Loading tests

At the two-multiple loading test, the samples were preliminarily exposed to the stretch exertions effect until the level G, which is O.S B (do not influence on the residual resistance) and the AE total calculation (Nl) was registered. After the test, samples were unloaded entirely, then loaded repeatedly until the initial level 6, and the AE total calculation (N2) was registered again. The ratio K=Nl / N2 was taken as a criteria parameter of the carbon plastic resistance (table 1). If the value of K is considerably exceeding 1, then the samples resistance is quite high. If the value of K is close to or less than 1 - it means that the samples have low resistance. 

Surface finish requirements for the Vickers test vary with the test load. Heavy load tests can be made on a 120 grit ground surface. At low loads increasingly finer surface preparation is required, approaching that for metaHographic specimens, to permit accurate diamond indentation measurements. 

Another measure of refractoriaess is the hot-compressive strength or hot-load test for refractory bricks or formed specialties. The specimen carries a static load from 69 kPa (10 psi) to 172 kPa (25 psi). It is heated at a specific rate to a specific temperature which is then held for 1.5 h, or it is heated at a specific rate until it fads. The percent deformation or the temperature of fadure is measured. The procedure is described ia ASTM C16. 

Weight considerations include (1) hve loads (contents, ice, and snow), (2) dead loads (pipe, valves, insulation, etc.), and (3) test loads (test fluid). 

In the constant-strain method, the specimen is stretched or bent to a fixed position at the start of the test. The most common shape of the specimens used for constant-strain testing is the U-beud, hairpin, or horseshoe type. A bolt is placed through holes in the legs of the specimen, and it is loaded by tightening a nut on the bolt. In some cases, the stress may be reduced during the test as a result of creep. In the constant-load test the specimen is supported horizontally at each end... 

Core friction and windage loss (obtained from the no-load test)... 

The no-load test is a very informative method to determine the no-load current, core and pulsation losses, friction and windage losses, magnetizing current and the no-load power factor. The test also reveals mechanical imbalance, if any, performance of the bearings, vibration and noise level of the motor. 

Philosophy of quality systems Testing of electrical machines Procedure for testing Load test No-load test Tolerances in test results Certification of motors used in hazardous locations... 

During the 4 hr hot no-load test the oil supply temperature shall be varied 10°F above and 10°F below the normal oil supply temperature to demonstrate stability of the rotorbearing system. 

Instruments and controls checked Refractory dried out Piping Strains on Equipment Electric Motors Rotation Drying out No-load tests Steam-Turbine Drivers... 

Auxiliary lubrication and cooling systems checked Instrumentation and speed control checked No-load tests Light-load tests Gas-Engine Drivers... 

Occasions arise when it is not practical to even run a no-load test on the reciprocating compressor because of certain driver arrangements. While it is recognized as being a compromise, a bar over test can be per-... 

Two particular test methods have become very widely used. They are the Vicat softening point test (VSP test) and the heat deflection temperature under load test (HDT test) (which is also widely known by the earlier name of heat distortion temperature test). In the Vicat test a sample of the plastics material is heated at a specified rate of temperature increase and the temperature is noted at which a needle of specified dimensions indents into the material a specified distance under a specified load. In the most common method (method A) a load of ION is used, the needle indentor has a cross-sectional area of 1 mm, the specified penetration distance is 1 mm and the rate of temperature rise is 50°C per hour. For details see the relevant standards (ISO 306 BS 2782 method 120 ASTM D1525 and DIN 53460). (ISO 306 describes two methods, method A with a load of ION and method B with a load of SON, each with two possible rates of temperature rise, 50°C/h and 120°C/h. This results in ISO values quoted as A50, A120, B50 or B120. Many of the results quoted in this book predate the ISO standard and unless otherwise stated may be assumed to correspond to A50.)... 

In the deflection temperature under load test (heat distortion temperature test) the temperature is noted at which a bar of material subjected to a three-point bending stress is deformed a specified amount. The load (F) applied to the sample will vary with the thickness (t) and width (tv) of the samples and is determined by the maximum stress specified at the mid-point of the beam (P) which may be either 0.45 MPa (661bf/in ) or 1.82 MPa (264Ibf/in ). 

The ASTM heat distortion temperature (deflection temperature under load) test may be used to characterise a resin. Resins must, however, be compared using identical hardeners and curing conditions. 

Leerversuch, m. blank experiment or test no-load test. 

Upon completion of the load test, the unit shall be disassembled and the dimensions of each part shall be checked carefully for evidence of yielding. 

Load Testing Apparatus. The load apparatus used to simulate the working load on the test unit shall be calibrated in accordance with ASTM E-4 Standard Methods of Verification of Testing Machines, so as to assure that the prescribed test load is obtained. 

Plumbing and sanitary fittings Domestic water supply Tanks/reservoirs Site investigations and ground Loading tests... 

The implications of a significant role for strain rate are wider than the obvious one that stress corrosion should only occur over a restricted range of strain rates. Thus, in constant load tests, since cracks will continue to propagate only if their rate of advancement is sufficient to maintain the crack-tip strain rate above the minimum rate for cracking, it is to be expected that cracks will sometimes stop propagating, particularly below the threshold stress. Such non-propagating cracks are indeed observed below the thres-hold . Moreover, in constant-load or constant-strain tests, the strain rate diminishes with time after loading, by creep exhaustion if the stress remains sensibly constant, and it is found that the stress-corrosion results are sensitive to the relative times at which the stress and electrochemical... 

Fig. 8.2S Long-time constant-load tests demonstrating a distinct stress-corrosion cracking threshold stress in the case of a straight l3Cr martensitic SS as opposed to a nickel-bearing SS...

In constant-load tests a 22Cr-5Ni-3Mo stainless steel was prevented from cracking by applying a cathodic potential of -130 mV SHE, but the environment for the tests was not specified. Similarly, an 18Cr-1.5Ni steel was prevented from cracking by applying potentials of about -250 mV SHE or less, down to —650 mV, for tests in 42% MgClj at 143°C. 

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