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Shear properties experimental determination

The ronaining sections of this chapter treat dynamic or oscillatory measurements of viscoelastic properties. Here, in simple shear, the experimental determination is usually a complex ratio of force to displacement (or torque to angular displacement) measured at a surface in contact with the sample or else a force measured... [Pg.107]

To constitute the We number, characteristic values such as the drop diameter, d, and particularly the interfacial tension, w, must be experimentally determined. However, the We number can also be obtained by deduction from mathematical analysis of droplet deforma-tional properties assuming a realistic model of the system. For a shear flow that is still dominant in the case of injection molding, Cox [25] derived an expression that for Newtonian fluids at not too high deformation has been proven to be valid ... [Pg.695]

Experimental results are presented that show that high doses of electron radiation combined with thermal cycling can significantly change the mechanical and physical properties of graphite fiber-reinforced polymer-matrix composites. Polymeric materials examined have included 121 °C and 177°C cure epoxies, polyimide, amorphous thermoplastic, and semicrystalline thermoplastics. Composite panels fabricated and tested included four-ply unidirectional, four-ply [0,90, 90,0] and eight-ply quasi-isotropic [0/ 45/90]s. Test specimens with fiber orientations of [10] and [45] were cut from the unidirectional panels to determine shear properties. Mechanical and physical property tests were conducted at cold (-157°C), room (24°C) and elevated (121°C) temperatures. [Pg.224]

Model constants were found by the results of solid expansion and mechanical researches on installation [4] (measuring error was less than 3%). In Drst case models were chilled from 150 to 25°C with ratio 0.4°C/mim Relaxation operator of shear pliability was determined by Equation (1) on the base of experimental meastrred deformation of model and known value of applied mechanical tension. For exception of thermal prehistory inOtence on properties of experimental objects before each test models were heated to 150°C, were kept at that temperatirre 3 hr and chilled with ratio 0.2°C/min to temperature 25°C. [Pg.77]

These presumptions are based on the results of chanical composition analyses and structural determinations by beam-based analytical methods. To verify the mechanisms involved, it is essential to clarify the frictional and mechanical properties of each layer in the multilayered structure of the tribofilm. Most importantly, with respect to the uppermost surface and the underlying area, which are thought to control the macroscale friction behavior, it is indispensable to determine differences not only in surface roughness, but also in shear strength and frictional behavior relative to depth on a nanometer scale. It is also important to make clear the distribution of the chemical composition relative to the tribofilm depth and to make this chemical distribution consistent with the nanometer-scale frictional and mechanical properties. However, estimating these properties experimentally on a nanometer scale is a difficult task, although several attempts have been made [24-28],... [Pg.193]

The flow properties of a SmC phase with fixed director orientation and a flow parallel to the layers can, therefore, be described by seven independent viscosity coefficients. The experimental determination of these coefficients should be connected with a series of problems. If the coefficients 774 or 775 are determined in a capillary with a rectangular cross section with T< W and the layer parallel to one of the plates as in Fig. 20 I. The thickness has to be constant over the whole sample with an accuracy that is not easy achieved [63,64]. There are similar problems in the measurement of the other coefficients. Minor difficulties should occur in a shear experiment with a small lateral movement of one of the plates. [Pg.505]

Equations (4.8)-(4.10) have been solved in simple steady state shear flow using Mathematica software (Leonov and Chen 2010). The stress components are expressed as function of shear rate y with the values of constitutive parameters 00, a,p, r, r2,Xe, and t o. Here Oq and t]o represent relaxation time and zero shear viscosity respectively. The other parameters XgandXv represent the tumbling for elasticity and viscosity. Rest of the characteristic parameters a,p,ri,r2 represent anisotropic properties of liquid crystal polymers. Among the eight parameters, only relaxation time and zero shear viscosity are determined from experimental data. The other six parameters can be obtained from cinve fitting data using the Mathematica software. [Pg.95]

