NACE TM0198-98

The SSR test incorporates a slow (compared with conventional tensile tests), dynamic strain applied at a constant extension rate. Extension rates of 2.5 x 10(-9) to 2.5 x 10(-7) m/s (1.0 x 10(-7) to 1.0 x 10(-5) in./s) are commonly used. The principal effect of the constant extension rate, in combination with environmental or corrosive attack, is to accelerate the initiation of cracking in susceptible materials. By doing so, the slow strain rate acts in much the same way as a notch or precrack in statically stressed environmental cracking tests. Failure is obtained within a few days for commonly used extension rates. Because of its relatively short test duration, the SSR test has been found useful in evaluating stainless steels and nickel-based alloys for resistance to SCC in simulated oilfield production environments at elevated temperatures. By comparison, it has been observed that it may take thousands of hours of exposure time to evaluate these materials using more conventional statically stressed specimens.