Macroscopic testing

We saw earlier (on p. 33) that measuring the temperature is the simplest macroscopic test for an increased energy content. Therefore, we understand that the tyre becomes warmer during inflation because interactions form between the particles with the concurrent release of energy (Equation (2.5)). 

After eight years of exposure, an extensive examination was started in 1994 to evaluate the effectivity and durability of the water repellent treatments [4]. Macroscopic tests as water uptake measurements were carried out to determine the remaining effect of the protective organosilicon layer. Due to the fact that surface information from hydrophobic treatment of mineral surfaces is supplied by surface sensitive measuring techniques, TOF-SIMS and additional DRJFT-studies on treated and exposed material were performed. 

It should be emphasized that the values measured using this technique are usually not as precise as those from other more macroscopic tests. 

Surprising results, compared with macroscopic friction, were obtained for PDMS 6, with a higher nanoscale friction before extraction of free chains. The influence of extraction was also more pronounced for lower normal loads. Macroscopic tests previously showed a sHght increase in friction after extraction. 

Kinematics analysis is a very important step to relate the micromechanics result with the macroscopic constitutive behavior. The reason is that the material parameters involved in the subphases and RVE need to be determined through macroscopic testing. For example, a... 

To summarize in guinea pigs sensitif ed to PNDMA, the macroscopic test is generally distinct whereas, histological examination yields a great variability in the epidermal as well as in the dermal lesions. 

In the above equation, c is the flaw length, A is a constant, and n is a model-derived constant varying between 1.0 and 3.0 depending on the model used. When K values as derived from macroscopic tests on polycrystalline samples are used, 4 values several orders of magnitude too high are predicted from those observed to produce cracks in the /3-AI2O3 membrane. 

Results are presented for different kinds of analyzed objects. Two macroscopic test objects were manufactured from teflon and PVC with diameters of approximately lO cm Fig. 5 shows the macroscopic objects in different orientations together with the three dimensional reconstruction in corresponding orientations. To verify the method, the volumes of these objects were calculated as well as experimentally determined. The maximum deviation between the two methods was 3 %. Fig. 6 shows the reconstruction of a limestone particle with an equivalent diameter Xp = 90 pm. The reconstructions reveal the typical shape characteristics for this material with a relative smooth surface. 

Indentation tests are performed to evaluate the elastic modulus and the hardness of the coating. In macroscopic test, the radius of residual impression is easily measured with an optical observation, while it is difficult to measure in micro- or nanoindentation tests. In such a case, a method to estimate the residual impression radius is proposed. 

Wear is a result of frictional work pWV, To remove polymer the strain must be large and hence is proportional to, say, tan 9 where is the mean asperity slope angle. The eflSciency of the work done per removal operation is inversely proportional to the toughness of the polymer which may be approximated as OyCy, where Gy and Cy are the stress and strains at rupture in a macroscopic test. The volume of material deformed at the interface will be inversely proportional to the hardness H, If the rate of wear is expressed as W/V then... 

Interestingly, it was found that the thermodynamic glass transition matched not only the change in coefficient of expansion which accompanies the glass transition found by thermomechanical analysis (TMA), but also the heat distortion temperature as measured on macroscopic test bars. This finding permitted the use of DSC data with confidence for cure checks, in preference to the more complex and time-consuming preparation of heat distortion test bars. 

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