Elevated Temperature Tensile Creep Strain, Rate, and Time-to-Failure ASTM C1291

Elevated Temperature Tensile Creep Strain, Rate, and Time-to-Failure ASTM C1291

For advanced monolithic ceramics, the ASTM C1291 test method covers the assessment of tensile creep strain, creep strain rate, and creep time-to-failure at elevated temperatures, typically between 1073 and 2073 K. Advanced ceramics that act as macroscopically isotropic and homogeneous are covered by ASTM C1291.


    The ASTM C1291 test method for advanced monolithic ceramics evaluates tensile creep strain,  creep strain rate, and creep time-to-failure at elevated temperatures. Creep tests determine the material’s load-carrying capability for limited deformations by measuring the time-dependent deformation under load at a specific temperature. Creep-rupture tests, when correctly interpreted,  provide a measure of the material’s load-carrying capacity as a function of time and temperature. Material development, quality assurance, characterization, and design data generation are all possible applications for this test procedure. 

    Test Procedure:

    Creep & stress rupture testing can be conducted in two different ways :

    ❖ By applying constant load

    A machine with a straight lever arm is used to do constant load testing. The capstan on the frame adjusts automatically as the specimen lengthens to keep the lever arm horizontal and the load application at a constant length along with the lever. The test would not be conducted under a consistent load or stress state if the auto-leveling feature was unavailable.

    ❖ By applying constant stress

    A curved lever or cam is used in constant stress machines. The frames, unlike the continuous load machines, do not have any automatic cam leveling. Instead, when the cam descends, the applied load’s distance from the pivot reduces, reducing the force exerted on the specimen. The cam’s design (i.e., curvature) is such that the reduction in cross-section of the specimen is proportional to the drop in load, maintaining constant stress on the test piece.

    These two tests complement each other in defining the load-carrying capability of a material for a  given period.

    Specimen Size : 

    According to ASTM C1291, the variety of test specimens required for stress rupture testing and creep testing include smooth, notched, combination smooth & notched, and flat. 

    Cross-sectional tolerances are 0.05 mm, and parallelism tolerances on the faces of the specimen are 0.03 mm.


    The creep strain of the specimen at any time is determined from:

    ε = ( L – Lo ) / Lo


    L = the measured gage length

    Lo = the initial gage length under load and at a temperature at the start of the creep measurement


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