ISSN:
1551-2916
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
Transient creep and attenuation (internal friction) of a β-spodumene glass-ceramic has been examined. Four-point flexural creep tests have been performed at high tempera-ture(T = 925°-1000°C) and modest stress levels (σl,max= 7-25 MPa). The flexural creep response of the glass-ceramic is characterized by a large decelerating transient that precedes the establishment of a steady state. The creep response is transformed via a numerical algorithm to give the attenuation spectrum. In addition, low-stress (2.5-30 MPa), subresonant-frequency (10 −5 Hz ≤ f ≤ 1 Hz), com-pression-compression attenuation experiments have been performed. A first-order thermodynamic analysis of the effect of effective pressure on the volume fraction of re-sidual glass suggests that the dilatational process that is associated with the flexural deformation mode should be characterized by a single loss mechanism. The predictions that are available from the flexural creep tests, as well as those that have been directly measured in experiments, in-dicate that attenuation behavior is insensitive to both fre-quency and temperature and exhibits a characteristic band of absorption. The weak frequency dependence of this an-elastic response is well-characterized by a power law of the form Q−1χfα, where 0.15 ≥ a ≥ 0.3, which suggests a physical mechanism that possesses a distribution of relax-ation times. A plausible explanation exists in the fluid-mechanics description of deformation-induced melt migra-tion, in which the crystalline β-spodumene “matrix” undergoes compaction or dilatation while the residual glass phase, which forms an interpenetrative network along grain triple junctions of the matrix, flows: the evolution with time of the compacted (and/or dilated) layer thickness of the deforming matrix produces a distribution of compli-ances.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1151-2916.1997.tb03212.x
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