What is the type of your load applied, axial static, moment or cyclic load?

Emerson:

It is perfectly acceptable to measure the fracture toughness with a single-edge notched tensile SEN(T) specimen, as it is with a compact-tension C(T) or single-edge notched bend SEN(B) sample. You simply have to use the correct stress-intensity solution, which should be able to find in the Fracture Toughness standard (e.g., ASTM E 1820) or in books that list K-solutions, such as T. L. Anderson's text book: Fracture Mechanics: Fundamentals and Applications.

As to whether your measured KQ provisional fracture toughness value pertains to the actual KIc fracture toughness, again the approach is identical to the other specimen geometries in that you have to satisfy the various validity requirements of small-scale yielding (i.e., the plastic-zone size must be small compared to the in-plane sample dimensions of crack length and uncracked ligament depth) and plane strain (i.e., the plastic-zone size must also be small compared to the out-of-plane thickness dimension). There is another validity criterion that states that the maximum load during your test must not be greater than 1.1 times the load to measure the KQ value; this essentially restrict the amount of plasticity associated with your measurement. All these criteria are detailed in the ASTM E399 or 1820 Standards. Provided you meet these validity criteria, your measured fracture toughness should be independent of geometry and sample size. If you don't, then your result will either be incorrect, if you don't meet the small-scale yielding criterion (as the crack-tip K-field will not describe the actual stresses at the crack tip), or be size- and geometry-dependent, if you're not in plane strain (the non plane strain toughness will be a function of sample thickness and possibly geometry).

ROR

Dear Professor Ahmed Shandookh , thank you for question. The test was performed using quasi-static load.

Dear Professor Robert O Ritchie, thank you so much for your answer. I appreciate your recommendation of ASTM E 1820 and, especially the T. L. Anderson's text book. I hope find there a solution for the SENT geometry.

Vahid:

Thank you for your comments. I was uncertain whether the single-edge notched tension sample was in the ASTM Standard; I haven't checked but if you say that it is not - then OK. Another geometry that is not there is the four-point single-edge notched geometry, which is one of my favorites because of the constant bending moment between the inner two loading points. However, since the validity (specimen-size) criteria for linear-elastic KIc fracture toughness measurements are geometry-independent (unlike those for nonlinear-elastic JIc measurements which can be highly geometry-dependent), and the stress-intensity K solutions are readily available for both these two geometries, even though they are not included in the ASTM Standard I would maintain that you can still measure an accurate KIc value with the requirement that you satisfy the small-scale yielding and plane-strain criteria. The value would not strictly conform to the standard as you correctly point out, but they still would be accurate. Personally I would still call it a KIc value myself, but with the proviso that it was measured with a non-standard geometry.

However, if you cannot satisfy the plane-strain condition, i.e., the plastic-zone size is not small compared to the out-of-plane thickness B, then using either of these non-standard geometries, i.e., the single-edge notched tension and three-point bend, might be a trifle more "iffy" as, even under linear-elastic (small-scale yielding) conditions, the non-plane strain Kc toughness values are not only thickness-dependent but can be geometry-dependent too.

ROR

Emerson,

You can check the following literature that includes K solutions for SENT specimens. Note that the solutions are different for pin-loaded and clamp-end specimens.

X.K. Zhu, Full-range stress intensity factor solutions for clamped SENT

specimens, Int. J. Press. Vessels Pip. 149 (2017) 1–13.

S. Cravero, C. Ruggieri, Estimation procedure of J-resistance curves for SE(T)

fracture specimens using unloading compliance, Eng. Fract. Mech. 74 (17)

(2007) 2735–2757.

R. John, B. Rigling, Effect of height to width ratio on K and CMOD solutions for a

single edge cracked geometry with clamped ends, Eng. Fract. Mech. 60 (2)

(1998) 147–156.

Shen G, Tyson W R. Crack size evaluation using unloading compliance in single-specimen single-edge-notched tension fracture toughness testing. Journal of Testing and Evaluation, 2009, 37(4): 347-357.