Elastic property advantages

Converting penetration depth to hardness has the advantage of normalizing consistency values so that they are less dependent on the penetration load. This is the rationale behind hardness testing in metallurgy. In these cases, the contact pressure as defined by hardness in Equation 2 is used to deduce the yield stress of a material (Tabor, 1996). However, the yield stress is the resistance to an applied shear stress, but it is not the only resistance to a penetrating body. The elastic properties of a fat, and the coefficient of friction between the cone and the fat sample will also impede the penetration of the cone (Tabor, 1948). Kruisher et al. (1938) tried to eliminate friction effects and advocated the use of a flat circular penetrometer with concave sides. 

Sections A and B of this chapter dealt with purely elastic deformations, i.e. deformations in which the strain was assumed to be a time-independent function of the stress and vice versa. In reality, materials are never purely elastic under certain circumstances they have non-elastic properties. This is especially true of polymers, which may show non-elastic deformation under circumstances in which metals may be regarded as purely elastic. For a better understanding three phenomena may be distinguished, the combination of which is called viscoelasticity. This is elucidated in Table 13.8. The only modulus which is time-independent is the bulk modulus hence its advantage as a basis for additivity. 

Polysaccharides, proteins, and nucleic acids are all polymers. Polymers such as collagen are Wologically important, and the elastic properties of collagen are often used to advantage for energy storage in tendons. 

Perturbations of the medium adjacent to the device surface result in variations in the phase, amplitude, and velocity of the surface acoustic wave. Specifically, these properties will be affected by changes in the density, viscosity, or elastic properties of the medium in contact with the surface. Since the acoustic wave has an electric potential wave associated with it as well, the SAW can also be used to probe the dielectric and conductive properties of this surface medium. By far, the largest number of chemical sensor applications of SAW devices take advantage of the mass sensitivity of SAW oscillators. 

In the area of chemical sensors, thin polymer films are routinely used as coatings for the semi-selective sorption of chemical vapors. One sensor technology, the surface acoustic wave (SAW) device, has demonstrated excellent sensitivity as a vapor sensor when coated with films having appropriate solubility properties (2). To date, most sensor applications have utilized the extreme mass sensitivity of the devices. In this paper, we will examine the response mechanisms of the SAW sensor and demonstrate its sensitivity to changes in the elastic properties of the coating materials. Finally, we will discuss the significance of these results in terms of current sensor applications, and the advantages of the SAW for polymeric materials characterization. 

In sensor applications, greater care should be taken in the selection and application of polymer films to minimize modulus effects. The effect of elastic properties of the coating materials must be taken Into consideration in the interpretation of SAW sensor data. Alternatively, the sensor community ml t take advantage of the SAW sensitivity to elastic properties to devise more sensitive sensors, and to expand the applications of these sensors. 

Magnesium oxychloride cement (see section 15.1) is also well suited to be combined with wood. Such a combination is most commonly used for industrial floorings. The main advantage of this material in such applications is its favorable elastic properties. 

The advantage of PBT fibers over Kevla/ consists of not only the high elastic properties but also the elevated thermal... 

It is most natural to consider next the elastic properties of the crystal because this is the dependence of the total energy upon the size and shape of the unit cell. As was discussed above, it is a great advantage to use the direct calculation of stress from the "stress theorem." This has been applied to accurate calculations of the elastic properties of the crystals Si, Ge, and GaAs, using methods which have general applicability to all solids. 

The advantage of this approach is obvious. Maximum elastance that has been corrected for resistive effects can easily be obtained from the elastance function without having (1) to perturb the system and (2) to identify the end of systole. In addition, information concerning the resistive behavior of the ventricle is obtained. Because the myocardium is a viscoelastic material, the pressure generated by the ejecting left ventricle will not solely reflect its elastic properties. Instead, a... 

In ceramic matrix composites (CMC), the fibres mainly serve to increase the fracture toughness. Because one important property of the fibres is their small defect size, it is possible to use the same material for fibre and matrix. The advantage of this is that the elastic properties of fibre and matrix are identical, avoiding the formation of stress concentrations, and that the coefficient of thermal expansion is also the same, so no residual stresses are generated during cooling. Chemical reactions do not occur as well. Possible fibre materials are mainly ceramics. 

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