Hardness accelerated tests

In considering the corrosion of magnesium and its alloys it is important to examine the methods available for assessing corrosion tendencies and particularly those known as accelerated tests. Tests carried out by immersion in salt water or by spraying specimens regularly with sea-water are worthless as a means of determining the resistance of magnesium alloys under any other than the particular test conditions. Extrapolation to less corrosive conditions is not valid and even the assessment of the value of protective measures by such means is hardly possible. The reason is to be found in the fact that corrosion behaviour is directly related to the formation of insoluble... 

Accelerated testing was performed by immersing polyurethane liner specimens in water at several elevated temperatures. Periodically, the samples were removed from their respective water baths, dried and then subjected to hardness and compressive stress-strain measurements. An Arrhenius relationship was employed to estimate the expected life of the pads under the severe condition of being continually immersed in water at 35 C. The pads were considered to have failed when their compressive stress fell to 80 percent of the original value. 

The most straightforward version of this test involves a hard acceleration to maximum speed, followed by hard braking at full regen to wheels stop, followed by a wait for 20s. This is repeated continuously until the battery is not capable of providing full power. Although this test may appear at first inspection to be overly aggressive, it is nevertheless appropriate on the basis that at some time, some fraction of the fleet will be exposed to such a cycle and it is wise to test this scenario. 

The slow strain-rate test method (10 s" to 10" s" ) is an accelerated test method when compared with a sustained-load test method. The slow strain-rate test provides an "accelerated test for measuring the threshold when compared with the 5000 hours required by ASTM E 1681, for steels at a hardness of 50-52 HRC. 

The crystalliza tion resistance of vulcaniza tes can be measured by following hardness or compression set at low temperature over a period of time. The stress in a compression set test accelerates crystallization. Often the curve of compression set with time has an S shape, exhibiting a period of nucleation followed by rapid crystallization (Fig. 3). The mercaptan modified homopolymer, Du Pont Type W, is the fastest crystallizing, a sulfur modified homopolymer, GN, somewhat slower, and a sulfur modified low 2,3-dichlorobutadiene copolymer, GRT, and a mercaptan modified high dichlorobutadiene copolymer, WRT, are the slowest. The test is often mn near the temperature of maximum crystallization rate of —12° C (99). Crystallization is accelerated by polyester plasticizers and delayed with hydrocarbon oil plasticizers. Blending with hydrocarbon diene mbbers may retard crystallization and improve low temperature britdeness (100). 

Failure to meet the acceptance criteria for appearance, physical attributes, and functionality test (e.g., color, phase separation, resuspendability, caking, hardness, and dose delivery per actuation) however, some changes in physical attributes (e.g., softening of suppositories and melting of creams) may be expected under accelerated conditions. 

Using formulae (3.11)-(3.15), it should be assumed that the data obtained are estimates, and in scientific tests they should be verified by instrumental methods. It is convenient, nevertheless, especially in mineral syntheses, to use an accelerated hardness measurement as a parameter enabling preliminary checking of the crystallomechanical parameters of an artificially grown crystal, so that a speedy modification of the process is made possible. 

The influence of atmospheric air on the properties of mineral materials manufactured in thermal processes is generally known. An example of the nature of this phenomenon as regards hardness, is a series of Vickers hardness tests of a material made of sintered corundum modified with 0.6% MgO sintered at 1950-2050 K in various environments. The sintering process is accelerated in the presence of hydrogen and is slowest in air thus allowing a material with optimum parameters to be obtained at a significantly lower temperature. The results, specified in Table 6.2.4, show the gases used as... 

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