Prediction of ceramic fracture with normal distribution pertinent to grain size. (15th February 2018)

• Record Type: Journal Article
• Authors: Zhang, Chunguo; Hu, Xiaozhi; Sercombe, Tim; Li, Qingbin; Wu, Zhimin; Lu, Pengmin
• Is Part Of: Acta materialia. Volume 145(2018)
• Page Start: 41
• Page End: 48
• Publication Date: 2018-02-15
• Subjects: Grain size -- Strength -- Fracture -- Normal distribution -- Ceramics; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2017.11.041
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: Fracture of brittle ceramics initiated from shallow surface cracks comparable to their average grain sizes ( G ) can fluctuate significantly. Such fluctuations can contain crucial information on the inherent relations between the average grain size G and bulk ceramic properties such as the tensile strength f t and fracture toughness K IC . It was proposed in this study that the characteristic crack a *ch = 0.25( K IC / f t ) 2 = constant × G, inspired by observations of strength distributions with different a *ch / G ratios. It was found that normal distributions with the smallest standard deviation exist around a *ch = (2.5–3.5) × G, based on quasi-brittle fracture results of four different ceramics with G from 2 to 20 μm and shallow surface cracks from 100 nm to 650 μm. Using the average value of the relative characteristic crack a *ch / G ≈ 3, the mean and standard deviation (σ) were determined by normal distributions for both the tensile strength ft and fracture toughness K IC . Quasi-brittle fracture of those fine-grained ceramics based on the mean values and standard deviations was thus predicted. The upper and lower bounds with 96% reliability (±2σ) specified by the normal distributions covered nearly all experimental data ranging from the strength-controlled to toughness-controlled asymptotic limits, and quasi-brittle fracture between the two. With the knowledge of the average grain size G, the tensile strength f t becomes the sole parameter required to describe the entire fracture range. Graphical abstract: Image 1