Experimental load-displacement history and creep data were used to estimate the partitioned viscoplastic constitutive properties. Load isplacement loops from double lap-shear tests were used in conjunction with finite element (FE) models to refine the estimates of the effective viscoplastic constitutive properties of the three Pb-free solders and eutectic Sn Pb. The constitutive equations for the four solders were used as initial estimates when iterating to match experimental and predicted hysteresis loops. That is, experimentally determined double lap-shear specimen load-displacement hysteresis loops were compared with the FE simulations. The constitutive properties were then adjusted iteratively to improve agreement the equations and properties are presented in Table 16. [Pg.684]

For the purposes of constant consideration the most significant is the circumstance that all these data on the whole give the information which is equivalent or close to that obtained during measurements of rheological properties under the conditions of shear flow. Therefore a method of investigation here is determined by the taste of the experimenter and measuring technique available. [Pg.95]

Viscosity, defined as the resistance of a liquid to flow under an applied stress, is not only a property of bulk liquids but of interfacial systems as well. The viscosity of an insoluble monolayer in a fluid-like state may be measured quantitatively by the viscous traction method (Manheimer and Schechter, 1970), wave-damping (Langmuir and Schaefer, 1937), dynamic light scattering (Sauer et al, 1988) or surface canal viscometry (Harkins and Kirkwood, 1938 Washburn and Wakeham, 1938). Of these, the last is the most sensitive and experimentally feasible, and allows for the determination of Newtonian versus non-Newtonian shear flow. [Pg.57]

Fig 3.8 shows the interface shear bond strength, tb, determined from Eq. (3.7), which is not a material constant but varies substantially with embedded fiber length, L. However, to evaluate all the relevant interface properties properly, which include the interface fracture toughness, Gic, the coefficient of friction, p, and the residual clamping stress, qo, it is necessary to obtain experimental results for a full range of L and plot these characteristic fiber stresses as a function of L. More details of the... [Pg.52]

The work of Laufer (L3) indicates that eddy viscosity is not isotropic in shear flow. For this reason it is unlikely that eddy conductivity is isotropic in such flows. Therefore, uncertainties in the application of eddy conductivities must arise when it is assumed that this transport coefficient is isotropic. Until additional experimental information is available, it appears reasonable to consider eddy conductivity as isotropic except in circumstances when the vectorial nature (J4, R2) of the eddy viscosity may be estimated. Such an approximation appears acceptable since the measurements available described the conductivity normal to the axis of flow, which is the direction in which most detail is required in the prediction of temperature distribution in turbulently flowing streams. Throughout the remainder of this discussion all eddy properties will be treated as isotropic. Such a simplification is open to uncertainty, and further experimentation will be required in order to determine the error introduced by neglect of the vectorial characteristics of these macroscopic transport quantities. [Pg.258]

The properties of i (0) for narrow distribution polymers have already been discussed in Section 5. The behavior of f jfy) at higher shear rates has only been determined for a few systems of well-characterized molecular structure. The experimental problems are more difficult than in the case of rj(y), so the conclusions here must be regarded as somewhat more tentative. Experimentally, t(y) and tj(y) depart from their zero shear values within the same range of shear rates (172). Shear rate sensitivity is much smaller when N is expressed as a function of shear stress (350). [Pg.148]

When the experimentalist set an ambitious objective to evaluate micromechanical properties quantitatively, he will predictably encounter a few fundamental problems. At first, the continuum description which is usually used in contact mechanics might be not applicable for contact areas as small as 1 -10 nm [116,117]. Secondly, since most of the polymers demonstrate a combination of elastic and viscous behaviour, an appropriate model is required to derive the contact area and the stress field upon indentation a viscoelastic and adhesive sample [116,120]. In this case, the duration of the contact and the scanning rate are not unimportant parameters. Moreover, bending of the cantilever results in a complicated motion of the tip including compression, shear and friction effects [131,132]. Third, plastic or inelastic deformation has to be taken into account in data interpretation. Concerning experimental conditions, the most important is to perform a set of calibrations procedures which includes the (x,y,z) calibration of the piezoelectric transducers, the determination of the spring constants of the cantilever, and the evaluation of the tip shape. The experimentalist has to eliminate surface contamination s and be certain about the chemical composition of the tip and the sample. [Pg.128]

If this approach is valid, the shear rate constant can be determined from experimental measurements of torque vs impeller speed for non-Newtonian fluids of known properties (10). [Pg.349]


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Shear properties

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