Effect of strain rate on tensile test results in hydrogen and
other concerns
☆
M.L. Martin
*
, Z.N. Buck , A.C. Eckhardt , D.S. Lauria , A.J. Slifka , M.J. Connolly
Materials Measurement Laboratory, National Institute of Standards and Technology, 325 Broadway, MS 647, Boulder, CO 80305, United States
ARTICLE INFO
Keywords:
Hydrogen embrittlement
Tensile testing
Fracture
Steel
Mechanical properties
ABSTRACT
Tensile tests of an X52 pipeline steel were conducted in air and in hydrogen gas at strain rates
covering ve orders of magnitude. Properties such as elastic modulus, yield strength, and ultimate
tensile strength were unaffected by hydrogen or by strain rate. Ductility was greatly reduced in
hydrogen, compared to in-air, with a moderate decrease of ductility with decreasing strain rate.
Different methods of calculating the ductility, such as elongation to failure and reduction in area,
are discussed, as are the consequences of these methods on the calculated Hydrogen Embrittle-
ment Index.
1. Introduction
Tensile testing is the default mechanical test to determine material properties across many industries, especially metallurgical
industries [1]. It is quick, simple to execute, and simple to analyze. As such, it is often the rst to be adapted to environmental
conditions, such as high-pressure hydrogen gas, especially as it is useful to compare data from samples tested in environment to those
tested in laboratory air [2–6]. In fact, the name of the predominant phenomenon seen in metals in the presence of hydrogen, hydrogen
embrittlement, comes from the result of tensile tests showing a loss in ductility, or embrittlement. The tensile test allows exibility
when probing environment: in-situ gas testing, in-situ electrochemical charging while testing, and pre-charged specimens. However,
the apparent simplicity of the test, and its ubiquity, camouage some of the nuance necessary to fully understand tensile test results.
Basic materials science textbooks typically present an idealized tensile curve from which mechanical properties can be easily
extracted. Mechanical testing of metals is typically more complicated, and the governing testing standards, such as ASTM E8/E8M [1],
display that complexity in the number of analysis methods that are considered acceptable. For instance, there are three different
accepted methods of determining offset for elastic modulus and yield strength, of which the 0.2 % offset is the best known. It is worth
recognizing that a tensile test is not considered a good test for measuring the elastic modulus, due to issues such as sampling/sensitivity
at low strains and microplasticity as the yield point is approached. However, the analysis of tensile test data is simple and gives
comparable results for material-to-material comparisons, which is why it remains popular.
There have been studies looking at whether hydrogen affects the elastic modulus of metals. An early study on
α
-Fe showed a
reduction in the modulus with hydrogen charging [7]. Another study on 1070 and 1005 steels also showed a decrease in elastic
modulus with hydrogen content [8]. A nanoindentation study showed local decreases in modulus of low carbon steel [9]. However, a
stress relaxation study of stainless steel showed an increase in modulus with hydrogen [10]. The conicting results may be due to the
☆
This article is part of a special issue entitled: ‘Hydrogen Embrittlement’ published in Engineering Fracture Mechanics.
* Corresponding author.
E-mail address: may.martin@nist.gov (M.L. Martin).
Contents lists available at ScienceDirect
Engineering Fracture Mechanics
journal homepage: www.elsevier.com/locate/engfracmech
https://doi.org/10.1016/j.engfracmech.2025.111461
Received 21 February 2025; Received in revised form 30 June 2025; Accepted 28 July 2025
Engineering Fracture Mechanics 327 (2025) 111461
Available online 29 July 2025
0013-7944/© 2025 Published by Elsevier Ltd.
