STP488

    A Method for Extrapolating Rupture Ductility

    Published: Jan 1971


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    Abstract

    The prediction of long time, elevated temperature properties of useful alloys is of great practical importance. Time-temperature parametric relationships for correlating short time strength and predicting the long time residual strength at temperature have been developed and verified in long time testing. Equal in importance to the residual strength, however, is the capacity for deformation prior to failure, and many applications would appear to be limited by this characteristic. The object of this paper is to present an approximate but useful method for correlating and predicting characteristic, smooth test bar ductility.

    The essence of the method presented is to obtain data which contain rupture ductility in a form that leads to a consistent array which can be treated by parameter techniques. To this end the rupture elongation and rupture time are ratioed to form the average creep rate, which can be treated parametrically and, when combined with the usual stress rupture parameter, provides the elements of this simple technique.

    Several sets of high temperature data are treated to illustrate the technique and compare the results with actual long time data. Some attempt is made to determine how well the method may be expected to work when few data points are available. Further, the method is adaptable to prediction of either elongation or reduction of area at rupture, and this too is illustrated in the text. It is suggested that the method, while approximate, can serve as a quality control tool and should, therefore, be useful to materials engineers.

    Keywords:

    ductility, deformation, elongation, creep properties, creep rupture strength, reduction of area, residual stress, stresses, failure, high temperature tests, alloy steels, stainless steels, quality control


    Author Information:

    Goldhoff, RM
    Manager, Applied Metals Research, Materials and Processes Laboratory, General Electric Co., Schenectady, N. Y.


    Paper ID: STP26910S

    Committee/Subcommittee: E08.05

    DOI: 10.1520/STP26910S


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