Testing hardness tests

Despite variatioas ia hardness test procedures and the variations ia physical properties of the materials tested, hardness conversions from one test to another are possible (see ASTM E140 and Table 2). This approximate relationship is only consistent within a single-material system, eg, iron, steel, or aluminum. 

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. 

Because of the simplicity of doing scratch tests, hardness has been an important diagnostic tool for mineralogists and prospectors by helping them to identify various rocks and minerals. 

The compounds were mixed on a two-roll mill at 320°F. for 8 minutes, then molded into test plaques at 340°F. and 1500 p.s.i. Samples for mechanical testing, hardness, compatibility, and Clash-Berg temperature were 0.075 inch thick while carbon black volatility and extractions were performed on 0.010 inch films. All testing was in accordance with ASTM specifications, and results are summarized in Tables II through V. 

The most practical tests specifically followed for rubber lining are hardness test, spark test and immersion test. Hardness test is invariably the most frequently prescribed test for rubber lining quality by clients, though it is an inadequate test. The term hardness is a vague one the different expressions such as "Scratch Hardness","Cutting Hardness" "Abrasion Hardness" etc. illustrate that different concepts of hardness exist. 

It is perhaps less easy to excuse the lack of a chapter on non-destructive testing. The reason is a mixture of the fact that the major NDT techniques are, in the main only applied to a few particular rubber products and the realisation that to properly describe all methods would require a book, not a chapter. It is, however, worth remembering that it is not only ultrasonics, radiography, holography and so on which are non-destructive. A number of the more traditional rubber tests, for example electrical properties, many dynamic tests, hardness and dimensional measures leave you with the product intact. There are text books which deal with NDT techniques generally and. a comprehensive review of NDT of polymers by Gross in Handbook of Polymer Testing3. 

A further development of static methods of hardness testing was a method devised by Brinell (1900), which consisted of driving a steel ball into the mineral to be tested for hardness under a pressure of 29.4 kN for about 30 seconds. Brinell hardness is defined as the ratio of load to surface of round indentation. The method has found wide use in engineering—for metals it is excellent, but in mineralogy it has proved unsatisfactory because of the high brittleness of most minerals and their non-deformability under the action of the steel ball. The ever wider application of Brinell s method and of a similar method developed by Janko in hardness determination of wood (Krzysik, 1974) should be noted. They are most useful in testing hard wood-base materials, such as compressed wood. 

The test for disintegration is performed as described in the USP, and the results are rounded to the nearest half-min. Disintegration time varied over a narrow range for all batches studied. The 15-batch average for the tray dryer process (2.7 min) is well below the specification (10 min) for this test. Hardness of tablets from the tray dryer process averaged 15 Strong-Cobb units (SCU). All batches exceeded the minimum specification (9 SCU) there is no upper... 

Element Flame test Hardness (Mohs scale) Melting Point (°C) Boiling Point ( C) Density (g/cm ) Atomic radius (pm)... 

Numerous methods are required to characterize drug substances and drug products (Chapter 10). Specifications may include description identification assay (of composite sample) tests for organic synthetic process impurities, inorganic impurities, degradation products, residual solvents, and container extractables tests of various physicochemical properties, chiral purity, water content, content uniformity, and antioxidant and antimicrobial preservative content microbial tests dissolution/disintegration tests hardness/friability tests and tests for particle size and polymorphic form. Some of these tests may be precluded, or additional tests may be added as dictated by the chemistry of the pharmaceutical or the dosage form. 

Mechanical Tests. Hardness measurements taken with a Shore A durometer are reported every time a pad specimen has been removed from its water bath for compression-deflection tests. Separate flat slabs, 0.12 and 0.50 in. thick, of polyurethane elastomer, which were cast from the same batch of material and given identical exposure to water as the pads, were employed for the hardness tests. 

Four hundred bars of duralumin and the same number of shock test pieces were treated simultaneously, i.e. heated to 475° in the nitrate-nitrite bath and quenched in water. Tensi e tests, hardness tests, and shock tests were carried out under the following conditions —... 

Mechanical properties. Hardness is the most common mechanical test. See Chapter 5, Mechanical Testing. Hardness testing, for instance, may be used to indicate whether fasteners in specific critical services are greater or less than the value required to avoid a premature failure. Mechanical tests other than hardness are destructive. If a destructive test is required to ensure compliance it is performed on a sample piece from the lot. Mechanical tests are time consuming and only used when required by the specification. 

Characters and Tests.—Hard white pencils, very deliquescent, powerfully alkaline, and corrosive. A watery solution acidulated by nitric acid gives a yellow precipitate (potassium-platinic chloride) with platinic chloride, indicating the presence of potassium. It should dissolve in diluted nitric acid without effervescence, showing the absence of carbonate, and give but scanty white precipitates with barium chloride and silver nitrate, showing the presence of traces only of sulphate and chloride respectively. 

Characters and Tests.—Hard and greyish-white, very alkaline and corrosive. Does not deliquesce on exposure to the atmosphere. It imparts a yellow colour to flame, indicating the presence of sodium, and its solution in water, acidulated by nitric acid, should give only scanty white precipitates with argentum nitrate and barium chloride, showing the presence of traces only of chlorides and sulphates respectively. 

Field tests hardly allow the assessment of the effects of certain molecules, shown to be toxic in the laboratory, in particular the synthetic pyrethroids. With this kind of product, used at very low doses per hectare (a few grams), mortality is almost never observed in or near the hive. 

Hardness is a property that is intuitively understood but difficult to define. It is usually taken to be a measure of the resistance of a material to permanent (plastic) local deformation and is often measured by forcing a chosen solid into the surface of the material to be tested. Hardness therefore measures... 

Tests hardly used Tests most frequently used (except O2 consumed which is hardly used) ... 

Vicat test See test, hardness Vicat test, softening point Vicat. 

The primary purposes of testing related to shock and vibration are to verify and characterize the dynamic response of the product to a dynamic environment and to demonstrate that the final design will withstand the test environment specified for the product under evaluation. Basic characterization testing is usually performed on an electrodynamic vibration machine with the unit under test hard-mounted to a vibration fixture that has no resonance in the pass band of the excitation spectrum. The test input is a low-displacement-level sinusoid that is slowly varied in firequency (swept) over the frequency range of interest. Sine sweep testing produces a history of the response (displacement or acceleration) at selected points on the equipment to... 

The resistance of a material to the formation of a permanent surface impression by an indenter is termed hardness. The deformation process must be inelastic and, hence, it is inherently related to the resistance of a material to such a deformation (indentation). Hardness impressions can be formed even in brittle materials, though at higher loads this is usually accompanied by localized cracking. For more ductile materials, however, one would expect hardness to be related to the yield stress of a material. In order to create the surface impression, various geometries are used for the indenter (Fig. 6.30). In most tests, hardness is defined as the applied load divided by the actual or projected area of the impression and, thus, the units are the same as stress (Pa). 

In all methods of testing hardness, the thickness of the material and the type of substrate are very important because the elasticity is usually also measured. In addition, it should be noted that hardness tests always measure the hardness of the surface, and not that of the material within the sample. The surface of a sample can be plasticized, for example, by water vapor from the air. If a plastic that can be crystallized is injected into a cold mold, then in some cases the surface is less crystalline than the interior, etc. 

A few experiments were performed with the system to test hard- and software. 

Gen] Optical microscopy, friction tests, resistance tests, hardness tests Meehanical and electrieal properties of laser surface remelting/resolidifying proeessed Cr-Cu-Fe contact material manufactured by powder metallurgy... 

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