予き裂導入試片を用いた構造用セラミックスの破壊靱性評価(第2報) : ポップイン予き裂発生源としての圧子圧入き裂が有する残留応力の影響

概要

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Fracture toughness (K_<IC>) of polycrystalline silicon carbide and alumina was evaluated using a single edge precracked beam (SEPB) technique. A Knoop indentation-induced microcrack was introduced into a specimen, and then a sharp pop-in pre-crack was followed by appling the bridge indentation method. The relative precrack length ( a/ W) was varied by changing the indentation load (20, 30, 50 kgf) and/or the width of support groove (4, 5, 6 mm) . The precracked specimens were fractured by three-point bending under a cross-head speed of 0.5 mm/ min at room temperature. K_<IC> values decreased with the increase in the indentation load in the range of 0.2<a/ W<0.8 for silicon carbide and a/W<0.35 for alumina, respectively. The indentation load dependence on the Klc values was discussed from the residual stress around the indentation-induced crack and the crack mouth opening displacement (CMOD) of SEPB specimens.
1989-07-01