Simulation of Field Test Conditions at Laboratory

A few simulative studies addressing the processes occurring on the steel surface that cause atmospheric corrosion at sites have been carried out and mechanism of rusting process of WS and MS has been proposed. The aim is to develop an early formation of protective rust on WS by applying various surface treatments using electrolytes and suggesting ways to improve the weathering characteristics. 

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In summary, it can be said that the data generated with laboratory tests, though predict the trend of field tests, are grossly insufiicient to predict field behaviour of WS and MS in absolute terms. Since SO2 is a factor which gives some convergence at some points of two types of tests, separate set of experiments was contemplated to simulate similar field conditions at laboratory. 

A further difficulty with this method is that for many soils, the behavior in a laboratory test does not lead to a well-defined failure condition. Rather, the sample simply strains progressively with increasing number of cycles. This difficulty is overcome by defining failure of a laboratory test specimen in terms of developed strain amplitude. Five percent single amplitude is a common criterion, but other strain amplitudes have also been used. The strain amplitude refers to the cyclic strain developed in a laboratory test specimen imder-going the simulated cyclic field stresses superimposed on static-field consolidation stresses. The F.S. at each element is therefore a comparison between the dynamic-induced stress in the field and the cyclic stress required to cause 5% strain in a laboratory test specimen. 

Aqueous solutions were used to simulate specific conditions to carry out electrochemical tests on both field exposed and fresh panels. The test electrolytes are SAEJ 2334 solution (0.25 % NaHCOs -I- 0.5 % NaCl -I- 0.1 % CaCb, pH 9.1) to simulate the atmospheric conditions in the laboratory at 25 3 °C, neutral salt solution (3.5 % NaCl, pH 6.7) and weakly alkaline solution (0.1 M Na2S04 -I-0.1 N NaCl, pH 8.5) to get chloride and sulphate ions in the environment for carrying out tests. Electrolyte used in SAEJ 2334 test was used to determine corrosion performance for coating system as this solution shows a high degree of correlation with field service conditions [5]. 

While mechanistic simulators, based on the population balance and other methods, are being developed, it is appropriate to test the abilities of conventional simulators to match data from laboratory mobility control experiments. The chapter by Claridge, Lescure, and Wang describes mobility control experiments (which use atmospheric pressure emulsions scaled to match miscible-C02 field conditions) and attempts to match the data with a widely used field simulator that does not contain specific mechanisms for surfactant-based mobility control. Chapter 21, by French, also describes experiments on emulsion flow, including experiments at elevated temperatures. 

Field smdies limit the number of dependent variables to be recorded. In addition, changes in working conditions carmot be eontrolled as easily as in the laboratory, which limits the isolation of independent variables. Therefore, psychophysiological methods should be tested in simulated workplaces before being applied in the field. This can be done easily for most automated workplaces where the human-machine interaction takes place using a computer. With such a combined laboratory-field approach, hypotheses from field observations can be tested under highly controlled laboratory conditions. Subsequent studies at real workplaces may be performed only with psychophysiological variables that have been shown to be relevant measures at simulated workplaces. 

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