Solid mechanics compression tests

Mechanical and Chemical Characterization Enamel has often been viewed as a homogeneous solid [2, 3], but Knoop microhardness tests [4, 5] and compression tests [6] have shown that the Young s modulus (E) and hardness (H) are higher for cusp (or surface) enamel than for side (or subsurface) enamel. Depth-sensing Vickers indentation [7] has shown that the H and E obtained from an occlusal section of enamel are higher than those for an axial section. The variations in mechanical properties with location have been explained in terms of the degree of tissue mineralization. Notably,... 

The quality of eucalypt woods for producing chemical pulps was evaluated using NIR spectra and chemometric methods [124]. NIR spectroscopy was used to predict pulp yield and cellulose content from spectra of powdered wood samples [137]. In another application, in addition to estimating lignin content, NIR spectra were used to quantify hardwood-softwood ratios in paperboard [138]. NIR spectra taken from solid European larch samples subjected to axial bending and compression tests revealed an excellent ability to model the variability of mechanical properties [139]. The study demonstrated that the model is based not only on the measurement of density, but also on surface geometry, composition, and, possibly, lignin content. The authors concluded that NIR spectroscopy shows considerable potential to become a tool for nondestructive evaluation of small clear wood specimens, e.g., increment cores. 

Li, G. and Xu, W. (2011) Thermomechanical behavior of thermoset shape memory polymer programmed by cold-compression testing and constitutive modeUng. Journal of the Mechanics and Physics of Solids, 59, 1231-1250. 

The compressibility of cakes, i.e. the increasing resistance of cakes with pressure, can be tested in various ways. As was briefly mentioned in section 9.2.2, one way of testing the relationship a =/(Apc) is in the compression-permeability cell. The solids compression is created by the mechanical action of the piston—an obvious assumption made is that hydraulic pressime can be simulated by mechanical compression. 

To prepare samples for mechanical properties testing, the aqueous copolymer solutions (50/50 wt/wt) in Table 1 were formulated with the CaFAlSi glass powders used in the two commercial Gls Fuji II and Fuji IX. In the blending of the solid glass powder with the aqueous solution of the copolymers, at the same P/L ratios recommended for Fuji II and Fuji IX, it was observed that the presence of the NVP allowed generation of a more smooth blend compared to the two commercial materials. Mechanical properties of the experimental materials were compared to the Fuji 11 and Fuji IX controls, where all test samples (n = 6) were prepared and conditioned under the same procedure. The flexmal strengths (FS), flexural moduli (FM), compressive strengths (CS), and compressive moduli (CM) of the experimental copolymers were compared to the same Fuji II and Fuji IX mechanical properties, as shown... 

To determine the mechanical behavior of plastics under compressive load, it is possible to carry out the compressive test described in DIN ISO 604 for the testing of plastics [9]. By contrast to tensile tests, cylindrical, solid-material specimens are compressed between two plane-parallel plates and the compressive stress/compression behavior is recorded. One problematical aspect of these tests is that the friction that occurs between the plane-parallel clamping surfaces and the specimen inhibit the lateral extension of the test specimen and hence leads to a convex barrel shape, which is the manifestation of a multiaxial stress state inside the specimen. 

Rheometric Scientific markets several devices designed for characterizing viscoelastic fluids. These instruments measure the response of a liquid to sinusoidal oscillatory motion to determine dynamic viscosity as well as storage and loss moduli. The Rheometric Scientific line includes a fluids spectrometer (RFS-II), a dynamic spectrometer (RDS-7700 series II), and a mechanical spectrometer (RMS-800). The fluids spectrometer is designed for fairly low viscosity materials. The dynamic spectrometer can be used to test solids, melts, and liquids at frequencies from 10-3 to 500 rad/s and as a function of strain amplitude and temperature. It is a stripped down version of the extremely versatile mechanical spectrometer, which is both a dynamic viscometer and a dynamic mechanical testing device. The RMS-800 can carry out measurements under rotational shear, oscillatory shear, torsional motion, and tension compression, as well as normal stress measurements. Step strain, creep, and creep recovery modes are also available. It is used on a wide range of materials, including adhesives, pastes, mbber, and plastics. 

The mechanical properties of Micelle-Templated Silicas (MTS) are very sensitive items for industrial process applications which might submit catalysts or adsorbents to relevant pressure levels, either in the shaping of the solid or in the working conditions of catalysis or separation vessels. First studies about compression of these highly porous materials have shown a very low stability against pressure. These results concern these specific materials tested. In this study, we show very stable MTS with only a loss of 25% of the pore volume at 3 kbar. The effects of several synthesis parameters on the mechanical strength are discussed. 

Figure 14.8 shows stress-strain curves for polycarbonate at 77 K obtained in tension and in uniaxial compression (12), where it can be seen that the yield stress differs in these two tests. In general, for polymers the compressive yield stress is higher than the tensile yield stress, as Figure 14.8 shows for polycarbonate. Also, yield stress increases significantly with hydrostatic pressure on polymers, though the Tresca and von Mises criteria predict that the yield stress measured in uniaxial tension is the same as that measured in compression. The differences observed between the behavior of polymers in uniaxial compression and in uniaxial tension are due to the fact that these materials are mostly van der Waals solids. Therefore it is not surprising that their mechanical properties are subject to hydrostatic pressure effects. It is possible to modify the yield criteria described in the previous section to take into account the pressure dependence. Thus, Xy in Eq. (14.10) can be expressed as a function of hydrostatic pressure P as... 

---