Hardness values

Mohs hardness values may vary Shore hardness number is derived from rebound height of standard steel ball when dropped on material from standard height. 

Other Bulk Physical Properties. The hardness of asbestos fibers is comparable to that of other crystalline or glassy siHcates. Compared to glass fibers, amphiboles have similar hardness values, while chrysotile shows lower hardness values. 

Global consumption of thermoplastic mbbers of all types is estimated at about 600,000 t/yr (51). Of this, 42% was estimated to be consumed in the United States, 39% in Western Europe, and 19% in Japan. At present, the woddwide market is estimated to be divided as follows styrenic block copolymers, 48% hard polymer/elastomer combinations, 26% thermoplastic polyurethanes, 12% thermoplastic polyesters, 4% and others, 9%. The three largest end uses were transportation, 23% footwear, 18% and adhesives, coatings, etc, 16%. The ranges of the hardness values, prices, and specific gravities of commercially available materials are given in Table 4. 

Assuming that a diamond-pyramid hardness test creates a further nominal strain, on average, of 0.08, and that the hardness value is 3.0 times the true stress with this extra strain, construct the curve of nominal stress against nominal strain, and find ... 

The thermoplastic polyamide elastomers may be considered as premium grade materials available in a wide range of hardness values with, in some instances, very good heat resistance. Particular properties of interest are the flexibility and impact resistance at low temperatures and the good dynamic properties and related resilience, hysteresis and alternating flexural properties. 

In perhaps the most important technological observation, it was found that the reacted Ni3Al products have hardness values equivalent to cold-rolled or rapidly solidified NijAl containing boron additives. The hardness is notable in that the material contains a low density of dislocations. It is observed that crystallites are less than 10 nm in dimension. 

Where high hardness values are required with steels such as 420S37, it is customary to use low temperature tempering in order to obtain optimum corrosion resistance. Such treatments are usually confined to lighter sections as the toughness is limited. Typical properties of 420S37 are given in Table 3.16. 

All these alloys are characterised by high hardness values and low resistance to impact. In this they are probably more similar to stoneware than to other metals but they are superior to stoneware in thermal conductivity and in their resistance to thermal shock, which, however, is poor compared with that of other metals. Moreover, it is usually easier to make castings of silicon iron than to fabricate required parts from stoneware. 

Spraying conditions make hardness values so variable that unless they are accurately known no comparisons are possible. Brinell hardness figures for sprayed molybdenum vary from 350 when produced with a reducing flame to 725 with an oxidising flame, and while a thick sprayed deposit of 0-8% carbon steel can give a figure of 330, the hardness of a particle obtained by micro hardness methods will be about 550. 

Table 12.8 Hardness values (Brinell) for solid blocks of sprayed metal ...

Hardness values ascertained for solid blocks of sprayed metal are given in Table 12.8. Values obtained in America on deposits 0-76mm in thickness were about two-thirds of those given in this table. Figures for shrinkage of various deposits are given in Table 12.9. 

Copper-tin deposits can be plated from cyanide or pyrophosphate -baths and deposits are of good corrosion resistance (approximately equivalent to the same thickness of nickel). Hardness values of up to 314 Hy are obtainable for the copper-rich alloys , and up to 530 Hy for the tin-rich alloys can be obtained. (See also Section 13.5.)... 

Increased hardness and wear resistance may also be achieved by incorporating approximately 25-50% by volume of small non-metallic particles. These may be carbides, oxides, borides or nitrides, and hardness values up to 560 Hy have been reported. ... 

In general, the water uptake of D films tended to be higher than that of / films, but a more significant difference was shown by microhardness measurements. The results obtained with all three vehicles showed that the D areas were significantly softer than the / areas and that the distribution of the hardness values corresponded to that of the resistances. It was concluded that these films have a very heterogeneous structure and that / and D areas are brought about by differences in crosslinking density within the film. 

The concept of relative hardness and topological resonance energy per electron as a measure of aromaticity, with a relative hardness value of zero as the border for antiaromaticity, failed for 1-benzothiepin,3 2... 

