Stressing data

Creep. The creep characteristic of plastic foams must be considered when they are used in stmctural appHcations. Creep is the change in dimensions of a material when it is maintained under a constant stress. Data on the deformation of polystyrene foam under various static loads have been compiled (158). There are two types of creep in this material short-term and long-term. Short-term creep exists in foams at all stress levels however, a threshold stress level exists below which there is no detectable long-term creep. The minimum load required to cause long-term creep in molded polystyrene foam varies with density ranging from 50 kPa (7.3 psi) for foam density 16 kg/m (1 lb /ft ) to 455 kPa (66 psi) at foam density 160 kg/m (10... 

Data establishing the stability of the device, accelerated stress data is acceptable Indication for use form... 

Consistency Indices for the reciprocating capillary viscometers are calculated In a similar manner except that 1C 1s determined directly from log shear rate vs log shear stress data. 

FIGURE 9.2 EPR powder pattern of the [2Fe-2S]1+ cluster in spinach ferredoxin. Trace A shows an attempt to fit the spectrum with the diagonal linewidth Equation 9.1. In trace B the spectrum is fitted with the nondiagonal g-strain Equation 9.18. Trace C shows an experiment in which the spectral features are slightly shifted (solid trace) under the influence of an external hydrostatic stress. (Data replotted from Hagen and Albracht 1982.)... 

The question whether or not stirred tank flow is locally isotropic, may be investigated with the help of a LES which resolves a great deal of the Reynolds stresses. To this end, the Reynolds stress data are best presented in terms of the so-called anisotropy tensor and its invariants Ah A2< and A3. 

When an unlisted material is to be used, or when a listed material is to be used above the highest temperature for which stress values appear in the tables of Appendix IX, the designer is responsible for demonstrating the validity of the allowable stresses and other limits used in design and of the approach taken in using the material, including the derivation of stress data and the establishment of temperature limits. 

The original solids-conveying model developed by Darnel and Mol [7] assumed that the pressure (or stress) in the solid bed is isotropic. This assumption was made to simplify the mathematics and because of the lack of stress data for solid bed compacts. Previous research, however, showed that stresses in solid compacts are not isotropic [8]. Anisotropic stresses can be represented by the lateral stress ratio. It is defined as the ratio of the compressive stress in the secondary direction to the compressive stress in the primary direction, as shown in Fig. 4.7 and Eq. 4.1. 

For a specific resin, the shear stress at the interface depends on the temperature of the interface, pressure, and the sliding velocity, it also depends on resin type, additives and additive levels, and the rheological properties of the resin. Stresses at the interface and the coefficients of friction for numerous resins have been published previously from two sources, and the data can be found in the references [15-31]. Additional stress data are provided in Appendix A4 and in several of the case studies in Chapter 12. 

Fernandez, C., Alvarez, M. D., Canet, W. (2007). Steady shear and yield stress data of fresh and frozen/thawed mashed potatoes effect of biopolymers addition. Food Hydrocolloid. 

Preliminary Shelf Life Calculation from Stressed Data... 

Tanner,R. L A correlation of normal stress data for polydisobutylene solutions. Trans. Soc. Rheol. 17, 365-373 (1973). 

Recommendation 5c. The Army and its operating contractors should automate as much as feasible important medical information related to worker exposure to facilitate epidemiological studies. Automated information, available at the programmatic level, should include, but should not be limited to, results of medical examinations, evaluations of exposure to agents, measurements of cholinesterase levels, heat-stress data, and accident/injury information. 

Newtonian and non-Newtonian calibration fluids were used to determine the necessary calibration constants for the impeller method. It has been previously determined that the impeller method is only valid for a Reynolds number (Re) <10. Impeller rotational speed and torque data from Newtonian calibration fluids of known viscosity were employed to determine the Newtonian calibration constant, c. Cone-and plate-viscometer data from non-Newtonian calibration fluids were used to determine a viscosity vs shear rate relationship. Impeller rotational speed and torque data of the non-Newtonian calibration fluids combined with a determined viscosity vs shear rate correlation were utilized to calculate the shear rate constant, k. The impeller method calibration constants allow the calculation of viscosity, shear rate, and shear stress data of non-Newtonian suspensions. Metz et al. (2) have thoroughly discussed the equations utilized in the impeller method. 

