R-Curve에 의한 破壞靭性 K_RC 결정에 관한 기초적연구 = A Basic Study on the Determining of Fracture Toughness K_RC by Means of R-Curve Method

다국어 초록 (Multilingual Abstract)

The crack extension resistance curve (R-curve) is a plot of material resistance values (K_R) versus crack extension values (Δa). It is considered that for a given material, the R-curve depends only on temperature and specimen thickness.
As was suggested by Irwin, the critical avlues K_RC and Δa_c at instability point are defined as the coordinate values of the tangential point between the R-curve and the crack extension force curve appropriate for the specific loading method.
This paper covers the determination of critical resistance value K_RC for fracturing of Aluminum Alloy 2024-F by R-curves using the compact tension specimen.
Conclusions are summarized as follows:
(1) The shape of R-curve of a material having a given thickness does not depend on the initial crack length.
(2) The value of critical stress intensity factor K_RC of a material having a given thickness and size does not depend on the initial crack length but retains a constant value. For Aluminum Alloy 2024-F, K_RC value is found to be around 165-170kg.mm^(3/2)
(3) As the load increases, the curve of compliance EB2V_1/P vs. a/W has a steep positive slope.
(4) The fracture appearances of the compact tension specimen are presented in two shapes in the process of fracturing, plane stress condition is considered to be prevailing in the specimen.