Fatigue crack growth from indentation flaw in ceramics

Abstract

The indentation crack has been used as a model of surface flaw in the strength tests of ceramics. In evaluation of such strength properties, some attention should be paid to the residual stress effect due to indentation. In this study, fatigue crack growth behavior from indentation flaws was investigated in sintered silicon nitride and alumina. In both materials, a V-shaped behavior was observed in the relation between the maximum stress intensity factor and the crack growth rate. The indentation crack was analyzed using fracture mechanics procedure to take account of the residual component. On the basis of the analysis, an effective stress intensity factor for crack growth was successfully evaluated. The growth rate was correlated to the effective stress intensity factor, and the relation was found to be approximated by a power law equation. The fatigue crack growth property obtained as above was applied to an estimation of fatigue life of specimens without artificial flaws. The flaw size effect was also discussed based on the result,

Cyclic Fatigue Crack Growth in Three‐Point Bending PZT Ceramics under Electromechanical Loading

“…Crack growth rates exhibited a local minimum, resulting in V-shaped growth rate behavior, similar to the behavior reported for cyclic fatigue in other non-piezoelectric brittle materials. 17,18 Under E 0 5 0 V/m, multiple crack growth minima 19 seemed to occur. The minimum is probably associated with local microstructural barriers to crack extension, such as the interaction of microcracks with the main crack, from mechanisms such as crack wedging by fracture surface asperities (roughness-induced crack closure) and crack bridging from uncracked ligaments, e.g., interlocking grains due to the intergranular nature of the fracture surface.…”

Fracture and electric‐field‐induced crack growth behavior in NBT‐6BT relaxor ferroelectrics

“…It was seen that the crack growth rate generally showed a clear monotonic decrease with increasing field intensity factor, corresponding to the crack arrest in Figure 8, which are similar to findings in a study on Si 3 N 4 . 90,91 The recommencement of crack growth at a higher number of cycles is mostly seen for poled samples and is shown as a rise in crack growth rate. In the end, the decreasing crack growth rate (Figure 9) coincides with the plateau in the crack growth plot (Figure 8).…”

Life Prediction and Reliability Analysis of Ceramic Structures Under Combined Static and Cyclic Fatigue

“…A dependency of lifetime on cyclic loading frequency was also observed which is in contrast to the predictions of static tests [9,11]. Test data verifying enhanced crack growth rate under cyclic loading compared with static loading now exist for other brittle monolithic ceramics (e.g., silicon nitride [12][13][14][15][16][17]), toughened ceramics (e.g.,magnesia-partially-stabilized zirconia [18][19][20][21][22][23][24][25][26][27][28]), sintered zirconia (e.g., ytt<ia-stabilized zircons [29][30][31]), and reinforced alumina [32].…”