Apparent Elastic Properties Research Articles

Effect of adsorbed water on the ultrasonic velocity in alumina powder compacts

The presence of surface adsorbed water has been found to significantly increase the apparent elastic properties of unsintered alumina powder compacts. It is proposed that the increase in the elastic moduli results from the formation of `interparticle bridges' between adjacent particles and, thus, increased effective interparticle contact area. The effects upon the elastic moduli in the unsintered powder compacts were monitored by measurement of the changes in the ultrasonic velocity. The ultrasonic data are consistent with thermogravimetric analysis and mass spectrometry results which indicate the presence of multiple adsorbed water species. Understanding the effect of adsorbed water on the processing characteristics of ceramic powders may lead to better process control during green state consolidation and ultimately to higher quality sintered products.

Relationships between bone morphology and bone elastic properties can be accurately quantified using high-resolution computer reconstructions.

It would be advantageous if the mechanical properties of trabecular bone could be directly inferred from stereomorphometric parameters. For that purpose, apparent density and mean intercept length, as measures of bone mass and directionality (fabric), are commonly correlated with the elastic characteristics of bone samples, as determined in compression tests. However, complete and accurate relationships have not yet been established in this way. This may be due not only to the occurrence of artifacts in both the stereomorphometric and the mechanical assessments but also to an inherent inadequacy of mean intercept length in characterizing the full mechanical significance of bone architecture or nonhomogeneities in trabecular tissue properties not accounted for in stereomorphometry. In this study, we introduce a computer modeling approach allowing these biases to be eliminated. With use of high-resolution three-dimensional computer reconstructions of trabecular bone specimens for stereomorphometry and for microstructural finite element models to simulate mechanical tests, unbiased comparisons become feasible. The purpose was to investigate if accurate and complete relationships can be established in this way. Four different fabric measures were considered: mean intercept length and three volume-based ones. Compliance matrices were calculated from fabric tensors, with use of the mathematical relationship proposed by Cowin for 29 vertebral whale-bone specimens. These were correlated with the compliance constants determined directly from the microstructural finite element model simulation. The nine orthotropic elastic constants of all 29 specimens were well predicted from their stereomorphometric fabric and volume fraction values, with correlation coefficients ranging from R2adj = 0.9934 to 0.9963. When individual compliance components were considered (1/Ei, 1/Gij, or -v[ij]/Ei), correlation coefficients ranged from R2adj = 0.924 to 0.982. All four fabric measures performed equally well. It is concluded that volume fraction and fabric measures correlate highly with the apparent elastic properties of bone samples, provided that anisotropy and nonhomogeneity in the elastic properties of the trabecular tissue itself have negligible effects on the apparent properties. Whether this is true for bone in general remains to be seen, as only a subset was analyzed here. These methods, however, can be valuable in similar assessments of other subsets.

Prediction of the Effect of Craze Damage on Apparent Elastic Properties of Polystyrene by FEM

Prediction of the Effect of Craze Damage on Apparent Elastic Properties of Polystyrene by FEM

TEXTURAL AND ELASTIC PROPERTIES OF IRISH POTATOES II..

Unprocessed steam-peeled potatoes exhibited lower apparent moduli of deformability and elasticity than unpeeled or abrasion-peeled potatoes. Both moduli decreased upon thermal processing and on storage of the processed product. The degree of elasticity and energy capacity decreased, while mechanical hysteresis increased, due to peeling prior to processing. The processed Sebago variety showed greater mechanical hysteresis than the Red LaSoda variety. The apparent elastic properties of processed potatoes exhibited varied trends due to the peeling method and storage as evidenced by the significant interaction of these two main variables. The results obtained suggest that apparent elastic moduli are not reliable indices of the degree of firmness of the peeled and processed Irish potatoes. Texture measurements on these potatoes should involve destructive forces and deformations to give true indications of differences in firmness.