Tests surface-roughness

Convection Heat Transfer. Convective heat transfer occurs when heat is transferred from a soHd surface to a moving fluid owing to the temperature difference between the soHd and fluid. Convective heat transfer depends on several factors, such as temperature difference between soHd and fluid, fluid velocity, fluid thermal conductivity, turbulence level of the moving fluid, surface roughness of the soHd surface, etc. Owing to the complex nature of convective heat transfer, experimental tests are often needed to determine the convective heat-transfer performance of a given system. Such experimental data are often presented in the form of dimensionless correlations. 

Years of development have led to a standardized system for objective evaluation of fabric hand (129). This, the Kawabata evaluation system (KES), consists of four basic testing machines a tensile and shear tester, a bending tester, a compression tester, and a surface tester for measuring friction and surface roughness. To complete the evaluation, fabric weight and thickness are determined. The measurements result in 16 different hand parameters or characteristic values, which have been correlated to appraisals of fabric hand by panels of experts (121). Translation formulas have also been developed based on required levels of each hand property for specific end uses (129). The properties include stiffness, smoothness, and fullness levels as well as the total hand value. In more recent years, abundant research has been documented concerning hand assessment (130—133). 

Product quality control relates to appearance and methods of assessing it either by subjective visual inspection or by objective tests such as reflectivity or surface roughness. 

The influence of compressibility was assessed by varying the Mach number in the range 0 < Ma < 0.38, while Kn and ks/H were kept low. Friction factor data were reported only with Ma < 1 at the exit, to ensure the flow rate was controlled by viscous forces alone. A mild increase in the friction factor (8%) was observed as Ma approached 0.38. This effect was verified independently by numerical analysis for the same conditions as in the experiment. The range of relative surface roughness tested was 0.001 < ka/H < 0.06, yet there was no significant influence on the friction factor for laminar gas flow. 

According to the experimental data presented above, the dependence of the contact ratio a on the test conditions and material properties, such as viscosity, speed, surface roughness, pressure, and elastic module can be descried by an exponential function as ... 

Effect of surface conditions While the value of the CHF is assumed not to be significantly affected by variation in heating surface roughness for ordinary liquids, some experiments with boiling liquid metals (cesium) on horizontal 0.43-in. (ll-mm)-diameter stainless steel-clad cylindrical heaters of three different surface types (Kutateladze et al., 1973 Avksentyuk and Mamontova, 1973) showed different magnitudes and kinds of crisis. These experimenters tested three types of surfaces ... 

The DTS has been used as a strength criterion for meeting American Dental Association specification 27. Reported DTS values for microfilled composites range from 30-50 MPa and for the conventional and hybrid composites, from 45-75 MPa [199-204], The wide variation in the ranges of properties reported may relate not only to differences in materials, but also to test methodologies such as state of hydration, surface roughness of the samples, and strain rates [205,206]. 

It is self evident that tack is very much influenced by the surface condition of the rubber as well as dwell time and pressure this includes contamination and the surface roughness of the test piece. Measurements should be distributed over a fairly large area of the rubber sheet in question to obtain representative results. 

The most common dimensional measurements relate to the size of test pieces because this information is required for virtually all physical test methods. There is also sometimes need to measure dimensions of components of the apparatus, such as the thickness of spacers in compression set tests. Other aspects of dimensional measurement that are relevant to rubber testing include extensometry, surface roughness, dimensional stability and dispersion. 

Metal knives can have various geometries, including a mesh and a raised pattern on a wheel. The important characteristic is the sharpness of the edges in contact with the rubber test piece, and this can be difficult to accurately maintain. Plane smooth surfaces are usually metal and are characterized by the material and the surface roughness. 

The curve of distribution of grain striking at the surface of the material under test follows a normal distribution, hence the depth of the resultant indentation varies with position of test, being roughly constant at points equidistant from the centre of the indentation. The bottom of the indentation thus formed has the shape of a spherical cup. The radius of the sphere has been determined experimentally, and in measurements with the Mackensen blower it is 3 mm, equal to the radius of the circle on the plane of tested material, within which abrasion proceeds. From examination of the forma-... 

Many kinds of artificial hip joints are available commercially, but they all consist of the same parts, i.e. a metal stem or shaft, usually made of a titanium alloy and a ceramic head of aluminium or zirconium oxide. The production of the ceramic head starts with a powder and ends with the sintering process. The heat treatment will cause the head to shrink. After production, the head is thoroughly tested, e.g. on its spherical shape and surface roughness. 

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