Influence of Ligament Size on Charpy Impact Test Results

NIST Publications

Published March 1st, 2026

Detected February 27th, 2026

Summary

NIST published a study on the influence of ligament size and tolerances on Charpy impact test results. The study supports a proposal to revise ASTM standards to align with ISO 148-1 regarding ligament length specifications.

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What changed

A study published by NIST investigated how variations in specimen ligament length and dimensional tolerances affect Charpy impact test results, referencing international standards like ASTM E23, ASTM A370, and ISO 148-1. The findings indicate significant differences in prescribed tolerances among these standards, with NIST's research supporting a revision to ASTM standards to achieve consistency with ISO 148-1, specifically concerning the ligament length specification of 8 mm ± 0.075 mm.

This research highlights potential inconsistencies in material testing methodologies across different standards. While this document is a publication and not a direct regulatory mandate, it informs the ongoing development and potential revision of industry standards. Manufacturers and testing laboratories relying on ASTM E23 and ASTM A370 should monitor updates to these standards for potential alignment with ISO 148-1, which may necessitate adjustments in specimen preparation and testing protocols to ensure consistent and comparable results.

What to do next

Monitor updates to ASTM E23 and ASTM A370 for potential revisions aligning with ISO 148-1.
Review internal specimen preparation and testing protocols for Charpy impact tests to ensure consistency with proposed standard changes.

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PUBLICATIONS

Influence of Ligament Size and Corresponding Tolerances on the Results of Charpy Impact Tests

Published

March 1, 2026

Author(s)

Enrico Lucon

Abstract

The most popular international test standards for Charpy testing, namely ASTM E23, ASTM A370, and ISO 148-1, prescribe significantly different tolerances for the specimen ligament length, ranging from ±0.025 mm (E23) to ±0.01 mm (A370). A study conducted at NIST investigated the influence of ligament length on the absorbed energy obtained from testing reference Charpy specimens at three energy levels (low, high, and super-high). The results obtained and the outcomes of multiple statistical analyses conducted on them support the proposal to revise the ASTM standards to make them consistent with each other and with ISO 148-1 (ligament length: 8 mm ± 0.075 mm). Citation ASTM Journal of Testing and Evaluation Issue January 0001 Pub Type Journals

Download Paper

https://doi.org/10.1520/JTE20250268 Local Download

Keywords

Absorbed energy, ASTM A370, ASTM E23, Charpy testing, dimensional tolerances, ISO 148-1, ligament length Standards, Materials characterization and Materials

Citation

Lucon, E.

(2026),
Influence of Ligament Size and Corresponding Tolerances on the Results of Charpy Impact Tests, ASTM Journal of Testing and Evaluation, [online], https://doi.org/10.1520/JTE20250268, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=960214       
  (Accessed February 27, 2026)