Stiffnesses measurement

Bearing Load and Cross-Coupling Stiffness Measurements... 

The shape of AFM cantilevers (much thinner than the width) results in torsional deflection when forces push the tip laterally as in friction measurements (when the tip is sliding) or lateral stiffness measurements (when the tip is stuck). 

Asif, S.A.S., Wahl, K.J. and Colton, R.J., Nanoindentation and contact stiffness measurement using force modulation with a capacitive load-displacement transducer. Rev. Sci. Instrum., 70, 2408-2413 (1999). 

Figure 5.6 Correlation of octahedral shear stiffnesses with bond moduli for Group IV crystals. The octahedral stiffnesses measure the elastic shear resistances of the covalent bonds across the (111) planes.

Li, X., and B. Bhushan, A review of nanoindentation continuous stiffness measurement technique and its applications. Mater. Char., 48, 11-36 (2002). 

Fig. 13.5. Quantitative measurements of contact stiffness by UFM (a) theoretical calculation of the UFM response on Si (1) and Ge (2) surface, using the engineering parameters ESi = 164 GPa, EGe = 121 GPa, surface energy in an ambient environment y = 1 N m-1, and the manufacturer s data for cantilever stiffness kc = 2.8 nN nm-1 and tip radius Rt = 10 nm (b) experimentally measured UFM response of a silicon surface (c) schematic illustration of the differential UFM approach to the measurement of contact stiffness (Kolosov and Yamanaka 1993), from the threshold amplitude values (ai and a2) for two different normal force values (Fi and P2), the contact stiffness Seff is given by Seff = (F2 — -Fi)/(a2 — ) (d) experimental stiffness measurements... 

Figure 13.5(d) presents experimental stiffness measurements using differential UFM for three high modulus surfaces sapphire, Si(100) and LiF(lOO) (Dinelli et al. 2000b). The samples were probed with the same silicon tip on a V-shaped cantilever (nominally cantilever stiffness was kc - 2.8 nN nm 1,and radius of curvature R = 10 nm). The surface RMS roughness of the surfaces was less than 0.2 nm over a few square micrometres for all three samples. The relative difference between the three sets of data reveals that the elastic properties of these three materials can be distinguished by differential UFM the relative independence of the applied force may indicate the fact that the tip had been flattened by extended contact with such hard samples. 

Hardness is a stiffness measurement. Stiffness is a stress/strain relationship. In load-carrying applications the stiffness is a bulk property, whereas measuring hardness is only a surface measurement. Two polyurethanes with completely different chemistries can have the same hardness. There are up to six completely different chemistries that are in common use (as shown in Table 7.1) that can give the same hardness. 

Figure 1. Temperature stiffness measurements of poly(p-xylylenes)...

AC — D (carbon-deuterium) bond is electronically much like a C — H bond, and it has a similar stiffness, measured by the spring constant, k. The deuterium atom has twice the mass (m) of a hydrogen atom, however. 

Benkelman beam rebound deflection measurements have been obtained during each of these testing phases. The SDHPT Dynaflect Unit has been used to obtain dynamic stiffness measurements. These results also indicate that the sulfur-asphalt mixes and the asphalt mixes are displaying comparable characteristics. 

Table 1 Influence of visbreaking on the fracture toughness (NIS according to 179/leA) and stiffness measured in bending after ISO 178, bending. of non-nucleated and / -nucleated grades. CR means controlled rheology, PI polydispersity. AH (a) is the melt enthalpy of the a-phase (2nd scan), AH(fi) that of the -modification (2nd scan), Tc is the crystallization temperature determined by DSC with the scanning program + 10/ - 10/ + lOKmur1...

Such a dramatic change in both properties is clearly evident despite the large scatter in both the jaggedness and stiffness measures. Both indicate the occurrence of a sharp transition at almost the same water activity. (The shown large scatter in the mechanical tests results was inevitable because the agglomerates were tested intact. Although they had been gently sieved to obtain a uniform size, their shape was not the same. Therefore, much of the scatter can be attributed to the variability... 

The mechanical properties of hardened concrete can be classified as (1) short term or instantaneous properties and (2) long term properties. The short term properties can be enumerated as (a) strength in compression, tension and shear and (b) stiffness measured by modulus of elasticity. The long term prop-... 

A significant improvement in nanoindentation testing is continuous stiffness measurement (CSM). ... 

The measurements were performed with an automated torsion pendulum (DMA) apparatus working at a frequency of about 0.5 Hz. (varying frequency system, see Chapter 4). The use of a low-stiffness suspension wire permitted stiffness measurements as low as 5H4 N/m2. These DMA measurements were performed from 50°C up to 250°C using a heating rate of l°C/minute the samples were, during these experiments, purged with nitrogen. 

Both perilymph and endolymph have the viscosity and density of water. The bone of the wall and the bony shelf appear to be similar to compact bone, with density approximately twice that of water. The remaining components of the cochlea are soft tissue with density near that of water. The stiffnesses of the components vary over a wide range, as indicated by the values of Young s modulus listed in Table 63.1. These values are taken directly or estimated from many sources, including the stiffness measurements in the cochlea by Bekesy [1960], Gummer and coworkers [1981], Strelioff and Flock [1984], Miller [1985], Zwislocki and Cefaratti [1989], and Olson and Mountain [1994]. 

The motility appears to be due to a passive piezoelectric behavior of the ceU plasma membrane [Kahnec and colleagues, 1992]. Iwasa and Chadwick [1992] measured the deformation of a ceU under pressure loading and voltage clamping and computed the elastic properties of the wall, assuming isotropy. It appears that for agreement with both the pressure and axial stiffness measurements, the ceU wall must be... 

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