Short-term test

Slow Strain-Rate Test In its present state of development, the results from slow strain-rate tests (SSRT) with electrochemical monitoring are not always completely definitive but, for a short-term test, they do provide considerable useful SCC information. Work in our laboratory shows that the SSRT with electrochemical monitoring and the U-bend tests are essentially equivalent in sensitivity in finding SCC. The SSRT is more versatile and faster, providing both mechanical and electrochemical feedback during testing. 

Often, analysts will want to run special short-term tests with the operating unit in order to identify the cause of the trouble being experienced By the unit. Operators are naturally leery of running tests outside their normal operating experience because their primaiy focus is the stable control of the unit, and tests outside their experience may result in loss of control. Multiple tests with few results may decrease their cooperation. 

The American Society for Testing Materials (ASTM) recommends 250 ml of solution for every square inch of area of test metal. Exposure time is also critical. Often it is desirable to extrapolate results from short time tests to long service periods. Typically, corrosion is more intense in its early stages (before protective coatings of corrosion products build up). Results obtained from short-term tests tend to overestimate corrosion rates which often results in an overly conservative design. 

The questionable validity if animal studies and short-term tests with respect to the prediction of long-term, adverse liealUi impacts in a human population... 

Since lead is protected by relatively thick films of corrosion products, short-term tests can be misleading, as once the film has formed there will be a significant decrease in the corrosion rate. 

Uranium Short-term tests indicate that the practical upper limit for niobium as a container material for uranium is about 1 400°C . Niobium is dissolved in a uranium-bismuth alloy in less than lOOh at a temperature of 800°C". Uranium eutectics with iron, manganese or nickel, corroded niobium at 800°C and 1 000°C It is significantly attacked by uranium-chromium at 1 000°C . 

Uranium Short-term tests indicate the practical upper limits for tantalum as a container material for uranium to be 1450°C . However, attack below these temperatures is significant, since a tantalum crucible with a wall 1 52 mm thick was completely corroded in 50 h in 1275°C. 

The fatigue strength of most TPs is about 20 to 30% of the ultimate tensile strength determined in the short-term test but higher for RPs. It decreases with increases in temperature and stress-cycle frequency and with the presence of stress concentration peaks, as in notched components. 

This is the one serious limitation in plastic design problems. Even if the designer did wait for data on one material, chances are the final design might be switched to another plastic or formulation. Thus, as a compromise, data from relatively short-term tests are extrapolated by means of theory to long-term problems. However, when this is done, the limitations inherent in the procedure should be kept in mind. 

Waters MD, Stack HF, Jackson MA, et al. 1994. The performance of short-term tests in identifying potential germ cell mutagens A qualitative and quantitative analysis. Mutat Res 341 109-131. 

The advantages of these methods are that they are generally short-term tests giving results in few hours or days, they require only small amount of chemical and space and they are generally cheap to run compared to in vivo experiments. 

Arni P. 1985. Induction of various genetic effects in the yeast Saccharomyces cerevisiae strain D7. In Ashby J, de Serres FJ, et al., eds. Progress in mutation research, Vol. 5. Evaluation of short-term tests for carcinogens. Amsterdam, The Netherlands Elsevier Science Publishers, 217-224. 

Progress in mutation research. Vol. 5. Evaluation of short-term tests for carcinogens. Amsterdam,... 

Hradec J, Spiegelhalder B, Preussmann R. 1988. The initiator tRNA acceptance assay as a shortterm test for carcinogens. 2. Results with ten compounds selected by the International Programme on Chemical Safety for the evaluation of short-term tests for carcinogens. Carcinogenesis 9 843-846. 

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