PSI - Issue 68

Mr. Parthasarathy Iyengar et al. / Procedia Structural Integrity 68 (2025) 446–452 P. Iyengar, J. Mardaras, S. Soe / Structural Integrity Procedia 00 (2025) 000–000

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Table 1. A comparison of select mechanical properties published by MMPDS (2019)

*Calc G is G = E / 2*(1+v) *assumed value from www.matweb.com 2023-T351 has an average K 1C of 34.06 MPa√m and minimum K 1C of 29.66 MPa√m listed in MMPDS-14. In order to obtain a high-level view of stress-strain curves, indicative Stress-Strain curves are developed based upon MMPDS 14 by MMPDS (2019) properties assuming parameters based upon the principle within Ramberg and Osgood (1943). They are presented as Fig. 1 alongside a picture of actual curves for plate provided by Arconic.

Fig. 1. (a) indicative σ-ε curves developed using Ramberg-Osgood approach; (b) A photo of real σ-ε curves of 2024-T351 plate 2024-T351 is seen to elongate to ~13% unlike 2219-T851. A typical 2024-T351 curve is shown alongside. The decay after UTS is usually negligible. Linear portion of σ-ε curves extends to nearly 2/3rd of the Yield Point. 2.2. Metallic Fracture toughness as K 1C and in the aircraft industry When a pre-cracked specimen or component is monotonically loaded to fracture, crack extension begins macroscopically flat but is immediately accompanied by small ‘shear lips’ at the side surfaces as described by Wanhill et al (2024). Crack Mouth Opening Displacement (CMOD) & the applied load are traditionally used to calculate K 1C from CT specimen in accordance with ASTM (2023). As the crack shear lips widen to cover the entire fracture surface, which then becomes fully slanted either as single or double shear. This behaviour is usually attributed to crack extension under predominantly plane strain conditions being superseded by fracture under plane stress. Mode 1 Fracture toughness is commonly applied to design of metallic parts or interrogate production quality of raw materials, semi-finished products or parts in either Plane strain ( K 1C ) or Plane stress condition (R-curve). Ø R-curves are generally applicable where the ratio [Minimum (length, width)] / thickness ≥ 100 Ø K 1C is applied in practice to parts which do not fall into the above generalization.