ASTM E23

Overview

ASTM E23 is the primary test method for determining the notched-bar impact resistance of metallic materials. This procedure evaluates how much energy a material absorbs during fracture, using either Charpy or Izod pendulum impact configurations. Most commonly, it refers to Charpy V-notch testing, especially for steel and other ductile metals.

Charpy impact testing is essential for assessing the toughness of metals, especially when subject to sudden or dynamic loads, or when determining ductile-to-brittle transition behavior.

What Is Charpy Impact Testing?

Charpy testing involves striking a notched specimen with a pendulum hammer and measuring the energy absorbed to fracture the specimen. The V-notch reduces the cross-section and localizes stress to initiate fracture in a consistent location.

Key Measurement:

• Absorbed Energy (in Joules) = Energy lost by the pendulum due to breaking the specimen.

Equipment Required for ASTM E23 Testing

1. Pendulum Impact Tester

A robust machine consisting of:

• A pendulum hammer that swings from a known height.

• A pair of anvils that support the specimen horizontally.

• A digital encoder or dial indicator to measure energy loss.

• Safety guards to protect operators.

• Optional: Automatic brake, motorized pendulum lift, and touchscreen controls.

Example: Galdabini STRIKE 300J / 450J

• Test capacities of 300 or 450 Joules.

• ASTM and ISO test modes preloaded.

• Touchscreen interface with data logging.

• Optional sample centering, motorized lift, and safety shield interlocks.

• Compatible with low-temperature conditioning.

2. Specimen Notching Machine (Broaching Machine)

• Machines a precise V-notch (2 mm deep, 45°) into each sample.

• Ensures consistency in notch geometry and surface finish.

3. Sample Chiller or Conditioning Bath

• For low-temperature impact testing, use a liquid nitrogen bath, dry ice/alcohol mixture, or refrigerated chamber.

• Samples must be held at temperature for at least 5 minutes, per ASTM E23.

4. Charpy Tongs

• Used to safely transfer chilled specimens from the bath to the tester without affecting the temperature.

5. Automatic Centering Device (Optional)

• Ensures precise placement of the specimen between the anvils, improving repeatability and reducing user error.

Test Specimen Dimensions (Charpy V-Notch)

Standard Charpy V-notch specimen per ASTM E23:

• 55 mm long × 10 mm wide × 10 mm thick

• 2 mm deep V-notch, 45° angle, with 0.25 mm radius at the base

Sub-size specimens may be used if full-size samples are not available.

Step-by-Step Testing Procedure

1. Prepare Test Specimens

• Machine to exact dimensions.

• Cut the V-notch using a broaching machine.

• Verify dimensions with a micrometer or calibrated gauge.

2. Condition the Specimens (If Applicable)

• Submerge in cooling bath for at least 5 minutes to reach test temperature.

• Keep temperature between −196°C to room temperature, depending on application.

• Transfer using Charpy tongs.

3. Set Up the Tester

• Raise the pendulum to its calibrated height (potential energy known).

• Place the specimen flat across the anvils, notch facing away from the pendulum striker.

• Engage the safety guard.

• Use automatic centering, if available.

4. Execute the Test

• Release the pendulum.

• The hammer strikes the specimen and fractures it.

• The remaining kinetic energy is measured electronically or via a pointer dial.

5. Record the Results

• Report absorbed energy in Joules.

• Optionally note fracture appearance (% shear, brittle zone).

• Record the test temperature, specimen ID, and machine settings.

Interpreting the Results

• High energy absorption → Tough, ductile material.

• Low energy absorption → Brittle, fracture-prone material.

• For materials like steel, tests at various temperatures can reveal the ductile-to-brittle transition temperature (DBTT).

Applications of ASTM E23

• Structural steel and pipeline materials

• Weld qualification

• Heat-treated components

• Fracture toughness comparisons

• Crashworthiness in automotive and aerospace

Similar and Related Standards

ISO 148-1

• International equivalent of ASTM E23.

• Slightly different dimensions and calibration methods but tests the same properties.

ASTM A370

• Covers mechanical testing of steel products, including Charpy impact as one component.

ASTM E208

• Drop-weight testing for nil-ductility transition (NDT) temperature—used on ferritic steels.

EN 10045-1

• European Charpy test standard—comparable to ISO 148-1.

ASTM E2298

• Instrumented Charpy testing: Measures force-time data during impact, not just total energy absorbed.

Summary

ASTM E23 Charpy Impact Testing is a cornerstone method for evaluating the toughness of metallic materials. With modern machines like the Galdabini STRIKE 300J and 450J, users benefit from automated features, digital precision, and compatibility with all test conditions—room temperature or cryogenic.

Proper sample preparation, accurate centering, and correct temperature handling are crucial for valid results. When performed correctly, this test provides vital data for safety, performance, and material selection across critical industries.