Charpy Program

The Charpy impact test uses a swinging pendulum to assess the resistance of a material to fracture, and characterize the ductile-to-brittle transition in steel. The energy absorbed by the material being tested is measured by determining the energy lost by the pendulum during the impact. The low cost and simple configuration of the test have made it a common requirement in codes for critical structures such as pressure vessels and bridges. However, the test is not useful if the variation in test results between laboratories is not tightly controlled. The control is accomplished by requiring the indirect verification of impact machines.  NIST certifies SRMs used for the verification of impact machines.  

The NIST Charpy Program provides certified reference materials (SRMs), supported by a traceable measurement system, to facilitate accurate predictions of structural steel reliability.

The program maintains an accurate target for the verification of absorbed energy measurements, supplies SRMs for the indirect verification of impact machines, assists our SRM users in meeting and documenting their contractual requirements for impact testing, and supports our customer's standardization needs.

NIST SRMs for Indirect Verification of Charpy Impact Machines:

Absorbed energy	(SRMs 2092, 2096, and 2098)	full service
Absorbed energy	(SRMs 2093 and 2097 in 2011)	self-verification
Dynamic Force	(SRMs 2112 and 2113 in 2010)	full service

NIST SRMs for Indirect Verification of Izod Impact Machines:

Absorbed energy

(SRM 2115)

full service

The analysis of the indirect verification test depends on whether the SRM is provided with full or limited service. Please see the details for the particular SRM tested (above).


Proficiency Testing (PT):

NIST PT Analysis

Link to information

• Program overview
• Computing Uncertainty for Charpy Tests (SP2602)
• Verification Limits and Uncertainty (SP260-171)