H. L. LaNieve IE, and D. C. Bogue, Correlation of Capillary Entrance Pressure Drops with Normal Stress Data, J. Appl. Polym. Sci., 12, 353 (1968). 

Figure 13. Experimental stress-stretch curves for solithane under uniaxial straining at several ambient pressures. A positive pressure corresponds to a negative mean stress. Data are re-plotted from Quested et al. Ref [16].

Figure 7.9 Effect of Initial Film Thickness on Life of a Bonded Molybdenum Disulphide Film Under High Contact Stress (Data from Ref. 179)...

The data in Table 5 show that both values are of the same order of magnitude, though the number of elastic strands determined from the stress data are systematically lower than those determined from the form factor. The difference becomes even stronger if the viscous contribution Go is subtracted from the stress according to Eq. 18. 

An upper-convected Maxwell model has been used with the full relaxation spectrum for the calculation of the stress, but for calculating the birefringence this spectrum has been restricted to long relaxation times as shown in Fig. 12. The model predictions for the data of the Fig. 9 are shown in Fig. 13. The deviations from the linear stress-optical nole are well accounted for by this very simple model. However, the model does not describe the stress data in simple elongation, and in particular the initial stress values at temperatures close to the Tg. 

Because it contains only two parameters (K and n) that can describe shear rate-shear stress data, the power law model has been used extensively to characterize fluid foods. 

A general model for shear rate-shear stress data that under specific assumptions reduces to the Herschel-Bulkley, the Casson, and other models was presented by Ofoli et al. (1987) ... 

Figure 3-9 Schematic Diagram of a Vane that can be Used for Obtaining Yield Stress, and Shear Rate versus Shear Stress Data.

Figure 3-18 Shear Rate-Shear Stress Data on Guava Puree Obtained with a Tube Viscometer (Vitaii and Rao, 1982). Both pseudo and true shear rates are shown.

A pressurized direct-drive concentric cylinder viscometer system (Figure 3-21) was used to obtain shear rate versus shear stress data on a tomato puree at several fixed temperatures between 76 and 120°C (Figure 3-22), and temperature versus apparent viscosity data at several shear rates on a 4% waxy rice (WR) starch dispersion during gelatinization over the temperature range 30 to 110°C (Figure 3-23) (Rao et al., 1998). The drive motor, torque unit, and concentric cylinder unit and temperature control vessel of a Haake RV2 viscometer system (Haake Inc.) were placed in a chamber (PRC) that could be pressurized to 0.2 MPa (two atmospheres). The temperature control vessel was insulated to minimize heat loss. A eopper-constantan (36 gage wires) thermocouple plaeed in the well of the inner eoneentric eylinder measured the temperature of the test sample. 

In Equation 3.116, is rigorously defined as [(an - 022)I(S 2 > 1 is the sum of a constant term and two oscillating terms, accounted by ijr[ and y i is the strain rate amplitude. Equations 6 to 8 suggest that oscillatory shear stress data are related to oscillatory primary normal stress difference data (Ferry, 1980). Youn and Rao (2003) calculated values of (co) for starch dispersions is applicable to oscillatory shear fields. 

Because shear rate-shear stress data can be obtained relatively easily, a number of rheologists explored the possibility of determining the time constants from these data. Most shear-thiiming (pseudoplastic) fluids behave as Newtonian fluids at low shear rates and at a particular shear rate they begin to show their pseudoplastic behavior the reciprocal of the shear rate at which the transition from Newtonian to pseudoplastic behavior occurs is the characteristic time or the time constant. 

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