

Q3: Why is ISO 148-2 extremely important?

A:A machine without valid ISO 148-2 verification produces unreliable impact data, which cannot be accepted for quality inspection, product certification or international trade.

It solves the common problem that two machines meeting basic dimensions may yield inconsistent test values.

It provides unified metrological rules to guarantee accuracy, repeatability and traceability of Charpy impact tests.

It helps diagnose machine faults when test data fluctuates abnormally.

Q4: What machines does ISO 148-2 apply to?

A: It applies to all standard Charpy pendulum impact machines with 2 mm or 8 mm radius strikers for metallic material tests. It does not cover Izod impact machines, drop-weight impact testers or other impact equipment.

Q5: What are the key requirements for machine installation and stability?

A:The machine base mass is recommended to be at least 12 times the pendulum mass.

The pendulum rotation axis must be horizontal within 2/1000 (4/1000 for machines without a reference plane).

No obvious external vibration during testing (a water container placed on the frame shows no ripples).

Q6: What are the limits for pendulum bearing play?

A:Transverse play (under 4% of pendulum weight): ≤ 0.25 mm

Radial play (under 150 N load): ≤ 0.08 mm

Q7: What is the tolerance for the pendulum’s potential energy?

A: The actual potential energy shall not differ from the machine’s nominal energy by more than ±1%.

Q8: What are the requirements for impact velocity?

A:Machines manufactured after 1998: 5.0 m/s ~ 5.5 m/s (tolerance < 0.1 m/s).

Older machines (before 1998): Permitted range is 4.3 m/s to 7 m/s.

Q9: What is the maximum allowable total friction and windage loss?

A: The total energy loss from bearing friction, air resistance and pointer friction shall not exceed 0.5% of the machine’s nominal energy. If over the limit, clean or replace bearings.

Q10: What accuracy rules apply to the machine’s indicating scale?

A:Above 50% of nominal energy: Reading deviation ≤ 1% of the indicated value.

Below 50% of nominal energy: Reading deviation ≤ 0.5% of the nominal energy.

Q11: How to check full contact between striker and specimen?

A: Use carbon paper wrapped on the striker and thin paper on a standard specimen. After light contact, the carbon mark must cover the full width of the specimen.

Q12: What is indirect verification?

A: It is a dynamic verification method: test ISO 148-3 certified reference specimens with known absorbed energy values, then compare the average measured data with the certified value to evaluate machine bias and repeatability.

Q13: How many reference specimens are required for one indirect verification?

A: At least five valid reference specimens must be tested per verification round.

Q14: What key indicators are evaluated in indirect verification?

A: Two core indicators: machine bias (BV) (difference between measured value and certified value) and test repeatability (data dispersion of multiple specimens). Both must meet standard acceptance limits.

Q15: Where do we get qualified reference specimens?

A: Reference specimens shall be prepared and certified in accordance with ISO 148-3.

Q16: What is the difference between ISO 148-2 and ASTM E23 machine verification rules?

A: They belong to two independent systems. ISO 148-2 has stricter friction and pendulum parameter limits, and uses ISO-certified reference specimens; ASTM E23 adopts NIST reference samples with different evaluation thresholds. Their verification results are not interchangeable.

Q17: The machine passes direct verification but gives inconsistent test results. Why?

A: Direct verification only checks static geometry. The problem usually lies in dynamic performance. Complete indirect verification with reference specimens to locate machine bias or poor repeatability.

Q18: Friction loss exceeds the standard limit, what should I do?

A: First check pointer friction; if normal, clean, lubricate or replace pendulum bearings, then re-test friction loss.

Q19: Can I use only direct verification and skip indirect verification?

A: No. ISO 148-2 requires both methods for full valid verification. Either single check is incomplete.

Q20: Can old impact machines (pre-1998) still be used?

A: Yes. Their impact velocity range (4.3 ~ 7 m/s) is permitted by the standard, but the actual velocity must be recorded in the verification report.

Q21: Does ISO 148-2 cover instrumented Charpy machines?

A: The basic mechanical verification rules apply to instrumented Charpy machines. The extra sensor and data system follow ISO 14556 separately.

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