Relation of ηpl and γpl with separation parameter (S) and their usefulness for fracture toughness evaluation

• Published in: Engineering fracture mechanics Vol. 289
• Main Authors: Bind, A.K., Singh, R.N.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.09.2023
• Subjects: Load separation method; Separation parameter; γpl; ηpl; Load separation method; Separation parameter; γpl; ηpl
• ISSN: 0013-7944; 1873-7315
• DOI: 10.1016/j.engfracmech.2023.109487

Comparison of the γpl values of the clamped SENT specimen calculated using present method (Equation (29) and Ernst equation (Equation (26). The γpl values obtained using present method and 3rd and higher order polynomial function between ηpl and b/W are comparable. [Display omitted] •For the first time the relation between γpl and separation parameter (S) has been derived.•Usefulness of the derived relation was demonstrated using CCT and clamped SENT specimens.•Use of polynomial functions over power law function between S and b/W is recommended.•Limit of exponent of power law fit between S and b/W and d2S/dbW2 obtained from the polynomial fit is reported.•Problem with Ernst’s type equation of Jpl for growing crack is brought out for both the specimens. Geometrical factor ηpl and γpl are required for fracture toughness evaluation in terms of JIC, JQ and J-R curve. Load separation method is said to be most accurate method to evaluate the ηpl. In this method, established relation between ηpl and separation parameter (S) as well as fitted function between S and b/W is used to obtain the relation between ηpl and b/W. In this paper, relations of ηpl and γpl with the S are derived. Based on the fact that the value of γpl cannot be negative, limit of exponent of power law function between S and b/W as well as second order derivative of polynomial functions between S and b/W are evaluated. Limitations of power law function and usefulness of polynomial functions are highlighted. Usefulness of the relationships are discussed for CCT and clamped SENT specimens. The problem with Ernst type equation to calculate Jpl for growing crack are also discussed for CCT.