摘要:

The static fatigue behavior of an extruded graphite was determined. The relation between time‐to‐rupture and the homologous fatigue stress (i.e. the ratio of the applied stress to the instantaneous fracture stress) is shown at two levels of applied stress. The significance of this relation is discussed, and its use in predicting cumulative fatigue damage is indica

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb16011.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

The microstructure of TiO2−opacified porcelain enamels was examined by optical microscopy and by transmission electron microscopy. The mosaic pattern found appears to correspond to the positions of the frit particles from which the enamel was made. Significant differences were observed in the crystallization behavior of adjoining frit particles. There is evidence that rutile grows from frit particle surfaces, whereas anatase is body‐nucleated. The anatase‐to‐rutile inversion is a ripening process rather than a phase transformation. Processes occurring during the firing of a TiO2enamel include crystallization from single‐phase glass, crystallization from multiphase glass, and a ripenin

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb16012.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Fatigue of silicate glasses was studied using both static and dynamic tests. Static fatigue data for acid‐etched soda‐lime silicate glass determined at 74°F in 50 and 100% rh can be represented by a single universal fatigue curve (UFC). The UFC for acid‐etched glass does not lie on the UFC of Mould and Southwick, which was determined for abraded soda‐lime silicate glass; the acid‐etched glass was less susceptible to static fatigue. The susceptibility of acid‐etched soda‐lime silicate glass to static fatigue differed little from that of pristine E‐glass and fused SiO2fibers. Dynamic fatigue data for soda‐lime, E, borosilicate, and fused quartz glasses agreed well qualitatively and quantitatively with fundamental crack velocity data for these glasses; the dynamic fatigue theory of Charles was used in the comparison. The theoretical implications of these res

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb16013.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Alloys of pyrolytic carbon and silicon codeposited in beds of fluidized particles were investigated. X‐ray diffraction measurements revealed only two phases, turbostratic C and β‐SiC. Since the C crystallites are oriented randomly, the C was macroscopically isotropic, with apparent crystallite sizes in the range found for pure C deposited under similar conditions. Transmission and scanning electron microscopy showed that the SiC was generally distributed as small particles which tended toward larger particles and continuous laminations at high SiC concentrations. The fracture stress and Young's modulus were measured in 3‐point bending; they increased continuously with increasing SiC content from values for pure isotropic carbons to values for chemically‐vapor‐dep

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb16014.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

A thermodynamic and high‐temperature X‐ray diffraction study was performed on polycrystalline nonstoichiometric BaTiO3. The oxygen composition was measured from 940° to 1215°C at O2partial pressures between 10−10and 10−21atm by a thermogravimetric technique. The isothermal weight change data exhibit a two‐slope behavior. The data at the lower pressures indicate that the maximum observable weight change is influenced by impurities, whereas the data at the higher pressures appear to exhibit native nonstoichiometric behavior. Values of ΔH̄o2and ΔS̄o2were calculated for the higher O2partial pressure region; ΔH̄o2is consistent with the O vacancy formation energies obtained by Long and Blumenthal from electrical conductivity measurements. High‐temperature X‐ray measurements indicate that the cubic structure is stable in the range investigated. Lattice parameters and coefficients of expansion were obtained from 200° to 1100°C in pure O2; lattice parameters of reduced BaTiO3at 11

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb16015.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Fracture energy and strength were determined for three series within a sodium borosilicate glass‐Al2O3dispersed composite system. The average particle sizes of the Al2O3dispersions were, andμm. Within each series, composites containing 0.10, 0.25, and 0.40 vol fractions of the Al2O3dispersed phase were vacuum hot‐pressed. The fracture energy was determined at 77°K with the double cantilever specimen configuration. Strength was measured by a 4‐point flexural test. A significant increase in fracture energy was observed (up to 5 times the fracture energy of the glass without second‐phase dispersion). The fracture energy depended on the interparticle spacing and average particle size of the Al2O3dispersion. These results could best be explained by a previously proposed model for the interaction of a crack front with a second‐phase dispersion. Surface roughness also contributed to the increased fracture energy. Some composites were strengthened significantly relative to the glass without a dispersion. Calculation of the crack size showed that the Al2O3dispersion increased the crack size of the glass by ∼1 to 3 times the average particle size of the Al2O3dispersion. Thus, the dispersion increased both the fracture energy and the crack size. These opposing parameters ultimately determined the strength behavior of the

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb16016.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

A finite element analysis was used to calculate the internal stresses and deformations everywhere within spherically filled or porous ceramic materials. This analysis accounts for interactions between inclusions and demonstrates the importance of these interactions on stress fields around the inclusions. Modulus of elasticity and Poisson's ratio were calculated for porous and filled ceramics. The predicted modulus is compared with experimental data for two glass composites; the agreement is excellent.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb16017.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Stress distributions in Al2O3bicrystals were analyzed for certain misorientations across the grain boundary in straight‐sided tensile specimens with the grain boundary normal to the tensile axis. Stresses were found using the numerical analysis technique of direct stiffness calculations or by finite element analysis. When the anisotropy in elastic constants of the bicrystals was considered, misorientation of principal axes yielded stress concentrations at the boundary as high as 1.50. The assumption of uniform stress states in bicrystal mechanical response studies, therefore, is not generally accurat

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb16018.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Hyperstoichiometric UO2single crystals having O/M ratios from 2.06 to 2.10 were deformed in compression. The active slip plane for deformation, as evaluated from slip traces, has an orientation between (112) and (111). The critical resolved shear stresses for hyperstoichiometric specimens are approximately the same as those for stoichiometric specimens; the dislocation structures, as revealed by transmission electron microscopy, however, are very different and suggest more rapid motion and/or climb of dislocations in the hyperstoichiometric samples. The response to strain rate changes during deformation also reflects the difference in deformation behavior of hyperstoichiometric and stoichiometric crystals.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb16019.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb16020.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY