ISSN:
1573-4803
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Power-law creep parameters of brittle ceramic materials are commonly deduced from load-point displacement data generated by four-point bend experiments, under the assumption that tensile and compressive behaviours obey the same constitutive law. However, because of microcracking and cavitation, it is now well recognized that this premise may not always be valid. The present paper presents an analysis which takes the differences into account. Governing equations are first derived for the location of the neutral axis of a beam under bending which does not in general pass through the centroid of the cross-section, and for the creep response in terms of both curvature rate and load-point displacement rate as functions of the applied moment and power-law creep parameters. Numerical solutions are obtained for any given set of material constants over a wide range of applied moments. It is shown from the plots of creep response against applied moment on a logarithmic scale that even linear curves over a narrow range of applied moment do not necessarily imply identical stress exponents, and that non-linear curves concave upward signify a profound difference in stress exponent between tension and compression. An example is given of applying the present analysis to a set of load-point displacement data on glass-alumina beam specimens crept at 1100° C. The results show that the conventional method over/underestimates the creep rates in compression/tension by two orders of magnitude, indicating a need for using the more accurate analysis presented here. Several recommendations are offered to improve the estimation of power-law creep parameters from bend test data.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01144716
