Testing method and testing system for hydrogen-induced cracking threshold value based on notched round bar tensile specimen

A testing method for a hydrogen-induced cracking threshold value based on a notched round bar tensile specimen, comprising:

• S1:
• performing a slow strain rate tensile test on the notched round bar tensile specimen in a hydrogen environment to obtain test data, the test data including a yield strength, a tensile strength, a first maximum displacement, an engineering stress and an engineering strain, obtaining a first elongation rate using the first maximum displacement and an original length of the notched round bar tensile specimen;
• performing the slow strain rate tensile test on the same notched round bar tensile specimen in an inert gas environment to obtain a second maximum displacement, and obtaining a second elongation rate using the second maximum displacement and the original length;
• S2:
• obtaining a hydrogen embrittlement susceptibility index of material using the first elongation rate and the second elongation rate;
• and obtaining an elastoplastic parameter R using the hydrogen embrittlement susceptibility index of material, the yield strength and the tensile strength, a formula of the obtained elastoplastic parameter R expressed as:
• R
• =
• 6.32
• I
• HE
• +
• σ
• NTS
• σ
• y
• wherein, R is the elastoplastic parameter, σy is the yield strength, σNTS is the tensile strength and IHE is the hydrogen embrittlement susceptibility index of material;
• S3:
• determining whether the elastoplastic parameter R is greater than 3.5,
• if yes, obtaining the corresponding hydrogen-induced cracking threshold value using the following formula:
• K
• IH
• =
• J
• IH
• ⁢
• E
• Y
• (
• 1
• -
• v
• 2
• )
• wherein, KIH is the hydrogen-induced cracking threshold value, a unit is MPa·m0.5, JIH is a J-integral value of hydrogen-induced cracking, EY is an elastic modulus of material and ν is a Poisson's ratio;
• if no, obtaining the corresponding hydrogen-induced cracking threshold value using the following formula:
• K
• IH
• =
• P
• IH
• ⁢
• D
• 0.5
• ⁢
• F
• 1
• 0.5
• wherein, KIH is the hydrogen-induced cracking threshold value, a unit is MPa·m0.5, PIH is a critical load of hydrogen-induced cracking, D is an original diameter of the notched round bar tensile specimen and F1 is a first geometric function under a linear elastic crack growth mechanism.