Hardness meter

Unless test coupons are produced alongside the lining, the only method of testing the vulcanisation state is with a hand hardness meter. A Shore A or IRHD meter is used for soft rubber linings and a Shore D meter for ebonites. The usual specification is that the hardness has to conform to 5° of the specified hardness. There is no quantitative non-destructive test for the strength of the bond between the lining and the substrate and so such tests are usually carried out in the laboratory on a sample prepared from the materials used. 

ISO 7619 2004 Rubber - Determination of indentation hardness by means of pocket hardness meters... 

There was at one time several other hardness meters, both dead load and portable, but any surviving examples will be very rare. There are also variations on the durometers which have been introduced by particular manufacturers, often for very soft materials such as sponge, but they are also not often seen. 

Hardness tests attract more interest in their accuracy, reproducibiliy and intercomparison than any other test - which is probably a result of them being simple tests which are carried out particularly frequently, and because the situation is confused with several scales. The fact that the situation is far from clear cut owes as much to history as to logic. If the Shore durometers had not been the first hardness meters, it is highly doubtful that we would now have spring loaded instruments mounted on stands or use damage prone indentors. Neither would the IRHD scale have been contrived to mimic the status quo. Such is the effect of powerful established interests. 

ISO 7619-2 2004. Determination of indentation hardness - IRHD pocket hardness meter. 

The hardness measured with the small pocket type of hardness meter is associated with the durometer tests. Although there is not an international standard [1] that covers durometers, there is one for plastics, ISO R868 [10], which was used [9]. The two durometers specified are the Shore A and D which are also described in ASTM D2240 [11] where they are intended to cover both rubbers and plastics. The A scale corresponds approximately to the IRHD (International Rubber Hardness Degrees) scale and the D scale can be conveniently be used for hard rubbers above about 90 IRHD. 

The Shore A scale, or as it is sometimes called, durometer hardness, enjoys considerable success in North America and in particular is widely accepted by the automotive industry the scale is an integral part of the classification system for elastomeric materials used in automotive applications (ASTM D2000). Shore hardness has also become the industry standard for the rapidly growing thermoplastic rubber sector, where advantage can be taken of the complementary Shore D scale for harder grades and for rubber-modified plastics. Seven Shore scales are described in ASTM D2240, while Shore A and D hardness are also detailed in the international standard for pocket hardness meters. ISO 7619 (BS903. Part A57). The latter also specifies a pocket meter based on the IRHD scale. 

Various types of hardness meters are available from ATS FAAR inclnding International Rubber Hardness Degree, Shore, Rockwell, and Fiat for testing against ASTM, ISO, UNI, DIN and FIAT specifications. The Martin Instrument Company is also a supplier of Shore hardness meters. Hardness measurements have recently been reported on methacrylate dental resins [31], polymeric coatings based on polyester resin, PU and acrylic acid [32], polyacrylamide [33] and aged PE [34]. 

The hard rock deposits are mined mainly for feldspar with mica and quartz being accessory minerals. These deposits are extensive, often covering hundreds of square meters and are recognized by the light-colored, granite-like appearance with shiny mica flakes being a prominent feature. The mica content of these deposits ranges from approximately 6—10 wt %. 

Nitride Stmcture Lattice para-meter, a nm Density, g/cm Micro-hardness Maximum stabiHty tempera-ture, °C Heat con-ductivity, W/(m-K) Coefficient of thermal expansion, /3 X 10- ... 

Electroplating. Chromium is electroplated onto various substrates in order to realize a more decorative and corrosion- or wear-resistant surface (24—32). About 80% of the chromium employed in metal treatment is used for chromium plating over 50% is for decorative chromium plating (see Metal surface treatments). Hard chromium plating differs from decorative plating mostiy in terms of thickness. Hard chromium plate may be 10 to several 100 p.m thick, whereas the chromium layers in a decorative plate may be as thin as 0.25 p.m, which corresponds to about two grams Cr per square meter of surface. 

Filling pipes should be as short as possible and free from sharp bends. The terminal should be in a convenient position to allow easy coupling of the vehicle hose connection, wherever possible within 5 meters (15 ft) of the hard standing for vehicle delivery. The most suitable height for a filling pipe is about 1 m (3 ft) above ground level and clear of all obstructions. 

Some physicians recommend epinephrine metered-dose inhalers as an alternative to epinephrine autoinjectors. While a few inhalations might relieve mild or moderate respiratory symptoms, for relief of life-threatening airway obstruction or shock, adults need to inhale 20-30 puffs and children need to inhale 10-20 puffs, which is hard to do [35]. Epinephrine metered-dose inhalers contain chlorofluorocarbon propellants. For environmental reasons, they might not be manufactured in the future. 

With their Models 763 and 764 microprocessor-controlled pH meter, Knick deliver and adapted Model 790 serial printer this yields in a simple way by means of an AC-synchronous clock and two adjustment knobs a hard copy of measurements at intervals of 2, 5, 10, 30 or 60 s or minutes printed out in a 32.5-mm rule of 12 positions on a small paper roll. 

Very hard, steel-gray metal. Hardens platinum. The International Prototype Meter in Paris consists of a Pt-Ir alloy. Its hardness and corrosion resistance is exploited in fountain-pen tips, spark plugs in powerful engines (airplanes), and electrical contacts. Used as a material in shells for nuclide batteries in satellites. Responsible for the iridescent properties of vapor-treated sunglasses. 

The needle valves of Fig. 1 are operated choked, so that there is a constant flow independent of downstream resistances. However, the valve shown upstream of the bubble meter is very important. It is adjusted so that the pressures at the switching valve and upstream are hardly perturbed by a switch. The flows of both mixtures are adjusted to be identical by the needle valves and the bubble meter. When all is properly regulated, the ball in each rotameter makes a short, quick ( ls) excursion at the moment of the switch, and identically for the return to the first position of the valve. 

Historical data from industrial explosions are hard to accurately quantify as these can only be approximated by back calculating from observed deformations of structures. Blast overpressures from vapor cloud explosions are especially difficult to quantify because they tend to be directional, come from multiple sources, and vary with site conditions. Additionally, there is less information available than for high explosives. In one company s review of five recent vapor cloud explosion incidents, as measured at a range of 200 to 1,000 feet (60 to 300 meters), peak reflected pressures in the range from 2 psi (14 kPa) with a 35 ms duration to 12 psi (83 kPa) with a 33 ms duration have occurred. These pressures correspond to side-on overpressures ranging from 1 psi (7 kPa) to 5.5 psi (38 kPa). An extensive list of this type of explosion data is included in Lenoir 1993. 

ISO 7619-2 2004 Rubber, vulcanized or thermoplastic - Determination of indentation hardness - Part 2 IRHD pocket meter method ISO 7743 2004 Rubber, vulcanized or thermoplastic - Determination of compression stress-strain properties... 

---