Long time tests

Several sizes and shapes of specimens have been used in addition to the common ones already mentioned. In the long-time test of bare and zinc-coated steels undertaken by ASTM Committee A-5 on Corrosion of Iron and Steel, full-size sheets were used . This Committee has also exposed specimens in the form of hardware and wire and fencing . 

A sufficient number of specimens should be exposed initially to permit their withdrawal from test in appropriate groups, for example 3 to 5 duplicates after at least three time intervals. For long-time tests, a suitable schedule would call for removals after 1, 2, 5, 10 and 20 years. 

The extent of galvanic action in atmospheric exposure may also be restricted by the development of corrosion products of high electrical resistance between the contacting surfaces — this is especially likely to occur if one of the metals in the couple is an iron or steel that will rust. In long-time tests such possible interruptions in the galvanic circuit should be checked by resistance measurements from time to time so as to determine the actual periods in which galvanic effects could operate. 

Lasting a long time (test or exposure) it can involve a stimulus or stress that is lingering or continues for a long time it has a light onset (effect) as opposed to an acute one. Volume 1(3,5), Volume 2(2,5,11). 

Abstract. The degradation mechanism of field emission cathodes based on carbon nanostructural materials was investigated in the presented work. Emission current instability came from the adsorption desorption processes on the cathode surface. During the long-time tests the periodical variation of the electron work function (caused by switching on and off of the cathode) was detected. The numerical model was proposed to explain the experimentally observed variations of electron work function. 

During the entire long-time test (both operation and storage stages) the current voltage characteristics (I-V curves) were measured every 30 seconds. Then each I-V curve is represented in Fowler-Nordheim coordinates, where it could be interpolate by straight line ln(I/F2) = A + B/V. During the cathode operation, its parameters vary due to some physical phenomena such as ion bombardment and electrostatic force loads. We record those variations as dependence of parameters A and B in time. 

Figure 1. Voltage versus time at a constant current density j = 0,5 mA/cm2. The long-time test consisted of two periodic stages ( operation and storage ). During operation stage two degradation regions are presented (marked as I and IF ).

Figure 3. (a) Electron work function and (b) emission area variations during long-time test represented on Fig. 2. 

Figure 4. The electron work function variation during operation and storage stages. The solid line represents the simulation results (parameters are given in text) the black points -the values of the electron work function estimated from FN-charts, which are measured during long-time test.

Langzeit-Teste =long time test shelf life tests 114 285 large hole blasting 195 LASL = Los Alamos, National Scientific Laboratory (USA)... 

The tests actually employed vary with the kind of explosive tested (explosives, single-base, double-base or triple-base powders, or solid propellants) and the temporal and thermal exposure to be expected (railway transportation or many years storage under varying climatic conditions). In the case of propellants about to be transported by train, only short-time testing is required. However, to obtain an estimate of the expected service life is required, the so-called long-time tests must... 

Building and testing physical parts is costly and takes a long time Tests are usually destructive Multiple physical tests must be done to account for part and build variations Evaluation of different design alternatives is a long and costly process Design optimization cannot be done easily... 

Testing of plastics articles - Determination of the effect of internal pressure on hollow objects by long-time test... 

On basis of the short time tests the level of the long time load was established. The tested beams were loaded at the age of 90 days, applying two levels of loads 0,7 and 1,0 times the force at failure of plain concrete beams. The long time test were performed in constant environmental... 

The long time tests started at the age of specimens 90 days. For each type of a mixture and the load level, three specimens were loaded. The average mid-span deflection measured during the long time tests for different type of aggregate fibre reinforcement and load level are presented in the tables below. The mid-span deflections presented in this paper were recorded up to 280 days of load duration. The tests are still in progress and the results of longer load application will be reported in the future. 

Matzakos, 2005). For commercial applications, it is imperative that such long-time tests be carried out to evaluate the long-term stability of the membrane. 

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