William D. Callister, Jr. David G. Rethwisch
ISBN #9780471736967
7th Edition
771 Questions
Homework Questions
None
CONCEPT
DEFINITION
Ceramics Fabrication Techniques
The methods and processes used for shaping, forming, and consolidating ceramic materials into final products with desired properties.
What is the magnitude of the maximum stress that exists at the tip of an internal crack having a radius of curvature of $1.9 \times 10^{-4} \mathrm{mm}$ $\left(7.5 \times 10^{-6} \text {in. }\right)$ and a crack length of $3.8 \times$ $10^{-2} \mathrm{mm}\left(1.5 \times 10^{-3} \mathrm{in.}\right)$ when a tensile stress of $140 \mathrm{MPa}(20,000 \mathrm{psi})$ is applied?
Estimate the theoretical fracture strength of a brittle material if it is known that fracture occurs by the propagation of an elliptically shaped surface crack of length $0.5 \mathrm{mm}(0.02 \mathrm{in.})$ and having a tip radius of curvature of $5 \times$ $10^{-3} \mathrm{mm}\left(2 \times 10^{-4} \mathrm{in.}\right),$ when a stress of $1035 \mathrm{MPa}(150,000 \mathrm{psi})$ is applied.
If the specific surface energy for aluminum oxide is $0.90 \mathrm{J} / \mathrm{m}^{2},$ using data contained in Table $12.5,$ compute the critical stress required for the propagation of an internal crack of length $0.40 \mathrm{mm}$.
An MgO component must not fail when a tensile stress of $13.5 \mathrm{MPa}(1960 \mathrm{psi})$ is applied. Determine the maximum allowable surface crack length if the surface energy of $\mathrm{MgO}$ is $1.0 \mathrm{J} / \mathrm{m}^{2} .$ Data found in Table 12.5 may prove helpful.
A specimen of a 4340 steel alloy with a plane strain fracture toughness of $54.8 \mathrm{MPa} \sqrt{\mathrm{m}}$ $(50 \mathrm{ksi} \sqrt{\mathrm{in.}})$ is exposed to a stress of $1030 \mathrm{MPa}$ $(150,000 \mathrm{psi}) .$ Will this specimen experience fracture if it is known that the largest surface crack is $0.5 \mathrm{mm}(0.02 \text { in. })$ long? Why or why not? Assume that the parameter $Y$ has a value of 1.0.