Although hardness is a somewhat nebulous term, it can be defined in terms of the tensile modulus of elasticity. From a more practical side, it is usually characterized by a combination of three measurable parameters (1) scratch resistance (2) abrasion or mar resistance and (3) indentation under load. To measure scratch resistance or hardness, an approach is where a specimen is moved laterally under a loaded diamond point. The hardness value is expressed as the load divided by the width of the scratch. In other tests, especially in the paint industry, the surface is scratched with lead pencils of different hardnesses. The hardness of the surface is defined by the pencil hardness that first causes a visible scratch. Other tests include a sand-blast spray evaluation. 

The present review shows how the microhardness technique can be used to elucidate the dependence of a variety of local deformational processes upon polymer texture and morphology. Microhardness is a rather elusive quantity, that is really a combination of other mechanical properties. It is most suitably defined in terms of the pyramid indentation test. Hardness is primarily taken as a measure of the irreversible deformation mechanisms which characterize a polymeric material, though it also involves elastic and time dependent effects which depend on microstructural details. In isotropic lamellar polymers a hardness depression from ideal values, due to the finite crystal thickness, occurs. The interlamellar non-crystalline layer introduces an additional weak component which contributes further to a lowering of the hardness value. Annealing effects and chemical etching are shown to produce, on the contrary, a significant hardening of the material. The prevalent mechanisms for plastic deformation are proposed. Anisotropy behaviour for several oriented materials is critically discussed. 

The Vickers hardness measurement uses a square based pyramid of about 100 pm height as the indenter. The included angles between opposite faces are a = 136°. This corresponds to the tangential angle of an ideal ball impression, considered to have a diameter equal to 0.375 times that of the ball1 . The hardness value is equal to the applied force P in newtons divided by the actual area of impression in mm2. 

From a mechanical point of view the polymer may be regarded as a composite consisting of an alternative stiff (crystalline) and soft-compliant (disordered) elements. Given the geometrical arrangement of these two alternating phases and the hardness value of both of them, the arising question is to predict the hardness value of the material. On the other hand, it is known that density is a crystallinity parameter... 

The question whether hardness is a property related to modulus (E) or yield stress (Y) is a problem which has been commented before by Bowman and Bevis 13). These authors found an experimental relationship between microhardness and modu-lus/yield-stress for injection-moulded semicrystalline plastics. According to the clasical theory of plasticity the expected indentation hardness value for a Vickers indenter is approximaterly equal to three times the yield stress (Tabor s relation). This assump-... 

It has been shown that the anisotropy depends on the orientation of the diagonals of indentation relative to the axial direction 14). At least two well defined hardness values for draw ratios A. > 8 emerge. One value (maximum) can be derived from the indentation diagonal parallel to the fibre axis. The second one (minimum) is deduced from the diagonal perpendicular to it. The former value is, in fact, not a physical measure of hardness but responds to an instant elastic recovery of the fibrous network in the draw direction. The latter value defines the plastic component of the oriented material. 

Figure 32 shows the hardness of all samples. The monolayer Samples 1 and 2 have the highest and the lowest hardness, respectively. The multilayers have a higher hardness than the monolayer B, Sample 2. Among the multilayer samples. Sample 5 showed the highest hardness values, but the values are still lower than those obtained from the monolayer A film, Sample 1. 

The hardness of the Fe-N/Ti-N multilayers decreases with the thickness of the Fe-N layer, but increases with the applied normal force. Among the investigated samples, the Fe-N(5 nm)/Ti-N(2 nm) multilayer has the highest hardness. Under current experimental condition, its hardness value is about 50 % more than that of Fe-N. 

Luo and Domfeld [110] introduced a fitting parameter H , a d5mamical" hardness value of the wafer surface to show the chemical effect and mechanical effect on the interface in their model. It reflects the influences of chemicals on the mechanical material removal. It is found that the nonlinear down pressure dependence of material removal rate is related to a probability density function of the abrasive size and the elastic deformation of the pad. 

Plan Obtain the intrinsic sh by subtracting the weight-dependent part and taking the standard deviation of the residuals. Check the hardness values for... 

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